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     The optional boolean <ack> element, set to "true", if present,
     indicates that the CONF message also acknowledges the referred
     advertisement, by applying in that way a piggybacking mechanism for
     simultaneously acknowledging and replying to the ADV message.  In the
     above case, the CONF message MUST carry a 200 (Success) response code. 
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  ** Downref: Normative reference to an Experimental draft:
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2	CLUE Working Group                                             R. Presta
3	Internet-Draft                                                 S. Romano
4	Intended status: Standards Track                    University of Napoli
5	Expires: April 21, 2016                                 October 19, 2015

7	                             CLUE protocol
8	                      draft-ietf-clue-protocol-06

10	Abstract

12	   The CLUE protocol is an application protocol conceived for the
13	   description and negotiation of a CLUE telepresence session.  The
14	   design of the CLUE protocol takes into account the requirements and
15	   the framework defined, respectively, in [I-D.ietf-clue-framework] and
16	   [RFC7262].  The companion document [I-D.ietf-clue-signaling] delves
17	   into CLUE signaling details, as well as on the SIP/SDP session
18	   establishment phase.  CLUE messages flow upon the CLUE data channel,
19	   based on reliable and ordered SCTP over DTLS transport, as described
20	   in [I-D.ietf-clue-datachannel].  Message details, together with the
21	   behavior of CLUE Participants acting as Media Providers and/or Media
22	   Consumers, are herein discussed.

24	Status of This Memo

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

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

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

39	   This Internet-Draft will expire on April 21, 2016.

41	Copyright Notice

43	   Copyright (c) 2015 IETF Trust and the persons identified as the
44	   document authors.  All rights reserved.

46	   This document is subject to BCP 78 and the IETF Trust's Legal
47	   Provisions Relating to IETF Documents
48	   (http://trustee.ietf.org/license-info) in effect on the date of
49	   publication of this document.  Please review these documents
50	   carefully, as they describe your rights and restrictions with respect
51	   to this document.  Code Components extracted from this document must
52	   include Simplified BSD License text as described in Section 4.e of
53	   the Trust Legal Provisions and are provided without warranty as
54	   described in the Simplified BSD License.

56	Table of Contents

58	   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
59	   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
60	   3.  Overview of the CLUE protocol  . . . . . . . . . . . . . . . .  5
61	   4.  Protocol messages  . . . . . . . . . . . . . . . . . . . . . .  7
62	     4.1.  OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . .  9
63	     4.2.  OPTIONS RESPONSE . . . . . . . . . . . . . . . . . . . . . 11
64	     4.3.  ADVERTISEMENT  . . . . . . . . . . . . . . . . . . . . . . 12
65	     4.4.  ADVERTISEMENT ACKNOWLEDGEMENT  . . . . . . . . . . . . . . 13
66	     4.5.  CONFIGURE  . . . . . . . . . . . . . . . . . . . . . . . . 14
67	     4.6.  CONFIGURE RESPONSE . . . . . . . . . . . . . . . . . . . . 14
68	     4.7.  Response codes and reason strings  . . . . . . . . . . . . 15
69	   5.  Protocol state machines  . . . . . . . . . . . . . . . . . . . 17
70	   6.  CLUE Participant's state machine . . . . . . . . . . . . . . . 17
71	     6.1.  Media Provider's state machine . . . . . . . . . . . . . . 19
72	     6.2.  Media Consumer's state machine . . . . . . . . . . . . . . 22
73	   7.  Versioning . . . . . . . . . . . . . . . . . . . . . . . . . . 25
74	   8.  Extensions and options . . . . . . . . . . . . . . . . . . . . 26
75	   9.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 27
76	   10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
77	     10.1. Simple ADV . . . . . . . . . . . . . . . . . . . . . . . . 31
78	     10.2. ADV with MCCs  . . . . . . . . . . . . . . . . . . . . . . 37
79	   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 44
80	     11.1. URN Sub-Namespace Registration . . . . . . . . . . . . . . 44
81	     11.2. XML Schema registration  . . . . . . . . . . . . . . . . . 45
82	     11.3. MIME Media Type Registration for 'application/clue+xml'  . 45
83	     11.4. DNS Registrations  . . . . . . . . . . . . . . . . . . . . 46
84	       11.4.1.  Application Service tag . . . . . . . . . . . . . . . 46
85	       11.4.2.  Application Protocol tag  . . . . . . . . . . . . . . 46
86	     11.5. CLUE Protocol Registry . . . . . . . . . . . . . . . . . . 47
87	       11.5.1.  CLUE Message Types  . . . . . . . . . . . . . . . . . 47
88	       11.5.2.  CLUE Response Codes . . . . . . . . . . . . . . . . . 48
89	   12. Diff with draft-ietf-clue-protocol-05  . . . . . . . . . . . . 49
90	   13. Diff with draft-ietf-clue-protocol-04  . . . . . . . . . . . . 49
91	   14. Diff with draft-ietf-clue-protocol-03  . . . . . . . . . . . . 49
92	   15. Diff with draft-ietf-clue-protocol-02  . . . . . . . . . . . . 50
93	   16. Diff with draft-ietf-clue-protocol-01  . . . . . . . . . . . . 50
94	   17. Diff with draft-ietf-clue-protocol-00  . . . . . . . . . . . . 50
95	   18. Diff with draft-presta-clue-protocol-04  . . . . . . . . . . . 51
96	   19. Diff with draft-presta-clue-protocol-03  . . . . . . . . . . . 51
97	   20. Diff with draft-presta-clue-protocol-02  . . . . . . . . . . . 51
98	   21. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 51
99	   22. References . . . . . . . . . . . . . . . . . . . . . . . . . . 52
100	     22.1. Normative References . . . . . . . . . . . . . . . . . . . 52
101	     22.2. Informative References . . . . . . . . . . . . . . . . . . 53

103	1.  Introduction

105	   The CLUE protocol is an application protocol used by two CLUE
106	   Participants to enhance the experience of a multimedia telepresence
107	   session.  The main goals of the CLUE protocol are:

109	   1.  enabling a Media Provider (MP) to properly announce its current
110	       telepresence capabilities to a Media Consumer (MC) in terms of
111	       available media captures, groups of encodings, simultaneity
112	       constraints and other information envisioned in
113	       [I-D.ietf-clue-framework];

115	   2.  enabling an MC to request the desired multimedia streams from the
116	       offering MP.

118	   CLUE-capable endpoints are connected by means of the CLUE data
119	   channel, an SCTP over DTLS channel which is opened and established as
120	   described in [I-D.ietf-clue-signaling] and
121	   [I-D.ietf-clue-datachannel].  CLUE protocol messages flowing upon
122	   such a channel are detailed in this document, both syntactically and
123	   semantically.

125	   In Section 3 we provide a general overview of the CLUE protocol.
126	   CLUE protocol messages are detailed in Section 4.  The CLUE
127	   Participant state machine is introduced in Section 5.  Versioning and
128	   extensions are discussed in Section 7 and Section 8, respectively.
129	   The XML schema defining the CLUE messages is reported in Section 9.

131	2.  Terminology

133	   This document refers to the same terminology used in
134	   [I-D.ietf-clue-framework] and in [RFC7262].  We briefly recall herein
135	   some of the main terms used in the document.  The definition of "CLUE
136	   Participant" herein proposed is not imported from any of the above
137	   documents.

139	   CLUE Participant (CP):  An entity able to use the CLUE protocol
140	      within a telepresence session.  It can be an endpoint or an MCU
141	      able to use the CLUE protocol.

143	   CLUE-capable device:  A device that supports the CLUE data channel
144	      [I-D.ietf-clue-datachannel], the CLUE protocol and the principles
145	      of CLUE negotiation, and seeks CLUE-enabled calls.

147	   Endpoint:  The logical point of final termination through receiving,
148	      decoding and rendering, and/or initiation through capturing,
149	      encoding, and sending of media streams.  An endpoint consists of
150	      one or more physical devices which source and sink media streams,
151	      and exactly one [RFC4353] Participant (which, in turn, includes
152	      exactly one SIP User Agent).  Endpoints can be anything from
153	      multiscreen/multicamera room controllers to handheld devices.

155	   MCU:  Multipoint Control Unit (MCU) - a device that connects two or
156	      more endpoints together into one single multimedia conference
157	      [RFC5117].  An MCU may include a Mixer [RFC4353].

159	   Media:  Any data that, after suitable encoding, can be conveyed over
160	      RTP, including audio, video or timed text.

162	   Media Capture:  A "Media Capture", or simply "Capture", is a source
163	      of Media.

165	   Media Consumer (MC):  A CLUE Participant (i.e., an Endpoint or an
166	      MCU) able to receive Media Streams.

168	   Capture Encoding:  A specific encoding of a Media Capture, to be sent
169	      via RTP [RFC3550].

171	   Media Provider (MP):  A CLUE Participant (i.e., an Endpoint or an
172	      MCU) able to send Media Streams.

174	   Media Stream:  The term "Media Stream", or simply "Stream", is used
175	      as a synonym of Capture Encoding.

177	3.  Overview of the CLUE protocol

179	   The CLUE protocol is conceived to enable CLUE telepresence sessions.
180	   It is designed in order to address SDP limitations in terms of the
181	   description of some information about the multimedia streams that are
182	   involved in a real-time multimedia conference.  Indeed, by simply
183	   using SDP we are not able to convey information about the features of
184	   the flowing multimedia streams that are needed to enable a "being
185	   there" rendering experience.  Such information is designed in the
186	   CLUE framework document and formally defined and described in the
187	   CLUE data model document.  The CLUE protocol represents the mechanism
188	   for the exchange of CLUE information between CLUE Participants.  It
189	   mainly provides the messages to enable a Media Provider to advertise
190	   its telepresence capabilities and to enable a Media Consumer to
191	   select the desired telepresence options.

193	   The CLUE protocol, as defined in the following, is a stateful,
194	   client-server, XML-based application protocol.  CLUE protocol
195	   messages flow on a reliable and ordered SCTP over DTLS transport
196	   channel connecting two CLUE Participants.  Messages carry information
197	   taken from the XML-based CLUE data model
198	   ([I-D.ietf-clue-data-model-schema]).  Three main communication layers
199	   can be identified:

201	   1.  Establishment of the CLUE data channel: in this phase, the CLUE
202	       data channel setup takes place.  If it completes successfully,
203	       the CPs are able to communicate and start the initiation phase.

205	   2.  Negotiation of the CLUE protocol version and options (initiation
206	       phase): the CPs connected via the CLUE data channel agree on the
207	       version and on the options to be used during the telepresence
208	       session.  Special CLUE messages are used for such a task (OPTIONS
209	       and OPTIONS RESPONSE).  The version and options negotiation can
210	       be performed once and only at this stage.  At the end of that
211	       basic negotiation, each CP starts its activity as a CLUE MP
212	       and/or CLUE MC.

214	   3.  CLUE telepresence capabilities description and negotiation: in
215	       this phase, the MP-MC dialogues take place on the data channel by
216	       means of the CLUE protocol messages.

218	   As soon as the channel is ready, the CLUE Participants must agree on
219	   the protocol version and extensions to be used within the
220	   telepresence session.  CLUE protocol version numbers are
221	   characterized by a major version number and a minor version number,
222	   both unsigned integers, separated by a dot.  While minor version
223	   numbers denote backward compatible changes in the context of a given
224	   major version, different major version numbers generally indicate a
225	   lack of interoperability between the protocol implementations.  In
226	   order to correctly establish a CLUE dialogue, the involved CPs MUST
227	   have in common a major version number (see Section 7 for further
228	   details).  The subset of the protocol options and extensions that are
229	   allowed within the CLUE session is also determined in the initiation
230	   phase, such subset being the one including only the options that are
231	   supported by both parties.  A mechanism for the negotiation of the
232	   CLUE protocol version and extensions is is part of the initial phase.
233	   According to such a solution, the CP which is the CLUE Channel
234	   initiator (CI) issues a proper CLUE message (OPTIONS) to the CP which
235	   is the Channel Receiver (CR) specifying the supported version and
236	   extensions.  The CR then answers by selecting the subset of the CI
237	   extensions that it is able to support and determines the protocol
238	   version to be used.

240	   After that negotiation phase is completed, CLUE Participants describe
241	   and agree on the media flows to be exchanged.  In many cases CPs will
242	   seek to both transmit and receive media.  Hence in a call between two
243	   CPs, A and B, there would be two seperate dialogs, as follows:

245	   1.  the one needed to describe and set up the media streams sent from
246	       A to B, i.e., the dialogue between A's Media Provider side and
247	       B's Media Consumer side

249	   2.  the one needed to describe and set up the media streams sent from
250	       B to A, i.e., the dialogue between B's Media Provider side and
251	       A's Media Consumer side

253	   CLUE messages for the media session description and negotiation are
254	   designed by considering the MP side as the server side of the
255	   protocol, since it produces and provides media streams, and the MC
256	   side as the client side of the protocol, since it requests and
257	   receives media streams.  The messages that are exchanged to set up
258	   the telepresence media session are described by focusing on a single
259	   MP-MC dialogue.

