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2	Network Working Group                                       S. McGlashan
3	Internet-Draft                                           Hewlett-Packard
4	Intended status: Standards Track                            T. Melanchuk
5	Expires: July 10, 2011                        Rain Willow Communications
6	                                                              C. Boulton
7	                                                         NS-Technologies
8	                                                         January 6, 2011

10	    A Mixer Control Package for the Media Control Channel Framework
11	             draft-ietf-mediactrl-mixer-control-package-14

13	Abstract

15	   This document defines a Media Control Channel Framework Package for
16	   managing mixers for media conferences and connections.  The package
17	   defines request elements for managing conference mixers, managing
18	   mixers between conferences and/or connections, as well as associated
19	   responses and notifications.  The package also defines elements for
20	   auditing package capabilities and mixers.

22	Status of this Memo

24	   This Internet-Draft is submitted in full conformance with the
25	   provisions of BCP 78 and BCP 79.

27	   Internet-Drafts are working documents of the Internet Engineering
28	   Task Force (IETF).  Note that other groups may also distribute
29	   working documents as Internet-Drafts.  The list of current Internet-
30	   Drafts is at http://datatracker.ietf.org/drafts/current/.

32	   Internet-Drafts are draft documents valid for a maximum of six months
33	   and may be updated, replaced, or obsoleted by other documents at any
34	   time.  It is inappropriate to use Internet-Drafts as reference
35	   material or to cite them other than as "work in progress."

37	   This Internet-Draft will expire on July 10, 2011.

39	Copyright Notice

41	   Copyright (c) 2011 IETF Trust and the persons identified as the
42	   document authors.  All rights reserved.

44	   This document is subject to BCP 78 and the IETF Trust's Legal
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47	   publication of this document.  Please review these documents
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50	   include Simplified BSD License text as described in Section 4.e of
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52	   described in the Simplified BSD License.

54	   This document may contain material from IETF Documents or IETF
55	   Contributions published or made publicly available before November
56	   10, 2008.  The person(s) controlling the copyright in some of this
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58	   modifications of such material outside the IETF Standards Process.
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62	   not be created outside the IETF Standards Process, except to format
63	   it for publication as an RFC or to translate it into languages other
64	   than English.

66	Table of Contents

68	   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
69	   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   7
70	   3.  Control Package Definition  . . . . . . . . . . . . . . . . .   8
71	     3.1.  Control Package Name  . . . . . . . . . . . . . . . . . .   8
72	     3.2.  Framework Message Usage . . . . . . . . . . . . . . . . .   8
73	     3.3.  Common XML Support  . . . . . . . . . . . . . . . . . . .   9
74	     3.4.  CONTROL Message Body  . . . . . . . . . . . . . . . . . .   9
75	     3.5.  REPORT Message Body . . . . . . . . . . . . . . . . . . .   9
76	     3.6.  Audit . . . . . . . . . . . . . . . . . . . . . . . . . .  10
77	     3.7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  10
78	   4.  Element Definitions . . . . . . . . . . . . . . . . . . . . .  11
79	     4.1.  <mscmixer>  . . . . . . . . . . . . . . . . . . . . . . .  11
80	     4.2.  Mixer Elements  . . . . . . . . . . . . . . . . . . . . .  13
81	       4.2.1.  Conference Elements . . . . . . . . . . . . . . . . .  14
82	         4.2.1.1.  <createconference>  . . . . . . . . . . . . . . .  14
83	         4.2.1.2.  <modifyconference>  . . . . . . . . . . . . . . .  16
84	         4.2.1.3.  <destroyconference> . . . . . . . . . . . . . . .  18
85	         4.2.1.4.  Conference Configuration  . . . . . . . . . . . .  18
86	           4.2.1.4.1.  <audio-mixing>  . . . . . . . . . . . . . . .  18
87	           4.2.1.4.2.  <video-layouts> . . . . . . . . . . . . . . .  19
88	             4.2.1.4.2.1.  <video-layout>  . . . . . . . . . . . . .  20
89	           4.2.1.4.3.  <video-switch>  . . . . . . . . . . . . . . .  26
90	             4.2.1.4.3.1.  Priority assignment . . . . . . . . . . .  28
91	           4.2.1.4.4.  <subscribe> . . . . . . . . . . . . . . . . .  29
92	             4.2.1.4.4.1.  <active-talkers-sub>  . . . . . . . . . .  29
93	       4.2.2.  Joining Elements  . . . . . . . . . . . . . . . . . .  29
94	         4.2.2.1.  Joining Model . . . . . . . . . . . . . . . . . .  30
95	         4.2.2.2.  <join>  . . . . . . . . . . . . . . . . . . . . .  31
96	         4.2.2.3.  <modifyjoin>  . . . . . . . . . . . . . . . . . .  33
97	         4.2.2.4.  <unjoin>  . . . . . . . . . . . . . . . . . . . .  36
98	         4.2.2.5.  <stream>  . . . . . . . . . . . . . . . . . . . .  37
99	           4.2.2.5.1.  <volume>  . . . . . . . . . . . . . . . . . .  39
100	           4.2.2.5.2.  <clamp> . . . . . . . . . . . . . . . . . . .  39
101	           4.2.2.5.3.  <region>  . . . . . . . . . . . . . . . . . .  39
102	           4.2.2.5.4.  <priority>  . . . . . . . . . . . . . . . . .  40
103	       4.2.3.  <response>  . . . . . . . . . . . . . . . . . . . . .  40
104	       4.2.4.  <event> . . . . . . . . . . . . . . . . . . . . . . .  41
105	         4.2.4.1.  <active-talkers-notify> . . . . . . . . . . . . .  41
106	           4.2.4.1.1.  <active-talker> . . . . . . . . . . . . . . .  41
107	         4.2.4.2.  <unjoin-notify> . . . . . . . . . . . . . . . . .  42
108	         4.2.4.3.  <conferenceexit>  . . . . . . . . . . . . . . . .  43
109	     4.3.  Audit Elements  . . . . . . . . . . . . . . . . . . . . .  44
110	       4.3.1.  <audit> . . . . . . . . . . . . . . . . . . . . . . .  44
111	       4.3.2.  <auditresponse> . . . . . . . . . . . . . . . . . . .  46
112	         4.3.2.1.  <capabilities>  . . . . . . . . . . . . . . . . .  47
113	         4.3.2.2.  <mixers>  . . . . . . . . . . . . . . . . . . . .  48
114	           4.3.2.2.1.  <conferenceaudit> . . . . . . . . . . . . . .  48
115	             4.3.2.2.1.1.  <participants>  . . . . . . . . . . . . .  49
116	               4.3.2.2.1.1.1.  <participant> . . . . . . . . . . . .  49
117	           4.3.2.2.2.  <joinaudit> . . . . . . . . . . . . . . . . .  50
118	     4.4.  <codecs>  . . . . . . . . . . . . . . . . . . . . . . . .  50
119	       4.4.1.  <codec> . . . . . . . . . . . . . . . . . . . . . . .  51
120	     4.5.  <params>  . . . . . . . . . . . . . . . . . . . . . . . .  52
121	       4.5.1.  <param> . . . . . . . . . . . . . . . . . . . . . . .  52
122	     4.6.  Response Status Codes . . . . . . . . . . . . . . . . . .  53
123	     4.7.  Type Definitions  . . . . . . . . . . . . . . . . . . . .  57
124	   5.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .  59
125	   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  78
126	     6.1.  AS-MS Framework Interaction Examples  . . . . . . . . . .  78
127	       6.1.1.  Creating a conference mixer and joining a
128	               participant . . . . . . . . . . . . . . . . . . . . .  78
129	       6.1.2.  Receiving active talker notifications . . . . . . . .  79
130	       6.1.3.  Conference termination  . . . . . . . . . . . . . . .  79
131	     6.2.  Mixing Examples . . . . . . . . . . . . . . . . . . . . .  79
132	       6.2.1.  Audio conferencing  . . . . . . . . . . . . . . . . .  80
133	       6.2.2.  Bridging connections  . . . . . . . . . . . . . . . .  82
134	       6.2.3.  Video conferencing  . . . . . . . . . . . . . . . . .  83
135	   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  85
136	   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  88
137	     8.1.  Control Package Registration  . . . . . . . . . . . . . .  88
138	     8.2.  URN Sub-Namespace Registration  . . . . . . . . . . . . .  88
139	     8.3.  XML Schema Registration . . . . . . . . . . . . . . . . .  89
140	     8.4.  MIME Media Type Registration for
141	           'application/msc-mixer+xml' . . . . . . . . . . . . . . .  89
142	   9.  Change Summary  . . . . . . . . . . . . . . . . . . . . . . .  91
143	   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . . 101
144	   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 102
145	   12. References  . . . . . . . . . . . . . . . . . . . . . . . . . 103
146	     12.1. Normative References  . . . . . . . . . . . . . . . . . . 103
147	     12.2. Informative References  . . . . . . . . . . . . . . . . . 104
148	   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 105

150	1.  Introduction

152	   The Media Control Channel Framework
153	   [I-D.ietf-mediactrl-sip-control-framework] provides a generic
154	   approach for establishment and reporting capabilities of remotely
155	   initiated commands.  The Control Framework - an equivalent term for
156	   the Media Control Channel Framework - utilizes many functions
157	   provided by the Session Initiation Protocol [RFC3261] (SIP) for the
158	   rendezvous and establishment of a reliable channel for control
159	   interactions.  The Control Framework also introduces the concept of a
160	   Control Package.  A Control Package is an explicit usage of the
161	   Control Framework for a particular interaction set.  This
162	   specification defines a package for media conference mixers and media
163	   connection mixers.

165	   This package defines mixer management elements for creating,
166	   modifying and deleting conference mixers, elements for joining,
167	   modifying and unjoining media streams between connections and
168	   conferences (including mixers between connections), as well as
169	   associated responses and notifications.  The package also defines
170	   elements for auditing package capabilities and mixers.

172	   This package has been designed to satisfy media mixing requirements
173	   documented in the Media Server Control Protocol Requirements document
174	   ([RFC5167]); more specifically REQ-MCP-22, REQ-MCP-23, REQ-MCP-24,
175	   REQ-MCP-25, REQ-MCP-26 and REQ-MCP-27.

177	   The package provides the major conferencing functionality of SIP
178	   Media Server languages such as MSCML ([RFC5022]) and MSML
179	   ([RFC5707]).  A key differentiator is that this package provides such
180	   functionality using the Media Control Channel Framework.

182	   Out of scope for this mixer package are more advanced functions
183	   including personalized video mixes for conference participants,
184	   support for floor control protocols, as well as support for video
185	   overlays and text insertion.  Such functionality can be addressed by
186	   extensions to this package (through addition of foreign elements or
187	   attributes from another namespace) or use of other control packages
188	   which could build upon this package.

190	   The functionality of this package is defined by messages, containing
191	   XML [XML] elements, transported using the Media Control Channel
192	   Framework.  The XML elements can be divided into two types: mixer
193	   management elements; and elements for auditing package capabilities
194	   as well as mixers managed by the package.

196	   The document is organized as follows.  Section 3 describes how this
197	   control package fulfills the requirements for a Media Control Channel
198	   Framework control package.  Section 4 describes the syntax and
199	   semantics of defined elements, including mixer management
200	   (Section 4.2) and audit elements (Section 4.3).  Section 5 describes
201	   an XML schema for these elements and provides extensibility by
202	   allowing attributes and elements from other namespaces.  Section 6
203	   provides examples of package usage.  Section 7 describes important
204	   security considerations for use of this control package.  Section 8
205	   provides information on IANA registration of this control package,
206	   including its name, XML namespace and MIME media type.

208	2.  Conventions and Terminology

210	   In this document, BCP 14/RFC 2119 [RFC2119] defines the key words
211	   "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
212	   "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
213	   "OPTIONAL".  In addition, BCP 15 indicates requirement levels for
214	   compliant implementations.

216	   The following additional terms are defined for use in this document:

218	   Application server:  A SIP [RFC3261] application server (AS) is a
219	      control client that hosts and executes services such as
220	      interactive media and conferencing in an operator's network.  An
221	      AS controls the media server (MS), influencing and impacting the
222	      SIP sessions terminating on a media server, which the AS can have
223	      established for example using SIP third party call control.

225	   Media Server:  A media server (MS) processes media streams on behalf
226	      of an AS by offering functionality such as interactive media,
227	      conferencing, and transcoding to the end user.  Interactive media
228	      functionality is realized by way of dialogs, which are identified
229	      by a URI and initiated by the application server.

231	   MS Conference:  A MS Conference provides the media related mixing
232	      resources and services for conferences.  In this document, A MS
233	      Conference is often referred to simply as a conference.

235	   MS Connection:  A Media Server connection represents the termination
236	      on a media server of one or more RTP [RFC3550] sessions that are
237	      associated to a single SIP dialog.  A media server receives media
238	      from the output(s) of a connection and it transmits media on the
239	      input(s) of a connection.

241	   Media Stream:  A media stream on a media server represents a media
242	      flow between either a connection and a conference, between two
243	      connections, or between two conferences.  Streams can be audio or
244	      video and can be bi-directional or uni-directional.

246	3.  Control Package Definition

248	   This section fulfills the mandatory requirement for information that
249	   MUST be specified during the definition of a Control Framework
250	   Package, as detailed in Section 8 of
251	   [I-D.ietf-mediactrl-sip-control-framework].

253	3.1.  Control Package Name

255	   The Control Framework requires a Control Package definition to
256	   specify and register a unique name.  The name and version of this
257	   Control Package is "msc-mixer/1.0" (Media Server Control - Mixer -
258	   version 1.0).  Its IANA registration is specified in Section 8.1.

260	   Since this is the initial ("1.0") version of the control package,
261	   there are no backwards compatibility issues to address.

263	3.2.  Framework Message Usage

265	   The Control Framework requires a Control Package to explicitly detail
266	   the control messages that can be used as well as provide an
267	   indication of directionality between entities.  This will include
268	   which role type is allowed to initiate a request type.

270	   This package specifies CONTROL and response messages in terms of XML
271	   elements defined in Section 4, where the message bodies have the MIME
272	   media type defined in Section 8.4.  These elements describe requests,
273	   response and notifications and all are contained within a root
274	   <mscmixer> element (Section 4.1).

276	   In this package, the MS operates as a Control Server in receiving
277	   requests from, and sending responses to, the AS (operating as Control
278	   Client).  Mixer management requests and responses are defined in
279	   Section 4.2.  Audit requests and responses are defined in
280	   Section 4.3.  Mixer management and audit responses are carried in a
281	   framework 200 response or REPORT message bodies.  This package's
282	   response codes are defined in Section 4.6.

284	   Note that package responses are different from framework response
285	   codes.  Framework error response codes (see Section 8 of
286	   [I-D.ietf-mediactrl-sip-control-framework]) are used when the request
287	   or event notification is invalid; for example, a request is invalid
288	   XML (400), or not understood (500).

290	   The MS also operates as a Control Client in sending event
291	   notification to the AS (Control Server).  Event notifications
292	   (Section 4.2.4) are carried in CONTROL message bodies.  The AS MUST
293	   respond with a Control Framework 200 response.

295	3.3.  Common XML Support

297	   The Control Framework requires a Control Package definition to
298	   specify if the attributes for media dialog or conference references
299	   are required.

301	   This package requires that the XML Schema in Section 16.1 of
302	   [I-D.ietf-mediactrl-sip-control-framework] MUST be supported for
303	   media dialogs and conferences.

305	   The package uses "connectionid" and "conferenceid" attributes for
306	   various element definitions (Section 4).  The XML schema (Section 5)
307	   imports the definitions of these attributes from the framework
308	   schema.

310	3.4.  CONTROL Message Body

312	   The Control Framework requires a Control Package to define the
313	   control body that can be contained within a CONTROL command request
314	   and to indicate the location of detailed syntax definitions and
315	   semantics for the appropriate body types.

317	   When operating as Control Server, the MS receives CONTROL messages
318	   with the MIME media type defined in Section 8.4 and a body containing
319	   a <mscmixer> element (Section 4.1) with either a mixer management or
320	   audit request child element.

322	   The following mixer management request elements are carried in
323	   CONTROL message bodies to MS: <createconference> (Section 4.2.1.1),
324	   <modifyconference> (Section 4.2.1.2), <destroyconference>
325	   (Section 4.2.1.3), <join> (Section 4.2.2.2), <modifyjoin>
326	   (Section 4.2.2.3) and <unjoin> (Section 4.2.2.4) elements.

328	   The <audit> request element (Section 4.3.1) is also carried in
329	   CONTROL message bodies.

331	   When operating as Control Client, the MS sends CONTROL messages with
332	   the MIME media type defined in Section 8.4 and a body containing a
333	   <mscmixer> element (Section 4.1) with a notification <event> child
334	   element (Section 4.2.4).

336	3.5.  REPORT Message Body

338	   The Control Framework requires a control package definition to define
339	   the REPORT body that can be contained within a REPORT command
340	   request, or that no report package body is required.  This section
341	   indicates the location of detailed syntax definitions and semantics
342	   for the appropriate body types.

344	   When operating as Control Server, the MS sends REPORT bodies with the
345	   MIME media type defined in Section 8.4 and a <mscmixer> element with
346	   a response child element.  The response element for mixer management
347	   requests is a <response> element (Section 4.2.3).  The response
348	   element for an audit request is a <auditresponse> element
349	   (Section 4.3.2).

351	3.6.  Audit

353	   The Control Framework encourages Control Packages to specify whether
354	   auditing is available, how it is triggered as well as the query/
355	   response formats.

357	   This Control Packages supports auditing of package capabilities and
358	   mixers on the MS.  An audit request is carried in a CONTROL message
359	   and an audit response in a REPORT message (or a 200 response to the
360	   CONTROL if it can execute the audit in time).

362	   The syntax and semantics of audit request and response elements is
363	   defined in Section 4.3.

365	3.7.  Examples

367	   The Control Framework recommends Control Packages to provide a range
368	   of message flows that represent common flows using the package and
369	   this framework document.

371	   This Control Package provides examples of such message flows in
372	   Section 6.

374	4.  Element Definitions

376	   This section defines the XML elements for this package.  The elements
377	   are defined in the XML namespace specified in Section 8.2.

379	   The root element is <mscmixer> (Section 4.1).  All other XML elements
380	   (requests, responses and notification elements) are contained within
381	   it.  Child elements describe mixer management (Section 4.2) and audit
382	   (Section 4.3) functionality.  Response status codes are defined in
383	   Section 4.6 and type definitions in Section 4.7.

385	   Implementation of this control package MUST address the Security
386	   Considerations described in Section 7.

388	   Implementation of this control package MUST adhere to the syntax and
389	   semantics of XML elements defined in this section and the schema
390	   (Section 5).  The XML schema supports extensibility by allowing
391	   attributes and elements from other namespaces.  Implementations MAY
392	   support attributes and elements from other (foreign) namespaces.  If
393	   an MS implementation receives a <mscmixer> element containing
394	   attributes or elements from another namespace which it does not
395	   support, the MS sends a 428 response (Section 4.6).

397	   Extensible attributes and elements are not described in this section.
398	   In all other cases where there is a difference in constraints between
399	   the XML schema and the textual description of elements in this
400	   section, the textual definition takes priority.

402	   Some elements in this control package contain attributes whose value
403	   is descriptive text primarily for diagnostic use.  The implementation
404	   can indicated the language used in the descriptive text by means of a
405	   'desclang' attribute ([RFC2277]).  The desclang attribute can appear
406	   on the root element as well as selected subordinate elements (see
407	   Section 4.1).  The desclang attribute value on the root element
408	   applies to all desclang attributes in subordinate elements unless the
409	   subordinate element has an explicit desclang attribute which
410	   overrides it.

412	   Usage examples are provided in Section 6.

414	4.1.  <mscmixer>

416	   The <mscmixer> element has the following attributes (in addition to
417	   standard XML namespace attributes such as xmlns):

419	   version:  a string specifying the mscmixer package version.  The
420	      value is fixed as '1.0' for this version of the package.  The
421	      attribute is mandatory.

423	   desclang:  specifies the language used in descriptive text attributes
424	      of subordinate elements (unless the subordinate element provides a
425	      desclang attribute which overrides the value for its descriptive
426	      text attributes).  The descriptive text attributes on subordinate
427	      elements include: the reason attribute on <response>
428	      (Section 4.2.3), <unjoin-notify> (Section 4.2.4.2),
429	      <conferenceexit> (Section 4.2.4.3) and <auditresponse>
430	      (Section 4.3.2).  A valid value is a language identifier
431	      (Section 4.7.7).  The attribute is optional.  The default value is
432	      i-default (BCP47 [RFC5646]).

434	   The <mscmixer> element has the following defined child elements, only
435	   one of which can occur:

437	   1.  mixer management elements defined in Section 4.2:

439	       <createconference>  create and configure a new conference mixer.
440	          See Section 4.2.1.1

442	       <modifyconference>  modify the configuration of an existing
443	          conference mixer.  See Section 4.2.1.2

445	       <destroyconference>  destroy an existing conference mixer.  See
446	          Section 4.2.1.3

448	       <join>  create and configure media streams between connections
449	          and/or conferences (for example, add a participant to a
450	          conference).  See Section 4.2.2.2

452	       <modifyjoin>  modify the configuration of joined media streams.
453	          See Section 4.2.2.3

455	       <unjoin>  delete a media stream (for example, remove a
456	          participant from a conference).  See Section 4.2.2.4

458	       <response>  response to a mixer request.  See Section 4.2.3

460	       <event>  mixer or subscription notification.  See Section 4.2.4

462	   2.  audit elements defined in Section 4.3:

464	       <audit>  audit package capabilities and managed mixers.  See
465	          Section 4.3.1

467	       <auditresponse>  response to an audit request.  See Section 4.3.2

469	   For example, a request to the MS to create a conference mixer:

471	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
472	    <createconference/>
473	   </mscmixer>

475	   and a response from the MS that the conference was successfully
476	   created:

478	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer"
479	     desclang="en">
480	    <response status="200" conferenceid="conference1"
481	      reason="conference created"/>
482	   </mscmixer>

484	4.2.  Mixer Elements

486	   This section defines the mixer management XML elements for this
487	   control package.  These elements are divided into requests, responses
488	   and notifications.