261	   The MP first advertises its available media captures and encoding
262	   capabilities to the MC, as well as its simultaneity constraints,
263	   according to the information model defined in
264	   [I-D.ietf-clue-framework].  The CLUE message conveying the MP's
265	   multimedia offer is the ADVERTISEMENT message.  Such message
266	   leverages the XML data model definitions provided in
267	   [I-D.ietf-clue-data-model-schema].

269	   The MC selects the desired streams of the MP by using the CONFIGURE
270	   message, which makes reference to the information carried in the
271	   previously received ADVERTISEMENT.

273	   Besides ADVERTISEMENT and CONFIGURE, other messages have been
274	   conceived in order to provide all the needed mechanisms and
275	   operations.  Such messages will be detailed in the following
276	   sections.

278	4.  Protocol messages

280	   CLUE protocol messages are textual, XML-based messages that enable
281	   the configuration of the telepresence session.  The formal definition
282	   of such messages is provided in the XML Schema provided at the end of
283	   this document (Section 9).

285	   The XML definitions of the CLUE information provided in
286	   [I-D.ietf-clue-data-model-schema] are included within some CLUE
287	   protocol messages (namely the ADVERTISEMENT and the CONFIGURE
288	   messages), in order to use the concepts defined in
289	   [I-D.ietf-clue-framework].

291	   The CLUE protocol messages are the following:

293	   o  OPTIONS

295	   o  OPTIONS RESPONSE

297	   o  ADVERTISEMENT (ADV)

299	   o  ADVERTISEMENT ACKNOWLEDGEMENT (ACK)

301	   o  CONFIGURE (CONF)

303	   o  CONFIGURE RESPONSE (CONF RESPONSE)

305	   While the OPTIONS and OPTIONS RESPONSE messages are exchanged in the
306	   initiation phase between the CPs, the other messages are involved in
307	   MP-MC dialogues.

309	   Each CLUE message inherits a basic structure depicted in the
310	   following excerpt:

312	<!-- CLUE MESSAGE TYPE -->
313	<xs:complexType name="clueMessageType" abstract="true">
314	<xs:sequence>
315	<xs:element name="clueId" type="xs:string"/>
316	<xs:element name="sequenceNr" type="xs:positiveInteger"/>
317	</xs:sequence>
318	<xs:attribute name="protocol" type="xs:string" fixed="CLUE" use="required"/>
319	<xs:attribute name="v" type="versionType" use="required"/>
320	</xs:complexType>

322	<!-- VERSION TYPE -->
323	<xs:simpleType name="versionType">
324	<xs:restriction base="xs:string">
325	<xs:pattern value="([0-9])+\.([0-9]+)"></xs:pattern>
326	</xs:restriction>
327	</xs:simpleType>

329	   The basic structure determines the mandatory information that is
330	   carried within each CLUE message.  Such an information is made by:

332	   o  clueId: an XML element containing the identifier (in the form of a
333	      generic string) of the CP within the telepresence system;

335	   o  sequenceNr: an XML element containing the local message sequence
336	      number.  The sender must increment the sequence numbers by one for
337	      each new message sent, the receiver must remember the most recent
338	      sequence number received and send back a 401 error if it receives
339	      a message with an unexpected sequence number;

341	   o  protocol: a mandatory attribute set to "CLUE", identifying the
342	      procotol the messages refer to;

344	   o  v: a mandatory attribute carrying the version of the protocol.
345	      The content of the "v" attribute is composed by the major version
346	      number followed by a dot and then by the minor version number of
347	      the CLUE protocol in use.  Allowed values are of this kind: "1.3",
348	      "2.45", etc.

350	   Each CP should manage up to three (independent) streams of sequence
351	   numbers: (i) one for the messages exchanged in the initiation phase,
352	   (ii) one for the messages exchanged as MP, and (iii) one for the
353	   messages exchanged as MC.

355	4.1.  OPTIONS

357	   The OPTIONS message is sent by the CP which is the CI to the CP which
358	   is the CR as soon as the CLUE data channel is ready.  Besides the
359	   information envisioned in the basic structure, it specifies:

361	   o  mediaProvider: a mandatory boolean field set to "true" if the CP
362	      is able to act as a MP

364	   o  mediaConsumer: a mandatory boolean field set to "true" if the CP
365	      is able to act as a MC

367	   o  supportedVersions: the list of the supported versions

369	   o  supportedOptions: the list of the supported options

371	   The XML Schema of such a message is reported below:

373	<!-- CLUE OPTIONS -->
374	<xs:complexType name="optionsMessageType">
375	<xs:complexContent>
376	<xs:extension base="clueMessageType">
377	<xs:sequence>
378	<xs:element name="mediaProvider" type="xs:boolean"/>
379	<xs:element name="mediaConsumer" type="xs:boolean"/>
380	<xs:element name="supportedVersions" type="versionsListType" minOccurs="0"/>
381	<xs:element name="supportedOptions" type="optionsListType" minOccurs="0"/>
382	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
383	</xs:sequence>
384	<xs:anyAttribute namespace="##other" processContents="lax"/>
385	</xs:extension>
386	</xs:complexContent>
387	</xs:complexType>

389	<!-- VERSIONS LIST TYPE -->
390	<xs:complexType name="versionsListType">
391	<xs:sequence>
392	<xs:element name="version" type="versionType" minOccurs="1"
393	 maxOccurs="unbounded"/>
394	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
395	</xs:sequence>
396	<xs:anyAttribute namespace="##other" processContents="lax"/>
397	</xs:complexType>

399	<!-- OPTIONS LIST TYPE -->
400	<xs:complexType name="optionsListType">
401	<xs:sequence>
402	<xs:element name="option" type="optionType" minOccurs="1"
403	 maxOccurs="unbounded"/>
404	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
405	</xs:sequence>
406	<xs:anyAttribute namespace="##other" processContents="lax"/>
407	</xs:complexType>

409	<!-- OPTION TYPE -->
410	<xs:complexType name="optionType">
411	<xs:sequence>
412	<xs:element name="name" type="xs:string" />
413	<xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
414	<xs:element name="version" type="versionType" minOccurs="0"/>
415	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
416	</xs:sequence>
417	<xs:anyAttribute namespace="##other" processContents="lax"/>
418	</xs:complexType>
419	   <supportedVersions> contains the list of the versions that are
420	   supported by the CI, each one represented in a child <version>
421	   element.  The content of each <version> element is a string made by
422	   the major version number followed by a dot and then by the minor
423	   version number (e.g., 1.3 or 2.43).  Only one <version> element MUST
424	   be provided for each major version supported, containing the maximum
425	   minor version number of such a version, since all minor versions are
426	   backward compatible.  If no <supportedVersions> is carried within the
427	   OPTIONS message, the CI supports only the version declared in the "v"
428	   attribute and all the versions having the same major version number
429	   and lower minor version number.  For example, if the "v" attribute
430	   has a value of "3.4" and there is no <supportedVersions> tag in the
431	   OPTIONS message, it means the CI supports only major version 3 with
432	   all the minor versions comprised between 3.0 and 3.4, with version
433	   3.4 included.  If a <supportedVersion> is provided, at least one
434	   <version> tag MUST be included.

436	   The <supportedOptions> element specifies the list of options
437	   supported by the CI.  If there is no <supportedOptions> in the
438	   OPTIONS message, the CI does not support anything other than what is
439	   envisioned in the versions it supports.  For each option, an <option>
440	   element is provided.  An option is characterized by a name, an XML
441	   schema of reference where the option is defined, and the version of
442	   the protocol which the option refers to.

444	4.2.  OPTIONS RESPONSE

446	   The OPTIONS RESPONSE is sent by a CR to a CI as a reply to the
447	   OPTIONS message.  As depicted in the figure below, the OPTIONS
448	   RESPONSE contains mandatorily a response code and a reason string
449	   indicating the processing result of the OPTIONS message.  If the
450	   responseCode is of the type 2xx the response MUST also include
451	   <mediaProvider>, <mediaConsumer>, <version> and <commonOptions>
452	   elements; it MAY include them for any other response code.
453	   <mediaProvider> and <mediaConsumer> elements are associated with the
454	   supported roles (in terms of, respectively MP and MC), similarly to
455	   what the CI does in the OPTIONS message.  The <version> field
456	   indicates the highest commonly supported version number.  The content
457	   of the <version> element MUST be a string made of the major version
458	   number followed by a dot and then by the minor version number (e.g.,
459	   1.3 or 2.43).  Finally, the commonly supported options are copied in
460	   the the <commonOptions> field.

462	 <!-- CLUE OPTIONS RESPONSE -->
463	 <xs:complexType name="optionsResponseMessageType">
464	 <xs:complexContent>
465	 <xs:extension base="clueMessageType">
466	 <xs:sequence>
467	 <xs:element name="responseCode" type="xs:short"/>
468	 <xs:element name="reasonString" type="xs:string"/>
469	 <xs:element name="mediaProvider" type="xs:boolean" minOccurs="0"/>
470	 <xs:element name="mediaConsumer" type="xs:boolean" minOccurs="0"/>
471	 <xs:element name="version" type="versionType" minOccurs="0"/>
472	 <xs:element name="commonOptions" type="optionsListType" minOccurs="0"/>
473	 <xs:any namespace="##other"
474	 processContents="lax" minOccurs="0"/>
475	 </xs:sequence>
476	 <xs:anyAttribute namespace="##other" processContents="lax"/>
477	 </xs:extension>
478	 </xs:complexContent>
479	 </xs:complexType>

481	   After the reception of such a message, the version to be used is
482	   determined by each part of the conversation.  Indeed, it is the one
483	   provided in the <version> tag of the OPTIONS RESPONSE message.  The
484	   following CLUE messages MUST use such a version number in the "v"
485	   attribute.  The allowed options in the CLUE dialogue will be those
486	   indicated in the <commonOptions> of the OPTIONS RESPONSE message.

488	4.3.  ADVERTISEMENT

490	   The ADVERTISEMENT message (ADV) is used by the MP to advertise the
491	   available media captures and related information to the MC.  The MP
492	   sends to the MC an ADV as soon as it is ready after the successful
493	   completion of the initiation phase, i.e., as soon as the version and
494	   the options of the CLUE protocol are agreed between the CPs.  During
495	   a single CLUE session, an MP may send new ADV messages to replace the
496	   previously advertised options, if, for instance, its media CLUE
497	   telepresence capabilities change mid-call.  A new ADV completely
498	   invalidates the previous ADV.

500	   The ADV structure is defined in the picture below.  The ADV contains
501	   elements compliant with the CLUE data model that characterize the
502	   MP's telepresence offer.  Namely, such elements are: the list of the
503	   media captures (<mediaCaptures>), of the encoding groups
504	   (<encodingGroups>), of the capture scenes (<captureScenes>), of the
505	   simultaneous sets (<simultaneousSets>), of the global views
506	   (<globalViews>), and of the represented participants (<people>).
507	   Each of them is fully described in the CLUE framework document and
508	   formally defined in the CLUE data model document.

510	   <!-- CLUE ADVERTISEMENT MESSAGE TYPE -->
511	   <xs:complexType name="advertisementMessageType">
512	   <xs:complexContent>
513	   <xs:extension base="clueMessageType">
514	   <xs:sequence>
515	   <!-- mandatory -->
516	   <xs:element name="mediaCaptures" type="dm:mediaCapturesType"/>
517	   <xs:element name="encodingGroups" type="dm:encodingGroupsType"/>
518	   <xs:element name="captureScenes" type="dm:captureScenesType"/>
519	   <!-- optional -->
520	   <xs:element name="simultaneousSets" type="dm:simultaneousSetsType"
521	    minOccurs="0"/>
522	   <xs:element name="globalViews" type="dm:globalViewsType"
523	    minOccurs="0"/>
524	   <xs:element name="people" type="dm:peopleType" minOccurs="0"/>
525	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
526	   </xs:sequence>
527	   <xs:anyAttribute namespace="##other" processContents="lax"/>
528	   </xs:extension>
529	   </xs:complexContent>
530	   </xs:complexType>

532	4.4.  ADVERTISEMENT ACKNOWLEDGEMENT

534	   The ADVERTISEMENT ACKNOWLEDGEMENT message (ACK) is sent by a MC to a
535	   MP to acknowledge an ADV message.  As it can be seen from the message
536	   schema provided in the following, the ACK contains a response code
537	   and a reason string for describing the processing result of the ADV.
538	   The <advSequenceNr> carries the sequence number of the ADV the ACK
539	   refers to.

541	   <!-- ADV ACK MESSAGE TYPE -->
542	   <xs:complexType name="advAcknowledgementMessageType">
543	   <xs:complexContent>
544	   <xs:extension base="clueMessageType">
545	   <xs:sequence>
546	   <xs:element name="responseCode" type="xs:short"/>
547	   <xs:element name="reasonString" type="xs:string"/>
548	   <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
549	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
550	   </xs:sequence>
551	   <xs:anyAttribute namespace="##other" processContents="lax"/>
552	   </xs:extension>
553	   </xs:complexContent>
554	   </xs:complexType>

556	4.5.  CONFIGURE

558	   The CONFIGURE message (CONF) is sent from a MC to a MP to list the
559	   advertised captures the MC wants to receive.  The MC can send a CONF
560	   after the reception of an ADV or each time it wants to request other
561	   captures that have been previously advertised by the MP.  The content
562	   of the CONF message is shown below.

564	    <!-- CLUE CONFIGURE MESSAGE TYPE -->
565	   <xs:complexType name="configureMessageType">
566	   <xs:complexContent>
567	   <xs:extension base="clueMessageType">
568	   <xs:sequence>
569	   <!-- mandatory fields -->
570	   <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
571	   <xs:element name="ack" type="xs:boolean" minOccurs="0" fixed="true"/>
572	   <xs:element name="captureEncodings" type="dm:captureEncodingsType"
573	    minOccurs="0"/>
574	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
575	   </xs:sequence>
576	   <xs:anyAttribute namespace="##other" processContents="lax"/>
577	   </xs:extension>
578	   </xs:complexContent>
579	   </xs:complexType>

581	   The <advSequenceNr> element contains the sequence number of the ADV
582	   message the CONF refers to.

584	   The optional boolean <ack> element, set to "true", if present,
585	   indicates that the CONF message also acknowledges the referred
586	   advertisement, by applying in that way a piggybacking mechanism for
587	   simultaneously acknowledging and replying to the ADV message.  In the
588	   above case, the CONF message MUST carry a 200 (Success) response
589	   code.  The <ack> element MUST not be present if an ACK message has
590	   been already sent back to the MP.

592	   The most important content of the CONFIGURE message is the list of
593	   the capture encodings provided in the <captureEncodings> element.
594	   Such an element contains a sequence of capture encodings,
595	   representing the streams to be instantiated.

597	4.6.  CONFIGURE RESPONSE
598	   <!-- CONFIGURE RESPONSE MESSAGE TYPE -->
599	   <xs:complexType name="configureResponseMessageType">
600	   <xs:complexContent>
601	   <xs:extension base="clueMessageType">
602	   <xs:sequence>
603	   <xs:element name="responseCode" type="xs:short"/>
604	   <xs:element name="reasonString" type="xs:string"/>
605	   <xs:element name="confSequenceNr" type="xs:positiveInteger"/>
606	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
607	   </xs:sequence>
608	   <xs:anyAttribute namespace="##other" processContents="lax"/>
609	   </xs:extension>
610	   </xs:complexContent>
611	   </xs:complexType>

613	   The CONFIGURE RESPONSE message (CONF RESPONSE) is sent from the MP to
614	   the MC to communicate the processing result of requests carried in
615	   the previously received CONF message.  It contains a response code
616	   with a reason string indicating either the success or the failure
617	   (along with failure details) of a CONF request processing.
618	   Following, the <confSequenceNr> field contains the sequence number of
619	   the CONF message the response refers to.

621	4.7.  Response codes and reason strings

623	   The response codes and strings defined for use with CLUE are as
624	   follows:

626	   +-----------------+----------------------+--------------------------+
627	   |                 |                      |                          |
628	   |  Response code  |  Reason string       |       Description        |
629	   |                 |                      |                          |
630	   +-----------------+----------------------+--------------------------+
631	   |                 |                      |                          |
632	   |   200           |  Success             |  The request has been    |
633	   |                 |                      |  successfully processed. |
634	   |                 |                      |                          |
635	   +-----------------+----------------------+--------------------------+
636	   |                 |                      |                          |
637	   |   300           |  Bad syntax          |  The XML syntax of the   |
638	   |                 |                      |  message is not          |
639	   |                 |                      |  correct.                |
640	   +-----------------+----------------------+--------------------------+
641	   |                 |                      |                          |
642	   |   301           |  Invalid value       |  The message             |
643	   |                 |                      |  contains an invalid     |
644	   |                 |                      |  parameter value.        |
645	   +-----------------+----------------------+--------------------------+
646	   |                 |                      |                          |
647	   |   302           |  Conflicting values  |  The message             |
648	   |                 |                      |  contains values that    |
649	   |                 |                      |  cannot be used together.|
650	   +-----------------+----------------------+--------------------------+
651	   |                 |                      |                          |
652	   |   400           | Version not supported|  The protocol version    |
653	   |                 |                      |  used in the message     |
654	   |                 |                      |  is not supported.       |
655	   |                 |                      |                          |
656	   +-----------------+----------------------+--------------------------+
657	   |                 |                      |                          |
658	   |   401           |  Invalid sequencing  |  The sequence number of  |
659	   |                 |                      |  the message is out      |
660	   |                 |                      |  of date.                |
661	   +-----------------+----------------------+--------------------------+
662	   |                 |                      |                          |
663	   |   402           |  Invalid identifier  |  The identifier used in  |
664	   |                 |                      |  the message is          |
665	   |                 |                      |  not valid or unknown.   |
666	   +-----------------+----------------------+--------------------------+
667	   |                 |                      |                          |
668	   |   403           |  ADV Expired         |  The number of the ADV   |
669	   |                 |                      |  the CONF refers to is   |
670	   |                 |                      |  out of date.            |
671	   +-----------------+----------------------+--------------------------+
672	   |                 |                      |                          |
673	   |   404           |  Subset choice not   |  The subset choice is not|
674	   |                 |  allowed             | allowed for the specified|
675	   |                 |                      |  MCC                     |
676	   +-----------------+----------------------+--------------------------+

678	   Response codes are defined as a sequence of three digits.  A well-
679	   defined meaning is associated with the first digit.  Response codes
680	   beginning with "2" are associated with successful responses.
681	   Response codes beginning with "1" will represent a delayed or
682	   incomplete response.  Response codes that do not begin with either
683	   "2" or "1" indicate an error response, i.e., that an error occurred
684	   while processing a CLUE request.  In particular, response codes
685	   beginning with "3" indicate problems with the XML content of the
686	   message ("Bad syntax", "Invalid value", etc.), while response codes
687	   beginning with "4" refer to problems related to CLUE protocol
688	   semantics ("Invalid sequencing", "Version not supported", etc.).
689	   Further response codes can be designed in future versions of the
690	   protocol, provided they do not overwrite the ones here defined and
691	   they respect the semantics of the first code digit.

693	5.  Protocol state machines

695	   The CLUE protocol is an application protocol used between two CPs in
696	   order to properly configure a multimedia telepresence session.  CLUE
697	   protocol messages flow upon the CLUE Data Channel, a DTLS/SCTP
698	   channel established as depicted in [I-D.ietf-clue-datachannel].  We
699	   herein discuss the state machines associated, respectively, with the
700	   CLUE Participant, with the MC process and with the MP process.
701	   Endpoints often wish to both send a receive media, i.e., act as both
702	   MP and MC.  As such there will often be two sets of messages flowing
703	   in opposite directions; the state machines of these two flows do not
704	   interact with each other.  Only the CLUE application logic is
705	   considered.  The interaction of CLUE protocol and SDP negotiations
706	   for the media streams exchanged is treated in
707	   [I-D.ietf-clue-signaling].

709	6.  CLUE Participant's state machine

711	   The main state machines focus on the behavior of the CLUE Participant
712	   (CP) acting as a CLUE channel initiator/receiver (CI/CR).

714	   The initial state is the IDLE one.  When in the IDLE state, the CLUE
715	   data channel is not established and no CLUE-controlled media are
716	   exchanged between the two considered CLUE-capable devices (if there
717	   is an ongoing exchange of media streams, such media streams are not
718	   currently CLUE-controlled).

720	   When the CLUE data channel set up starts ("start channel"), the CP
721	   moves from the IDLE state to the CHANNEL SETUP state.

723	   If the CLUE data channel is successfully set up ("channel
724	   established"), the CP moves from the CHANNEL SETUP state to the
725	   OPTIONS state.  Otherwise ("channel error"), it moves back to the
726	   IDLE state.  The same transition happens if the CLUE-enabled
727	   telepresence session ends ("session ends"), i.e., when an SDP
728	   negotiation for removing the CLUE channel is performed.

730	   When in the OPTIONS state, the CP addresses the initiation phase
731	   where both parts agree on the version and on the options to be used
732	   in the subsequent CLUE messages exchange phase.  If the CP is the
733	   Channel Initiator (CI), it sends an OPTIONS message and waits for the
734	   OPTIONS RESPONSE message.  If the CP is the Channel Receiver (CR), it
735	   waits for the OPTIONS message and, as soon as it arrives, replies
736	   with the OPTIONS RESPONSE message.  If the negotiation is
737	   successfully completed ("OPTIONS phase success"), the CP moves from
738	   the OPTIONS state to the ACTIVE state.  If the initiation phase fails
739	   ("OPTIONS phase failure"), the CP moves from the OPTIONS state to the
740	   IDLE state.  The initiation phase might fail because of one of the
741	   following reasons:

743	   1.  the CI receives an OPTIONS RESPONSE with an error response code

745	   2.  the CI does not receive any OPTIONS RESPONSE and a timeout error
746	       is raised

748	   3.  the CR does not receive any OPTIONS and a timeout error is raised

750	   When in the ACTIVE state, the CP starts the envisioned sub-state
751	   machines (i.e., the MP state machine and the MC state machine)
752	   according to the roles it plays in the telepresence sessions.  Such
753	   roles have been previously declared in the OPTIONS and OPTIONS
754	   RESPONSE messages involved in the initiation phase (see OPTIONS
755	   sections Section 4.1 and Section 4.2 for the details).  When in the
756	   ACTIVE state, the CP delegates the sending and the processing of the
757	   CLUE messages to the appropriate MP/MC sub-state machines.  If the CP
758	   receives a further OPTIONS/OPTIONS RESPONSE message, it MUST ignore
759	   the message and stay in the ACTIVE state.

761	   The CP moves from the ACTIVE state to the IDLE one when the sub-state
762	   machines that have been activated are (both) in the relative
763	   TERMINATED state (see sections Section 6.1 and Section 6.2).

765	                                  +----+
766	          +---------------------->|IDLE|<----------------------------+
767	          |                       +-+--+                             |
768	          |                         |                                |
769	          |                         |  start                         |
770	          |                         |  channel                       |
771	          |                         v                                |
772	          |  channel error/      +--------+                          |
773	          |  session ends        | CHANNEL|                          |
774	          +----------------------+ SETUP  |                          |
775	          |                      +--+-----+                          |
776	          |                         |                                |
777	          |                         |  channel                       |
778	          |                         |  established                   |
779	          |  channel error/         v                 OPTIONS phase  |
780	          |  session ends         +-------+           failure        |
781	          +-----------------------+OPTIONS+--------------------------+
782	          |                       +-+-----+                          |
783	          |                         |                                |
784	          |                         |  OPTIONS phase                 |
785	          |                         |  success                       |
786	          |                         v                                |
787	          |   channel error/     +---------+                         |
788	          |   session ends       | ACTIVE  |                         |
789	          +----------------------+         |                         |
790	                                 | +----+  +------------------+      |
791	                                 | | MP |  |    send/receive  |      |
792	                                 | +----+  |    CLUE messages |      |
793	                                 |         |<-----------------+      |
794	                                 | +----+  |                         |
795	                                 | | MC |  |both sub state machines  |
796	                                 | +----+  |terminated               |
797	                                 |         |                         |
798	                                 +---------+-------------------------+

800	6.1.  Media Provider's state machine

802	   As soon as the sub-state machine of the MP is activated, it is in the
803	   ADV state.  In the ADV state, the MP is preparing the ADV message
804	   reflecting its actual telepresence capabilities.

806	   After the ADV has been sent ("ADV sent"), the MP moves from the ADV
807	   state to the WAIT FOR ACK state.  If an ACK message with a successful
808	   response code arrives ("ACK received"), the MP moves to the WAIT FOR
809	   CONF state.  If a NACK arrives (i.e., an ACK message with an error
810	   response code), and the number of NACKs for the issued ADV is under
811	   the retry threshold ("NACK received && retry not expired"), the MP
812	   moves back to the ADV state for preparing a new ADV.  If a NACK
813	   arrives and the number of received NACKs for that ADV overcomes the
814	   threshold ("NACK received and && retry expired"), the MP goes to the
815	   MP-TERMINATED state.  The same happens if the waiting time for the
816	   ACK is fired a number of times under the retry threshold ("timeout &&
817	   retry not expired"): also in this case, the MP goes back to the ADV
818	   state to send a new copy of the ADV.  If the number of retries
819	   overcomes the threshold ("timeout && retry expired"), the MP moves
820	   from the WAIT FOR ACK state to the MP-TERMINATED state.  When in the
821	   WAIT FOR ACK state, if a CONFIGURE message with the <ack> element set
822	   to TRUE arrives ("CONF+ACK received"), the MP goes directly to the
823	   CONF RESPONSE state.  CONF+ACK messages referring to out-of-date
824	   (i.e., having a sequence number equal to or less than the highest
825	   seen so far) ADVs MUST be ignored, i.e., they do not trigger any
826	   state transition.  If the telepresence settings of the MP change
827	   while in the WAIT FOR ACK state ("changed telepresence settings"),
828	   the MP switches from the WAIT FOR ACK state to the ADV state to
829	   create a new ADV.