490	   Request elements are sent to the MS to request a specific mixer
491	   operation to be executed.  The following request elements are
492	   defined:

494	   <createconference>  create and configure a new a conference mixer.
495	      See Section 4.2.1.1

497	   <modifyconference>  modify the configuration of an existing
498	      conference mixer.  See Section 4.2.1.2

500	   <destroyconference>  destroy an existing conference mixer.  See
501	      Section 4.2.1.3

503	   <join>  create and configure media streams between connections and/or
504	      conferences (for example, add a participant to a conference).  See
505	      Section 4.2.2.2

507	   <modifyjoin>  modify the configuration of joined media streams.  See
508	      Section 4.2.2.3

510	   <unjoin>  delete a media stream (for example, remove a participant
511	      from a conference).  See Section 4.2.2.4

513	   Responses from the MS describe the status of the requested operation.
514	   Responses are specified in a <response> element (Section 4.2.3) which
515	   includes a mandatory attribute describing the status in terms of a
516	   numeric code.  Response status codes are defined in Section 4.6.  The
517	   MS MUST respond to a request message with a response message.  If the
518	   MS is not able to process the request and carry out the mixer
519	   operation (in whole or in part), then the request has failed: the MS
520	   MUST ensure that no part of the requested mixer operation is carried
521	   out, and the MS MUST indicate the class of failure using an
522	   appropriate 4xx response code.  Unless an error response code is
523	   specified for a class of error within this section, implementations
524	   follow Section 4.6 in determining the appropriate status code for the
525	   response.

527	   Notifications are sent from the MS to provide updates on the status
528	   of a mixer operation or subscription.  Notifications are specified in
529	   an <event> element (Section 4.2.4).

531	4.2.1.  Conference Elements

533	4.2.1.1.  <createconference>

535	   The <createconference> element is sent to the MS to request creation
536	   of a new conference (multiparty) mixer.

538	   The <createconference> element has the following attributes:

540	   conferenceid:  string indicating a unique name for the new
541	      conference.  If this attribute is not specified, the MS MUST
542	      create a unique name for the conference.  The value is used in
543	      subsequent references to the conference (e.g. as conferenceid in a
544	      <response>).  The attribute is optional.  There is no default
545	      value.

547	   reserved-talkers:  indicates the requested number of guaranteed
548	      speaker slots to be reserved for the conference.  A valid value is
549	      a non-negative integer (see Section 4.7.2).  The attribute is
550	      optional.  The default value is 0.

552	   reserved-listeners:  indicates the requested number of guaranteed
553	      listener slots to be reserved for the conference.  A valid value
554	      is a non-negative integer (see Section 4.7.2).  The attribute is
555	      optional.  The default value is 0.

557	   The <createconference> element has the following sequence of child
558	   elements:

560	   <codecs>:  an element to configure the codecs supported by the
561	      conference (see Section 4.4).  If codecs are specified, then they
562	      impose limitations in media capability when the MS attempts to
563	      join the conference to other entities (see Section 4.2.2.2 and
564	      Section 4.2.2.3).  The element is optional.

566	   <audio-mixing>:  an element to configure the audio mixing
567	      characteristics of a conference (see Section 4.2.1.4.1).  The
568	      element is optional.

570	   <video-layouts>:  an element to configure the video layouts of a
571	      conference (see Section 4.2.1.4.2).  The element is optional.

573	   <video-switch>:  an element to configure the video switch policy for
574	      the layout of a conference (see Section 4.2.1.4.3).  The element
575	      is optional.

577	   <subscribe>:  an element to request subscription to conference
578	      events. (see Section 4.2.1.4.4).  The element is optional.

580	   If the conferenceid attribute specifies a value which is already used
581	   by an existing conference, the MS reports an error (405) and MUST NOT
582	   create a new conference and MUST NOT affect the existing conference.

584	   If the MS is unable to configure the conference according to
585	   specified reserved-talkers or reserved-listeners attributes, the MS
586	   reports an error (420) and MUST NOT create the conference.

588	   If the MS is unable to configure the conference according to a
589	   specified <audio-mixing> element, the MS reports an error (421) and
590	   MUST NOT create the conference.

592	   If the MS is unable to configure the conference according to a
593	   specified <video-layouts> element, the MS reports an error (423) and
594	   MUST NOT create the conference.

596	   If the MS is unable to configure the conference according to a
597	   specified <video-switch> element, the MS reports an error (424) and
598	   MUST NOT create the conference.

600	   If the MS is unable to configure the conference according to a
601	   specified <codecs> element, the MS reports an error (425) and MUST
602	   NOT create the conference.

604	   When a MS has finished processing a <createconference> request, it
605	   MUST reply with an appropriate <response> element (Section 4.2.3).

607	   For example, a request to create an audio video conference mixer with
608	   specified codecs, video layout, video switch and subscription:

610	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
611	    <createconference conferenceid="conference1"
612	          reserved-talkers="1" reserved-listeners="10">
613	      <codecs>
614	       <codec name="video">
615	        <subtype>H264</subtype>
616	       </codec>
617	       <codec name="audio">
618	        <subtype>PCMA</subtype>
619	       </codec>
620	      </codecs>
621	      <audio-mixing type="nbest"/>
622	      <video-layouts>
623	       <video-layout min-participants="1"><single-view/></video-layout>
624	       <video-layout min-participants="2"><dual-view/></video-layout>
625	       <video-layout min-participants="3"><quad-view/></video-layout>
626	      </video-layouts>
627	      <video-switch interval="5"><vas/></video-switch>
628	      <subscribe>
629	       <active-talkers-sub interval="4"/>
630	      </subscribe>
631	    </createconference>
632	   </mscmixer>

634	   and a response from the MS if the conference was successfully
635	   created:

637	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
638	    <response status="200" conferenceid="conference1"/>
639	   </mscmixer>

641	   alternatively, a response if MS could not create the conference due
642	   to a lack of support for the H264 codec:

644	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
645	    <response status="425" conferenceid="conference1"
646	              reason="H264 codec not supported"/>
647	   </mscmixer>

649	4.2.1.2.  <modifyconference>

651	   The <modifyconference> element is sent to the MS to request
652	   modification of an existing conference.

654	   The <modifyconference> element has the following attributes:

656	   conferenceid:  string indicating the name of the conference to
657	      modify.  This attribute is mandatory.

659	   The <modifyconference> element has the following sequence of child
660	   elements (1 or more):

662	   <codecs>:  an element to configure the codecs supported by the
663	      conference (see Section 4.4).  If codecs are specified, then they
664	      impose limitations in media capability when the MS attempts to
665	      join the conference to other entities (see Section 4.2.2.2 and
666	      Section 4.2.2.3).  Existing conference participants are unaffected
667	      by any policy change.  The element is optional.

669	   <audio-mixing>:  an element to configure the audio mixing
670	      characteristics of a conference (see Section 4.2.1.4.1).  The
671	      element is optional.

673	   <video-layouts>:  an element to configure the video layouts of a
674	      conference (see Section 4.2.1.4.2).  The element is optional.

676	   <video-switch>:  an element to configure the video switch policy for
677	      the layout of a conference (see Section 4.2.1.4.3).  The element
678	      is optional.

680	   <subscribe>:  an element to request subscription to conference
681	      events. (see Section 4.2.1.4.4).  The element is optional.

683	   If the conferenceid attribute specifies the name of a conference
684	   which does not exist, the MS reports an error (406).

686	   If the MS is unable to configure the conference according to a
687	   specified <audio-mixing> element, the MS reports an error (421) and
688	   MUST NOT modify the conference in any way.

690	   If the MS is unable to configure the conference according to a
691	   specified <video-layouts> element, the MS reports an error (423) and
692	   MUST NOT modify the conference in any way.

694	   If the MS is unable to configure the conference according to a
695	   specified <video-switch> element, the MS reports an error (424) and
696	   MUST NOT modify the conference in any way.

698	   If the MS is unable to configure the conference according to a
699	   specified <codecs> element, the MS reports an error (425) and MUST
700	   NOT modify the conference.

702	   When a MS has finished processing a <modifyconference> request, it
703	   MUST reply with an appropriate <response> element (Section 4.2.3).

705	4.2.1.3.  <destroyconference>

707	   The <destroyconference> element is sent to the MS to request
708	   destruction of an existing conference.

710	   The <destroyconference> element has the following attributes:

712	   conferenceid:  string indicating the name of the conference to
713	      destroy.  This attribute is mandatory.

715	   The <destroyconference> element does not specify any child elements.

717	   If the conferenceid attribute specifies the name of a conference
718	   which does not exist, the MS reports an error (406).

720	   When a MS has finished processing a <destroyconference> request, it
721	   MUST reply with an appropriate <response> element (Section 4.2.3).

723	   Successfully destroying the conference (status code 200) will result
724	   in all connection or conference participants being removed from the
725	   conference mixer, <unjoin-notify> notification events
726	   (Section 4.2.4.2) being sent for each conference participant and a
727	   <conferenceexit> notification event (Section 4.2.4.3) indicating that
728	   conference has exited.  A <response> with any other status code
729	   indicates that the conference mixer still exists and participants are
730	   still joined to the mixer.

732	4.2.1.4.  Conference Configuration

734	   The elements in this section are used to establish and modify the
735	   configuration of conferences.

737	4.2.1.4.1.  <audio-mixing>

739	   The <audio-mixing> element defines the configuration of the
740	   conference audio mix.

742	   The <audio-mixing> element has the following attributes:

744	   type:  is a string indicating the audio stream mixing policy.
745	      Defined values are: "nbest" (where the N best (loudest)
746	      participant signals are mixed) and "controller" (where the
747	      contributing participant(s) is/are selected by the controlling AS
748	      via an external floor control protocol).  The attribute is
749	      optional.  The default value is "nbest".

751	   n: indicates the number of eligible participants included in the
752	      conference audio mix.  An eligible participant is a participant
753	      who contributes audio to the conference.  Inclusion is based on
754	      having the greatest audio energy.  A valid value is a non-negative
755	      integer (see Section 4.7.2).  A value of 0 indicates that all
756	      participants contributing audio to the conference are included in
757	      the audio mix.  The default value is 0.  The element is optional.

759	   If the type attribute does not have the value "nbest", the MS ignores
760	   the "n" attribute.

762	   The <audio-mixing> element has no child elements.

764	   For example, a fragment where the audio mixing policy is set to
765	   "nbest" with 3 participants to be included:

767	      <audio-mixing type="nbest" n="3"/>

769	   If the conference had 200 participants of whom 30 contributed audio,
770	   then there would be 30 eligible participants for the audio mix.  Of
771	   these, the 3 loudest participants would have their audio included in
772	   the conference.

774	4.2.1.4.2.  <video-layouts>

776	   The <video-layouts> element describe the video presentation layout
777	   configuration for participants providing a video input stream to the
778	   conference.  This element allows multiple video layouts to be
779	   specified so that the MS automatically changes layout depending on
780	   the number of video-enabled participants.

782	   The <video-layouts> element has no attributes.

784	   The <video-layouts> element has the following sequence of child
785	   elements (1 or more):

787	   <video-layout>:  element describing a video layout
788	      (Section 4.2.1.4.2.1).

790	   If the MS does not support video conferencing at all, or does not
791	   support multiple video layouts, or does not support a specific video
792	   layout, the MS reports an 423 error in the response to the request
793	   element containing the <video-layouts> element.

795	   An MS MAY support more than one <video-layout> element, although only
796	   one layout can be active at a time.  A <video-layout> is active if
797	   the number of participants in the conference is equal to or greater
798	   than the value of its "min-participants" attribute, but less than the
799	   value of the "min-participants" attribute for any other <video-
800	   layout> element.  An MS reports an error (400) if more than one
801	   <video-layout> has the same value for the "min-participants"
802	   attribute.  When the number of regions within the active layout is
803	   greater than the number of participants in the conference, the
804	   display of unassigned regions is implementation-specific.

806	   The assignment of participant video streams to regions within the
807	   layout is according to the video switch policy specified by the
808	   <video-switch> element (Section 4.2.1.4.3).

810	   For example, a fragment describing a single layout:

812	   <video-layouts>
813	     <video-layout><single-view/></video-layout>
814	   </video-layouts>

816	   And a fragment describing a sequence of layouts:

818	   <video-layouts>
819	     <video-layout min-participants="1"><single-view/></video-layout>
820	     <video-layout min-participants="2"><dual-view/></video-layout>
821	     <video-layout min-participants="3"><quad-view/></video-layout>
822	     <video-layout min-participants="5"><multiple-3x3/></video-layout>
823	   </video-layouts>

825	   When the conference has one participant providing a video input
826	   stream to the conference, then the single-view format is used.  When
827	   the conference has two such participants, the dual-view layout is
828	   used.  When the conference has three or four participants, the quad-
829	   view layout is used.  When the conference has five or more
830	   participants, the multiple-3x3 layout is used.

832	4.2.1.4.2.1.  <video-layout>

834	   The <video-layout> element describes a video layout containing one or
835	   more regions in which participant video input streams are displayed.

837	   The <video-layout> element has the following attributes:

839	   min-participants:  the minimum number of conference participants
840	      needed to allow this layout to be active.  A valid value is a
841	      positive integer (see Section 4.7.3).  The attribute is optional.
842	      The default value is 1.

844	   The <video-layout> element has one child element specifying the video
845	   layout.  An MS MAY support the predefined video layouts defined in
846	   the XCON conference information data model
847	   ([I-D.ietf-xcon-common-data-model]): <single-view>, <dual-view>,
848	   <dual-view-crop>, <dual-view-2x1>, <dual-view-2x1-crop>, <quad-view>,
849	   <multiple-3x3>, <multiple-4x4> and <multiple-5x1>.

851	   The MS MAY support other video layouts.  Non-XCON layouts MUST be
852	   specified using an element from a namespace other than the one used
853	   in this specification.  For example,

855	   <video-layout>
856	    <mylayout xmlns='http://example.com/foo'>my-single-view</mylayout>
857	   </video-layout>

859	   If the MS does not support the specified video layout configuration,
860	   then the MS reports a 423 error (Section 4.6) in the response to the
861	   request element containing the <video-layout> element.

863	   Each video layout has associated with it one or more regions.  The
864	   XCON layouts are associated with the following named regions:

866	   <single-view/>  layout with one stream in a single region as shown in
867	      Figure 1.

869	                               +-----------+
870	                               |           |
871	                               |           |
872	                               |     1     |
873	                               |           |
874	                               |           |
875	                               +-----------+

877	                      Figure 1: single-view video layout

879	   <dual-view/>  layout presenting two streams side-by-side in two
880	      regions as shown in Figure 2.  The MS MUST NOT alter the aspect
881	      ratio of each stream to fit the region and hence the MS might need
882	      to blank out part of each region.

884	                         +-----------+-----------+
885	                         |           |           |
886	                         |           |           |
887	                         |     1     |     2     |
888	                         |           |           |
889	                         |           |           |
890	                         +-----------+-----------+

892	                       Figure 2: dual-view video layout

894	   <dual-view-crop/>  layout presenting two streams side-by-side in two
895	      regions as shown in Figure 3.  The MS MUST alter the aspect ratio
896	      of each stream to fit its region so that no blanking is required.

898	                         +-----------+-----------+
899	                         |           |           |
900	                         |           |           |
901	                         |     1     |     2     |
902	                         |           |           |
903	                         |           |           |
904	                         +-----------+-----------+

906	                    Figure 3: dual-view-crop video layout

908	   <dual-view-2x1/>  layout presenting two streams one above the other
909	      in two regions as shown in Figure 4.  The MS MUST NOT alter the
910	      aspect ratio of each stream to fit its region and hence the MS
911	      might need to blank out part of each region.

913	                               +-----------+
914	                               |           |
915	                               |           |
916	                               |     1     |
917	                               |           |
918	                               |           |
919	                               +-----------+
920	                               |           |
921	                               |           |
922	                               |     2     |
923	                               |           |
924	                               |           |
925	                               +-----------+

927	                     Figure 4: dual-view-2x1 video layout

929	   <dual-view-2x1-crop/>  layout presenting two streams one above the
930	      other in two regions as shown in Figure 5.  The MS MUST alter the
931	      aspect ratio of each stream to fit its region so that no blanking
932	      is required.

934	                               +-----------+
935	                               |           |
936	                               |           |
937	                               |     1     |
938	                               |           |
939	                               |           |
940	                               +-----------+
941	                               |           |
942	                               |           |
943	                               |     2     |
944	                               |           |
945	                               |           |
946	                               +-----------+

948	                  Figure 5: dual-view-2x1-crop video layout

950	   <quad-view/>  layout presenting four equal-sized regions in a 2x2
951	      layout as shown in Figure 6.  Typically the aspect ratio of the
952	      streams is preserved, so blanking is required.

954	                         +-----------+-----------+
955	                         |           |           |
956	                         |           |           |
957	                         |     1     |     2     |
958	                         |           |           |
959	                         |           |           |
960	                         +-----------+-----------+
961	                         |           |           |
962	                         |           |           |
963	                         |     3     |     4     |
964	                         |           |           |
965	                         |           |           |
966	                         +-----------+-----------+

968	                       Figure 6: quad-view video layout

970	   <multiple-3x3/>  layout presenting nine equal-sized regions in a 3x3
971	      layout as shown in Figure 7.  Typically the aspect ratio of the
972	      streams is preserved, so blanking is required.

974	                   +-----------+-----------+-----------+
975	                   |           |           |           |
976	                   |           |           |           |
977	                   |     1     |     2     |     3     |
978	                   |           |           |           |
979	                   |           |           |           |
980	                   +-----------+-----------+-----------+
981	                   |           |           |           |
982	                   |           |           |           |
983	                   |     4     |     5     |     6     |
984	                   |           |           |           |
985	                   |           |           |           |
986	                   +-----------+-----------+-----------+
987	                   |           |           |           |
988	                   |           |           |           |
989	                   |    7      |     8     |     9     |
990	                   |           |           |           |
991	                   |           |           |           |
992	                   +-----------+-----------+-----------+

994	                     Figure 7: multiple-3x3 video layout

996	   <multiple-4x4/>  layout presenting sixteen equal-sized regions in a
997	      4x4 layout as shown in Figure 8.  Typically the aspect ratio of
998	      the streams is preserved, so blanking is required.

1000	             +-----------+-----------+-----------+-----------+
1001	             |           |           |           |           |
1002	             |           |           |           |           |
1003	             |     1     |     2     |     3     |     4     |
1004	             |           |           |           |           |
1005	             |           |           |           |           |
1006	             +-----------+-----------+-----------+-----------+
1007	             |           |           |           |           |
1008	             |           |           |           |           |
1009	             |     5     |     6     |     7     |     8     |
1010	             |           |           |           |           |
1011	             |           |           |           |           |
1012	             +-----------+-----------+-----------+-----------+
1013	             |           |           |           |           |
1014	             |           |           |           |           |
1015	             |     9     |    10     |    11     |    12     |
1016	             |           |           |           |           |
1017	             |           |           |           |           |
1018	             +-----------+-----------+-----------+-----------+
1019	             |           |           |           |           |
1020	             |           |           |           |           |
1021	             |    13     |    14     |    15     |    16     |
1022	             |           |           |           |           |
1023	             |           |           |           |           |
1024	             +-----------+-----------+-----------+-----------+

1026	                     Figure 8: multiple-4x4 video layout

1028	   <multiple-5x1/>  layout presents a 5x1 layout as shown in Figure 9
1029	      where one region will occupy 4/9 of the mixed video stream while
1030	      the others will each occupy 1/9 of the stream.  Typically the
1031	      aspect ratio of the streams is preserved, so blanking is required.

1033	                   +-----------------------+-----------+
1034	                   |                       |           |
1035	                   |                       |           |
1036	                   |                       |     2     |
1037	                   |                       |           |
1038	                   |                       |           |
1039	                   |           1           +-----------+
1040	                   |                       |           |
1041	                   |                       |           |
1042	                   |                       |     3     |
1043	                   |                       |           |
1044	                   |                       |           |
1045	                   +-----------+-----------+-----------+
1046	                   |           |           |           |
1047	                   |           |           |           |
1048	                   |    4      |     5     |     6     |
1049	                   |           |           |           |
1050	                   |           |           |           |
1051	                   +-----------+-----------+-----------+

1053	                     Figure 9: multiple-5x1 video layout

1055	4.2.1.4.3.  <video-switch>

1057	   The <video-switch> element describe the configuration of the
1058	   conference policy for how participant's input video streams are
1059	   assigned to regions within the active video layout.

1061	   The <video-switch> element has the following child elements defined
1062	   (one child occurrence only) indicating the video switching policy of
1063	   the conference:

1065	   <vas/>  (Voice Activated Switching) enables automatic display of the
1066	      loudest speaker participant also providing a video input stream to
1067	      the conference.  Participants who do not provide an audio stream
1068	      are not considered for automatic display.  If a participant
1069	      provides more than one audio stream, then the policy for inclusion
1070	      of such a participant in the VAS is implementation-specific; an MS
1071	      could select one stream, sum audio streams or ignore the
1072	      participant for VAS consideration.  If there is only one region in
1073	      the layout, then the loudest speaker is displayed there.  If more
1074	      than one region is available, then the loudest speaker is
1075	      displayed in the largest region, if any, and then in the first
1076	      region from the top-left corner of the layout.  The MS assigns the
1077	      remaining regions based on the priority mechanism described in
1078	      Section 4.2.1.4.3.1.

1080	   <controller/>  enables manual control over video switching.  The
1081	      controller AS determines how the regions are assigned based on an
1082	      external floor control policy.  The MS receives <join>,
1083	      <modifyjoin> and <unjoin> commands with a <stream> element
1084	      (Section 4.2.2.5) indicating the region where the stream is
1085	      displayed.  If no explicit region is specified, the MS assigns the
1086	      region based on the priority mechanism described in
1087	      Section 4.2.1.4.3.1.