831	   When in the WAIT FOR CONF state, the MP listens to the channel for a
832	   CONF request coming from the MC.  If a CONF arrives ("CONF
833	   received"), the MP switches to the CONF RESPONSE state.  If the CONF
834	   does not arrive within the timeout interval and the retry threshold
835	   has not been overcome ("timeout && retry not expired"), the MP moves
836	   back to the ADV state.  When the retry expires ("timeout && retry
837	   expired") the MP moves to the MP TERMINATED state.  If the
838	   telepresence settings change in the meanwhile ("changed telepresence
839	   settings"), the MP moves from the WAIT FOR CONF back to the ADV state
840	   to create the new ADV to be sent to the MC.

842	   The MP in the CONF RESPONSE state processes the received CONF in
843	   order to produce a CONF RESPONSE message.  If the MP successfully
844	   processes the MC's configuration, then it sends a 200 CONF RESPONSE
845	   ("success CONF RESPONSE sent") and moves to the ESTABLISHED state.
846	   If there are errors in the CONF processing, then the MP issues a CONF
847	   RESPONSE carrying an error response code and, if under the retry
848	   treshold ("error CONF RESPONSE sent && retry not expired"), it goes
849	   back to the WAIT FOR CONF state to wait for a new configuration
850	   request.  If the number of trials exceeds the retry threshold ("error
851	   CONF RESPONSE sent && retry expired"), the state MP TERMINATED is
852	   reached.  Finally, if there are changes in the MP's telepresence
853	   settings ("changed telepresence settings"), the MP switches to the
854	   ADV state.

856	   The MP in the ESTABLISHED state has successfully negotiated the media
857	   streams with the MC by means of the CLUE messages.  If there are
858	   changes in the MP's telepresence settings ("changed telepresence
859	   settings"), the MP moves back to the ADV state.  In the ESTABLISHED
860	   state, the CLUE-controlled media streams of the session are those
861	   described in the last successfully processed CONF message.

863	+------------------------->+-----+<---------------------------+
864	|            +------------>| ADV |<-------------------+       |
865	|            |             +-+---+                    |       |timeout
866	|            |               |       NACK received    |       |&&
867	|            |       ADV sent|             &&         |       |retry
868	|            |               v       retry not expired|       |not
869	|     changed|             +--------+                 |       |expired
870	|telepresence+-------------+WAIT FOR+-----------------+       |
871	|    settings|   +---------+  ACK   +-------------------------+
872	|            |   |CONF+ACK +-+------+------------------------------------+
873	|            |   |received   |                          NACK received && |
874	|            |   |           |ACK received                 retry expired,|
875	|            |   |           v                   timeout && retry expired|
876	+------------|-------------+--------+                                    |
877	timeout      +-------------+WAIT FOR| timeout && retry expired           |
878	&&           |   |         |  CONF  +------------------------------------+
879	retry        |   |         +-+------+<-------------------------------+   |
880	not expired  |   |           |                                       |   |
881	             |   |           |CONF received                          |   |
882	             |   |           v               error CONF RESPONSE sent|   |
883	             |   +-------->+---------+        && retry not expired   |   |
884	             +-------------+CONF     |-------------------------------+   |
885	    +--------------------->|RESPONSE +-----------------------------------+
886	    |        |             +-+-------+           error CONF RESPONSE sent|
887	    |        |               |                           && retry expired|
888	    |        |               |  success                                  |
889	    |        |               |  CONF RESPONSE                            |
890	    |        |               |  sent                                     |
891	    |        |               |                                           |
892	    |        |               |                                           |
893	    |CONF    |               |                                           |
894	    |received|               v                                           |
895	    |        |             +------------+                                |
896	    |        +-------------+ESTABLISHED |                                |
897	    +----------------------+------------+                                |
898	                                                                         |
899	                                                                         |
900	                                                                         |
901	                           +-----------+                                 |
902	                           !    MP     |                                 |
903	                           |TERMINATED |                                 |
904	                           +-----------+<--------------------------------+

906	6.2.  Media Consumer's state machine

908	   As soon as the sub-state machine of the MC is activated, it is in the
909	   WAIT FOR ADV state.  An MC in the WAIT FOR ADV state is waiting for
910	   an ADV coming from the MP.  If the ADV arrives ("ADV received"), the
911	   MC reaches the ADV PROCESSING state.  Otherwise, the MC is stuck in
912	   the WAIT FOR ADV state.

914	   In the ADV PROCESSING state, the ADV is parsed by the MC.  If the ADV
915	   is successfully processed, there are two possibilities.  According to
916	   the first one, the MC issues a successful ACK message to the MP ("ACK
917	   sent") and moves to the CONF state.  In the second one, the MC
918	   prepares and sends a CONF message with the <ack> field set to "true"
919	   ("CONF+ACK sent") and goes directly to the WAIT FOR CONF RESPONSE
920	   state.

922	   If the ADV elaboration is unsuccessful (bad syntax, missing XML
923	   elements, etc.), and the number of times this has happened is under
924	   the retry treshold, the MC sends a NACK message (i.e., an ACK with an
925	   error response code) to the MP describing the problem via a proper
926	   reason phrase.  By this way ("NACK sent && retry not expired"), the
927	   MC switches back to the WAIT FOR ADV state, waiting for a new ADV.
928	   If the NACK retry expires ("NACK sent && retry expired"), the MC
929	   moves to the MC TERMINATED state.

931	   When in the CONF state, the MC is preparing the CONF request to be
932	   issued to the MP on the basis of the previously ACK-ed ADV.  When the
933	   CONF has been sent ("CONF sent"), the MC moves to the WAIT FOR CONF
934	   RESPONSE state.  If a new ADV arrives in the meanwhile ("ADV
935	   received"), the MC goes back to the ADV PROCESSING state.

937	   In the WAIT FOR CONF RESPONSE state, the MC is waiting for the MP's
938	   response to the issued CONF or CONF+ACK.  If a 200 CONF RESPONSE
939	   message is received ("successful CONF RESPONSE received"), it means
940	   that the MP and the MC have successfully agreed on the media streams
941	   to be shared.  Then, the MC can move to the ESTABLISHED state.  On
942	   the other hand, if an error response is received and the associated
943	   retry counter does not overcome the threshold ("error CONF RESPONSE
944	   received && retry not expired"), the MC moves back to the CONF state
945	   to prepare a new CONF request.  In case of "error CONF RESPONSE
946	   received && retry expired", the MC moves to the MC TERMINATED state.
947	   If no CONF RESPONSE arrives and the number of timeouts is under the
948	   threshold ("timeout && retry not expired"), the MC moves to the CONF
949	   state and sends again the CONF message.  If no CONF RESPONSE arrives
950	   and the number of timeouts is over the threshold ("timeout && retry
951	   expired"), the MC moves to the MC TERMINATED state.  If a new ADV is
952	   received in the WAIT FOR CONF RESPONSE state, the MC switches to the
953	   ADV PROCESSING state.

955	   When the MC is in the ESTABLISHED state, the telepresence session
956	   configuration has been set up at the CLUE application level according
957	   to the MC's preferences.  Both the MP and the MC have agreed on (and
958	   are aware of) the CLUE-controlled media streams to be exchanged
959	   within the call.  While in the ESTABLISHED state, it might happen
960	   that the MC decides to change something in the call settings.  The MC
961	   then issues a new CONF ("CONF sent") and goes to wait for the new
962	   CONF RESPONSE in the WAIT FOR CONF RESPONSE state.  On the other
963	   hand, in the ESTABLISHED state, if a new ADV arrives from the MP
964	   ("ADV received"), it means that something has changed on the MP's
965	   side.  The MC then moves to the ADV PROCESSING state.

967	                           +----------+
968	                           | WAIT FOR |
969	                           |   ADV    |
970	                           +----+-----+<--------+
971	                                |               |
972	                        ADV     |      NACK sent|
973	                        received|      && retry |
974	                                v    not expired|    NACK sent &&
975	                           +-----------+--------+    retry expired
976	                           |  ADV      +---------------------------+
977	                           | PROCESSING|<-----------------------+  |
978	                           +-+-----+---+                        |  |
979	                             |     |                            |  |
980	                   CONF+ACK  |     |  ACK                       |  |
981	                     sent    |     |  sent                      |  |
982	                             |     v                            |  |
983	                             |  +-----+                         |  |
984	                             |  |CONF |            ADV received |  |
985	       +----------------------->|     +-------------------------+  |
986	       |                     |  +--+--+                         |  |
987	       |error CONF RESPONSE  |     |        error CONF RESPONSE |  |
988	       |received &&          |     | CONF   received &&         |  |
989	       |retry not expired,   |     | sent   retry expired       |  |
990	       |timeout &&           |     |      +------------------------+
991	       |retry not expired    v     v      |                     |  |
992	       +------------------+---------------+        ADV received |  |
993	               +--------->|   WAIT FOR    +---------------------+  |
994	               |          |  CONF RESPONSE+------------------------+
995	               |          +-------+-------+       timeout&&     |  |
996	               |                  |             retry expired   |  |
997	               |                  |                             |  |
998	               |                  |successful                   |  |
999	               |                  |CONF RESPONSE                |  |
1000	               |                  |received                     |  |
1001	               |                  v                             |  |
1002	               |CONF sent   +-----------+           ADV received|  |
1003	               +------------+ESTABLISHED+-----------------------+  |
1004	                            +-----------+                          |
1005	                                                                   |
1006	                                                                   |
1007	                                                                   |
1008	                             +-----------+                         |
1009	                             |   MC      |<------------------------+
1010	                             |TERMINATED |
1011	                             +-----------+

1013	7.  Versioning

1015	   CLUE protocol messages are XML messages compliant to the CLUE
1016	   protocol XML schema [I-D.ietf-clue-data-model-schema].  The version
1017	   of the protocol corresponds to the version of the schema.  Both
1018	   client and server have to test the compliance of the received
1019	   messages with the XML schema of the CLUE protocol.  If the compliance
1020	   is not verified, the message cannot be processed further.

1022	   Obviously, client and server cannot communicate if they do not share
1023	   exactly the same XML schema.  Such a schema associated with the CLUE
1024	   URN "urn:ietf:params:xml:ns:clue-protocol".  If all CLUE-enabled
1025	   devices use that schema there will be no interoperability problems
1026	   due to schema issues.

1028	   The version of the XML schema contained in the standard document
1029	   deriving from this draft will be 1.0.  The version usage is similar
1030	   in philosophy to XMPP ([RFC6120]).  A version number has major and
1031	   minor components, each a non-negative integer.  Major version changes
1032	   denote non-interoperable changes.  Minor version changes denote
1033	   schema changes that are backward compatible by ignoring unknown XML
1034	   elements, or other backward compatible changes.

1036	   The minor versions of the XML schema MUST be backward compatible, not
1037	   only in terms of schema but also semantically and procedurally as
1038	   well.  This means that they should define further features and
1039	   functionality besides those defined in the previous versions, in an
1040	   incremental way, without impacting the basic rules defined in the
1041	   previous version of the schema.  In this way, if a MP is able to
1042	   speak, e.g., version 1.5 of the protocol while the MC only
1043	   understands version 1.4, the MP should have no problem in reverting
1044	   the dialogue back to version 1.4 without exploiting 1.5 features and
1045	   functionality.

1047	   It is expected that, before the CLUE protocol XML schema reaches a
1048	   steady state, prototypes developed by different organizations will
1049	   conduct interoperability testing.  In that case, in order to
1050	   interoperate, they have to be compliant to the current version of the
1051	   XML schema, i.e., the one copied in the most up-to-date version of
1052	   the draft defining the CLUE protocol.  The versions of the non-
1053	   standard XML schema will be numbered as 0.01, 0.02, and so on.
1054	   During the standard development phase, the versions of the XML schema
1055	   will probably not be backward compatible so it is left to prototype
1056	   implementers the responsibility of keeping their products up to date.

1058	8.  Extensions and options

1060	   Although the standard version of the CLUE protocol XML schema is
1061	   designed to thoroughly cope with the requirements emerging from the
1062	   application domain, new needs might arise and extensions can be
1063	   designed.  Extensions specify information and behaviors that are not
1064	   described in a certain version of the protocol.  They can relate to:

1066	   1.  new information, to be carried in the existing messages.  For
1067	       example, we may want to add more fields within an existing
1068	       message;

1070	   2.  new messages.  This is the case if there is no proper message for
1071	       a certain task, so a brand new CLUE message needs to be defined.

1073	   As to the first type of extensions, it is possible to distinguish
1074	   between protocol-specific and data model information.  Indeed, CLUE
1075	   messages are envelopes carrying both:

1077	   o  (i) XML elements defined within the CLUE protocol XML schema
1078	      itself (protocol-specific information)

1080	   o  (ii) other XML elements compliant to the CLUE data model schema
1081	      (data model information)

1083	   When new protocol-specific information is needed somewhere in the
1084	   protocol messages, it can be added in place of the <any> elements and
1085	   <anyAttribute> elements envisioned by the protocol schema.  The
1086	   policy currently defined in the protocol schema for handling <any>
1087	   and <anyAttribute> elements is:

1089	   o  elementFormDefault="qualified"

1091	   o  attributeFormDefault="unqualified"

1093	   In that case, the new information must be qualified by namespaces
1094	   other than "urn:ietf:params:xml:ns:clue-protocol" (the protocol URN)
1095	   and "urn:ietf:params:xml:ns:clue-info" (the data model URN).
1096	   Elements or attributes from unknown namespaces MUST be ignored.

1098	   The other matter concerns data model information.  Data model
1099	   information is defined by the XML schema associated with the URN
1100	   "urn:ietf:params:xml:ns:clue-info".  Also for the XML elements
1101	   defined in such a schema there are extensibility issues.  Those
1102	   issues are overcome by using <any> and <anyAttribute> placeholders.
1103	   Similarly to what said before, new information within data model
1104	   elements can be added in place of <any> and <anyAttribute> schema
1105	   elements, as long as they are properly namespace qualified.

1107	   On the other hand (second type of extensions), "extra" CLUE protocol
1108	   messages, i.e., messages not envisioned in the latest standard
1109	   version of the schema, can be needed.  In that case, the messages and
1110	   the associated behavior should be defined in external documents that
1111	   both communication parties must be aware of.

1113	   Both types of extensions, i.e., new information and new messages, can
1114	   be characterized by:

1116	   o  a name;

1118	   o  an external XML Schema defining the XML information and/or the XML
1119	      messages representing the extension;

1121	   o  the standard version of the protocol the extension refers to.

1123	   For that reason, the extensions can be represented by means of the
1124	   <option> element as defined below, which is carried within the
1125	   OPTIONS and OPTIONS RESPONSE messages to represent the extensions
1126	   supported by the CI and by the CR.

1128	   <!-- OPTION TYPE -->
1129	   <xs:complexType name="optionType">
1130	   <xs:sequence>
1131	   <xs:element name="name" type="xs:string" />
1132	   <xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1133	   <xs:element name="version" type="versionType" minOccurs="0"/>
1134	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1135	   </xs:sequence>
1136	   <xs:anyAttribute namespace="##other" processContents="lax"/>
1137	   </xs:complexType>

1139	9.  XML Schema

1141	   In this section, the XML schema defining the CLUE messages is
1142	   provided.

1144	<?xml version="1.0" encoding="UTF-8" ?>
1145	<xs:schema
1146	version="0.6"
1147	targetNamespace="urn:ietf:params:xml:ns:clue-protocol"
1148	xmlns:tns="urn:ietf:params:xml:ns:clue-protocol"
1149	xmlns:xs="http://www.w3.org/2001/XMLSchema"
1150	xmlns:dm="urn:ietf:params:xml:ns:clue-info"
1151	xmlns="urn:ietf:params:xml:ns:clue-protocol"
1152	elementFormDefault="qualified"
1153	attributeFormDefault="unqualified">

1155	<!-- Import data model schema -->
1156	<xs:import namespace="urn:ietf:params:xml:ns:clue-info"
1157	schemaLocation="data-model-schema-09.xsd"/>

1159	<!-- ELEMENT DEFINITIONS -->
1160	<xs:element name="options" type="optionsMessageType"/>
1161	<xs:element name="optionsResponse" type="optionsResponseMessageType"/>
1162	<xs:element name="advertisement" type="advertisementMessageType"/>
1163	<xs:element name="ack" type="advAcknowledgementMessageType"/>
1164	<xs:element name="configure" type="configureMessageType"/>
1165	<xs:element name="configureResponse" type="configureResponseMessageType"/>

1167	<!-- CLUE MESSAGE TYPE -->
1168	<xs:complexType name="clueMessageType" abstract="true">
1169	<xs:sequence>
1170	<xs:element name="clueId" type="xs:string"/>
1171	<xs:element name="sequenceNr" type="xs:positiveInteger"/>
1172	</xs:sequence>
1173	<xs:attribute name="protocol" type="xs:string" fixed="CLUE" use="required"/>
1174	<xs:attribute name="v" type="versionType" use="required"/>
1175	</xs:complexType>

1177	<!-- VERSION TYPE -->
1178	<xs:simpleType name="versionType">
1179	<xs:restriction base="xs:string">
1180	<xs:pattern value="([0-9])+\.([0-9]+)"></xs:pattern>
1181	</xs:restriction>
1182	</xs:simpleType>

1184	<!-- RESPONSE CODE TYPE -->
1185	<xs:simpleType name="responseCodeType">
1186	  <xs:restriction base="xs:integer">
1187	   <xs:pattern value="[1-9][0-9][0-9]"/>
1188	  </xs:restriction>
1189	</xs:simpleType>

1191	<!-- CLUE OPTIONS -->
1192	<xs:complexType name="optionsMessageType">
1193	<xs:complexContent>
1194	<xs:extension base="clueMessageType">
1195	<xs:sequence>
1196	<xs:element name="mediaProvider" type="xs:boolean"/>
1197	<xs:element name="mediaConsumer" type="xs:boolean"/>
1198	<xs:element name="supportedVersions" type="versionsListType" minOccurs="0"/>
1199	<xs:element name="supportedOptions" type="optionsListType" minOccurs="0"/>
1200	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1201	</xs:sequence>
1202	<xs:anyAttribute namespace="##other" processContents="lax"/>
1203	</xs:extension>
1204	</xs:complexContent>
1205	</xs:complexType>

1207	<!-- VERSIONS LIST TYPE -->
1208	<xs:complexType name="versionsListType">
1209	<xs:sequence>
1210	<xs:element name="version" type="versionType" minOccurs="1"
1211	 maxOccurs="unbounded"/>
1212	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1213	</xs:sequence>
1214	<xs:anyAttribute namespace="##other" processContents="lax"/>
1215	</xs:complexType>

1217	<!-- OPTIONS LIST TYPE -->
1218	<xs:complexType name="optionsListType">
1219	<xs:sequence>
1220	<xs:element name="option" type="optionType" minOccurs="1"
1221	 maxOccurs="unbounded"/>
1222	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1223	</xs:sequence>
1224	<xs:anyAttribute namespace="##other" processContents="lax"/>
1225	</xs:complexType>

1227	<!-- OPTION TYPE -->
1228	<xs:complexType name="optionType">
1229	<xs:sequence>
1230	<xs:element name="name" type="xs:string" />
1231	<xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1232	<xs:element name="version" type="versionType" minOccurs="0"/>
1233	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1234	</xs:sequence>
1235	<xs:anyAttribute namespace="##other" processContents="lax"/>
1236	</xs:complexType>

1238	<!-- CLUE OPTIONS RESPONSE -->
1239	<xs:complexType name="optionsResponseMessageType">
1240	<xs:complexContent>
1241	<xs:extension base="clueMessageType">
1242	<xs:sequence>
1243	<xs:element name="responseCode" type="responseCodeType"/>
1244	<xs:element name="reasonString" type="xs:string"/>
1245	<xs:element name="mediaProvider" type="xs:boolean" minOccurs="0"/>
1246	<xs:element name="mediaConsumer" type="xs:boolean" minOccurs="0"/>
1247	<xs:element name="version" type="versionType" minOccurs="0"/>
1248	<xs:element name="commonOptions" type="optionsListType" minOccurs="0"/>
1249	<xs:any namespace="##other"
1250	processContents="lax" minOccurs="0"/>
1251	</xs:sequence>
1252	<xs:anyAttribute namespace="##other" processContents="lax"/>
1253	</xs:extension>
1254	</xs:complexContent>
1255	</xs:complexType>

1257	<!-- CLUE ADVERTISEMENT MESSAGE TYPE -->
1258	<xs:complexType name="advertisementMessageType">
1259	<xs:complexContent>
1260	<xs:extension base="clueMessageType">
1261	<xs:sequence>
1262	<!-- mandatory -->
1263	<xs:element name="mediaCaptures" type="dm:mediaCapturesType"/>
1264	<xs:element name="encodingGroups" type="dm:encodingGroupsType"/>
1265	<xs:element name="captureScenes" type="dm:captureScenesType"/>
1266	<!-- optional -->
1267	<xs:element name="simultaneousSets" type="dm:simultaneousSetsType"
1268	 minOccurs="0"/>
1269	<xs:element name="globalViews" type="dm:globalViewsType"
1270	 minOccurs="0"/>
1271	<xs:element name="people" type="dm:peopleType" minOccurs="0"/>
1272	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1273	</xs:sequence>
1274	<xs:anyAttribute namespace="##other" processContents="lax"/>
1275	</xs:extension>
1276	</xs:complexContent>
1277	</xs:complexType>

1279	<!-- ACK MESSAGE TYPE -->
1280	<xs:complexType name="advAcknowledgementMessageType">
1281	<xs:complexContent>
1282	<xs:extension base="clueMessageType">
1283	<xs:sequence>
1284	<xs:element name="responseCode" type="responseCodeType"/>
1285	<xs:element name="reasonString" type="xs:string"/>
1286	<xs:element name="advSequenceNr" type="xs:positiveInteger"/>
1287	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1288	</xs:sequence>
1289	<xs:anyAttribute namespace="##other" processContents="lax"/>
1290	</xs:extension>
1291	</xs:complexContent>
1292	</xs:complexType>

1294	<!-- CLUE CONFIGURE MESSAGE TYPE -->
1295	<xs:complexType name="configureMessageType">
1296	<xs:complexContent>
1297	<xs:extension base="clueMessageType">
1298	<xs:sequence>
1299	<xs:element name="advSequenceNr" type="xs:positiveInteger"/>
1300	<xs:element name="ack" type="xs:boolean"
1301	 minOccurs="0" fixed="true"/>
1302	<xs:element name="captureEncodings" type="dm:captureEncodingsType"
1303	 minOccurs="0"/>
1304	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1305	</xs:sequence>
1306	<xs:anyAttribute namespace="##other" processContents="lax"/>
1307	</xs:extension>
1308	</xs:complexContent>
1309	</xs:complexType>

1311	<!-- CONFIGURE RESPONSE MESSAGE TYPE -->
1312	<xs:complexType name="configureResponseMessageType">
1313	<xs:complexContent>
1314	<xs:extension base="clueMessageType">
1315	<xs:sequence>
1316	<xs:element name="responseCode" type="responseCodeType"/>
1317	<xs:element name="reasonString" type="xs:string"/>
1318	<xs:element name="confSequenceNr" type="xs:positiveInteger"/>
1319	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1320	</xs:sequence>
1321	<xs:anyAttribute namespace="##other" processContents="lax"/>
1322	</xs:extension>
1323	</xs:complexContent>
1324	</xs:complexType>

1326	</xs:schema>

1328	10.  Examples

1330	   In the following we provide an example of ADVERTISEMENT representing
1331	   the telepresence environment described in
1332	   [I-D.ietf-clue-data-model-schema], Section "Sample XML file" and
1333	   Section "MCC example" respectively.

1335	10.1.  Simple ADV

1337	   The associated Media Provider's telepresence capabilities are
1338	   described in [I-D.ietf-clue-data-model-schema], Section "Sample XML
1339	   file".