1089	   An MS MAY support other video switching policies.  Other policies
1090	   MUST be specified using an element from a namespace other than the
1091	   one used in this specification.  For example,

1093	   <video-switch>
1094	    <mypolicy xmlns='http://example.com/foo'/>
1095	   </video-switch>

1097	   The <video-switch> element has the following attributes:

1099	   interval:  specifies the period between video switches as a number of
1100	      seconds.  In the case of <vas/> policy, a speaker needs to be the
1101	      loudest speaker for the interval before the switch takes place.  A
1102	      valid value is a non-negative integer (see Section 4.7.2).  A
1103	      value of 0 indicates that switching is applied immediately.  The
1104	      attribute is optional.  The default value is 3 (seconds).

1106	   activespeakermix:  indicates whether or not the active (loudest)
1107	      speaker participant receives a video stream without themselves
1108	      displayed in the case of the <vas/> switching policy.  If enabled,
1109	      the MS needs to generate two video streams for each conference
1110	      mix: one for the active speaker participant without themselves
1111	      displayed - details of this video layout are implementation-
1112	      specific; and one for other participants as described in the
1113	      <vas/> switch policy above.  A valid value is a boolean (see
1114	      Section 4.7.1).  A value of true indicates that a separate video
1115	      mix is generated for the active speaker without themselves being
1116	      displayed.  A value of false indicates that all participants
1117	      receive the same video mix.  The attribute is optional.  The
1118	      default value is false.  If the type attribute is not set to
1119	      <vas/>, the MS ignores this attribute.

1121	   If the MS does not support the specified video switching policy or
1122	   other configuration parameters (including separate active speaker
1123	   video mixes), then MS reports a 424 error (Section 4.6) in the
1124	   response to the request element containing the <video-switch>
1125	   element.

1127	   If the MS receives a <join> or <modifyjoin> request containing a
1128	   <stream> element (Section 4.2.2.5) specifying a region and the
1129	   conference video switching policy is set to <vas/>, then the MS
1130	   ignores the region (i.e. conference switching policy takes
1131	   precedence).

1133	   If the MS receives a <join> or <modifyjoin> request containing a
1134	   <stream> element (Section 4.2.2.5) specifying a region which is not
1135	   defined for the currently active video layout, the MS MUST NOT report
1136	   an error.  Even though the participant is not currently visible, the
1137	   MS displays the participant if the layout changes to one which
1138	   defines the specified region.

1140	   For example, a fragment specifying a <vas/> video switching policy
1141	   with an interval of 2s

1143	    <video-switch interval="2"><vas/></video-switch>

1145	   For example, a fragment specifying a <controller/> video switching
1146	   policy where video switching takes place immediately:

1148	    <video-switch interval="0"><controller/></video-switch>

1150	4.2.1.4.3.1.  Priority assignment

1152	   In cases where the video switching policy does not explicitly
1153	   determine the region to which a participant is assigned, the
1154	   following priority assignment mechanism applies:

1156	   1.  Each participant has an (positive integer) priority value: the
1157	       lower the value, the higher the priority.  The priority value is
1158	       determined by the <priority> child element (Section 4.2.2.5.4) of
1159	       <stream>.  If not explicitly specified, the default priority
1160	       value is 100.

1162	   2.  The MS uses priority values to assign participants to regions in
1163	       the video layout which remain unfilled after application of the
1164	       video switching policy.  The MS MUST dedicate larger and/or more
1165	       prominent portions of the layout to participants with higher
1166	       priority values first (e.g. first, all participants with priority
1167	       1, then those with 2, 3, etc).

1169	   3.  The policy for displaying participants with the same priority is
1170	       implementation-specific.

1172	   The MS applies this priority policy each time the video layout is
1173	   changed or updated.  It is RECOMMENDED that the MS does not move a
1174	   participant from one region to another unless required by the video
1175	   switching policy when an active video layout is updated.

1177	   This model allows the MS to apply default video layouts after
1178	   applying the video switch policy.  For example, region 2 is
1179	   statically assigned to Bob, so the priority mechanism only applies to
1180	   regions 1, 3, 4, etc.

1182	4.2.1.4.4.  <subscribe>

1184	   The <subscribe> element is a container for specifying conference
1185	   notification events to which a controlling entity subscribes.
1186	   Notifications of conference events are delivered using the <event>
1187	   element (see Section 4.2.4).

1189	   The <subscribe> element has no attributes, but has the following
1190	   child element:

1192	   <active-talkers-sub>:  subscription to active talker events
1193	      (Section 4.2.1.4.4.1).  The element is optional.

1195	   The MS MUST support a <active-talkers-sub> subscription.  It MAY
1196	   support other event subscriptions (specified using attributes and
1197	   child elements from a foreign namespace).  If the MS does not support
1198	   a subscription specified in a foreign namespace, it sends a
1199	   <response> with a 428 status code (see Section 4.6).

1201	4.2.1.4.4.1.  <active-talkers-sub>

1203	   The <active-talkers-sub> element has the following attributes:

1205	   interval:  the minimum amount of time (in seconds) that elapses
1206	      before further active talker events can be generated.  A valid
1207	      value is a non-negative integer (see Section 4.7.2).  A value of 0
1208	      suppresses further notifications.  The attribute is optional.  The
1209	      default value is 3 (seconds).

1211	   The <active-talkers-sub> element has no child elements.

1213	   Active talker notifications are delivered in the <active-talkers-
1214	   notify> element (Section 4.2.4.1).

1216	4.2.2.  Joining Elements

1218	   In this section, the joining model is defined (Section 4.2.2.1) as
1219	   well as definitions of the <join> (Section 4.2.2.2), <modifyjoin>
1220	   (Section 4.2.2.3), <unjoin> (Section 4.2.2.4) and <stream>
1221	   (Section 4.2.2.5) elements.

1223	4.2.2.1.  Joining Model

1225	   The <join> operation creates a media stream between a connection and
1226	   a conference, between connections, or between conferences.  This
1227	   section describes the model of conferences and connections and
1228	   specifies the behavior for join requests to targets that already have
1229	   an associated media stream.

1231	   Conferences support multiple inputs and have resources to mix them
1232	   together.  A media server conference in essence is a mixer that
1233	   combines media streams.  A simple audio mixer simply sums its input
1234	   audio signals to create a single common output.  Conferences however
1235	   use a more complex algorithm so that participants do not hear
1236	   themselves as part of the mix.  That algorithm, sometimes called an
1237	   n-minus mix, subtracts each participants input signal from the summed
1238	   input signals, creating a unique output for each contributing
1239	   participant.  Each <join> operation to a conference uses one of the
1240	   conference's available inputs and/or outputs, to the maximum number
1241	   of supported participants.

1243	   A connection is the termination of a RTP session(s) on a media
1244	   server.  It has a single input and output for each media session
1245	   established by its SIP dialog.  The output of a connection can feed
1246	   several different inputs such as both a conference mixer and a
1247	   recording of that participant's audio.

1249	   Joining two connections which are are not joined to anything else
1250	   simply creates a media stream from the outputs(s) of one connection
1251	   to the corresponding inputs(s) of the other connection.  It is not
1252	   necessary to combine media from multiple sources in this case.  There
1253	   are however several common scenarios where combining media from
1254	   several sources to create a single input to a connection is needed.

1256	   In the first case, a connection can be receiving media from one
1257	   source, for example a conference, and it is necessary to play an
1258	   announcement to the connection so that both the conference audio and
1259	   announcement can be heard by the conference participant.  This is
1260	   sometimes referred to as a whisper announcement.  An alternative to a
1261	   whisper announcement is to have the announcement pre-empt the
1262	   conference media.

1264	   Another common case is the call center coaching scenario where a
1265	   supervisor can listen to the conversation between an agent and a
1266	   customer, and provide hints to the agent, which are not heard by the
1267	   customer.

1269	   Both of these cases can be solved by having the controlling AS create
1270	   one or more conferences for audio mixing, and then join and unjoin
1271	   the media streams as required.  A better solution is to have the
1272	   media server automatically mix media streams that are requested to be
1273	   joined to a common input when only the simple summing of audio
1274	   signals as described above is required.  This is the case for both
1275	   the use cases presented above.

1277	   Automatically mixing streams has several benefits.  Conceptually, it
1278	   is straight forward and simple, requiring no indirect requests on the
1279	   part of the controlling AS.  This increases transport efficiency and
1280	   reduces the coordination complexity and the latency of the overall
1281	   operation.  Therefore, it is RECOMMENDED that a media server be able
1282	   to automatically mix at least two audio streams where only the simple
1283	   summing of signals is required.

1285	   When a media server receives a <join> request, it MUST automatically
1286	   mix all of the media streams included in the request with any streams
1287	   already joined to one of the entities identified in the request, or
1288	   it MUST fail the request and MUST NOT join any of the streams (and
1289	   MUST NOT change existing streams of the entities).  A controlling AS
1290	   uses the <createconference> request for generic conferences where the
1291	   complex mixing algorithm is required.

1293	   Specifications which extend this package to handle additional media
1294	   types such as text, MUST define the semantics of the join operation
1295	   when multiple streams are requested to be joined to a single input,
1296	   such as that for a connection with a single RTP session per media
1297	   type.

1299	4.2.2.2.  <join>

1301	   The <join> element is sent to the MS to request creation of one or
1302	   more media streams either between a connection and a conference,
1303	   between connections, or between conferences.  The two entities to
1304	   join are specified by the attributes of <join>.

1306	   Streams can be of any media type, and can be bi-directional or uni-
1307	   directional.  A bi-directional stream is implicitly composed of two
1308	   uni-directional streams that can be manipulated independently.  The
1309	   streams to be established are specified by child <stream> elements
1310	   (see Section 4.2.2.5).

1312	   The <join> element has the following attributes:

1314	   id1:  an identifier for either a connection or a conference.  The
1315	      identifier MUST conform to the syntax defined in Section 16.1 of
1316	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1317	      mandatory.

1319	   id2:  an identifier for either a connection or a conference.  The
1320	      identifier MUST conform to the syntax defined in Section 16.1 of
1321	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1322	      mandatory.

1324	   Note: Section 16.1 of [I-D.ietf-mediactrl-sip-control-framework]
1325	   defines the semantics for a conference identifier but not its syntax.
1326	   Media server implementations need to distinguish between conferences
1327	   and connections based upon the values of the "id1" and "id2"
1328	   attributes.

1330	   If id1 or id2 specify a conference identifier and the conference does
1331	   not exist on the MS, the MS reports an error (406).  If id1 or id2
1332	   specify a connection identifier and the connection does not exist on
1333	   the MS, the MS reports an error (412).

1335	   The <join> element has the following child element (0 or more):

1337	   <stream>:   an element that both identifies the media streams to join
1338	      and defines the way that they are to be joined (see
1339	      Section 4.2.2.5).  The element is optional.

1341	   If no <stream> elements are specified, then the default is to join
1342	   all streams between the entities according to the media configuration
1343	   of the connection or conference.

1345	   One or more <stream> elements can be specified so that individual
1346	   media streams can be controlled independently.  For example, if a
1347	   connection supports both audio and video streams, a <stream> element
1348	   could be used to indicate that only the audio stream is used in
1349	   receive mode.  In cases where there are multiple media streams of the
1350	   same type for a connection or conference, the configuration MUST be
1351	   explicitly specified using <stream> elements.

1353	   Multiple <stream> elements can be specified for precise control over
1354	   the media flow in different directions within the same media stream.
1355	   One <stream> element can be specified for the receiving media flow
1356	   and another element for the sending media flow, where each
1357	   independently controls features such as volume (see child element of
1358	   <stream> in Section 4.2.2.5).  If there is only one <stream> element
1359	   for a given media specifying a 'sendonly' or 'recvonly' direction,
1360	   then the media flow in the opposite direction is inactive
1361	   (established but no actual flow of media) unless this leads to a
1362	   stream conflict.

1364	   If the MS is unable to execute the join as specified in <stream>
1365	   because a <stream> element is in conflict with (a) another <stream>
1366	   element, (b) with specified connection or conference media
1367	   capabilities (including supported or available codec information), or
1368	   (c) with a SDP label value as part of the connection-id (see Section
1369	   16.1 of [I-D.ietf-mediactrl-sip-control-framework]), then the MS
1370	   reports an error (407) and MUST NOT join the entities and MUST NOT
1371	   change existing streams of the entities.

1373	   If the MS is unable to execute the join as specified in <stream>
1374	   elements because the MS does not support the media stream
1375	   configuration, the MS reports an error (422) and MUST NOT join the
1376	   entities and MUST NOT change existing streams of the entities.

1378	   If the MS is unable to join an entity to a conference because it is
1379	   full, then the MS reports an error (410).

1381	   If the specified entities are already joined, then the MS reports an
1382	   error (408).

1384	   If the MS does not support joining two specified connections
1385	   together, the MS reports an error (426).

1387	   If the MS does not support joining two specified conferences
1388	   together, the MS reports an error (427).

1390	   If the MS is unable to join the specified entities for any other
1391	   reason, the MS reports an error (411).

1393	   When the MS has finished processing a <join> request, it MUST reply
1394	   with an <response> element (Section 4.2.3).

1396	   For example, a request to join two connection together:

1398	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1399	    <join id1="1536067209:913cd14c" id2="1536067209:913cd14c"/>
1400	   </mscmixer>

1402	   and the response if the MS doesn't support joining media streams
1403	   between connections:

1405	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1406	    <response status="426" reason="mixing connections not supported"/>
1407	   </mscmixer>

1409	4.2.2.3.  <modifyjoin>

1411	   The <modifyjoin> element is sent to the MS to request changes in the
1412	   configuration of media stream(s) that were previously established
1413	   between a connection and a conference, between two connections, or
1414	   between two conferences.

1416	   The <modifyjoin> element has the following attributes:

1418	   id1:  an identifier for either a connection or a conference.  The
1419	      identifier MUST conform to the syntax defined in Section 16.1 of
1420	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1421	      mandatory.

1423	   id2:  an identifier for either a connection or a conference.  The
1424	      identifier MUST conform to the syntax defined in Section 16.1 of
1425	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1426	      mandatory.

1428	   The <modifyjoin> element has the following child elements (1 or
1429	   more):

1431	   <stream>:   an element that both identifies the media streams to
1432	      modify and defines the way that each stream is now to be
1433	      configured (see Section 4.2.2.5).

1435	   The MS MUST support <modifyjoin> for any stream that was established
1436	   using <join>.

1438	   The MS MUST configure the streams that are included within
1439	   <modifyjoin> to that stated by the child elements.

1441	   If the MS is unable to modify the join as specified in <stream>
1442	   elements because a <stream> element is in conflict with (a) another
1443	   <stream> element, (b) with specified connection or conference media
1444	   capabilities (including supported or available codec information), or
1445	   (c) with a SDP label value as part of the connection-id (see Section
1446	   16.1 of [I-D.ietf-mediactrl-sip-control-framework]), then the MS
1447	   reports an error (407) and MUST NOT modify the join between the
1448	   entities and MUST NOT change existing streams of the entities.

1450	   If the MS is unable to modify the join as specified in <stream>
1451	   elements because the MS does not support the media stream
1452	   configuration, the MS reports an error (422) and MUST NOT modify the
1453	   join between the entities and MUST NOT change existing streams of the
1454	   entities.

1456	   If the specified entities are not already joined, then the MS reports
1457	   an error (409).

1459	   If the MS is unable to modify the join between the specified entities
1460	   for any other reason, the MS reports an error (411).

1462	   When an MS has finished processing a <modifyjoin> request, it MUST
1463	   reply with an appropriate <response> element (Section 4.2.3).

1465	   In cases where stream characteristics are controlled independently
1466	   for each direction, then a <modifyjoin> request needs to specify a
1467	   child element for each direction in order to retain the original
1468	   stream directionality.  For the example, if a <join> request
1469	   establishes independent control for each direction of an audio stream
1470	   (see Section 4.2.2.5):

1472	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1473	    <join id1="1536067209:913cd14c" id2="conference1">
1474	     <stream media="audio" direction="sendonly">
1475	      <volume controltype="setgain" value="-3"/>
1476	     </stream>
1477	     <stream media="audio" direction="recvonly">
1478	      <volume controltype="setgain" value="+3"/>
1479	     </stream>
1480	    </join>
1481	   </mscmixer>

1483	   then the following <modifyjoin> request

1485	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1486	    <modifyjoin id1="1536067209:913cd14c" id2="conference1">
1487	     <stream media="audio" direction="sendonly">
1488	       <volume controltype="setgain" value="0"/>
1489	     </stream>
1490	     </modifyjoin>
1491	   </mscmixer>

1493	   would cause, in addition to the sendonly volume being modified, that
1494	   the overall stream directionality changes from sendrecv to sendonly
1495	   since there is no <stream> element in this <modifyjoin> request for
1496	   the recvonly direction.  The following would change the sendonly
1497	   volume and retain the recvonly stream together with its original
1498	   characteristics such as volume:

1500	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1501	    <modifyjoin id1="1536067209:913cd14c" id2="conference1">
1502	     <stream media="audio" direction="sendonly">
1503	       <volume controltype="setgain" value="0"/>
1504	     </stream>
1505	     <stream media="audio" direction="recvonly"/>
1506	     </modifyjoin>
1507	   </mscmixer>

1509	4.2.2.4.  <unjoin>

1511	   The <unjoin> element is sent to the MS to request removal of
1512	   previously established media stream(s) from between a connection and
1513	   a conference, between two connections, or between two conferences.

1515	   The <unjoin> element has the following attributes:

1517	   id1:  an identifier for either a connection or a conference.  The
1518	      identifier MUST conform to the syntax defined in Section 16.1 of
1519	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1520	      mandatory.

1522	   id2:  an identifier for either a connection or a conference.  The
1523	      identifier MUST conform to the syntax defined in Section 15.1 of
1524	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1525	      mandatory.

1527	   The <unjoin> element has the following child element (0 or more
1528	   occurrences):

1530	   <stream>:   an element that identifies the media stream(s) to remove
1531	      (see Section 4.2.2.5).  The element is optional.  When not
1532	      present, all currently established streams between "id1" and "id2"
1533	      are removed.

1535	   The MS MUST support <unjoin> for any stream that was established
1536	   using <join> and has not already been removed by a previous <unjoin>
1537	   on the same stream.

1539	   If the MS is unable to terminate the join as specified in <stream>
1540	   elements because a <stream> element is in conflict with (a) another
1541	   <stream> element, (b) with specified connection or conference media
1542	   capabilities or (c) with a SDP label value as part of the
1543	   connection-id (see Section 16.1 of
1544	   [I-D.ietf-mediactrl-sip-control-framework]), then the MS reports an
1545	   error (407) and MUST NOT terminate the join between the entities and
1546	   MUST NOT change existing streams of the entities.

1548	   If the MS is unable to terminate the join as specified in <stream>
1549	   elements because the MS does not support the media stream
1550	   configuration, the MS reports an error (422) and MUST NOT terminate
1551	   the join between the entities and MUST NOT change existing streams of
1552	   the entities.

1554	   If the specified entities are not already joined, then the MS reports
1555	   an error (409).

1557	   If the MS is unable to terminate the join between the specified
1558	   entities for any other reason, the MS reports an error (411).

1560	   When an MS has successfully processed a <unjoin> request, it MUST
1561	   reply with a successful <response> element (Section 4.2.3).

1563	4.2.2.5.  <stream>

1565	   <join>, <modifyjoin> and <unjoin> require the identification and
1566	   manipulations of media streams.  Media streams represent the flow of
1567	   media between a participant connection and a conference, between two
1568	   connections, or between two conferences.  The <stream> element is
1569	   used (as a child to <join>, <modifyjoin> and <unjoin) to identify the
1570	   media stream(s) for the request and to specify the configuration of
1571	   the media stream.

1573	   The <stream> element has the following attributes:

1575	   media:  a string indicating the type of media associated with the
1576	      stream.  A valid value is a MIME type-name as defined in Section
1577	      4.2 of [RFC4288].  The following values MUST be used for common
1578	      types of media: "audio" for audio media, and "video" for video
1579	      media.  See IANA ([IANA]) for registered MIME type names.  The
1580	      attribute is mandatory.

1582	   label:  a string indicating the SDP label associated with a media
1583	      stream ([RFC4574]).  The attribute is optional.

1585	   direction:  a string indicating the allowed media flow of the stream
1586	      relative to the value of the "id1" attribute of the parent
1587	      element.  Defined values are: "sendrecv" (media can be sent and
1588	      received), "sendonly" (media can only be sent), "recvonly" (media
1589	      can only be received) and "inactive" (stream established but no
1590	      media flow).  The default value is "sendrecv".  The attribute is
1591	      optional.

1593	   The <stream> element has the following sequence of child elements:

1595	   <volume>:  an element (Section 4.2.2.5.1) to configure the volume or
1596	      gain of the media stream.  The element is optional.

1598	   <clamp>:  an element (Section 4.2.2.5.2) to configure filtering and
1599	      removal of tones from the media stream.  The element is optional.

1601	   <region>:  an element (Section 4.2.2.5.3) to configure a region
1602	      within a video layout where the media stream is displayed.  The
1603	      element is optional.

1605	   <priority>:  an element (Section 4.2.2.5.4) to configure priority
1606	      associated with the stream in the media mix.  The element is
1607	      optional.

1609	   In each child element, the media stream affected is indicated by the
1610	   value of the direction attribute of the parent element.

1612	   If the media attribute does not have the value of "audio", then the
1613	   MS ignores <volume> and <clamp> elements.

1615	   If the media attribute does not have the value of "video", then the
1616	   MS ignores a <region> element.

1618	   For example, a request to join a connection to conference in both
1619	   directions with volume control:

1621	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1622	    <join id1="1536067209:913cd14c" id2="conference1">
1623	     <stream media="audio" direction="sendrecv">
1624	      <volume controltype="setgain" value="-3"/>
1625	     </stream>
1626	    </join>
1627	   </mscmixer>

1629	   where audio flow from the connection (id1) to the conference (id2)
1630	   has the volume lowered by 3dB, and likewise the volume of the audio
1631	   flow from the conference to the connection is lowered by 3 dB.

1633	   In this example, the volume is independently controlled for each
1634	   direction.

1636	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1637	    <join id1="1536067209:913cd14c" id2="conference1">
1638	     <stream media="audio" direction="sendonly">
1639	      <volume controltype="setgain" value="-3"/>
1640	     </stream>
1641	     <stream media="audio" direction="recvonly">
1642	      <volume controltype="setgain" value="+3"/>
1643	     </stream>
1644	    </join>
1645	   </mscmixer>

1647	   where audio flow from the connection (id1) to the conference (id2)
1648	   has the volume lowered by 3dB, but the volume of the audio flow from
1649	   the conference to the connection is raised by 3 dB.

1651	4.2.2.5.1.  <volume>

1653	   The <volume> element is used to configure the volume of an audio
1654	   media stream.  It can be set to a specific gain amount, to
1655	   automatically adjust the gain to a desired target level, or to mute
1656	   the volume.

1658	   The <volume> element has no child elements but has the following
1659	   attributes:

1661	   controltype:  a string indicating the type of volume control to use
1662	      for the stream.  Defined values are: "automatic" (the volume will
1663	      be adjusted automatically to the level specified by the "value"
1664	      attribute), "setgain" (use the value of the "value" attribute as a
1665	      specific gain measured in dB to apply), "setstate" (set the state
1666	      of the stream to "mute" or "unmute" as specified by the value of
1667	      the "value" attribute).  The attribute is mandatory.

1669	   value:  a string specifying the amount or state for the volume
1670	      control defined by the value of the "controltype" attribute.  The
1671	      attribute is optional.  There is no default value.

1673	   If the audio media stream is in a muted state, then the MS also
1674	   changes automatically the state to unmuted with an "automatic" or
1675	   "setgain" volume control.  For the example, assume an audio stream
1676	   has been muted with <volume controltype="setstate" value="mute"/>.
1677	   If the gain on the same stream is changed with <volume
1678	   controltype="setgain" value="+3"/>, then the volume is increased and
1679	   stream state is also changed to unmuted.

1681	4.2.2.5.2.  <clamp>

1683	   The <clamp> element is used to configure whether tones are filtered
1684	   and removed from a media stream.

1686	   The <clamp> element has no child elements but has the following
1687	   attributes:

1689	   tones:  A space-separated list of the tones to remove.  The attribute
1690	      is optional.  The default value is "1 2 3 4 5 6 7 8 9 0 * # A B C
1691	      D" (i.e. all DTMF (Dual-Tone Multi-Frequency) tones removed).

1693	4.2.2.5.3.  <region>

1695	   As described in Section 4.2.1.4.2.1, each <video-layout> is composed
1696	   of one or more named regions (or areas) in which video media can be
1697	   presented.  For example, the XCON layout <dual-view> has two regions
1698	   named "1" and "2" respectively.

1700	   The <region> element is used to explicitly specify the name of the
1701	   area within a video layout where a video media stream is displayed.

1703	   The <region> element has no attributes and its content model
1704	   specifies the name of the region.

1706	4.2.2.5.4.  <priority>

1708	   The <priority> element is used to explicitly specify the priority of
1709	   a participant.  The MS uses this priority to determine where the
1710	   media stream is displayed within a video layout
1711	   (Section 4.2.1.4.3.1).

1713	   The <priority> element has no attributes and its content model
1714	   specifies a positive integer (see Section 4.7.3).  The lower the
1715	   value, the higher the priority.

1717	4.2.3.  <response>

1719	   Responses to requests are indicated by a <response> element.

1721	   The <response> element has following attributes:

1723	   status:  numeric code indicating the response status.  Valid values
1724	      are defined in Section 4.6.  The attribute is mandatory.

1726	   reason:  string specifying a reason for the response status.  The
1727	      attribute is optional.

1729	   desclang:  specifies the language used in the value of the the reason
1730	      attribute.  A valid value is a language identifier
1731	      (Section 4.7.7).  The attribute is optional.  If not specified,
1732	      the value of the desclang attribute on <mscmixer> (Section 4.1)
1733	      applies.

1735	   conferenceid:  string identifying the conference (see Section 16.1 of
1736	      [I-D.ietf-mediactrl-sip-control-framework]).  The attribute is
1737	      optional.

1739	   connectionid:  string identifying the SIP dialog connection (see
1740	      Section 16.1 of [I-D.ietf-mediactrl-sip-control-framework]).  The
1741	      attribute is optional.

1743	   For example, a response when a conference was created successfully:

1745	   <response code="200"/>

1747	   The response if conference creation failed due to the requested
1748	   conference id already existing:

1750	   <response code="405" reason="Conference already exists"/>

1752	4.2.4.  <event>

1754	   When a mixer generates a notification event, the MS sends the event
1755	   using an <event> element.

1757	   The <event> element has no attributes, but has the following sequence
1758	   of child elements (0 or more instances of each child):

1760	   <active-talkers-notify>  specifies an active talkers notification
1761	      (Section 4.2.4.1).

1763	   <unjoin-notify>  notifies that a connection or conference has been
1764	      completely unjoined (Section 4.2.4.2).

1766	   <conferenceexit>  notifies that a conference has exited
1767	      (Section 4.2.4.3).

1769	4.2.4.1.  <active-talkers-notify>

1771	   The <active-talkers-notify> element describes zero or more speakers
1772	   that have been active in a conference during the specified interval
1773	   (see Section 4.2.1.4.4.1).

1775	   The <active-talkers-notify> element has the following attributes:

1777	   conferenceid:  string indicating the name of the conference from
1778	      which the event originated.  This attribute is mandatory.

1780	   The <active-talkers-notify> element has the following sequence of
1781	   child elements (0 or more occurrences):

1783	   <active-talker>  element describing an active talker
1784	      (Section 4.2.4.1.1).

1786	4.2.4.1.1.  <active-talker>

1788	   The <active-talker> element describes an active talker, associated
1789	   with either a connection or conference participant in a conference.

1791	   The <active-talker> element has the following attributes:

1793	   connectionid:  string indicating the connectionid of the active
1794	      talker.  This attribute is optional.  There is no default value.

1796	   conferenceid:  string indicating the conferenceid of the active
1797	      talker.  This attribute is optional.  There is no default value.

1799	   Note that the element does not describe an active talker if both the
1800	   connectionid and conferenceid attributes are specified, or if neither
1801	   attribute is specified.

1803	   The <active-talker> element has no child elements.

1805	4.2.4.2.  <unjoin-notify>

1807	   The <unjoin-notify> element describes a notification event where a
1808	   connection and/or conference have been completely unjoined.

1810	   The <unjoin-notify> element has the following attributes:

1812	   status:  a status code indicating why the unjoin occurred.  A valid
1813	      value is a non-negative integer (see Section 4.7.2).  The MS MUST
1814	      support the following values:

1816	      0  indicates the join has been terminated by a <unjoin> request.

1818	      1  indicates the join terminated due to an execution error.

1820	      2  indicates that the join terminated because a connection or
1821	         conference has terminated.

1823	      All other valid but undefined values are reserved for future use,
1824	      where new status codes are assigned using the Standards Action
1825	      process defined in [RFC5226].  The AS MUST treat any status code
1826	      it does not recognize as being equivalent to 1 (join execution
1827	      error).  The attribute is mandatory.

1829	   reason:  a textual description providing a reason for the status
1830	      code; e.g. details about an error.  A valid value is a string (see
1831	      Section 4.7.4).  The attribute is optional.  There is no default
1832	      value.

1834	   desclang:  specifies the language used in the value of the the reason
1835	      attribute.  A valid value is a language identifier
1836	      (Section 4.7.7).  The attribute is optional.  If not specified,
1837	      the value of the desclang attribute on <mscmixer> (Section 4.1)
1838	      applies.

1840	   id1:  an identifier for either a connection or a conference.  The
1841	      identifier MUST conform to the syntax defined in Section 16.1 of
1842	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1843	      mandatory.

1845	   id2:  an identifier for either a connection or a conference.  The
1846	      identifier MUST conform to the syntax defined in Section 16.1 of
1847	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
1848	      mandatory.

1850	   The <unjoin-notify> element has no child elements.

1852	4.2.4.3.  <conferenceexit>

1854	   The <conferenceexit> element indicates that a conference has exited
1855	   because it has been terminated or because a error occurred (for
1856	   example, a hardware error in the conference mixing unit).  This event
1857	   MUST be sent by the MS whenever a successfully created conference
1858	   exits.

1860	   The <conferenceexit> element has the following attributes:

1862	   conferenceid:  string indicating the name of the conference.  This
1863	      attribute is mandatory.

1865	   status:  a status code indicating why the conference exited.  A valid
1866	      value is a non-negative integer (see Section 4.7.2).  The MS MUST
1867	      support the following values:

1869	      0  indicates the conference has been terminated by a
1870	         <destroyconference> request.

1872	      1  indicates the conference terminated due to an execution error.

1874	      2  indicates the conference terminated due to exceeding the
1875	         maximum duration for a conference.

1877	      All other valid but undefined values are reserved for future use,
1878	      where new status codes are assigned using the Standards Action
1879	      process defined in [RFC5226].  The AS MUST treat any status code
1880	      it does not recognize as being equivalent to 1 (conference
1881	      execution error).  The attribute is mandatory.

1883	   reason:  a textual description providing a reason for the status
1884	      code; e.g. details about an error.  A valid value is a string (see
1885	      Section 4.7.4).  The attribute is optional.  There is no default
1886	      value.

1888	   desclang:  specifies the language used in the value of the the reason
1889	      attribute.  A valid value is a language identifier
1890	      (Section 4.7.7).  The attribute is optional.  If not specified,
1891	      the value of the desclang attribute on <mscmixer> (Section 4.1)
1892	      applies.

1894	   The <conferenceexit> element has no child elements.

1896	   When a MS sends a <conferenceexit> event, the identifier for the
1897	   conference (conferenceid attribute) is no longer valid on the MS and
1898	   can be reused for another conference.

1900	   For example, the following notification event would be sent from the
1901	   MS when the conference with identifier "conference99" exits due to a
1902	   successful <destroyconference/>:

1904	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1905	    <event>
1906	     <conferenceexit conferenceid="conference99"
1907	        status="0"/>
1908	    </event>
1909	   </mscmixer>

1911	4.3.  Audit Elements

1913	   The audit elements defined in this section allow the MS to be audited
1914	   for package capabilities as well as mixers managed by the package.
1915	   Auditing is particularly important for two use cases.  First, it
1916	   enables discovery of package capabilities supported on an MS before
1917	   an AS creates a conference mixer or joins connections and
1918	   conferences.  The AS can then use this information to create request
1919	   elements using supported capabilities and, in the case of codecs, to
1920	   negotiate an appropriate SDP for a user agent's connection.  Second,
1921	   auditing enables discovery of the existence and status of mixers
1922	   currently managed by the package on the MS.  This could be used when
1923	   one AS takes over management of mixers if the AS which created the
1924	   mixers fails or is no longer available (see Security Considerations
1925	   described in Section 7).

1927	4.3.1.  <audit>

1929	   The <audit> request element is sent to the MS to request information
1930	   about the capabilities of, and mixers currently managed with, this
1931	   control package.  Capabilities include supported conference codecs
1932	   and video layouts.  Mixer information includes the status of managed
1933	   mixers as well as codecs.

1935	   The <audit> element has the following attributes:

1937	   capabilities:  indicates whether package capabilities are to be
1938	      audited.  A valid value is a boolean (see Section 4.7.1).  A value
1939	      of true indicates that capability information is to be reported.
1940	      A value of false indicates that capability information is not to
1941	      be reported.  The attribute is optional.  The default value is
1942	      true.

1944	   mixers:  indicates whether mixers currently managed by the package
1945	      are to be audited.  A valid value is a boolean (see
1946	      Section 4.7.1).  A value of true indicates that mixer information
1947	      is to be reported.  A value of false indicates that mixer
1948	      information is not to be reported.  The attribute is optional.
1949	      The default value is true.

1951	   conferenceid:  string identifying a specific conference mixer to
1952	      audit.  It is an error (406) if the conferenceid attribute is
1953	      specified and the conference identifier is not valid.  The
1954	      attribute is optional.  There is no default value.

1956	   If the mixers attribute has the value true and conferenceid attribute
1957	   is specified, then only audit information about the specified
1958	   conference mixer is reported.  If the mixers attribute has the value
1959	   false, then no mixer audit information is reported even if a
1960	   conferenceid attribute is specified.

1962	   The <audit> element has no child elements.

1964	   When the MS receives an <audit> request, it MUST reply with a
1965	   <auditresponse> element (Section 4.3.2) which includes a mandatory
1966	   attribute describing the status in terms of a numeric code.  Response
1967	   status codes are defined in Section 4.6.  If the request is
1968	   successful, the <auditresponse> contains (depending on attribute
1969	   values) a <capabilities> element (Section 4.3.2.1) reporting package
1970	   capabilities and a <mixers> element (Section 4.3.2.2) reporting
1971	   managed mixer information.  If the MS is not able to process the
1972	   request and carry out the audit operation, the audit request has
1973	   failed and the MS MUST indicate the class of failure using an
1974	   appropriate 4xx response code.  Unless an error response code is
1975	   specified for a class of error within this section, implementations
1976	   follow Section 4.6 in determining the appropriate status code for the
1977	   response.

1979	   For example, a request to audit capabilities and mixers managed by
1980	   the package:

1982	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1983	     <audit/>
1984	   </mscmixer>
1985	   In this example, only capabilities are to be audited:

1987	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1988	     <audit mixers="false"/>
1989	   </mscmixer>

1991	   With this example, only a specific conference mixer is to be audited:

1993	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
1994	     <audit capabilities="false" conferenceid="conf4"/>
1995	   </mscmixer>

1997	4.3.2.  <auditresponse>

1999	   The <auditresponse> element describes a response to a <audit>
2000	   request.

2002	   The <auditresponse> element has the following attributes:

2004	   status:  numeric code indicating the audit response status.  The
2005	      attribute is mandatory.  Valid values are defined in Section 4.6.

2007	   reason:  string specifying a reason for the status.  The attribute is
2008	      optional.

2010	   desclang:  specifies the language used in the value of the the reason
2011	      attribute.  A valid value is a language identifier
2012	      (Section 4.7.7).  The attribute is optional.  If not specified,
2013	      the value of the desclang attribute on <mscmixer> (Section 4.1)
2014	      applies.

2016	   The <auditresponse> element has the following sequence of child
2017	   elements:

2019	   <capabilities>  element (Section 4.3.2.1) describing capabilities of
2020	      the package.  The element is optional.

2022	   <mixers>  element (Section 4.3.2.2) describing information about
2023	      managed mixers.  The element is optional.

2025	   For example, a successful response to a <audit> request requesting
2026	   capabilities and mixer information:

2028	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
2029	    <auditresponse status="200">
2030	     <capabilities>
2031	      <codecs>
2032	       <codec name="video">
2033	        <subtype>H263</subtype>
2034	       </codec>
2035	       <codec name="video">
2036	        <subtype>H264</subtype>
2037	       </codec>
2038	       <codec name="audio">
2039	        <subtype>PCMU</subtype>
2040	       </codec>
2041	       <codec name="audio">
2042	        <subtype>PCMA</subtype>
2043	       </codec>
2044	      </codecs>
2045	     </capabilities>
2046	     <mixers>
2047	      <conferenceaudit conferenceid="conf1">
2048	       <codecs>
2049	        <codec name="audio">
2050	         <subtype>PCMA</subtype>
2051	        </codec>
2052	       </codecs>
2053	       <participants>
2054	        <participant id="1536067209:913cd14c"/>
2055	       </participants>
2056	      </conferenceaudit>
2057	      <joinaudit id1="1536067209:913cd14c" id2="conf1"/>
2058	      <joinaudit id1="1636067209:113cd14c" id2="1836067209:313cd14c"/>
2059	      <joinaudit id1="1736067209:213cd14c" id2="1936067209:413cd14c"/>
2060	     </mixers>
2061	    </auditresponse>
2062	   </mscmixer>

2064	4.3.2.1.  <capabilities>

2066	   The <capabilities> element provides audit information about package
2067	   capabilities.

2069	   The <capabilities> element has no attributes.

2071	   The <capabilities> element has the following sequence of child
2072	   elements:

2074	   <codecs>:  element (Section 4.4) describing codecs available to the
2075	      package.  The element is mandatory.

2077	   For example, a fragment describing capabilities:

2079	     <capabilities>
2080	      <codecs>
2081	       <codec name="video">
2082	        <subtype>H263</subtype>
2083	       </codec>
2084	       <codec name="video">
2085	        <subtype>H264</subtype>
2086	       </codec>
2087	       <codec name="audio">
2088	        <subtype>PCMU</subtype>
2089	       </codec>
2090	       <codec name="audio">
2091	        <subtype>PCMA</subtype>
2092	       </codec>
2093	      </codecs>
2094	     </capabilities>

2096	4.3.2.2.  <mixers>

2098	   The <mixers> element provides audit information about mixers.

2100	   The <mixers> element has no attributes.

2102	   The <mixers> element has the following sequence of child elements (0
2103	   or more occurrences, any order):

2105	   <conferenceaudit>:  audit information for a conference mixer
2106	      (Section 4.3.2.2.1).  The element is optional.

2108	   <joinaudit>:  audit information for a join mixer (Section 4.3.2.2.2).
2109	      The element is optional.

2111	4.3.2.2.1.  <conferenceaudit>

2113	   The <conferenceaudit> element has the following attributes:

2115	   conferenceid:  string identifying the conference (see Section 16.1 of
2116	      [I-D.ietf-mediactrl-sip-control-framework]).  The attribute is
2117	      mandatory.

2119	   The <conferenceaudit> element has the following sequence of child
2120	   elements:

2122	   <codecs>  element describing codecs used in the conference.  See
2123	      Section 4.4.  The element is optional.

2125	   <participants>  element listing connections or conferences joined to
2126	      the conference.  See Section 4.3.2.2.1.1.  The element is
2127	      optional.

2129	   <video-layout>  element describing the active video layout for the
2130	      conference.  See Section 4.2.1.4.2.1.  The element is optional.

2132	   For example, a fragment describing a conference which has been
2133	   created but has no participants:

2135	   <conferenceaudit conferenceid="conference1"/>

2137	   And a fragment when the same conference has three participants (two
2138	   connections and another conference) joined to it:

2140	   <conferenceaudit conferenceid="conference1">
2141	    <codecs>
2142	     <codec name="audio">
2143	      <subtype>PCMU</subtype>
2144	     </codec>
2145	    </codecs>
2146	    <participants>
2147	      <participant id="connection1"/>
2148	      <participant id="connection2"/>
2149	      <participant id="conference2"/>
2150	    </participants>
2151	   </conferenceaudit>

2153	4.3.2.2.1.1.  <participants>

2155	   The <participants> element is a container for <participant> elements
2156	   (Section 4.3.2.2.1.1.1).

2158	   The <participants> element has no attributes, but the following child
2159	   elements are defined (0 or more):

2161	   <participant>:  specifies a participant (Section 4.3.2.2.1.1.1).

2163	4.3.2.2.1.1.1.  <participant>

2165	   The <participant> element describes a participant.

2167	   The <participant> element has the following attributes:

2169	   id:  an identifier for either a connection or a conference.  The
2170	      identifier MUST conform to the syntax defined in Section 16.1 of
2171	      [I-D.ietf-mediactrl-sip-control-framework].  The attribute is
2172	      mandatory.

2174	   The <participant> element has no children.

2176	4.3.2.2.2.  <joinaudit>

2178	   The <joinaudit> element has the following attributes:

2180	   id1:  an identifier for either a connection or a conference.  The
2181	      identifier MUST conform to the syntax defined in Section 16.1 of
2182	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
2183	      mandatory.

2185	   id2:  an identifier for either a connection or a conference.  The
2186	      identifier MUST conform to the syntax defined in Section 16.1 of
2187	      [I-D.ietf-mediactrl-sip-control-framework] The attribute is
2188	      mandatory.

2190	   The <joinaudit> element has no children.

2192	   For example, a fragment describing an audit of two join mixers, one
2193	   between connections and the second between conferences:

2195	   <mixers>
2196	    <joinaudit id1="1536067209:913cd14" id2="1636067209:413cd14"/>
2197	    <joinaudit id1="conference1" id2="conference2"/>
2198	   </mixers>

2200	4.4.  <codecs>

2202	   The <codecs> element is a container for one or more codec
2203	   definitions.  Codec definitions are used by an AS to specify the
2204	   codecs allowed for a conference (e.g. when used as a child of
2205	   <createconference> or <modifyconference).  Codec definitions are used
2206	   by an MS to provide audit information about the codecs supported by
2207	   an MS and used in specific conferences.

2209	   The <codecs> element has no attributes.

2211	   The <codecs> element has the following sequence of child elements (0
2212	   or more occurrences):

2214	   <codec>:  defines a codec and optionally its policy (Section 4.4.1).
2215	      The element is optional.

2217	   For example, a fragment describing two codecs:

2219	   <codecs>
2220	     <codec name="audio">
2221	      <subtype>PCMA</subtype>
2222	     </codec>
2223	     <codec name="video">
2224	       <subtype>H263</subtype>
2225	     </codec>
2226	   </codecs>

2228	4.4.1.  <codec>

2230	   The <codec> element describes a codec.  The element is modeled on the
2231	   <codec> element in the XCON conference information data model
2232	   ([I-D.ietf-xcon-common-data-model]) and allows addition information
2233	   (e.g. rate, speed, etc) to be specified.

2235	   The <codec> element has the following attributes:

2237	   name:  indicates the type name of the codec's media format as defined
2238	      in IANA ([IANA]).  A valid value is a "type-name" as defined in
2239	      Section 4.2 of [RFC4288].  The attribute is manadatory.

2241	   The <codec> element has the following sequence of child elements:

2243	   <subtype>:  element whose content model describes the subtype of the
2244	      codec's media format as defined in IANA ([IANA]).  A valid value
2245	      is a "subtype-name" as defined in Section 4.2 of [RFC4288].  The
2246	      element is mandatory.

2248	   <params>:  element (Section 4.5) describing additional information
2249	      about the codec.  This package is agnostic to the names and values
2250	      of the codec parameters supported by an implementation.  The
2251	      element is optional.