1341	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1342	<advertisement xmlns="urn:ietf:params:xml:ns:clue-protocol"
1343	               xmlns:ns2="urn:ietf:params:xml:ns:clue-info"
1344	               xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0"
1345	               protocol="CLUE" v="0.4">
1346	    <clueId>Napoli</clueId>
1347	    <sequenceNr>45</sequenceNr>
1348	    <mediaCaptures>
1349	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1350	         xsi:type="ns2:videoCaptureType"  captureID="AC0" mediaType="video">
1351	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1352	            <ns2:encGroupIDREF>EG1</ns2:encGroupIDREF>
1353	            <ns2:spatialInformation>
1354	                <ns2:capturePoint>
1355	                    <ns2:x>0.5</ns2:x>
1356	                    <ns2:y>1.0</ns2:y>
1357	                    <ns2:z>0.5</ns2:z>
1358	                    <ns2:lineOfCapturePoint>
1359	                        <ns2:x>0.5</ns2:x>
1360	                        <ns2:y>0.0</ns2:y>
1361	                        <ns2:z>0.5</ns2:z>
1362	                    </ns2:lineOfCapturePoint>
1363	                </ns2:capturePoint>
1364	            </ns2:spatialInformation>
1365	            <ns2:individual>true</ns2:individual>
1366	            <ns2:description lang="en">main audio from the room</ns2:description>
1367	            <ns2:priority>1</ns2:priority>
1368	            <ns2:lang>it</ns2:lang>
1369	            <ns2:mobility>static</ns2:mobility>
1370	            <ns2:view>room</ns2:view>
1371	            <ns2:capturedPeople>
1372	                <ns2:personIDREF>alice</ns2:personIDREF>
1373	                <ns2:personIDREF>bob</ns2:personIDREF>
1374	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1375	            </ns2:capturedPeople>
1376	        </ns2:mediaCapture>
1377	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1378	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC0">
1379	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1380	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1381	            <ns2:spatialInformation>
1382	                <ns2:capturePoint>
1383	                    <ns2:x>0.5</ns2:x>
1384	                    <ns2:y>1.0</ns2:y>
1385	                    <ns2:z>0.5</ns2:z>
1386	                    <ns2:lineOfCapturePoint>
1387	                        <ns2:x>0.5</ns2:x>
1388	                        <ns2:y>0.0</ns2:y>
1389	                        <ns2:z>0.5</ns2:z>
1390	                    </ns2:lineOfCapturePoint>
1391	                </ns2:capturePoint>
1392	            </ns2:spatialInformation>
1393	            <ns2:individual>true</ns2:individual>
1394	            <ns2:description lang="en">left camera video capture
1395	            </ns2:description>
1396	            <ns2:priority>1</ns2:priority>
1397	            <ns2:lang>it</ns2:lang>
1398	            <ns2:mobility>static</ns2:mobility>
1399	            <ns2:view>individual</ns2:view>
1400	            <ns2:capturedPeople>
1401	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1402	            </ns2:capturedPeople>
1403	        </ns2:mediaCapture>
1404	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1405	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC1">
1406	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1407	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1408	            <ns2:spatialInformation>
1409	                <ns2:capturePoint>
1410	                    <ns2:x>0.5</ns2:x>
1411	                    <ns2:y>1.0</ns2:y>
1412	                    <ns2:z>0.5</ns2:z>
1413	                    <ns2:lineOfCapturePoint>
1414	                        <ns2:x>0.5</ns2:x>
1415	                        <ns2:y>0.0</ns2:y>
1416	                        <ns2:z>0.5</ns2:z>
1417	                    </ns2:lineOfCapturePoint>
1418	                </ns2:capturePoint>
1419	            </ns2:spatialInformation>
1420	            <ns2:individual>true</ns2:individual>
1421	            <ns2:description lang="en">central camera video capture
1422	            </ns2:description>
1423	            <ns2:priority>1</ns2:priority>
1424	            <ns2:lang>it</ns2:lang>
1425	            <ns2:mobility>static</ns2:mobility>
1426	            <ns2:view>individual</ns2:view>
1427	            <ns2:capturedPeople>
1428	                <ns2:personIDREF>alice</ns2:personIDREF>
1429	            </ns2:capturedPeople>
1430	        </ns2:mediaCapture>
1431	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1432	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC2">
1433	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1434	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1435	            <ns2:spatialInformation>
1436	                <ns2:capturePoint>
1437	                    <ns2:x>0.5</ns2:x>
1438	                    <ns2:y>1.0</ns2:y>
1439	                    <ns2:z>0.5</ns2:z>
1440	                    <ns2:lineOfCapturePoint>
1441	                        <ns2:x>0.5</ns2:x>
1442	                        <ns2:y>0.0</ns2:y>
1443	                        <ns2:z>0.5</ns2:z>
1444	                    </ns2:lineOfCapturePoint>
1445	                </ns2:capturePoint>
1446	            </ns2:spatialInformation>
1447	            <ns2:individual>true</ns2:individual>
1448	            <ns2:description lang="en">right camera video capture
1449	            </ns2:description>
1450	            <ns2:priority>1</ns2:priority>
1451	            <ns2:lang>it</ns2:lang>
1452	            <ns2:mobility>static</ns2:mobility>
1453	            <ns2:view>individual</ns2:view>
1454	            <ns2:capturedPeople>
1455	                <ns2:personIDREF>bob</ns2:personIDREF>
1456	            </ns2:capturedPeople>
1457	        </ns2:mediaCapture>
1458	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1459	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC3">
1460	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1461	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1462	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1463	            <ns2:composed>false</ns2:composed>
1464	            <ns2:switched>true</ns2:switched>
1465	            <ns2:policy>Soundlevel:0</ns2:policy>
1466	            <ns2:maxCaptures>1</ns2:maxCaptures>
1467	            <ns2:description lang="en">loudest room segment</ns2:description>
1468	            <ns2:priority>1</ns2:priority>
1469	            <ns2:lang>it</ns2:lang>
1470	            <ns2:mobility>static</ns2:mobility>
1471	            <ns2:view>individual</ns2:view>
1472	        </ns2:mediaCapture>
1473	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1474	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC4">
1475	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1476	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1477	            <ns2:spatialInformation>
1478	                <ns2:capturePoint>
1479	                    <ns2:x>0.5</ns2:x>
1480	                    <ns2:y>1.0</ns2:y>
1481	                    <ns2:z>0.5</ns2:z>
1482	                    <ns2:lineOfCapturePoint>
1483	                        <ns2:x>0.5</ns2:x>
1484	                        <ns2:y>0.0</ns2:y>
1485	                        <ns2:z>0.5</ns2:z>
1486	                    </ns2:lineOfCapturePoint>
1487	                </ns2:capturePoint>
1488	            </ns2:spatialInformation>
1489	            <ns2:individual>true</ns2:individual>
1490	            <ns2:description lang="en">zoomed out view of all people in
1491	            the room
1492	            </ns2:description>
1493	            <ns2:priority>1</ns2:priority>
1494	            <ns2:lang>it</ns2:lang>
1495	            <ns2:mobility>static</ns2:mobility>
1496	            <ns2:view>room</ns2:view>
1497	            <ns2:capturedPeople>
1498	                <ns2:personIDREF>alice</ns2:personIDREF>
1499	                <ns2:personIDREF>bob</ns2:personIDREF>
1500	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1501	            </ns2:capturedPeople>
1502	        </ns2:mediaCapture>
1503	    </mediaCaptures>
1504	    <encodingGroups>
1505	        <ns2:encodingGroup encodingGroupID="EG0">
1506	            <ns2:maxGroupBandwidth>600000</ns2:maxGroupBandwidth>
1507	            <ns2:encodingIDList>
1508	                <ns2:encID>ENC1</ns2:encID>
1509	                <ns2:encID>ENC2</ns2:encID>
1510	                <ns2:encID>ENC3</ns2:encID>
1511	            </ns2:encodingIDList>
1512	        </ns2:encodingGroup>
1513	        <ns2:encodingGroup encodingGroupID="EG1">
1514	            <ns2:maxGroupBandwidth>300000</ns2:maxGroupBandwidth>
1515	            <ns2:encodingIDList>
1516	                <ns2:encID>ENC4</ns2:encID>
1517	                <ns2:encID>ENC5</ns2:encID>
1518	            </ns2:encodingIDList>
1519	        </ns2:encodingGroup>
1520	    </encodingGroups>
1521	    <captureScenes>
1522	        <ns2:captureScene scale="unknown" sceneID="CS1">
1523	            <ns2:sceneViews>
1524	                <ns2:sceneView sceneViewID="SE1">
1525	                    <ns2:mediaCaptureIDs>
1526	                        <ns2:captureIDREF>VC0</ns2:captureIDREF>
1527	                        <ns2:captureIDREF>VC1</ns2:captureIDREF>
1528	                        <ns2:captureIDREF>VC2</ns2:captureIDREF>

1530	                    </ns2:mediaCaptureIDs>
1531	                </ns2:sceneView>
1532	                <ns2:sceneView sceneViewID="SE2">
1533	                    <ns2:mediaCaptureIDs>
1534	                        <ns2:captureIDREF>VC3</ns2:captureIDREF>
1535	                    </ns2:mediaCaptureIDs>
1536	                </ns2:sceneView>
1537	                <ns2:sceneView sceneViewID="SE3">
1538	                    <ns2:mediaCaptureIDs>
1539	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1540	                    </ns2:mediaCaptureIDs>
1541	                </ns2:sceneView>
1542	                <ns2:sceneView sceneViewID="SE4">
1543	                    <ns2:mediaCaptureIDs>
1544	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1545	                    </ns2:mediaCaptureIDs>
1546	                </ns2:sceneView>
1547	            </ns2:sceneViews>
1548	        </ns2:captureScene>
1549	    </captureScenes>
1550	    <simultaneousSets>
1551	        <ns2:simultaneousSet setID="SS1">
1552	            <ns2:mediaCaptureIDREF>VC3</ns2:mediaCaptureIDREF>
1553	            <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1554	        </ns2:simultaneousSet>
1555	        <ns2:simultaneousSet setID="SS2">
1556	            <ns2:mediaCaptureIDREF>VC0</ns2:mediaCaptureIDREF>
1557	            <ns2:mediaCaptureIDREF>VC2</ns2:mediaCaptureIDREF>
1558	            <ns2:mediaCaptureIDREF>VC4</ns2:mediaCaptureIDREF>
1559	            <ns2:mediaCaptureIDREF>VC3</ns2:mediaCaptureIDREF>
1560	        </ns2:simultaneousSet>
1561	    </simultaneousSets>
1562	    <people>
1563	        <ns2:person personID="bob">
1564	            <ns2:personInfo>
1565	                <ns3:fn>
1566	                    <ns3:text>Bob</ns3:text>
1567	                </ns3:fn>
1568	            </ns2:personInfo>
1569	            <ns2:personType>minute taker</ns2:personType>
1570	        </ns2:person>
1571	        <ns2:person personID="alice">
1572	            <ns2:personInfo>
1573	                <ns3:fn>
1574	                    <ns3:text>Alice</ns3:text>
1575	                </ns3:fn>
1576	            </ns2:personInfo>
1577	            <ns2:personType>presenter</ns2:personType>

1579	        </ns2:person>
1580	        <ns2:person personID="ciccio">
1581	            <ns2:personInfo>
1582	                <ns3:fn>
1583	                    <ns3:text>Ciccio</ns3:text>
1584	                </ns3:fn>
1585	            </ns2:personInfo>
1586	            <ns2:personType>chairman</ns2:personType>
1587	            <ns2:personType>timekeeper</ns2:personType>
1588	        </ns2:person>
1589	    </people>
1590	</advertisement>

1592	10.2.  ADV with MCCs

1594	   The associated Media Provider's telepresence capabilities are
1595	   described in [I-D.ietf-clue-data-model-schema], Section "MCC
1596	   example".