2253	   For example, a fragment with a <codec> element describing the H263
2254	   codec:

2256	   <codec name=video">
2257	    <subtype>H263</subtype>
2258	   </codec>

2260	   And a fragment where the <codec> element describes the H264 video
2261	   codec with additional information about the profile level and
2262	   packetization mode:

2264	   <codec name="video">
2265	    <subtype>H264</subtype>
2266	    <params>
2267	     <param name="profile-level-id">42A01E</param>
2268	     <param name="packetization-mode">0</param>
2269	    </params>
2270	   </codec>

2272	4.5.  <params>

2274	   The <params> element is a container for <param> elements
2275	   (Section 4.5.1).

2277	   The <params> element has no attributes, but the following child
2278	   elements are defined (0 or more):

2280	   <param>:  specifies a parameter name and value (Section 4.5.1).

2282	4.5.1.  <param>

2284	   The <param> element describes a parameter name and value.

2286	   The <param> element has the following attributes:

2288	   name:  a string indicating the name of the parameter.  The attribute
2289	      is mandatory.

2291	   type:  specifies a type indicating how the inline value of the
2292	      parameter is to be interpreted.  A valid value is a MIME media
2293	      type (see Section 4.7.6).  The attribute is optional.  The default
2294	      value is "text/plain".

2296	   encoding:  specifies a content-transfer-encoding schema applied to
2297	      the inline value of the parameter on top of the MIME media type
2298	      specified with the type attribute.  A valid value is a content-
2299	      transfer-encoding schema as defined by the "mechanism" token in
2300	      Section 6.1 of [RFC2045].  The attribute is optional.  There is no
2301	      default value.

2303	   The <param> element content model is the value of the parameter.
2304	   Note that a value which contains XML characters (e.g. "<") needs to
2305	   be escaped following standard XML conventions.

2307	4.6.  Response Status Codes

2309	   This section describes the response codes in Table 1 for the status
2310	   attribute of mixer management <response> (Section 4.2.3) and audit
2311	   <auditresponse> (Section 4.3.2) responses.  The MS MUST support the
2312	   status response codes defined here.  All other valid but undefined
2313	   values are reserved for future use, where new status codes are
2314	   assigned using the Standards Action process defined in [RFC5226].
2315	   The AS MUST treat any responses it does not recognize as being
2316	   equivalent to the x00 response code for all classes.  For example, if
2317	   an AS receives an unrecognized response code of 499, it can safely
2318	   assume that there was something wrong with its request and treat the
2319	   response as if it had received a 400 (Syntax error) response code.

2321	   4xx responses are definite failure responses from a particular MS.
2322	   The reason attribute in the response SHOULD identify the failure in
2323	   more detail, for example, "Mandatory attribute missing: id2 join
2324	   element" for a 400 (Syntax error) response code.

2326	   The AS SHOULD NOT retry the same request without modification (for
2327	   example, correcting a syntax error or changing the conferenceid to
2328	   use one available on the MS).  However, the same request to a
2329	   different MS might be successful; for example, if another MS supports
2330	   a capability required in the request.

2332	   4xx failure responses can be grouped into three classes: failure due
2333	   to a syntax error in the request (400); failure due to an error
2334	   executing the request on the MS (405-419); and failure due to the
2335	   request requiring a capability not supported by the MS (420-435).

2337	   In cases where more than one request code could be reported for a
2338	   failure, the MS SHOULD use the most specific error code of the
2339	   failure class for the detected error.  For example, if the MS detects
2340	   that the conference identifier in the request is invalid, then it
2341	   uses a 406 status code.  However, if the MS merely detects that an
2342	   execution error occurred, then 419 is used.

2344	   +-------+---------------+----------------------+--------------------+
2345	   | Code  | Summary       | Description          | Informational: AS  |
2346	   |       |               |                      | Possible Recovery  |
2347	   |       |               |                      | Action             |
2348	   +-------+---------------+----------------------+--------------------+
2349	   | 200   | OK            | request has          |                    |
2350	   |       |               | succeeded            |                    |
2351	   |       |               |                      |                    |
2352	   | 400   | Syntax error  | request is           | Change the request |
2353	   |       |               | syntactically        | so that it is      |
2354	   |       |               | invalid: it is not   | syntactically      |
2355	   |       |               | valid with respect   | valid.             |
2356	   |       |               | to the XML schema    |                    |
2357	   |       |               | specified in         |                    |
2358	   |       |               | Section 5 or it      |                    |
2359	   |       |               | violates a           |                    |
2360	   |       |               | co-occurrence        |                    |
2361	   |       |               | constraint for a     |                    |
2362	   |       |               | request element      |                    |
2363	   |       |               | defined in           |                    |
2364	   |       |               | Section 4.           |                    |
2365	   |       |               |                      |                    |
2366	   | 405   | Conference    | request uses an      | Send an <audit>    |
2367	   |       | already       | identifier to create | request            |
2368	   |       | exists        | a new conference     | (Section 4.3.1)    |
2369	   |       |               | (Section 4.2.1.1)    | requesting the     |
2370	   |       |               | which is already     | list of conference |
2371	   |       |               | used by another      | mixer identifiers  |
2372	   |       |               | conference on the    | already used by    |
2373	   |       |               | MS.                  | the MS and then    |
2374	   |       |               |                      | use a conference   |
2375	   |       |               |                      | identifier which   |
2376	   |       |               |                      | is not listed.     |
2377	   |       |               |                      |                    |
2378	   | 406   | Conference    | request uses an      | Send an <audit>    |
2379	   |       | does not      | identifier for a     | request            |
2380	   |       | exist         | conference which     | (Section 4.3.1)    |
2381	   |       |               | does not exist on    | requesting the     |
2382	   |       |               | the MS.              | list of conference |
2383	   |       |               |                      | mixer identifiers  |
2384	   |       |               |                      | used by the MS and |
2385	   |       |               |                      | then use a         |
2386	   |       |               |                      | conference         |
2387	   |       |               |                      | identifier which   |
2388	   |       |               |                      | is listed.         |
2389	   |       |               |                      |                    |
2390	   | 407   | Incompatible  | request specifies a  | Change the media   |
2391	   |       | stream        | media stream         | stream             |
2392	   |       | configuration | configuration which  | configuration to   |
2393	   |       |               | is in conflict with  | match the          |
2394	   |       |               | itself, or the       | capabilities of    |
2395	   |       |               | connection or        | the connection or  |
2396	   |       |               | conference           | conference         |
2397	   |       |               | capabilities (see    |                    |
2398	   |       |               | Section 4.2.2.2)     |                    |
2399	   |       |               |                      |                    |
2400	   | 408   | joining       | request attempts to  | Send an <audit>    |
2401	   |       | entities      | create a join mixer  | request            |
2402	   |       | already       | (Section 4.2.2.2)    | (Section 4.3.1)    |
2403	   |       | joined        | where the entities   | requesting the     |
2404	   |       |               | are already joined   | list of join       |
2405	   |       |               |                      | mixers on the MS   |
2406	   |       |               |                      | and then use       |
2407	   |       |               |                      | entities which are |
2408	   |       |               |                      | not listed.        |
2409	   |       |               |                      |                    |
2410	   | 409   | joining       | request attempts to  | Send an <audit>    |
2411	   |       | entities not  | manipulate a join    | request            |
2412	   |       | joined        | mixer where entities | (Section 4.3.1)    |
2413	   |       |               | which are not joined | requesting the     |
2414	   |       |               |                      | list of join       |
2415	   |       |               |                      | mixers on the MS   |
2416	   |       |               |                      | and then use       |
2417	   |       |               |                      | entities which are |
2418	   |       |               |                      | listed.            |
2419	   |       |               |                      |                    |
2420	   | 410   | Unable to     | request attempts to  |                    |
2421	   |       | join -        | join a participant   |                    |
2422	   |       | conference    | to a conference      |                    |
2423	   |       | full          | (Section 4.2.2.2)    |                    |
2424	   |       |               | but the conference   |                    |
2425	   |       |               | is already full      |                    |
2426	   |       |               |                      |                    |
2427	   | 411   | Unable to     | request attempts to  |                    |
2428	   |       | perform join  | create, modify or    |                    |
2429	   |       | mixer         | delete a join        |                    |
2430	   |       | operation     | between entities but |                    |
2431	   |       |               | fails                |                    |
2432	   |       |               |                      |                    |
2433	   | 412   | Connection    | request uses an      |                    |
2434	   |       | does not      | identifier for a     |                    |
2435	   |       | exist         | connection which     |                    |
2436	   |       |               | does not exist on    |                    |
2437	   |       |               | the MS.              |                    |
2438	   | 419   | Other         | requested operation  |                    |
2439	   |       | execution     | cannot be executed   |                    |
2440	   |       | error         | by the MS.           |                    |
2441	   |       |               |                      |                    |
2442	   | 420   | Conference    | request to create a  |                    |
2443	   |       | reservation   | new conference       |                    |
2444	   |       | failed        | (Section 4.2.1.1)    |                    |
2445	   |       |               | failed due to        |                    |
2446	   |       |               | unsupported          |                    |
2447	   |       |               | reservation of       |                    |
2448	   |       |               | talkers or           |                    |
2449	   |       |               | listeners.           |                    |
2450	   |       |               |                      |                    |
2451	   | 421   | Unable to     | request to create or |                    |
2452	   |       | configure     | modify a conference  |                    |
2453	   |       | audio mix     | failed due to        |                    |
2454	   |       |               | unsupported audio    |                    |
2455	   |       |               | mix.                 |                    |
2456	   |       |               |                      |                    |
2457	   | 422   | Unsupported   | request contains one |                    |
2458	   |       | media stream  | or more <stream>     |                    |
2459	   |       | configuration | elements             |                    |
2460	   |       |               | (Section 4.2.2.5)    |                    |
2461	   |       |               | whose configuration  |                    |
2462	   |       |               | is not supported by  |                    |
2463	   |       |               | the MS.              |                    |
2464	   |       |               |                      |                    |
2465	   | 423   | Unable to     | request to create or |                    |
2466	   |       | configure     | modify a conference  |                    |
2467	   |       | video layouts | failed due to        |                    |
2468	   |       |               | unsupported video    |                    |
2469	   |       |               | layout               |                    |
2470	   |       |               | configuration.       |                    |
2471	   |       |               |                      |                    |
2472	   | 424   | Unable to     | request to create or |                    |
2473	   |       | configure     | modify a conference  |                    |
2474	   |       | video switch  | failed due to        |                    |
2475	   |       |               | unsupported video    |                    |
2476	   |       |               | switch               |                    |
2477	   |       |               | configuration.       |                    |
2478	   |       |               |                      |                    |
2479	   | 425   | Unable to     | request to create or |                    |
2480	   |       | configure     | modify a conference  |                    |
2481	   |       | codecs        | failed due to        |                    |
2482	   |       |               | unsupported codec.   |                    |
2483	   |       |               |                      |                    |
2484	   | 426   | Unable to     | request to join      |                    |
2485	   |       | join - mixing | connection entities  |                    |
2486	   |       | connections   | (Section 4.2.2.2)    |                    |
2487	   |       | not supported | failed due lack of   |                    |
2488	   |       |               | support for mixing   |                    |
2489	   |       |               | connections.         |                    |
2490	   |       |               |                      |                    |
2491	   | 427   | Unable to     | request to join      |                    |
2492	   |       | join - mixing | conference entities  |                    |
2493	   |       | conferences   | (Section 4.2.2.2)    |                    |
2494	   |       | not supported | failed due lack of   |                    |
2495	   |       |               | support for mixing   |                    |
2496	   |       |               | conferences.         |                    |
2497	   |       |               |                      |                    |
2498	   | 428   | Unsupported   | the request contains |                    |
2499	   |       | foreign       | attributes or        |                    |
2500	   |       | namespace     | elements from        |                    |
2501	   |       | attribute or  | another namespace    |                    |
2502	   |       | element       | which the MS does    |                    |
2503	   |       |               | not support          |                    |
2504	   |       |               |                      |                    |
2505	   | 435   | Other         | request requires     |                    |
2506	   |       | unsupported   | another capability   |                    |
2507	   |       | capability    | not supported by the |                    |
2508	   |       |               | MS                   |                    |
2509	   +-------+---------------+----------------------+--------------------+

2511	                           Table 1: status codes

2513	4.7.  Type Definitions

2515	   This section defines types referenced in attribute definitions.

2517	4.7.1.  Boolean

2519	   The value space of boolean is the set {true, false, 1, 0} as defined
2520	   in Section 3.2.2 of [XMLSchema:Part2].  In accordance with this
2521	   definition, the concept of false can be lexically represented by the
2522	   strings "0" and "false" and the concept of true by the strings "1"
2523	   and "true"; implementations MUST support both styles of lexical
2524	   representation.

2526	4.7.2.  Non-Negative Integer

2528	   The value space of non-negative integer is the infinite set
2529	   {0,1,2,...} as defined in Section 3.3.20 of [XMLSchema:Part2].

2531	4.7.3.  Positive Integer

2533	   The value space of positive integer is the infinite set {1,2,...} as
2534	   defined in Section 3.3.25 of [XMLSchema:Part2].

2536	4.7.4.  String

2538	   A string in the character encoding associated with the XML element as
2539	   defined in Section 3.2.1 of [XMLSchema:Part2].

2541	4.7.5.  Time Designation

2543	   A time designation consists of a non-negative real number followed by
2544	   a time unit identifier.

2546	   The time unit identifiers are: "ms" (milliseconds) and "s" (seconds).

2548	   Examples include: "3s", "850ms", "0.7s", ".5s" and "+1.5s".

2550	4.7.6.  MIME Media Type

2552	   A string formated as an IANA MIME media type ([MIME.mediatypes]).
2553	   The ABNF ([RFC5234]) production for the string is:

2555	   type-name "/" subtype-name *(";" parameter)

2557	   parameter = parameter-name "=" value

2559	   where "type-name" and "subtype-name" are defined in Section 4.2 of
2560	   [RFC4288], "parameter-name" is defined in Section 4.3 of [RFC4288]
2561	   and "value" is defined in Section 5.1 of [RFC2045].

2563	4.7.7.  Language Identifier

2565	   A language identifier labels information content as being of a
2566	   particular human language variant.  Following the XML specification
2567	   for language identification [XML], a legal language identifier is
2568	   identified by a RFC5646 code ([RFC5646]) and matched according to
2569	   RFC4647 ([RFC4647]).

2571	5.  Formal Syntax

2573	   This section defines the XML schema for the Mixer Control Package.
2574	   The schema is normative.

2576	   The schema defines datatypes, attributes, and mixer elements in the
2577	   urn:ietf:params:xml:ns:msc-mixer namespace.  In most elements the
2578	   order of child elements is significant.  The schema is extensible:
2579	   elements allow attributes and child elements from other namespaces.
2580	   Elements from outside this package's namespace can occur after
2581	   elements defined in this package.

2583	   The schema is dependent upon the schema (framework.xsd) defined in
2584	   Section 16.1 of the Control Framework
2585	   [I-D.ietf-mediactrl-sip-control-framework].

2587	   <?xml version="1.0" encoding="UTF-8"?>
2588	   <xsd:schema targetNamespace="urn:ietf:params:xml:ns:msc-mixer"
2589	    xmlns:fw="urn:ietf:params:xml:ns:control:framework-attributes"
2590	    elementFormDefault="qualified"
2591	    xmlns:xs="http://www.w3.org/2001/XMLSchema"
2592	    xmlns="urn:ietf:params:xml:ns:msc-mixer"
2593	    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

2595	    <xsd:annotation>
2596	     <xsd:documentation>
2597	      IETF MediaCtrl Mixer 1.0 (20110104)

2599	      This is the schema of the Mixer control package. It
2600	      defines request, response and notification elements for
2601	      mixing.

2603	      The schema namespace is urn:ietf:params:xml:ns:msc-mixer

2605	     </xsd:documentation>
2606	    </xsd:annotation>

2608	    <!--
2609	     #############################################################

2611	     SCHEMA IMPORTS

2613	     #############################################################
2614	    -->

2616	    <xsd:import
2617	     namespace="urn:ietf:params:xml:ns:control:framework-attributes"
2618	     schemaLocation="framework.xsd">
2619	     <xsd:annotation>
2620	      <xsd:documentation>
2621	       This import brings in the framework attributes for
2622	       conferenceid and connectionid.
2623	      </xsd:documentation>
2624	     </xsd:annotation>
2625	    </xsd:import>

2627	    <!--
2628	     #####################################################

2630	     Extensible core type

2632	     #####################################################
2633	    -->

2635	    <xsd:complexType name="Tcore">
2636	     <xsd:annotation>
2637	      <xsd:documentation>
2638	       This type is extended by other (non-mixed) component types to
2639	       allow attributes from other namespaces.
2640	      </xsd:documentation>
2641	     </xsd:annotation>
2642	     <xsd:sequence/>
2643	     <xsd:anyAttribute namespace="##other" processContents="lax" />
2644	    </xsd:complexType>

2646	    <!--
2647	     #####################################################

2649	     TOP LEVEL ELEMENT: mscmixer

2651	     #####################################################
2652	    -->

2654	    <xsd:complexType name="mscmixerType">
2655	     <xsd:complexContent>
2656	      <xsd:extension base="Tcore">
2657	       <xsd:sequence>
2658	        <xsd:choice>
2659	         <xsd:element ref="createconference" />
2660	         <xsd:element ref="modifyconference" />
2661	         <xsd:element ref="destroyconference" />
2662	         <xsd:element ref="join" />
2663	         <xsd:element ref="unjoin" />
2664	         <xsd:element ref="modifyjoin" />
2665	         <xsd:element ref="response" />
2666	         <xsd:element ref="event" />
2667	         <xsd:element ref="audit" />
2668	         <xsd:element ref="auditresponse" />
2669	         <xsd:any namespace="##other" minOccurs="0"
2670	          maxOccurs="unbounded" processContents="lax" />
2671	        </xsd:choice>
2672	       </xsd:sequence>
2673	       <xsd:attribute name="version" type="version.datatype"
2674	        use="required" />
2675	       <xsd:attribute name="desclang" type="xsd:language"
2676	        default="i-default" />
2677	      </xsd:extension>
2678	     </xsd:complexContent>
2679	    </xsd:complexType>

2681	    <xsd:element name="mscmixer" type="mscmixerType" />

2683	    <!--
2684	     #####################################################

2686	     CONFERENCE MANAGEMENT TYPES

2688	     #####################################################
2689	    -->

2691	    <!--  createconference -->

2693	    <xsd:complexType name="createconferenceType">
2694	     <xsd:complexContent>
2695	      <xsd:extension base="Tcore">
2696	       <xsd:sequence>
2697	        <xsd:element ref="codecs" minOccurs="0"
2698	         maxOccurs="1" />
2699	        <xsd:element ref="audio-mixing" minOccurs="0"
2700	         maxOccurs="1" />
2701	        <xsd:element ref="video-layouts" minOccurs="0"
2702	         maxOccurs="1" />
2703	        <xsd:element ref="video-switch" minOccurs="0"
2704	         maxOccurs="1" />
2705	        <xsd:element ref="subscribe" minOccurs="0"
2706	         maxOccurs="1" />
2707	        <xsd:any namespace="##other"
2708	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />

2710	       </xsd:sequence>
2711	       <xsd:attribute name="conferenceid" type="xsd:string" />
2712	       <xsd:attribute name="reserved-talkers"
2713	        type="xsd:nonNegativeInteger" default="0" />
2714	       <xsd:attribute name="reserved-listeners"
2715	        type="xsd:nonNegativeInteger" default="0" />
2716	      </xsd:extension>
2717	     </xsd:complexContent>
2718	    </xsd:complexType>

2720	    <xsd:element name="createconference" type="createconferenceType" />

2722	    <!--  modifyconference -->

2724	    <xsd:complexType name="modifyconferenceType">
2725	     <xsd:complexContent>
2726	      <xsd:extension base="Tcore">
2727	       <xsd:sequence>
2728	        <xsd:element ref="codecs" minOccurs="0"
2729	         maxOccurs="1" />
2730	        <xsd:element ref="audio-mixing" minOccurs="0"
2731	         maxOccurs="1" />
2732	        <xsd:element ref="video-layouts" minOccurs="0"
2733	         maxOccurs="1" />
2734	        <xsd:element ref="video-switch" minOccurs="0"
2735	         maxOccurs="1" />
2736	        <xsd:element ref="subscribe" />
2737	        <xsd:any namespace="##other"
2738	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />
2739	       </xsd:sequence>
2740	       <xsd:attribute name="conferenceid" type="xsd:string"
2741	        use="required" />
2742	      </xsd:extension>
2743	     </xsd:complexContent>
2744	    </xsd:complexType>

2746	    <xsd:element name="modifyconference" type="modifyconferenceType" />

2748	    <!--  destroyconference -->

2750	    <xsd:complexType name="destroyconferenceType">
2751	    <xsd:complexContent>
2752	      <xsd:extension base="Tcore">
2753	      <xsd:sequence>
2754	       <xsd:any namespace="##other" minOccurs="0"
2755	         maxOccurs="unbounded" processContents="lax" />
2756	       </xsd:sequence>

2758	      <xsd:attribute name="conferenceid" type="xsd:string"
2759	      use="required" />
2760	      </xsd:extension>
2761	      </xsd:complexContent>
2762	    </xsd:complexType>

2764	    <xsd:element name="destroyconference"
2765	     type="destroyconferenceType" />

2767	    <!--
2768	     #####################################################

2770	     JOIN TYPES

2772	     #####################################################
2773	    -->

2775	    <xsd:complexType name="joinType">
2776	     <xsd:complexContent>
2777	      <xsd:extension base="Tcore">
2778	       <xsd:sequence>
2779	        <xsd:element ref="stream" minOccurs="0"
2780	         maxOccurs="unbounded" />
2781	        <xsd:any namespace="##other"
2782	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />
2783	       </xsd:sequence>
2784	       <xsd:attribute name="id1" type="xsd:string"
2785	        use="required" />
2786	       <xsd:attribute name="id2" type="xsd:string"
2787	        use="required" />
2788	      </xsd:extension>
2789	     </xsd:complexContent>
2790	    </xsd:complexType>

2792	    <xsd:element name="join" type="joinType" />

2794	    <xsd:complexType name="modifyjoinType">
2795	     <xsd:complexContent>
2796	      <xsd:extension base="Tcore">
2797	       <xsd:sequence>
2798	        <xsd:element ref="stream" minOccurs="0"
2799	         maxOccurs="unbounded" />
2800	        <xsd:any namespace="##other"
2801	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />
2802	       </xsd:sequence>
2803	       <xsd:attribute name="id1" type="xsd:string"
2804	        use="required" />
2805	       <xsd:attribute name="id2" type="xsd:string"
2806	        use="required" />
2807	      </xsd:extension>
2808	     </xsd:complexContent>
2809	    </xsd:complexType>

2811	    <xsd:element name="modifyjoin" type="modifyjoinType" />

2813	    <xsd:complexType name="unjoinType">
2814	     <xsd:complexContent>
2815	      <xsd:extension base="Tcore">
2816	       <xsd:sequence>
2817	        <xsd:element ref="stream" minOccurs="0"
2818	         maxOccurs="unbounded" />
2819	        <xsd:any namespace="##other"
2820	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />
2821	       </xsd:sequence>
2822	       <xsd:attribute name="id1" type="xsd:string"
2823	        use="required" />
2824	       <xsd:attribute name="id2" type="xsd:string"
2825	        use="required" />
2826	      </xsd:extension>
2827	     </xsd:complexContent>
2828	    </xsd:complexType>

2830	    <xsd:element name="unjoin" type="unjoinType" />

2832	    <!--
2833	     #####################################################

2835	     OTHER TYPES

2837	     #####################################################
2838	    -->

2840	    <xsd:complexType name="eventType">
2841	     <xsd:complexContent>
2842	      <xsd:extension base="Tcore">
2843	       <xsd:sequence>
2844	        <xsd:choice>
2845	         <xsd:element ref="active-talkers-notify"
2846	          minOccurs="0" maxOccurs="1" />
2847	         <xsd:element ref="unjoin-notify"
2848	          minOccurs="0" maxOccurs="1" />
2849	         <xsd:element ref="conferenceexit"
2850	          minOccurs="0" maxOccurs="1" />
2851	         <xsd:any namespace="##other" minOccurs="0"
2852	          maxOccurs="unbounded" processContents="lax" />
2853	        </xsd:choice>
2854	       </xsd:sequence>
2855	      </xsd:extension>
2856	     </xsd:complexContent>
2857	    </xsd:complexType>

2859	    <xsd:element name="event" type="eventType" />

2861	    <xsd:complexType name="activetalkersnotifyType">
2862	     <xsd:complexContent>
2863	      <xsd:extension base="Tcore">
2864	       <xsd:sequence>
2865	        <xsd:element ref="active-talker" minOccurs="0"
2866	         maxOccurs="unbounded" />
2867	        <xsd:any namespace="##other" minOccurs="0"
2868	         maxOccurs="unbounded" processContents="lax" />
2869	       </xsd:sequence>
2870	       <xsd:attribute name="conferenceid" type="xsd:string"
2871	        use="required" />
2872	      </xsd:extension>
2873	     </xsd:complexContent>
2874	    </xsd:complexType>

2876	    <xsd:element name="active-talkers-notify"
2877	     type="activetalkersnotifyType" />

2879	    <xsd:complexType name="activetalkerType">
2880	     <xsd:complexContent>
2881	      <xsd:extension base="Tcore">
2882	       <xsd:sequence>
2883	        <xsd:any namespace="##other" minOccurs="0"
2884	         maxOccurs="unbounded" processContents="lax" />
2885	       </xsd:sequence>
2886	       <xsd:attributeGroup ref="fw:framework-attributes" />
2887	      </xsd:extension>
2888	     </xsd:complexContent>
2889	    </xsd:complexType>

2891	    <xsd:element name="active-talker" type="activetalkerType" />

2893	    <xsd:complexType name="unjoinnotifyType">
2894	     <xsd:complexContent>
2895	      <xsd:extension base="Tcore">
2896	       <xsd:sequence>
2897	        <xsd:any namespace="##other" minOccurs="0"
2898	         maxOccurs="unbounded" processContents="lax" />
2899	       </xsd:sequence>
2900	       <xsd:attribute name="status" type="xsd:nonNegativeInteger"
2901	         use="required" />
2902	       <xsd:attribute name="reason" type="xsd:string" />
2903	         <xsd:attribute name="desclang" type="xsd:language"/>
2904	       <xsd:attribute name="id1" type="xsd:string"
2905	        use="required" />
2906	       <xsd:attribute name="id2" type="xsd:string"
2907	        use="required" />
2908	      </xsd:extension>
2909	     </xsd:complexContent>
2910	    </xsd:complexType>

2912	    <xsd:element name="unjoin-notify" type="unjoinnotifyType" />

2914	    <!--  conferenceexit-->

2916	    <xsd:complexType name="conferenceexitType">
2917	     <xsd:complexContent>
2918	      <xsd:extension base="Tcore">
2919	       <xsd:sequence>
2920	        <xsd:any namespace="##other" minOccurs="0"
2921	         maxOccurs="unbounded" processContents="lax" />
2922	       </xsd:sequence>
2923	       <xsd:attribute name="conferenceid" type="xsd:string"
2924	        use="required" />
2925	       <xsd:attribute name="status"
2926	        type="xsd:nonNegativeInteger" use="required" />
2927	       <xsd:attribute name="reason" type="xsd:string" />
2928	         <xsd:attribute name="desclang" type="xsd:language"/>
2929	      </xsd:extension>
2930	     </xsd:complexContent>
2931	    </xsd:complexType>

2933	    <xsd:element name="conferenceexit" type="conferenceexitType" />

2935	    <xsd:complexType name="responseType">
2936	     <xsd:complexContent>
2937	      <xsd:extension base="Tcore">
2938	      <xsd:sequence>
2939	       <xsd:any namespace="##other" minOccurs="0"
2940	         maxOccurs="unbounded" processContents="lax" />
2941	       </xsd:sequence>
2942	       <xsd:attribute name="status" type="status.datatype"
2943	        use="required" />
2944	       <xsd:attribute name="reason" type="xsd:string" />
2945	         <xsd:attribute name="desclang" type="xsd:language"/>
2946	       <xsd:attributeGroup ref="fw:framework-attributes" />
2947	      </xsd:extension>
2948	     </xsd:complexContent>
2949	    </xsd:complexType>

2951	    <xsd:element name="response" type="responseType" />

2953	    <xsd:complexType name="subscribeType">
2954	     <xsd:complexContent>
2955	      <xsd:extension base="Tcore">
2956	       <xsd:sequence>
2957	        <xsd:element ref="active-talkers-sub"
2958	         minOccurs="0" maxOccurs="1" />
2959	        <xsd:any namespace="##other" minOccurs="0"
2960	         maxOccurs="unbounded" processContents="lax" />
2961	       </xsd:sequence>
2962	      </xsd:extension>
2963	     </xsd:complexContent>
2964	    </xsd:complexType>

2966	    <xsd:element name="subscribe" type="subscribeType" />

2968	    <xsd:complexType name="activetalkerssubType">
2969	     <xsd:complexContent>
2970	      <xsd:extension base="Tcore">
2971	       <xsd:sequence>
2972	        <xsd:any namespace="##other" minOccurs="0"
2973	         maxOccurs="unbounded" processContents="lax" />
2974	       </xsd:sequence>
2975	       <xsd:attribute name="interval"
2976	        type="xsd:nonNegativeInteger" default="3" />
2977	      </xsd:extension>
2978	     </xsd:complexContent>
2979	    </xsd:complexType>

2981	    <xsd:element name="active-talkers-sub"
2982	     type="activetalkerssubType" />

2984	    <xsd:complexType name="streamType">
2985	     <xsd:complexContent>
2986	      <xsd:extension base="Tcore">
2987	       <xsd:sequence>
2988	        <xsd:element ref="volume" minOccurs="0"
2989	         maxOccurs="1" />
2990	        <xsd:element ref="clamp" minOccurs="0"
2991	         maxOccurs="1" />
2992	        <xsd:element ref="region" minOccurs="0"
2993	         maxOccurs="1" />
2994	        <xsd:element ref="priority" minOccurs="0"
2995	         maxOccurs="1" />
2996	        <xsd:any namespace="##other" minOccurs="0"
2997	         maxOccurs="unbounded" processContents="lax" />
2998	       </xsd:sequence>
2999	       <xsd:attribute name="media" type="media.datatype"
3000	        use="required" />
3001	       <xsd:attribute name="label" type="label.datatype" />
3002	       <xsd:attribute name="direction"
3003	        type="direction.datatype" default="sendrecv" />
3004	      </xsd:extension>
3005	     </xsd:complexContent>
3006	    </xsd:complexType>

3008	    <xsd:element name="stream" type="streamType" />

3010	    <xsd:complexType name="volumeType">
3011	     <xsd:complexContent>
3012	      <xsd:extension base="Tcore">
3013	       <xsd:sequence>
3014	        <xsd:any namespace="##other" minOccurs="0"
3015	         maxOccurs="unbounded" processContents="lax" />
3016	       </xsd:sequence>
3017	       <xsd:attribute name="controltype"
3018	        type="volumecontroltype.datatype" use="required" />
3019	       <xsd:attribute name="value" type="xsd:string" />
3020	      </xsd:extension>
3021	     </xsd:complexContent>
3022	    </xsd:complexType>

3024	    <xsd:element name="volume" type="volumeType" />

3026	    <xsd:complexType name="clampType">
3027	     <xsd:complexContent>
3028	      <xsd:extension base="Tcore">
3029	       <xsd:sequence>
3030	        <xsd:any namespace="##other" minOccurs="0"
3031	         maxOccurs="unbounded" processContents="lax" />
3032	       </xsd:sequence>
3033	       <xsd:attribute name="tones" type="xsd:string"
3034	        default="1 2 3 4 5 6 7 8 9 0 * # A B C D"/>
3035	      </xsd:extension>
3036	     </xsd:complexContent>
3037	    </xsd:complexType>

3039	    <xsd:element name="clamp" type="clampType" />

3041	    <!--  region  -->
3042	    <xsd:simpleType name="regionType">
3043	     <xsd:restriction base="xsd:NMTOKEN" />
3044	    </xsd:simpleType>

3046	    <xsd:element name="region" type="regionType" />

3048	    <!--  priority  -->
3049	    <xsd:simpleType name="priorityType">
3050	     <xsd:restriction base="xsd:positiveInteger" />
3051	    </xsd:simpleType>

3053	    <xsd:element name="priority" type="priorityType" />

3055	    <xsd:complexType name="audiomixingType">
3056	     <xsd:complexContent>
3057	      <xsd:extension base="Tcore">
3058	      <xsd:sequence>
3059	        <xsd:any namespace="##other" minOccurs="0"
3060	         maxOccurs="unbounded" processContents="lax" />
3061	       </xsd:sequence>
3062	       <xsd:attribute name="type" type="audiomix.datatype"
3063	        default="nbest" />
3064	       <xsd:attribute name="n" type="xsd:nonNegativeInteger"
3065	        default="0" />
3066	      </xsd:extension>
3067	     </xsd:complexContent>
3068	    </xsd:complexType>

3070	    <xsd:element name="audio-mixing" type="audiomixingType" />

3072	    <!-- video-switch -->

3074	    <xsd:complexType name="videoswitchType">
3075	     <xsd:complexContent>
3076	      <xsd:extension base="Tcore">
3077	       <xsd:sequence>
3078	         <xsd:choice>
3079	          <xsd:element name="vas" type="Tcore"/>
3080	          <xsd:element name="controller" type="Tcore"/>
3081	          <xsd:any namespace="##other" processContents="lax" />
3082	        </xsd:choice>
3083	       </xsd:sequence>
3084	       <xsd:attribute name="interval"
3085	        type="xsd:nonNegativeInteger" default="3" />
3086	       <xsd:attribute name="activespeakermix"
3087	        type="xsd:boolean" default="false" />
3088	      </xsd:extension>
3089	     </xsd:complexContent>
3090	    </xsd:complexType>

3092	    <xsd:element name="video-switch" type="videoswitchType" />

3094	    <!-- video-layouts -->

3096	    <xsd:complexType name="videolayoutsType">
3097	     <xsd:complexContent>
3098	      <xsd:extension base="Tcore">
3099	       <xsd:sequence>
3100	        <xsd:element ref="video-layout" minOccurs="0"
3101	         maxOccurs="unbounded" />
3102	        <xsd:any namespace="##other" minOccurs="0"
3103	         maxOccurs="unbounded" processContents="lax" />
3104	       </xsd:sequence>
3105	      </xsd:extension>
3106	     </xsd:complexContent>
3107	    </xsd:complexType>

3109	    <xsd:element name="video-layouts" type="videolayoutsType" />

3111	    <!-- video-layout -->
3112	    <xsd:complexType name="videolayoutType">
3113	    <xsd:complexContent>
3114	      <xsd:extension base="Tcore">
3115	       <xsd:sequence>
3116	        <xsd:choice>
3117	          <xsd:element name="single-view" type="Tcore"/>
3118	          <xsd:element name="dual-view" type="Tcore"/>
3119	          <xsd:element name="dual-view-crop" type="Tcore"/>
3120	          <xsd:element name="dual-view-2x1" type="Tcore"/>
3121	          <xsd:element name="dual-view-2x1-crop" type="Tcore"/>
3122	          <xsd:element name="quad-view" type="Tcore"/>
3123	          <xsd:element name="multiple-3x3" type="Tcore"/>
3124	          <xsd:element name="multiple-4x4" type="Tcore"/>
3125	          <xsd:element name="multiple-5x1" type="Tcore"/>
3126	          <xsd:any namespace="##other" processContents="lax" />
3127	        </xsd:choice>
3128	       </xsd:sequence>
3129	      <xsd:attribute name="min-participants"
3130	        type="xsd:positiveInteger" default="1" />
3131	      </xsd:extension>
3132	     </xsd:complexContent>
3133	    </xsd:complexType>

3135	    <xsd:element name="video-layout" type="videolayoutType" />

3137	    <xsd:complexType name="auditType">
3138	     <xsd:complexContent>
3139	      <xsd:extension base="Tcore">
3140	      <xsd:sequence>
3141	      <xsd:any namespace="##other" minOccurs="0"
3142	       maxOccurs="unbounded" processContents="lax" />
3143	      </xsd:sequence>
3144	       <xsd:attribute name="capabilities"
3145	        type="xsd:boolean" default="true" />
3146	       <xsd:attribute name="mixers" type="xsd:boolean"
3147	        default="true" />
3148	       <xsd:attribute name="conferenceid" type="xsd:string" />
3149	      </xsd:extension>
3150	     </xsd:complexContent>
3151	    </xsd:complexType>

3153	    <xsd:element name="audit" type="auditType" />

3155	    <xsd:complexType name="auditresponseType">
3156	     <xsd:complexContent>
3157	      <xsd:extension base="Tcore">
3158	       <xsd:sequence>
3159	        <xsd:element ref="capabilities" minOccurs="0"
3160	         maxOccurs="1" />
3161	        <xsd:element ref="mixers" minOccurs="0"
3162	         maxOccurs="1" />
3163	        <xsd:any namespace="##other" minOccurs="0"
3164	         maxOccurs="unbounded" processContents="lax" />
3165	       </xsd:sequence>
3166	       <xsd:attribute name="status" type="status.datatype"
3167	        use="required" />
3168	       <xsd:attribute name="reason" type="xsd:string" />
3169	         <xsd:attribute name="desclang" type="xsd:language"/>
3170	      </xsd:extension>

3172	     </xsd:complexContent>
3173	    </xsd:complexType>

3175	    <xsd:element name="auditresponse" type="auditresponseType" />

3177	    <!-- mixers -->

3179	    <xsd:complexType name="mixersType">
3180	     <xsd:complexContent>
3181	      <xsd:extension base="Tcore">
3182	       <xsd:sequence>
3183	        <xsd:element ref="conferenceaudit" minOccurs="0"
3184	         maxOccurs="unbounded" />
3185	        <xsd:element ref="joinaudit" minOccurs="0"
3186	         maxOccurs="unbounded" />
3187	        <xsd:any namespace="##other" minOccurs="0"
3188	         maxOccurs="unbounded" processContents="lax" />
3189	       </xsd:sequence>
3190	      </xsd:extension>
3191	     </xsd:complexContent>
3192	    </xsd:complexType>

3194	    <xsd:element name="mixers" type="mixersType" />

3196	    <!--  joinaudit -->

3198	    <xsd:complexType name="joinauditType">
3199	     <xsd:complexContent>
3200	      <xsd:extension base="Tcore">
3201	       <xsd:sequence>
3202	        <xsd:any namespace="##other"
3203	         processContents="lax" minOccurs="0" maxOccurs="unbounded" />
3204	       </xsd:sequence>
3205	       <xsd:attribute name="id1" type="xsd:string"
3206	        use="required" />
3207	       <xsd:attribute name="id2" type="xsd:string"
3208	        use="required" />
3209	      </xsd:extension>
3210	     </xsd:complexContent>
3211	    </xsd:complexType>

3213	    <xsd:element name="joinaudit" type="joinauditType" />

3215	    <!-- conferenceaudit -->

3217	    <xsd:complexType name="conferenceauditType">
3218	     <xsd:complexContent>
3219	      <xsd:extension base="Tcore">
3220	       <xsd:sequence>
3221	        <xsd:element ref="codecs" minOccurs="0"
3222	         maxOccurs="1" />
3223	        <xsd:element ref="participants" minOccurs="0"
3224	         maxOccurs="1" />
3225	        <xsd:element ref="video-layout" minOccurs="0"
3226	         maxOccurs="1" />
3227	        <xsd:any namespace="##other" minOccurs="0"
3228	         maxOccurs="unbounded" processContents="lax" />
3229	       </xsd:sequence>
3230	       <xsd:attribute name="conferenceid" type="xsd:string"
3231	        use="required" />
3232	      </xsd:extension>
3233	     </xsd:complexContent>
3234	    </xsd:complexType>

3236	    <xsd:element name="conferenceaudit" type="conferenceauditType" />

3238	    <!-- participants -->

3240	    <xsd:complexType name="participantsType">
3241	     <xsd:complexContent>
3242	      <xsd:extension base="Tcore">
3243	       <xsd:sequence>
3244	        <xsd:element ref="participant" minOccurs="0"
3245	         maxOccurs="unbounded" />
3246	        <xsd:any namespace="##other" minOccurs="0"
3247	         maxOccurs="unbounded" processContents="lax" />
3248	       </xsd:sequence>
3249	      </xsd:extension>
3250	     </xsd:complexContent>
3251	    </xsd:complexType>

3253	    <xsd:element name="participants" type="participantsType" />

3255	    <!-- participant -->

3257	    <xsd:complexType name="participantType">
3258	     <xsd:complexContent>
3259	      <xsd:extension base="Tcore">
3260	       <xsd:sequence>
3261	        <xsd:any namespace="##other" minOccurs="0"
3262	         maxOccurs="unbounded" processContents="lax" />
3263	       </xsd:sequence>
3264	       <xsd:attribute name="id" type="xsd:string"
3265	        use="required" />
3266	      </xsd:extension>

3268	     </xsd:complexContent>
3269	    </xsd:complexType>

3271	    <xsd:element name="participant" type="participantType" />

3273	    <!-- capabilities -->

3275	    <xsd:complexType name="capabilitiesType">
3276	     <xsd:complexContent>
3277	      <xsd:extension base="Tcore">
3278	       <xsd:sequence>
3279	        <xsd:element ref="codecs" minOccurs="1"
3280	         maxOccurs="1" />
3281	        <xsd:any namespace="##other" minOccurs="0"
3282	         maxOccurs="unbounded" processContents="lax" />
3283	       </xsd:sequence>
3284	      </xsd:extension>
3285	     </xsd:complexContent>
3286	    </xsd:complexType>

3288	    <xsd:element name="capabilities" type="capabilitiesType" />

3290	    <!-- codecs -->

3292	    <xsd:complexType name="codecsType">
3293	     <xsd:complexContent>
3294	      <xsd:extension base="Tcore">
3295	       <xsd:sequence>
3296	        <xsd:element ref="codec" minOccurs="0"
3297	         maxOccurs="unbounded" />
3298	        <xsd:any namespace="##other" minOccurs="0"
3299	         maxOccurs="unbounded" processContents="lax" />
3300	       </xsd:sequence>
3301	      </xsd:extension>
3302	     </xsd:complexContent>
3303	    </xsd:complexType>

3305	    <xsd:element name="codecs" type="codecsType" />

3307	    <!-- codec -->

3309	    <xsd:complexType name="codecType">
3310	     <xsd:complexContent>
3311	      <xsd:extension base="Tcore">
3312	       <xsd:sequence>
3313	        <xsd:element ref="subtype" minOccurs="1"
3314	         maxOccurs="1" />

3316	        <xsd:element ref="params" minOccurs="0"
3317	         maxOccurs="1" />
3318	        <xsd:any namespace="##other" minOccurs="0"
3319	         maxOccurs="unbounded" processContents="lax" />
3320	       </xsd:sequence>
3321	        <xsd:attribute name="name" type="xsd:string"
3322	        use="required" />
3323	      </xsd:extension>
3324	     </xsd:complexContent>
3325	    </xsd:complexType>

3327	    <xsd:element name="codec" type="codecType" />

3329	    <!-- subtype -->

3331	    <xsd:simpleType name="subtypeType">
3332	     <xsd:restriction base="xsd:string" />
3333	    </xsd:simpleType>

3335	    <xsd:element name="subtype" type="subtypeType" />

3337	    <!-- params -->
3338	    <xsd:complexType name="paramsType">
3339	     <xsd:complexContent>
3340	      <xsd:extension base="Tcore">
3341	       <xsd:sequence>
3342	        <xsd:element ref="param" minOccurs="0"
3343	         maxOccurs="unbounded" />
3344	        <xsd:any namespace="##other" minOccurs="0"
3345	         maxOccurs="unbounded" processContents="lax" />
3346	       </xsd:sequence>
3347	      </xsd:extension>
3348	     </xsd:complexContent>
3349	    </xsd:complexType>