1598	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1599	<advertisement xmlns="urn:ietf:params:xml:ns:clue-protocol"
1600	 xmlns:ns2="urn:ietf:params:xml:ns:clue-info"
1601	 xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0" protocol="CLUE" v="0.4">
1602	    <clueId>Napoli CLUE Endpoint</clueId>
1603	    <sequenceNr>34</sequenceNr>
1604	    <mediaCaptures>
1605	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1606	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="AC0">
1607	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1608	            <ns2:encGroupIDREF>EG1</ns2:encGroupIDREF>
1609	            <ns2:spatialInformation>
1610	                <ns2:capturePoint>
1611	                    <ns2:x>0.5</ns2:x>
1612	                    <ns2:y>1.0</ns2:y>
1613	                    <ns2:z>0.5</ns2:z>
1614	                    <ns2:lineOfCapturePoint>
1615	                        <ns2:x>0.5</ns2:x>
1616	                        <ns2:y>0.0</ns2:y>
1617	                        <ns2:z>0.5</ns2:z>
1618	                    </ns2:lineOfCapturePoint>
1619	                </ns2:capturePoint>
1620	            </ns2:spatialInformation>
1621	            <ns2:individual>true</ns2:individual>
1622	            <ns2:description lang="en">main audio from the room</ns2:description>
1623	            <ns2:priority>1</ns2:priority>
1624	            <ns2:lang>it</ns2:lang>
1625	            <ns2:mobility>static</ns2:mobility>
1626	            <ns2:view>room</ns2:view>
1627	            <ns2:capturedPeople>
1628	                <ns2:personIDREF>alice</ns2:personIDREF>
1629	                <ns2:personIDREF>bob</ns2:personIDREF>
1630	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1631	            </ns2:capturedPeople>
1632	        </ns2:mediaCapture>
1633	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1634	         xsi:type="ns2:videoCaptureType" captureID="VC0" mediaType="video" >
1635	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1636	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1637	            <ns2:spatialInformation>
1638	                <ns2:capturePoint>
1639	                    <ns2:x>0.5</ns2:x>
1640	                    <ns2:y>1.0</ns2:y>
1641	                    <ns2:z>0.5</ns2:z>
1642	                    <ns2:lineOfCapturePoint>
1643	                        <ns2:x>0.5</ns2:x>
1644	                        <ns2:y>0.0</ns2:y>
1645	                        <ns2:z>0.5</ns2:z>
1646	                    </ns2:lineOfCapturePoint>
1647	                </ns2:capturePoint>
1648	            </ns2:spatialInformation>
1649	            <ns2:individual>true</ns2:individual>
1650	            <ns2:description lang="en">left camera video capture</ns2:description>
1651	            <ns2:priority>1</ns2:priority>
1652	            <ns2:lang>it</ns2:lang>
1653	            <ns2:mobility>static</ns2:mobility>
1654	            <ns2:view>individual</ns2:view>
1655	            <ns2:capturedPeople>
1656	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1657	            </ns2:capturedPeople>
1658	        </ns2:mediaCapture>
1659	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1660	        xsi:type="ns2:videoCaptureType" captureID="VC1" mediaType="video">
1661	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1662	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1663	            <ns2:spatialInformation>
1664	                <ns2:capturePoint>
1665	                    <ns2:x>0.5</ns2:x>
1666	                    <ns2:y>1.0</ns2:y>
1667	                    <ns2:z>0.5</ns2:z>
1668	                    <ns2:lineOfCapturePoint>
1669	                        <ns2:x>0.5</ns2:x>
1670	                        <ns2:y>0.0</ns2:y>
1671	                        <ns2:z>0.5</ns2:z>
1672	                    </ns2:lineOfCapturePoint>
1673	                </ns2:capturePoint>
1674	            </ns2:spatialInformation>
1675	            <ns2:individual>true</ns2:individual>
1676	            <ns2:description lang="en">central camera video capture
1677	            </ns2:description>
1678	            <ns2:priority>1</ns2:priority>
1679	            <ns2:lang>it</ns2:lang>
1680	            <ns2:mobility>static</ns2:mobility>
1681	            <ns2:view>individual</ns2:view>
1682	            <ns2:capturedPeople>
1683	                <ns2:personIDREF>alice</ns2:personIDREF>
1684	            </ns2:capturedPeople>
1685	        </ns2:mediaCapture>
1686	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1687	        xsi:type="ns2:videoCaptureType" captureID="VC2" mediaType="video" >
1688	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1689	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1690	            <ns2:spatialInformation>
1691	                <ns2:capturePoint>
1692	                    <ns2:x>0.5</ns2:x>
1693	                    <ns2:y>1.0</ns2:y>
1694	                    <ns2:z>0.5</ns2:z>
1695	                    <ns2:lineOfCapturePoint>
1696	                        <ns2:x>0.5</ns2:x>
1697	                        <ns2:y>0.0</ns2:y>
1698	                        <ns2:z>0.5</ns2:z>
1699	                    </ns2:lineOfCapturePoint>
1700	                </ns2:capturePoint>
1701	            </ns2:spatialInformation>
1702	            <ns2:individual>true</ns2:individual>
1703	            <ns2:description lang="en">right camera video capture
1704	            </ns2:description>
1705	            <ns2:priority>1</ns2:priority>
1706	            <ns2:lang>it</ns2:lang>
1707	            <ns2:mobility>static</ns2:mobility>
1708	            <ns2:view>individual</ns2:view>
1709	            <ns2:capturedPeople>
1710	                <ns2:personIDREF>bob</ns2:personIDREF>
1711	            </ns2:capturedPeople>
1712	        </ns2:mediaCapture>
1713	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1714	        xsi:type="ns2:videoCaptureType" captureID="VC3" mediaType="video" >
1715	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1716	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1717	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1718	            <ns2:content>
1719	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1720	            </ns2:content>
1721	            <ns2:policy>Soundlevel:0</ns2:policy>
1722	            <ns2:maxCaptures>1</ns2:maxCaptures>
1723	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1724	            <ns2:description lang="en">loudest room segment</ns2:description>
1725	            <ns2:priority>1</ns2:priority>
1726	            <ns2:lang>it</ns2:lang>
1727	            <ns2:mobility>static</ns2:mobility>
1728	            <ns2:view>individual</ns2:view>
1729	        </ns2:mediaCapture>
1730	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1731	        xsi:type="ns2:videoCaptureType"  captureID="VC4" mediaType="video">
1732	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1733	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1734	            <ns2:spatialInformation>
1735	                <ns2:capturePoint>
1736	                    <ns2:x>0.5</ns2:x>
1737	                    <ns2:y>1.0</ns2:y>
1738	                    <ns2:z>0.5</ns2:z>
1739	                    <ns2:lineOfCapturePoint>
1740	                        <ns2:x>0.5</ns2:x>
1741	                        <ns2:y>0.0</ns2:y>
1742	                        <ns2:z>0.5</ns2:z>
1743	                    </ns2:lineOfCapturePoint>
1744	                </ns2:capturePoint>
1745	            </ns2:spatialInformation>
1746	            <ns2:individual>true</ns2:individual>
1747	            <ns2:description lang="en">zoomed out view of all people in the room
1748	            </ns2:description>
1749	            <ns2:priority>1</ns2:priority>
1750	            <ns2:lang>it</ns2:lang>
1751	            <ns2:mobility>static</ns2:mobility>
1752	            <ns2:view>room</ns2:view>
1753	            <ns2:capturedPeople>
1754	                <ns2:personIDREF>alice</ns2:personIDREF>
1755	                <ns2:personIDREF>bob</ns2:personIDREF>
1756	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1757	            </ns2:capturedPeople>
1758	        </ns2:mediaCapture>
1759	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1760	        xsi:type="ns2:videoCaptureType"  captureID="VC5" mediaType="video">
1761	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1762	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1763	            <ns2:content>
1764	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1765	            </ns2:content>
1766	            <ns2:policy>Soundlevel:1</ns2:policy>
1767	            <ns2:maxCaptures>1</ns2:maxCaptures>
1768	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1769	            <ns2:description lang="en">penultimate loudest room segment
1770	            </ns2:description>
1771	            <ns2:priority>1</ns2:priority>
1772	            <ns2:lang>it</ns2:lang>
1773	            <ns2:mobility>static</ns2:mobility>
1774	            <ns2:view>individual</ns2:view>
1775	        </ns2:mediaCapture>
1776	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1777	        xsi:type="ns2:videoCaptureType"  captureID="VC6" mediaType="video">
1778	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1779	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1780	            <ns2:content>
1781	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1782	            </ns2:content>
1783	            <ns2:composed>false</ns2:composed>
1784	            <ns2:switched>true</ns2:switched>
1785	            <ns2:policy>Soundlevel:2</ns2:policy>
1786	            <ns2:maxCaptures>1</ns2:maxCaptures>
1787	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1788	            <ns2:description lang="en">last but two loudest room segment
1789	            </ns2:description>
1790	            <ns2:priority>1</ns2:priority>
1791	            <ns2:lang>it</ns2:lang>
1792	            <ns2:mobility>static</ns2:mobility>
1793	            <ns2:view>individual</ns2:view>
1794	        </ns2:mediaCapture>
1795	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1796	        xsi:type="ns2:videoCaptureType" captureID="VC7" mediaType="video">
1797	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1798	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1799	            <ns2:content>
1800	                <ns2:captureIDREF>VC3</ns2:captureIDREF>
1801	                <ns2:captureIDREF>VC5</ns2:captureIDREF>
1802	                <ns2:captureIDREF>VC6</ns2:captureIDREF>
1803	            </ns2:content>
1804	            <ns2:composed>true</ns2:composed>
1805	            <ns2:switched>true</ns2:switched>
1806	            <ns2:maxCaptures>1</ns2:maxCaptures>
1807	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1808	            <ns2:description lang="en">big picture of the current speaker +
1809	            pips about previous speakers</ns2:description>
1810	            <ns2:priority>1</ns2:priority>
1811	            <ns2:lang>it</ns2:lang>
1812	            <ns2:mobility>static</ns2:mobility>
1813	            <ns2:view>individual</ns2:view>
1814	        </ns2:mediaCapture>

1816	    </mediaCaptures>
1817	    <encodingGroups>
1818	        <ns2:encodingGroup encodingGroupID="EG0">
1819	            <ns2:maxGroupBandwidth>600000</ns2:maxGroupBandwidth>
1820	            <ns2:encodingIDList>
1821	                <ns2:encID>ENC1</ns2:encID>
1822	                <ns2:encID>ENC2</ns2:encID>
1823	                <ns2:encID>ENC3</ns2:encID>
1824	            </ns2:encodingIDList>
1825	        </ns2:encodingGroup>
1826	        <ns2:encodingGroup encodingGroupID="EG1">
1827	            <ns2:maxGroupBandwidth>300000</ns2:maxGroupBandwidth>
1828	            <ns2:encodingIDList>
1829	                <ns2:encID>ENC4</ns2:encID>
1830	                <ns2:encID>ENC5</ns2:encID>
1831	            </ns2:encodingIDList>
1832	        </ns2:encodingGroup>
1833	    </encodingGroups>
1834	    <captureScenes>
1835	        <ns2:captureScene scale="unknown" sceneID="CS1">
1836	            <ns2:sceneViews>
1837	                <ns2:sceneView sceneViewID="SE1">
1838	                    <ns2:description lang="en">participants' individual videos
1839	                    </ns2:description>
1840	                    <ns2:mediaCaptureIDs>
1841	                        <ns2:captureIDREF>VC0</ns2:captureIDREF>
1842	                        <ns2:captureIDREF>VC1</ns2:captureIDREF>
1843	                        <ns2:captureIDREF>VC2</ns2:captureIDREF>
1844	                    </ns2:mediaCaptureIDs>
1845	                </ns2:sceneView>
1846	                <ns2:sceneView sceneViewID="SE2">
1847	                    <ns2:description lang="en">loudest segment of the room
1848	                    </ns2:description>
1849	                    <ns2:mediaCaptureIDs>
1850	                        <ns2:captureIDREF>VC3</ns2:captureIDREF>
1851	                    </ns2:mediaCaptureIDs>
1852	                </ns2:sceneView>
1853	                <ns2:sceneView sceneViewID="SE5">
1854	                    <ns2:description lang="en">loudest segment
1855	                    of the room + pips</ns2:description>
1856	                    <ns2:mediaCaptureIDs>
1857	                        <ns2:captureIDREF>VC7</ns2:captureIDREF>
1858	                    </ns2:mediaCaptureIDs>
1859	                </ns2:sceneView>
1860	                <ns2:sceneView sceneViewID="SE4">
1861	                    <ns2:description lang="en">room audio</ns2:description>
1862	                    <ns2:mediaCaptureIDs>
1863	                        <ns2:captureIDREF>AC0</ns2:captureIDREF>

1865	                    </ns2:mediaCaptureIDs>
1866	                </ns2:sceneView>
1867	                <ns2:sceneView sceneViewID="SE3">
1868	                    <ns2:description lang="en">room video</ns2:description>
1869	                    <ns2:mediaCaptureIDs>
1870	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1871	                    </ns2:mediaCaptureIDs>
1872	                </ns2:sceneView>
1873	            </ns2:sceneViews>
1874	        </ns2:captureScene>
1875	    </captureScenes>
1876	    <simultaneousSets>
1877	        <ns2:simultaneousSet setID="SS1">
1878	            <ns2:mediaCaptureIDREF>VC7</ns2:mediaCaptureIDREF>
1879	            <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1880	        </ns2:simultaneousSet>
1881	        <ns2:simultaneousSet setID="SS2">
1882	            <ns2:mediaCaptureIDREF>VC0</ns2:mediaCaptureIDREF>
1883	            <ns2:mediaCaptureIDREF>VC2</ns2:mediaCaptureIDREF>
1884	            <ns2:mediaCaptureIDREF>VC4</ns2:mediaCaptureIDREF>
1885	            <ns2:mediaCaptureIDREF>VC7</ns2:mediaCaptureIDREF>
1886	        </ns2:simultaneousSet>
1887	    </simultaneousSets>
1888	    <people>
1889	        <ns2:person personID="bob">
1890	            <ns2:personInfo>
1891	                <ns3:fn>
1892	                    <ns3:text>Bob</ns3:text>
1893	                </ns3:fn>
1894	            </ns2:personInfo>
1895	            <ns2:personType>minute taker</ns2:personType>
1896	        </ns2:person>
1897	        <ns2:person personID="alice">
1898	            <ns2:personInfo>
1899	                <ns3:fn>
1900	                    <ns3:text>Alice</ns3:text>
1901	                </ns3:fn>
1902	            </ns2:personInfo>
1903	            <ns2:personType>presenter</ns2:personType>
1904	        </ns2:person>
1905	        <ns2:person personID="ciccio">
1906	            <ns2:personInfo>
1907	                <ns3:fn>
1908	                    <ns3:text>Ciccio</ns3:text>
1909	                </ns3:fn>
1910	            </ns2:personInfo>
1911	            <ns2:personType>chairman</ns2:personType>
1912	            <ns2:personType>timekeeper</ns2:personType>

1914	        </ns2:person>
1915	    </people>
1916	</advertisement>

1918	11.  IANA Considerations

1920	   This document registers a new XML namespace, a new XML schema and the
1921	   MIME type for the schema.  This document also registers the "CLUE"
1922	   Application Service tag and the "CLUE" Application Protocol tag and
1923	   defines registries for the CLUE messages and response codes.

1925	11.1.  URN Sub-Namespace Registration

1927	   This section registers a new XML namespace,
1928	   ""urn:ietf:params:xml:ns:clue-protocol"".

1930	   URI: urn:ietf:params:xml:ns:clue-protocol

1932	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
1933	   Pietro Romano (spromano@unina.it).

1935	   XML:

1937	   BEGIN
1938	    <?xml version="1.0"?>
1939	    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
1940	      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1941	    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
1942	      <head>
1943	        <title>CLUE Messages</title>
1944	      </head>
1945	      <body>
1946	        <h1>Namespace for CLUE Messages</h1>
1947	        <h2>urn:ietf:params:xml:ns:clue-protocol</h2>
1948	   [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
1949	       with the RFC number for this specification.]]
1950	        <p>See <a href="[[RFC URL]]">
1951	           RFCXXXX</a>.</p>
1952	      </body>
1953	    </html>
1954	   END

1956	11.2.  XML Schema registration

1958	   This section registers an XML schema per the guidelines in [RFC3688].

1960	   URI: urn:ietf:params:xml:schema:clue-protocol

1962	   Registrant Contact: CLUE working group (clue@ietf.org), Simon Pietro
1963	   Romano (spromano@unina.it).

1965	   Schema: The XML for this schema can be found as the entirety of
1966	   Section 9 of this document.

1968	11.3.  MIME Media Type Registration for 'application/clue+xml'

1970	   This section registers the " "application/clue+xml"" MIME type.

1972	   To: ietf-types@iana.org

1974	   Subject: Registration of MIME media type application/clue+xml

1976	   MIME media type name: application

1978	   MIME subtype name: clue+xml

1980	   Required parameters: (none)

1982	   Optional parameters: charset
1983	   Same as the charset parameter of "application/xml" as specified in
1984	   [RFC3023], Section 3.2.