3351	    <xsd:element name="params" type="paramsType" />

3353	    <!--  param -->
3354	       <!--  doesn't extend tCore since its content model is mixed -->
3355	    <xsd:complexType name="paramType" mixed="true">
3356	     <xsd:sequence/>
3357	     <xsd:attribute name="name" type="xsd:string" use="required" />
3358	     <xsd:attribute name="type" type="mime.datatype"
3359	     default="text/plain" />
3360	        <xsd:attribute name="encoding" type="xsd:string"/>
3361	    </xsd:complexType>
3362	    <xsd:element name="param" type="paramType" />

3364	    <!--
3365	     ####################################################

3367	     DATATYPES

3369	     ####################################################
3370	    -->

3372	   <xsd:simpleType name="version.datatype">
3373	     <xsd:restriction base="xsd:NMTOKEN">
3374	      <xsd:enumeration value="1.0" />
3375	     </xsd:restriction>
3376	    </xsd:simpleType>

3378	    <xsd:simpleType name="eventname.datatype">
3379	     <xsd:restriction base="xsd:NMTOKEN">
3380	      <xsd:pattern value="[a-zA-Z0-9\.]+" />
3381	     </xsd:restriction>
3382	    </xsd:simpleType>

3384	    <xsd:simpleType name="audiomix.datatype">
3385	     <xsd:restriction base="xsd:NMTOKEN">
3386	      <xsd:enumeration value="nbest" />
3387	      <xsd:enumeration value="controller" />
3388	     </xsd:restriction>
3389	    </xsd:simpleType>

3391	    <xsd:simpleType name="media.datatype">
3392	     <xsd:restriction base="xsd:string" />
3393	    </xsd:simpleType>

3395	    <xsd:simpleType name="label.datatype">
3396	     <xsd:restriction base="xsd:string" />
3397	    </xsd:simpleType>

3399	    <xsd:simpleType name="status.datatype">
3400	     <xsd:restriction base="xsd:positiveInteger">
3401	      <xsd:pattern value="[0-9][0-9][0-9]" />
3402	     </xsd:restriction>
3403	    </xsd:simpleType>

3405	    <xsd:simpleType name="direction.datatype">
3406	     <xsd:restriction base="xsd:NMTOKEN">
3407	      <xsd:enumeration value="sendonly" />
3408	      <xsd:enumeration value="recvonly" />
3409	      <xsd:enumeration value="sendrecv" />
3410	      <xsd:enumeration value="inactive" />
3411	     </xsd:restriction>
3412	    </xsd:simpleType>

3414	    <xsd:simpleType name="mime.datatype">
3415	     <xsd:restriction base="xsd:string" />
3416	    </xsd:simpleType>

3418	    <xsd:simpleType name="volumecontroltype.datatype">
3419	     <xsd:restriction base="xsd:NMTOKEN">
3420	      <xsd:enumeration value="automatic" />
3421	      <xsd:enumeration value="setgain" />
3422	      <xsd:enumeration value="setstate" />
3423	     </xsd:restriction>
3424	    </xsd:simpleType>

3426	   </xsd:schema>

3428	                    Figure 10: Mixer Package XML Schema

3430	6.  Examples

3432	   This section provides examples of the Mixer Control package.

3434	6.1.  AS-MS Framework Interaction Examples

3436	   The following example assume a control channel has been established
3437	   and synced as described in the Media Control Channel Framework
3438	   ([I-D.ietf-mediactrl-sip-control-framework]).

3440	   The XML messages are in angled brackets (with the root <mscmixer> and
3441	   other details omitted for clarity); the REPORT status is in round
3442	   brackets.  Other aspects of the protocol are omitted for readability.

3444	6.1.1.  Creating a conference mixer and joining a participant

3446	   A conference mixer is created successfully and a participant is
3447	   joined.

3449	             Application Server (AS)                   Media Server (MS)
3450	                |                                             |
3451	                |       (1) CONTROL: <createconference>       |
3452	                |  ---------------------------------------->  |
3453	                |                                             |
3454	                |       (2) 202                               |
3455	                |  <---------------------------------------   |
3456	                |                                             |
3457	                |                                             |
3458	                |       (3) REPORT: <response status="200"/>  |
3459	                |                   (terminate)               |
3460	                |  <----------------------------------------  |
3461	                |                                             |
3462	                |       (4) 200                               |
3463	                |  ---------------------------------------->  |
3464	                |                                             |
3465	                |       (5) CONTROL: <join id1=.. id2=..>     |
3466	                |  ---------------------------------------->  |
3467	                |                                             |
3468	                |       (6) 202                               |
3469	                |  <---------------------------------------   |
3470	                |                                             |
3471	                |       (7) REPORT: <response status="200"/>  |
3472	                |                   (terminate)               |
3473	                |  <----------------------------------------  |
3474	                |                                             |
3475	                |       (8) 200                               |
3476	                |  ---------------------------------------->  |

3478	6.1.2.  Receiving active talker notifications

3480	   An active talker notification event is sent by the MS.

3482	             Application Server (AS)                   Media Server (MS)
3483	                |                                             |
3484	                |       (1) CONTROL: <event ...>              |
3485	                |  <---------------------------------------   |
3486	                |                                             |
3487	                |       (4) 200                               |
3488	                |  ---------------------------------------->  |
3489	                |                                             |

3491	6.1.3.  Conference termination

3493	   The MS receives a request to terminate the conference, resulting in
3494	   conferenceexit and participant unjoined notifications.

3496	             Application Server (AS)                   Media Server (MS)
3497	                |                                             |
3498	                |       (1) CONTROL: <destroyconference>      |
3499	                |  ---------------------------------------->  |
3500	                |                                             |
3501	                |       (2) 200: <response status="200"/>     |
3502	                |  <---------------------------------------   |
3503	                |                                             |
3504	                |       (3) CONTROL: <event ..>               |
3505	                |                   (unjoin-notify)           |
3506	                |  <----------------------------------------  |
3507	                |                                             |
3508	                |       (4) 200                               |
3509	                |  ---------------------------------------->  |
3510	                |                                             |
3511	                |       (5) CONTROL:  <event ..>              |
3512	                |                   (conferenceexit)          |
3513	                |  <----------------------------------------  |
3514	                |                                             |
3515	                |       (6) 200                               |
3516	                |  ---------------------------------------->  |

3518	6.2.  Mixing Examples

3520	   The following examples show how the mixing package can be used to
3521	   create audio conferences, bridge connections and video conferences.

3523	   The examples do not specify all messages between the AS and MS.

3525	6.2.1.  Audio conferencing

3527	   The AS sends a request to create a conference mixer:

3529	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3530	    <createconference conferenceid="conf1"
3531	     reserved-talkers="2" reserved-listeners="3">
3532	     <audio-mixing type="nbest"/>
3533	     <subscribe>
3534	      <active-talkers-sub interval="5"/>
3535	     </subscribe>
3536	    </createconference>
3537	   </mscmixer>

3539	   The request specifies that the conference is assigned the conference
3540	   id "conf1" and is configured with 2 reserved talkers, 3 reserved
3541	   listener slots, audio mixing policy set to nbest and with active
3542	   talkers notifications set to 5 seconds.

3544	   If the MS is able to create this conference mixer, it sends 200
3545	   response:

3547	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3548	    <response status="200" reason="conference created"
3549	              conferenceid="conf1"/>
3550	   </mscmixer>

3552	   The AS is now able to join connections to the conference as
3553	   participants.  A participant able to contribute to the audio mix
3554	   would be joined as follows:

3556	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3557	    <join id1="1536067209:913cd14c" id2="conf1">
3558	     <stream media="audio" direction="sendrecv"/>
3559	    </join>
3560	   </mscmixer>

3562	   If the MS can join the participant 1536067209:913cd14c to the
3563	   conference conf1 with audio in both directions, then it sends a
3564	   successful response:

3566	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3567	    <response status="200" reason="join successful"/>
3568	   </mscmixer>

3570	   The AS could also join listener-only participants to the conference
3571	   by setting the stream direction to receive only:

3573	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3574	    <join id1="9936067209:914cd14c" id2="conf1">
3575	     <stream media="audio" direction="recvonly"/>
3576	    </join>
3577	   </mscmixer>

3579	   If the MS can join the participant 9936067209:914cd14c to the
3580	   conference conf1 then it would send a successful response (not
3581	   shown).

3583	   As the active talker changes, the MS sends an active talker
3584	   notification to the AS:

3586	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3587	    <event>
3588	     <active-talkers-notify conferenceid="conf1">
3589	      <active-talker connectionid="1536067209:913cd14c"/>
3590	     </active-talkers-notify>
3591	    </event>
3592	   </mscmixer>

3594	   The AS could decide to change the status of a talker connection so
3595	   that they can only listen:

3597	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3598	    <modifyjoin id1="1536067209:913cd14c" id2="conf1">
3599	     <stream media="audio" direction="recvonly"/>
3600	    </modifyjoin>
3601	   </mscmixer>

3603	   Where the participant 1536067209:913cd14c is no longer able to
3604	   contribute to the audio mix on the conference.  If the MS is able to
3605	   execute this request, it would send a 200 response.

3607	   The AS could decide to remove this participant from the conference:

3609	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3610	    <unjoin id1="1536067209:913cd14c" id2="conf1"/>
3611	   </mscmixer>

3613	   Again, if the MS can execute this request, a 200 response would be
3614	   sent.

3616	   Finally, the AS terminates the conference:

3618	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3619	    <destroyconference conferenceid="conf1"/>
3620	   </mscmixer>
3621	   If the MS is able to destroy the conference conf1, it sends a 200
3622	   response:

3624	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3625	    <response status="200" conferenceid="conf1"/>
3626	   </mscmixer>

3628	   For each participant attached to the conference when it is destroyed,
3629	   the MS sends an unjoin notification event:

3631	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3632	    <event>
3633	     <unjoin-notify status="2" id1="9936067209:914cd14c"
3634	         id2="conf1"/>
3635	    </event>
3636	   </mscmixer>

3638	   And the MS sends a conferenceexit notification event when the
3639	   conference finally exits:

3641	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3642	    <event>
3643	     <conferenceexit status="0" conferenceid="conf1"/>
3644	    </event>
3645	   </mscmixer>

3647	6.2.2.  Bridging connections

3649	   The mixer package can be used to join connections to one another.  In
3650	   a call center scenario, for example, this package can be used to set
3651	   up and modify connections between a caller, agent and supervisor.

3653	   A caller is joined to an agent with bi-directional audio:

3655	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3656	    <join id1="caller:001" id2="agent:002">
3657	     <stream media="audio" direction="sendrecv"/>
3658	    </join>
3659	   </mscmixer>

3661	   If the MS is able to establish this connection, then it would send a
3662	   200 response:

3664	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3665	    <response status="200"/>
3666	   </mscmixer>

3668	   Now assume that the AS wants a supervisor to listen into the agent
3669	   conversation with the caller and provide whispered guidance to the
3670	   agent.  First the AS would send a request to join the supervisor and
3671	   the caller connections:

3673	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3674	    <join  id1="supervisor:003" id2="caller:001">
3675	     <stream media="audio" direction="recvonly"/>
3676	    </join>
3677	   </mscmixer>

3679	   If this request was successful, audio output from the caller
3680	   connection would now be sent to both the agent and the supervisor.

3682	   Second, the AS would send a request to join the supervisor and the
3683	   agent connections:

3685	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3686	    <join id1="supervisor:001" id2="agent:002">
3687	     <stream media="audio" direction="sendrecv"/>
3688	    </join>
3689	   </mscmixer>

3691	   If this request was successful, the audio mixing would occur on both
3692	   the agent and supervisor connections: the agent would hear the caller
3693	   and supervisor, and the supervisor would hear the agent and caller.
3694	   The caller would only hear the agent.  If the MS is unable to join
3695	   and mix connections in this way, it would send a 426 response.

3697	6.2.3.  Video conferencing

3699	   In this example, an audio video-conference is created with the
3700	   loudest participant has the most prominent region in the video
3701	   layout.

3703	   The AS sends a request to create an audio-video conference:

3705	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3706	    <createconference conferenceid="conf2">
3707	     <audio-mixing type="nbest"/>
3708	     <video-layouts>
3709	      <video-layout min-participants="1"><single-view/></video-layout>
3710	      <video-layout min-participants="2"><dual-view/></video-layout>
3711	      <video-layout min-participants="3"><quad-view/></video-layout>
3712	      <video-layout min-participants="5"><multiple-5x1/></video-layout>
3713	     </video-layouts>
3714	     <video-switch><vas/></video-switch>
3715	    </createconference>
3716	   </mscmixer>
3717	   In this configuration, the conference uses a nbest audio mixing
3718	   policy and a <vas/> video switch policy, so that the loudest speaker
3719	   receives the most prominent region in the layout.  Multiple video
3720	   layouts are specified and active one depends on the number of
3721	   participants.

3723	   Assume that 4 participants are already joined to the conference.  In
3724	   that case, the video layout will be quad-view (Figure 6) with the
3725	   most active speaker displayed in region 1.  When a fifth participant
3726	   joins, the video layout automatically switches to a multiple-5x1
3727	   layout (Figure 9), again with the most active speaker in region 1.

3729	   The AS can manipulate which participants are displayed in the
3730	   remaining regions.  For example, it could force an existing
3731	   conference participant to be displayed in region 2:

3733	   <mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
3734	    <modifyjoin id1="1536067209:913cd14c" id2="conf2">
3735	     <stream media="video">
3736	      <region>2</region>
3737	     </stream>
3738	    </modifyjoin>
3739	   </mscmixer>

3741	7.  Security Considerations

3743	   As this control package processes XML markup, implementations MUST
3744	   address the security considerations of [RFC3023].

3746	   As a Control Package of the Media Control Channel Framework,
3747	   security, confidentiality and integrity of messages transported over
3748	   the control channel MUST be addressed as described in Section 12 of
3749	   the Media Control channel Framework
3750	   ([I-D.ietf-mediactrl-sip-control-framework]), including Transport
3751	   Level Protection, Control Channel Policy Management and Session
3752	   Establishment.  In addition, implementations MUST address security,
3753	   confidentiality and integrity of User Agent sessions with the MS,
3754	   both in terms of SIP signaling and associated RTP media flow; see
3755	   [I-D.ietf-mediactrl-sip-control-framework] for further details on
3756	   this topic.

3758	   Adequate transport protection and authentication are critical,
3759	   especially when the implementation is deployed in open networks.  If
3760	   the implementation fails to correctly address these issues, it risks
3761	   exposure to malicious attacks, including (but not limited to):

3763	   Denial of Service:  An attacker could insert a request message into
3764	      the transport stream causing specific conferences or join mixers
3765	      on the MS to be destroyed.  For example, <destroyconference
3766	      conferenceid="XXXX">, where the value of "XXXX" could be guessed
3767	      or discovered by auditing active mixers on the MS using an <audit>
3768	      request.  Likewise, an attacker could impersonate the MS and
3769	      insert error responses into the transport stream so denying the AS
3770	      access to package capabilities.

3772	   Resource Exhaustion:  An attacker could insert into the control
3773	      channel new request messages (or modify existing ones) with, for
3774	      instance, <createconference> elements causing large numbers of
3775	      conference mixer resources to be allocated.  At some point this
3776	      will exhaust the number of conference mixers that the MS is able
3777	      to allocate.

3779	   The Media Control Channel Framework permits additional policy
3780	   management, including resource access and control channel usage, to
3781	   be specified at the control package level beyond that specified for
3782	   the Media Control Channel Framework (see Section 12.3 of
3783	   [I-D.ietf-mediactrl-sip-control-framework]).

3785	   Since creation of conference and join mixers is associated with media
3786	   mixing resources on the MS, the security policy for this control
3787	   package needs to address how such mixers are securely managed across
3788	   more than one control channel.  Such a security policy is only useful
3789	   for secure, confidential and integrity protected channels.  The
3790	   identity of control channels is determined by the channel identifier:
3791	   i.e. the value of the cfw-id attribute in the SDP and Dialog-ID
3792	   header in the channel protocol (see
3793	   [I-D.ietf-mediactrl-sip-control-framework]).  Channels are the same
3794	   if they have the same identifier; otherwise, they are different.
3795	   This control package imposes the following additional security
3796	   policies:

3798	   Responses:  The MS MUST only send a response to a mixer management or
3799	      audit request using the same control channel as the one used to
3800	      send the request.

3802	   Notifications:  The MS MUST only send notification events for
3803	      conference and join mixers using the same control channel as it
3804	      received the request creating the mixer.

3806	   Auditing:  The MS MUST only provide audit information about
3807	      conference and join mixers which have been created on the same
3808	      control channel as the one upon the <audit> request is sent.  For
3809	      example, if a join between two connections has been created on one
3810	      channel, then a request on another channel to audit all mixers -
3811	      <audit mixers="true"/> - would not report on this join mixer.

3813	   Rejection:  The MS SHOULD reject requests to audit or manipulate an
3814	      existing conference or join mixer on the MS if the channel is not
3815	      the same as the one used when the mixer was created.  The MS
3816	      rejects a request by sending a Control Framework 403 response (see
3817	      Section 7.4 and Section 12.3 of
3818	      [I-D.ietf-mediactrl-sip-control-framework]).  For example, if a
3819	      channel with identifier 'cfw1234' has been used to send a request
3820	      to create a particular conference and the MS receives on channel
3821	      'cfw98969' a request to audit or destroy this particular
3822	      conference, then the MS sends a 403 framework response.

3824	   There can be valid reasons why an implementation does not reject an
3825	   audit or mixer manipulation request on a different channel from the
3826	   one which created the mixer.  For example, a system administrator
3827	   might require a separate channel to audit mixer resources created by
3828	   system users and to terminate mixers consuming excessive system
3829	   resources.  Alternatively, a system monitor or resource broker might
3830	   require a separate channel to audit mixers managed by this package on
3831	   a MS.  However, the full implications need to be understood by the
3832	   implementation and carefully weighted before accepting these reasons
3833	   as valid.  If the reasons are not valid in their particular
3834	   circumstances, the MS rejects such requests.

3836	   There can also be valid reasons for 'channel handover' including high
3837	   availability support or where one AS needs to take over management of
3838	   mixers after the AS which created them has failed.  This could be
3839	   achieved by the control channels using the same channel identifier,
3840	   one after another.  For example, assume a channel is created with the
3841	   identifier 'cfw1234' and the channel is used to create mixers on the
3842	   MS.  This channel (and associated SIP dialog) then terminates due to
3843	   a failure on the AS.  As permitted by the Control Framework, the
3844	   channel identifier 'cfw1234' could then be reused so that another
3845	   channel is created with the same identifier 'cfw1234', allowing it to
3846	   'take over' management of the mixers on the MS.  Again, the
3847	   implementation needs to understand the full implications and
3848	   carefully weight them before accepting these reasons as valid.  If
3849	   the reasons are not valid for their particular circumstances, the MS
3850	   uses the appropriate SIP mechanisms to prevent session establishment
3851	   when the same channel identifier is used in setting up another
3852	   control channel (see Section 4 of
3853	   [I-D.ietf-mediactrl-sip-control-framework]).

3855	8.  IANA Considerations

3857	   This specification instructs IANA to register a new Media Control
3858	   Channel Framework Package, a new XML namespace, a new XML schema and
3859	   a new MIME type.

3861	8.1.  Control Package Registration

3863	   This section registers a new Media Control Channel Framework package,
3864	   per the instructions in Section 12.1 of
3865	   [I-D.ietf-mediactrl-sip-control-framework].

3867	      To: ietf-sip-control@iana.org
3868	      Subject: Registration of new Channel Framework package
3869	      Package Name: msc-mixer/1.0
3870	        [NOTE TO IANA/RFC-EDITOR: Please replace XXXX
3871	        with the RFC number for this specification.]
3872	      Published Specification(s): RFCXXXX
3873	      Person & email address to contact for further information:
3874	      IETF, MEDIACTRL working group, (mediactrl@ietf.org),
3875	      Scott McGlashan (smcg.stds01@mcglashan.org).

3877	8.2.  URN Sub-Namespace Registration

3879	   This section registers a new XML namespace,
3880	   "urn:ietf:params:xml:ns:msc-mixer", per the guidelines in RFC 3688
3881	   [RFC3688].

3883	         URI: urn:ietf:params:xml:ns:msc-mixer
3884	         Registrant Contact: IETF, MEDIACTRL working group,
3885	         (mediactrl@ietf.org), Scott McGlashan
3886	         (smcg.stds01@mcglashan.org).
3887	         XML:
3888	            BEGIN
3889	            <?xml version="1.0"?>
3890	            <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3891	                "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
3892	             <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
3893	              <head>
3894	               <title>Media Control Channel Framework Mixer
3895	                      Package attributes</title>
3896	              </head>
3897	              <body>
3898	               <h1>Namespace for Media Control Channel
3899	                   Framework Mixer Package attributes</h1>
3900	               <h2>urn:ietf:params:xml:ns:msc-mixer</h2>
3901	        [NOTE TO IANA/RFC-EDITOR: Please replace XXXX
3902	        with the RFC number for this specification.]
3903	                 <p>See RFCXXXX</p>
3904	              </body>
3905	             </html>
3906	            END

3908	8.3.  XML Schema Registration

3910	   This section registers an XML schema as per the guidelines in RFC
3911	   3688 [RFC3688].

3913	      URI:  urn:ietf:params:xml:ns:msc-mixer
3914	      Registrant Contact: IETF, MEDIACTRL working group,
3915	         (mediactrl@ietf.org), Scott McGlashan
3916	         (smcg.stds01@mcglashan.org).
3917	      Schema:  The XML for this schema can be found in
3918	         Section 5 of this document.

3920	8.4.  MIME Media Type Registration for  'application/msc-mixer+xml'

3922	   This section registers the "application/msc-mixer+xml" MIME type.

3924	   To:  ietf-types@iana.org
3925	    Subject:  Registration of MIME media type
3926	              application/msc-mixer+xml
3927	    MIME media type name:  application
3928	    MIME subtype name:  msc-mixer+xml
3929	    Required parameters:  (none)
3930	    Optional parameters:  charset
3931	       Indicates the character encoding of enclosed XML.  Default is
3932	       UTF-8.
3933	    Encoding considerations:  Uses XML, which can employ 8-bit
3934	       characters, depending on the character encoding used.  See RFC
3935	       3023 [RFC3023], section 3.2.
3936	    Security considerations:  No known security considerations outside
3937	       of those provided by the Media Control Channel Framework Mixer
3938	       Package.
3939	    Interoperability considerations:  This content type provides
3940	       constructs for the Media Control Channel Framework Mixer package.
3941	    Published specification:  RFC XXXX [NOTE TO IANA/RFC-EDITOR: Please
3942	       replace XXXX with the RFC number for this specification.]
3943	    Applications which use this media type:  Implementations of
3944	       the Media Control Channel Framework Mixer package.
3945	    Additional Information:  Magic Number(s): (none)
3946	       File extension(s): (none)
3947	       Macintosh File Type Code(s): (none)
3948	    Person & email address to contact for further information:  Scott
3949	       McGlashan <smcg.stds01@mcglashan.org>
3950	    Intended usage:  LIMITED USE
3951	    Author/Change controller:  The IETF
3952	    Other information:  None.

3954	9.  Change Summary

3956	   Note to RFC Editor: Please remove this whole section.

3958	   The following are the changes between the -14 and -13 versions
3959	   (addressing remaining IESG DISCUSS):

3961	   o  4.7.7 Language Identifier: deleted statement "where the language
3962	      code is required and a country code or other subtag identifier is
3963	      optional" and clarified that RFC 4647 specifies the matching
3964	      procedure.

3966	   The following are the changes between the -13 and -12 versions
3967	   (addressing remaining IESG DISCUSS):

3969	   o  4.0, 4.1, etc: Added language tags to identify the language of
3970	      descriptive text attributes.  A desclang attribute is added to the
3971	      root element and has a default value of i-default.  Subordinate
3972	      elements with descriptive text attributes also have this attribute
3973	      defined - if it is not specified on the subordinate element, then
3974	      the desclang value on the root element applies.  Added example of
3975	      desclang in 4.1.

3977	   o  5: Updated schema with desclang attributes

3979	   o  Section 4.7.6: Corrected ABNF definition of IANA MIME media type
3980	      to allow parameter values.

3982	   The following are the changes between the -12 and -11 versions
3983	   (primarily addressing IESG DISCUSS, comments and nits):

3985	   o  Introduction: Clarified that Control Framework is an equivalent
3986	      term for the Media Control Channel Framework.

3988	   o  4.2.4.2, 4.2.4.3, 4.5: Replaced reference to standards-tracks RFC
3989	      for assignment of new values, with reference to using Standards
3990	      Action process defined in RFC 5226.

3992	   o  4.0: Clarified that while some elements contain attributes whose
3993	      value is descriptive text, this descriptive text is for diagnostic
3994	      use only and does not require a language indicator such as a
3995	      language tag.

3997	   o  4.2.2.5.2: expanded DTMF acronym.

3999	   o  4.2.1.4.2.1: Changed <video-layout> so that the layout is a child
4000	      element rather than content value.  Changed examples to match.
4001	      Updated XML schema.

4003	   o  4.2.1.4.3: Changed <video-switch> so that the policy is a child
4004	      element rather than content value.  Changed examples to match.
4005	      Updated XML schema.

4007	   o  4.4.1: changed <codec> to include name attribute; aligned
4008	      definition with RFC4288; updated XML schema.

4010	   o  4.2.2.5: Clarified that the media attribute of <stream> is a MIME
4011	      type-name with reference to RFC 4288.

4013	   o  4.5.1: Added encoding attribute to <param> to allow for
4014	      specification of content-transfer-encoding schema.  Updated XML
4015	      schema.

4017	   o  4.5.1: Simplified content model of <param> to be text only.
4018	      Updated XML schema.

4020	   o  4.6.6: Clarified MIME media type format with ABNF production
4021	      referencing RFC 4288.

4023	   o  4.2.2.5.3: clarified the definition of <region> as an area in a
4024	      video layout

4026	   o  5: Stated that the schema is normative.

4028	   o  5: Corrected default value of tones attribute in schema to match
4029	      definition in 4.2.2.5.2.

4031	   o  4.6: Type definitions; added references to XML Schema datatypes
4032	      where appropriate; changed definition of boolean to match W3C
4033	      definition and updated boolean type in schema.

4035	   o  Typos: in 4.2.1.4.2.1, added '/' to <video-layout>; in 4.2.1.4.3
4036	      <video-switch>, replaced second <join> with <unjoin>; in 4.2.3,
4037	      corrected code and status in <response> examples;

4039	   o  Validated all examples against XML schema and corrected where
4040	      necessary.

4042	   The following are the changes between the -11 and -10 versions
4043	   (addressing IETF Last Call comments):

4045	   o  4.2.2.3: For <modifyjoin>, removed the statement "It MUST NOT
4046	      change the configuration of any streams not included as child
4047	      elements." since modifications in stream directionality can affect
4048	      other streams of the same type.

4050	   o  4.2.2.5.2: Changed definition of tones attribute of <clamp>
4051	      element so that if the element is specified, then all DTMF tones
4052	      are clamped by default.  Updated XML schema.

4054	   o  7: Corrected references from Section 11 to Section 12 in Control
4055	      Framework.

4057	   o  Fixed various typos.

4059	   The following are the changes between the -10 and -09 versions:

4061	   o  References: Moved the XCON reference to the Normative References
4062	      section.

4064	   o  4.2: Mixer Elements: clarified that when a requested mixer
4065	      operation (partially) fails, the MS carries out no part of the
4066	      operation and sends an error response.

4068	   The following are the changes between the -09 and -08 versions
4069	   following shepherd writeup:

4071	   o  4.2.4.1.1: <active-talker>: Removed the statement that it is an
4072	      error if an <active-talker> element has both connectionid and
4073	      conferenceid attributes specified because the AS always sends a
4074	      framework 200 in response to notification events, including active
4075	      talker events.  Instead, clarified that no active talker is
4076	      described if both attributes are specified or if neither attribute
4077	      is specified.

4079	   o  Various spelling and grammatical errors fixed.

4081	   The following are the changes between the -08 and -07 versions.

4083	   o  8.4: Changed file extension from '.xml' to (none)

4085	   o  Changed "~" to a ":" for connectionid

4087	   o  4.2.6.1: Clarified that <param> can contain an XML value.

4089	   o  4.2.4.2: Changed <unjoin-notify> status codes so that only 0-2
4090	      defined and all others are reserved for future use requiring a
4091	      standard-track RFC.

4093	   o  4.2.4.3: Changed <conferenceexit> status codes so that only 0-2
4094	      defined and all others are reserved for future use requiring a
4095	      standard-track RFC.

4097	   o  4.5: Changed status code for <response> and <auditresponse> so
4098	      that certain codes are defined and all others are reserved for
4099	      future use requiring a standard-track RFC.

4101	   The following are the changes between the -07 and -06 versions.

4103	   o  Generally corrected references from Section 17.1 to Section 16.1
4104	      of Control Channel Framework.

4106	   o  4.2.2.2: removed "is" in "unless this is leads to a stream
4107	      conflict"

4109	   o  4.2.2.3: corrected error code from 408 to 409 for "If the
4110	      specified entities are not already joined, then the MS reports an
4111	      error (408)."

4113	   o  4.2.1.4.3: corrected error code from 409 to 424 for "If the MS
4114	      does not support the specified video switching policy or ..., then
4115	      MS reports a 409 error".

4117	   o  4.2.1.4.2: corrected error code from 408 to 423 for "If the MS
4118	      does not support video conferencing at all, or ...., the MS
4119	      reports an 408 error ..."

4121	   o  4.2.1.1, 4.2.1.2, 4.2.2.2, 4.2.2.3: Clarified that <codecs>
4122	      specified in <createconference> or <modifyconference> impose a
4123	      limitation in the media capability of a conference and this
4124	      limitation affects whether the conference can be <join> or
4125	      <modifyjoin>ed to another entity.

4127	   The following are the changes between the -06 and -05 versions.

4129	   o  4.4.1: <codec>: corrected typos, added an example of <params>
4130	      usage, added a <subtype> section and moved the <params> section
4131	      inside this section.

4133	   o  8: IANA Considerations: Updated IANA registration information and
4134	      added registration for the XML Schema

4136	   The following are the changes between the -05 and -04 versions.

4138	   o  Schema: Fixed problem with non-deterministic content models.

4140	   o  7.  Security Considerations: Added requirement that
4141	      implementations need to secure SIP and RTP sessions with User
4142	      Agents.

4144	   The following are the changes between the -04 and -03 versions.

4146	   o  4.2.1.4.3: corrected typo

4148	   o  4.2.2.3: Clarified the behavior of <modifyjoin> for cases where
4149	      each direction of a stream is independently controlled.

4151	   o  4.2.2.5: Corrected syntax error in examples.

4153	   o  4.2.2.5.1: Clarified that when an audio stream is in the muted
4154	      state, then a <volume> automatic or setgain control causes the
4155	      state to change automatically to unmuted.

4157	   o  7 Security: Clarified that both conference and join mixers are
4158	      covered by the package security policies.

4160	   o  7 Security: Added a denial of service example where the attacker
4161	      impersonates the MS.

4163	   o  7 Security: Clarified that the package security policy for
4164	      multiple channels is only useful if the channels themselves are
4165	      secured.

4167	   o  Updated acknowledgements.

4169	   The following are the major changes between the -03 and -02 versions.

4171	   o  Corrected various typos and nits.

4173	   o  Conformance language: Removed unnecessary MUSTs, especially for
4174	      error codes.  Changed most RECOMMENDEDs to MUST or MAY.  Removed
4175	      lowercase 'should', 'must' and 'may'.

4177	   o  Tidied up Abstract

4179	   o  Removed old Introduction section (it just duplicated the
4180	      abstract).  Replaced it with the old Overview Section.  Section
4181	      numbering changed!

4183	   o  Introduction: Clarified which MediaCtrl Requirements are satisfied
4184	      by this package.

4186	   o  4.2.1.1: <createconference>: Clarified that an attempt to create a
4187	      conference with an identifier already used by an existing
4188	      conference does not affect the existing conference (405 error
4189	      response).

4191	   o  4.2.1.4.1: <audio-mixing>: Added a 'n' attribute for the number of
4192	      participants to be included in nbest audio mixing.

4194	   o  4.2.1.4.3: <video-switch>: Clarified that the active speaker in
4195	      video switching is the loudest speaker.

4197	   o  4.2.1.4.4: <subscribe>: Clarified that if a subscription specified
4198	      in a foreign namespace element or attribute is not supported by
4199	      the MS, then the MS generates a 428 error response.  Changed
4200	      conformance support for <active-talkers-sub> from SHOULD to MUST.
4201	      Removed 422 error response.

4203	   o  4.2.2: Joining Elements: Added text to the empty section.

4205	   o  4.2.2.2, 4.2.2.3, 4.2.2.4: <join>, <modifyjoin> and <unjoin>:
4206	      Clarified that join operation failures do not affect existing
4207	      stream properties of the entities (407 and new 422 error
4208	      response).  Clarified stream failure errors in <modifyjoin> and
4209	      <unjoin>.

4211	   o  4.2.2.2: <join>.  Clarified that <stream> elements can be used to
4212	      independently control properties of the media flow in different
4213	      directions.  Added a response code (422) for when the MS does not
4214	      support a media stream configuation.

4216	   o  4.2.2.2: <join>.  Clarified that error responses are generated if
4217	      id1 or id2 reference a conference or connection which does not
4218	      exist.  Added an error status code (412) for non-existant
4219	      connections.

4221	   o  4.2.2.5: <stream>: Changed the definition so that in each child
4222	      element, the media stream affected is indicated by the value of
4223	      the direction attribute of the parent element.  Added examples of
4224	      controlling the media flow properties.

4226	   o  4.2.4.2: <unjoin-notify>.  Added reserved range of status codes.
4227	      Changed code from 1 to 0 for the unjoin case.  Changed code from 3
4228	      to 1 for execution error.

4230	   o  4.2.4.3: <conferenceexit>.  Added reserved range of status codes.
4231	      Changed code from 1 to 0 for the destroyconference case (align
4232	      with IVR).  Added a code for conference exiting due to exceeding
4233	      its maximum duration.

4235	   o  Schema: Adding missing version attribute on <mscmixer>.

4237	   o  Security Considerations: Major update.  Added examples showing
4238	      malicious attacks when channel security is not correctly
4239	      addressed.  Added more details on multiple channel cases including
4240	      administrator and monitor channels as well as channel handover.

4242	   o  Removed affliations in Contributors section.

4244	   The following are the major changes between the -02 and -01 versions.

4246	   o  Section 4: Aligned Control Package definitions with requirements
4247	      in Section 8 of the Control Framework.

4249	   o  Following October Interim meeting discussion on response codes,
4250	      generally clarified usage of error status codes, modified some
4251	      codes and re-organized the response codes section (Section 4.6)
4252	      with more guidance and details.

4254	   o  MIXER-006.  No action required following October 2008 interim
4255	      discussion.

4257	   o  MIXER-008.  No action required following October 2008 interim
4258	      discussion.

4260	   o  MIXER-009.  No action required for control package - addressed in
4261	      -05 framework draft following interim October 2008 discussion.

4263	   o  MIXER-010/5.2.2.5: Clarified that in the <stream> element, an
4264	      "inactive" direction value indicates the stream is established but
4265	      there is no media flow.  Such a stream can be manipulated by
4266	      <modifyjoin> and <unjoin>.

4268	   o  5.2.2.5: <stream>: Clarified that the media stream specified in
4269	      child elements <volume>, <clamp>, <region> and <priority> is the
4270	      stream originating from the entity identified as id1.

4272	   o  5.2.1.4.3: <video-switch>: Clarified that it is not an error if a
4273	      <stream> specifies a region which is not defined for the currently
4274	      active video layout.

4276	   o  5.2.1.4.2.1: <video-layout>: Added descriptions and ASCII art for
4277	      layout and regions of XCON video layouts.

4279	   o  Added examples of audio conferencing, connection bridging and
4280	      video conferencing.

4282	   The following are the major changes between the -01 and -00 versions.

4284	   o  [MIXER-001]/5.2.4.3: Added <conferenceexit> notification event.

4286	   o  [MIXER-003]/5.2.1.4.2.1: Added ASCII diagrams for video layouts.

4288	   o  [MIXER-004]/5.3.2.2.1: Added active <video-layout> information to
4289	      <conferenceaudit>.

4291	   o  [MIXER-007]/5.4.1: Added <params> inside <codec> so additional
4292	      codec information can be specified.

4294	   o  5.2.1.1: Fixed <createconference> example with missing min-
4295	      participants attributes.

4297	   o  5: Changed handling of unsupported foreign namespace elements and
4298	      attributes.  The MS send a 427 error response if it encounters
4299	      foreign elements and attributes it does not support.

4301	   o  5.2.1.4.3: <video-switch>.  Clarified that the VAS policy is
4302	      implementation-specific if a participant provides more than one
4303	      audio stream.

4305	   o  5.2.2.2/5.2.2.3/5.2.2.4: Clarified that joining behavior so that
4306	      streams which have previously been <modifiedjoin>ed or <unjoin>ed
4307	      are not affected by a general <unjoin>.

4309	   o  5.2.1.4.3: <video-switch>: Added support for whether active
4310	      speaker is displayed on their video layout ('activespeakermix'
4311	      attribute) and clarified that personal video mixes are out of
4312	      scope for this package.

4314	   o  5.2.1.4.3/5.2.2.5.4: <video-switch>: Added support for a priority
4315	      mechanism in video switching policy and a <priority child element
4316	      on <stream>.

4318	   o  8:Updated security section

4320	   o  13:Updated references

4322	   o  5.2.1.4.4.1: Added default of 3 seconds for <active-talkers-sub>
4323	      interval.

4325	   o  5.2.2.5.1: <volume> controltype attribute set to mandatory.

4327	   o  Updated schema

4329	   The following are the major changes between the -00 of this work
4330	   group item draft and the individual submission -04 version.

4332	   o  Control package name is now 'msc-mixer/1.0'.  Namespace is now
4333	      'urn:ietf:params:xml:ns:msc-mixer'.  Mime type is now
4334	      'application/msc-mixer+xml'.

4336	   o  Added XML root element <mscmixer>.

4338	   o  Editorial tidy up of sections.

4340	   o  Added audit request/response elements.

4342	   o  Added video layout and switching conference configuration.

4344	   o  <audio-mixing>: changed 'mix-type' attribute to 'type'
4345	      (consistency with video-switch)

4347	   o  Added "inactive" as value of <stream>'s direction attribute.

4349	   o  Added <region> child to <stream> element.

4351	   o  <createconference>: <audio-mixing> element is no longer mandatory;
4352	      added <video-layouts> and <video-switch> child elements. reserved-
4353	      talkers and reserved-listeners as attributes.

4355	   o  replaced conf-id attribute with conferenceid attribute.

4357	   o  Removed <data> element.  Active talkers subscription and
4358	      notifications used dedicated elements now.

4360	   o  Added <unjoin-notify> notification event to indicate when
4361	      (un)expected joins occur.  Use case: connection or conference
4362	      joined to a conference and conference exits (either by request or
4363	      runtime error.

4365	   The following are the major changes between the -04 of the draft and
4366	   the -03 version.

4368	   o  Updated reference for Media Control Channel Framework

4370	   The following are the major changes between the -03 of the draft and
4371	   the -02 version.

4373	   o  None

4375	   The following are the major changes between the -02 of the draft and
4376	   the -01 version.

4378	   o  clarified the model for join operations and introduced several new
4379	      package error codes

4381	   o  added definition for MS connection

4383	   The following are the major changes between the -01 of the draft and
4384	   the -00 version.

4386	   o  restructured into single request response model for non-trivial
4387	      operations

4389	   o  aligned with XML structure of other control framework packages

4391	10.  Contributors

4393	   Asher Shiratzky provided valuable support and contributions to early
4394	   versions of this document.

4396	   The authors would like to thank the Mixer design team consisting of
4397	   Roni Even, Lorenzo Miniero, Adnan Saleem, Diego Besprosvan and Mary
4398	   Barnes who provided valuable feedback, input, diagrams and text to
4399	   this document.

4401	11.  Acknowledgments

4403	   The authors would like to thank Roni Even, Lorenzo Miniero, Steve
4404	   Buko and Stephane Bastien for expert reviews of this work.

4406	   Shawn Emery carried out a thorough security review.

4408	12.  References

4410	12.1.  Normative References

4412	   [I-D.ietf-mediactrl-sip-control-framework]
4413	              Boulton, C., Melanchuk, T., and S. McGlashan, "Media
4414	              Control Channel Framework",
4415	              draft-ietf-mediactrl-sip-control-framework-12 (work in
4416	              progress), September 2010.

4418	   [I-D.ietf-xcon-common-data-model]
4419	              Novo, O., Camarillo, G., Morgan, D., and J. Urpalainen,
4420	              "Conference Information Data Model for Centralized
4421	              Conferencing (XCON)", draft-ietf-xcon-common-data-model-22
4422	              (work in progress), December 2010.

4424	   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
4425	              Extensions (MIME) Part One: Format of Internet Message
4426	              Bodies", RFC 2045, November 1996.

4428	   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
4429	              Requirement Levels", BCP 14, RFC 2119, March 1997.

4431	   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
4432	              Types", RFC 3023, January 2001.

4434	   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
4435	              January 2004.

4437	   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
4438	              Registration Procedures", BCP 13, RFC 4288, December 2005.

4440	   [RFC4574]  Levin, O. and G. Camarillo, "The Session Description
4441	              Protocol (SDP) Label Attribute", RFC 4574, August 2006.

4443	   [RFC4647]  Phillips, A. and M. Davis, "Matching of Language Tags",
4444	              BCP 47, RFC 4647, September 2006.

4446	   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
4447	              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
4448	              May 2008.

4450	   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
4451	              Specifications: ABNF", STD 68, RFC 5234, January 2008.

4453	   [RFC5646]  Phillips, A. and M. Davis, "Tags for Identifying
4454	              Languages", BCP 47, RFC 5646, September 2009.

4456	   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C M., Maler, E.,
4457	              and F. Yergeau, "Extensible Markup Language (XML) 1.0
4458	              (Third Edition)", W3C Recommendation, February 2004.

4460	   [XMLSchema:Part2]
4461	              Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
4462	              Second Edition", W3C Recommendation, October 2004.

4464	12.2.  Informative References

4466	   [IANA]     "IANA registry for RTP Payload Types",
4467	              <http://www.iana.org/assignments/rtp-parameters>.

4469	   [MIME.mediatypes]
4470	              "IANA registry for MIME Media Types",
4471	              <http://www.iana.org/assignments/media-types/>.

4473	   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
4474	              Languages", BCP 18, RFC 2277, January 1998.

4476	   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
4477	              A., Peterson, J., Sparks, R., Handley, M., and E.
4478	              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
4479	              June 2002.

4481	   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
4482	              Jacobson, "RTP: A Transport Protocol for Real-Time
4483	              Applications", STD 64, RFC 3550, July 2003.

4485	   [RFC5022]  Van Dyke, J., Burger, E., and A. Spitzer, "Media Server
4486	              Control Markup Language (MSCML) and Protocol", RFC 5022,
4487	              September 2007.

4489	   [RFC5167]  Dolly, M. and R. Even, "Media Server Control Protocol
4490	              Requirements", RFC 5167, March 2008.

4492	   [RFC5707]  Saleem, A., Xin, Y., and G. Sharratt, "Media Server Markup
4493	              Language (MSML)", RFC 5707, February 2010.

4495	Authors' Addresses

4497	   Scott McGlashan
4498	   Hewlett-Packard

4500	   Email: smcg.stds01@mcglashan.org

4502	   Tim Melanchuk
4503	   Rain Willow Communications

4505	   Email: tim.melanchuk@gmail.com

4507	   Chris Boulton
4508	   NS-Technologies

4510	   Email: chris@ns-technologies.com