1986	   Encoding considerations: Same as the encoding considerations of
1987	   "application/xml" as specified in [RFC3023], Section 3.2.

1989	   Security considerations: This content type is designed to carry
1990	   protocol data related to telepresence session control.  Some of the
1991	   data could be considered private.  This media type does not provide
1992	   any protection and thus other mechanisms such as those described in
1993	   Section Security are required to protect the data.  This media type
1994	   does not contain executable content.

1996	   Interoperability considerations: None.

1998	   Published specification: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
1999	   replace XXXX with the RFC number for this specification.]]

2001	   Applications that use this media type: CLUE participants.

2003	   Additional Information: Magic Number(s): (none),
2004	   File extension(s): .clue,
2005	   Macintosh File Type Code(s): TEXT.

2007	   Person & email address to contact for further information: Simon
2008	   Pietro Romano (spromano@unina.it).

2010	   Intended usage: LIMITED USE

2012	   Author/Change controller: The IETF

2014	   Other information: This media type is a specialization of
2015	   application/xml [RFC3023], and many of the considerations described
2016	   there also apply to application/clue+xml.

2018	11.4.  DNS Registrations

2020	   Section 11.4.1 defines an Application Service tag of "CLUE", which is
2021	   used to identify the CLUE service.  The Application Protocol tag
2022	   "CLUE", defined in Section 11.4.2, is used to identify a CLUE
2023	   Participant that understands CLUE.

2025	11.4.1.  Application Service tag

2027	   This section registers a new S-NAPTR/U-NAPTR Application Service tag
2028	   for CLUE, as mandated by [RFC3958].

2030	   Application Service Tag: CLUE

2032	   Intended usage: Identifies a server that supports CLUE telepresence
2033	   conferencing.

2035	   Defining publication: RFCXXXX [[NOTE TO IANA/RFC-EDITOR: Please
2036	   replace XXXX with the RFC number for this specification.]]

2038	   Contact information: The authors of this document

2040	   Author/Change controller: The IESG

2042	11.4.2.  Application Protocol tag

2044	   This section registers a new S-NAPTR/U-NAPTR Application Protocol tag
2045	   for CLUE, as mandated by [RFC3958].

2047	   Application Service Tag: CLUE

2049	   Intended Usage: Identifies the CLUE Protocol.

2051	   Applicable Service Tag(s): CLUE
2052	   Terminal NAPTR Record Type(s): U

2054	   Defining Publication: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
2055	   replace XXXX with the RFC number for this specification.]]

2057	   Contact Information: The authors of this document

2059	   Author/Change Controller: The IESG

2061	11.5.  CLUE Protocol Registry

2063	   The document requests that the IANA creates new registries for CLUE
2064	   messages and response codes.

2066	11.5.1.  CLUE Message Types

2068	   The following summarizes the registry for CLUE messages:

2070	   Related Registry: CLUE Message Types Registry

2072	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2073	   with the RFC number for this specification.]]

2075	   Registration/Assignment Procedures: Following the policies outlined
2076	   in [RFC5226], the IANA policy for assigning new values for the CLUE
2077	   message types for the CLUE protocol is Specification Required.

2079	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2080	   Pietro Romano (spromano@unina.it).

2082	   The initial Message table is populated using the CLUE messages
2083	   described in Section 4 and defined in the XML schema in Section 9.

2085	   o  OPTIONS

2087	   o  OPTIONS RESPONSE

2089	   o  ADVERTISEMENT (ADV)

2091	   o  ADVERTISEMENT ACKNOWLEDGEMENT (ACK)

2093	   o  CONFIGURE (CONF)

2095	   o  CONFIGURE RESPONSE (CONF RESPONSE)

2097	11.5.2.  CLUE Response Codes

2099	   The following summarizes the requested registry for CLUE response
2100	   codes:

2102	   Related Registry: CLUE Response Code Registry

2104	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2105	   with the RFC number for this specification.]]

2107	   Registration/Assignment Procedures: Following the policies outlined
2108	   in [RFC5226], the IANA policy for assigning new values for the
2109	   Response codes for CLUE shall be Specification Required.

2111	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2112	   Pietro Romano (spromano@unina.it).

2114	   The initial Response-code table is populated using the Response codes
2115	   defined in Section 4.7 as follows:

2117	   +-----------------+----------------------+--------------------------+
2118	   |                 |                      |                          |
2119	   |  Response code  |  Response string     |       Description        |
2120	   |                 |                      |                          |
2121	   +-----------------+----------------------+--------------------------+
2122	   |                 |                      |                          |
2123	   |   200           |  Success             |  The request has been    |
2124	   |                 |                      |  successfully processed. |
2125	   |                 |                      |                          |
2126	   +-----------------+----------------------+--------------------------+
2127	   |                 |                      |                          |
2128	   |   300           |  Bad syntax          |  The XML syntax of the   |
2129	   |                 |                      |  message is not          |
2130	   |                 |                      |  correct.                |
2131	   +-----------------+----------------------+--------------------------+
2132	   |                 |                      |                          |
2133	   |   301           |  Invalid value       |  The message             |
2134	   |                 |                      |  contains an invalid     |
2135	   |                 |                      |  parameter value.        |
2136	   +-----------------+----------------------+--------------------------+
2137	   |                 |                      |                          |
2138	   |   302           |  Conflicting values  |  The message             |
2139	   |                 |                      |  contains values that    |
2140	   |                 |                      |  cannot be used together.|
2141	   +-----------------+----------------------+--------------------------+
2142	   |                 |                      |                          |
2143	   |   400           | Version not supported|  The protocol version    |
2144	   |                 |                      |  used in the message     |
2145	   |                 |                      |  is not supported.       |
2146	   |                 |                      |                          |
2147	   +-----------------+----------------------+--------------------------+
2148	   |                 |                      |                          |
2149	   |   401           |  Invalid sequencing  |  The sequence number of  |
2150	   |                 |                      |  the message is out      |
2151	   |                 |                      |  of date.                |
2152	   +-----------------+----------------------+--------------------------+
2153	   |                 |                      |                          |
2154	   |   402           |  Invalid identifier  |  The identifier used in  |
2155	   |                 |                      |  the message is          |
2156	   |                 |                      |  not valid or unknown.   |
2157	   +-----------------+----------------------+--------------------------+
2158	   |                 |                      |                          |
2159	   |   403           |  ADV Expired         |  The number of the ADV   |
2160	   |                 |                      |  the CONF refers to is   |
2161	   |                 |                      |  out of date.            |
2162	   +-----------------+----------------------+--------------------------+
2163	   |                 |                      |                          |
2164	   |   404           |  Subset choice not   |  The subset choice is not|
2165	   |                 |  allowed             | allowed for the specified|
2166	   |                 |                      |  MCC                     |
2167	   +-----------------+----------------------+--------------------------+

2169	12.  Diff with draft-ietf-clue-protocol-05

2171	   o  This document corrects some versioning errors of
2172	      draft-ietf-clue-protocol-05.

2174	13.  Diff with draft-ietf-clue-protocol-04

2176	   o  The document has been revised based on feedback recevied on the
2177	      ML.  No major modification is included in this version.

2179	14.  Diff with draft-ietf-clue-protocol-03

2181	   o  Response codes section updated.

2183	   o  maxCaptureEncodings removed from examples, allowSubsetChoice
2184	      added.

2186	   o  State machines descriptions aligned with pictures.

2188	   o  Applied recommended updates indicated in Christian's review (2015-
2189	      03-19).

2191	15.  Diff with draft-ietf-clue-protocol-02

2193	   o  CLUE Participant state machine: TERMINATED state replaced with
2194	      IDLE.

2196	   o  MP and MC state machines: SDP O/A state removed.

2198	   o  Diff mechanism (and related example) removed.

2200	   o  Schema updates: versionType used as the data type for all versions
2201	      fields, xs:unsignedInt used as the data type for all sequence
2202	      number fields, diff support removed from the ADV definition.

2204	16.  Diff with draft-ietf-clue-protocol-01

2206	   o  The diff mechanism for the ADV message has been introduced.

2208	   o  READV and READV RESPONSE message have been both removed.

2210	   o  The state machines have been deeply reviewed and changed.

2212	   o  References: references have been updated and splitted into
2213	      Informative references and Normative references as in framework
2214	      v17.

2216	   o  Schema: <globalSceneEntries> changed in <globalViews>,
2217	      <participants> in <people>

2219	   o  Terminology: many definitions added.

2221	   o  Response codes updated.

2223	17.  Diff with draft-ietf-clue-protocol-00

2225	   1.  The XML schema of the ADVERTISEMENT and of the READV have been
2226	       aligned with the current definitions in
2227	       [I-D.ietf-clue-data-model-schema] (example of updates:
2228	       <participants> --> <people>, <globalCaptureEntries> -->
2229	       <globalSceneEntries>)

2231	   2.  Text has been added to clarify that, in the OPTIONS RESPONSE,
2232	       when the response code is not an error response code, both
2233	       <mediaProvider> and <mediaConsumer> are mandatory.

2235	   3.  The content of the "v" attribute and of the <version> elements
2236	       carried in the OPTIONS and OPTIONS RESPONSE messages has been
2237	       described more precisely.

2239	   4.  Advertisement examples have been added.

2241	18.  Diff with draft-presta-clue-protocol-04

2243	   1.  The response code type error in the OPTIONS response (and in
2244	       other parts) has been corrected.

2246	19.  Diff with draft-presta-clue-protocol-03

2248	   1.  The XML Schema has been deeply revised and completed.

2250	   2.  The descriptions of the CLUE messages have been added.

2252	   3.  The distinction between major version numbers and minor version
2253	       numbers has been cut and pasted from [I-D.ietf-clue-signaling].

2255	   4.  Besides the two way one, a three way mechanism for the options
2256	       negotiation has been proposed and provided to foster discussion.

2258	20.  Diff with draft-presta-clue-protocol-02

2260	   1.  "Terminology" section added.

2262	   2.  Introduced the concept of "CLUE Participant" - an Endpoint or a
2263	       MCU able to use the CLUE protocol within a telepresence session.
2264	       A CLUE Participant can act as a Media Provider and/or as a Media
2265	       Consumer.

2267	   3.  Introduced the ACK/NACK mechanism for the ADVERTISEMENT.

2269	   4.  MP and MC state machines have been updated.  The CP state machine
2270	       has been added.

2272	21.  Acknowledgments

2274	   The authors thank all the CLUErs for their precious feedbacks and
2275	   support, in particular Paul Kyzivat, Christian Groves and Scarlett
2276	   Liuyan.

2278	22.  References
2279	22.1.  Normative References

2281	   [I-D.ietf-clue-data-model-schema]  Presta, R. and S. Romano, "An XML
2282	                                      Schema for the CLUE data model", d
2283	                                      raft-ietf-clue-data-model-schema-
2284	                                      10 (work in progress), June 2015.

2286	   [I-D.ietf-clue-datachannel]        Holmberg, C., "CLUE Protocol data
2287	                                      channel",
2288	                                      draft-ietf-clue-datachannel-10
2289	                                      (work in progress),
2290	                                      September 2015.

2292	   [I-D.ietf-clue-framework]          Duckworth, M., Pepperell, A., and
2293	                                      S. Wenger, "Framework for
2294	                                      Telepresence Multi-Streams",
2295	                                      draft-ietf-clue-framework-23 (work
2296	                                      in progress), September 2015.

2298	   [I-D.ietf-clue-signaling]          Kyzivat, P., Xiao, L., Groves, C.,
2299	                                      and R. Hansen, "CLUE Signaling",
2300	                                      draft-ietf-clue-signaling-06 (work
2301	                                      in progress), August 2015.

2303	   [RFC3023]                          Murata, M., St. Laurent, S., and
2304	                                      D. Kohn, "XML Media Types",
2305	                                      RFC 3023, DOI 10.17487/RFC3023,
2306	                                      January 2001, <http://
2307	                                      www.rfc-editor.org/info/rfc3023>.

2309	   [RFC3550]                          Schulzrinne, H., Casner, S.,
2310	                                      Frederick, R., and V. Jacobson,
2311	                                      "RTP: A Transport Protocol for
2312	                                      Real-Time Applications", STD 64,
2313	                                      RFC 3550, DOI 10.17487/RFC3550,
2314	                                      July 2003, <http://
2315	                                      www.rfc-editor.org/info/rfc3550>.

2317	   [RFC3688]                          Mealling, M., "The IETF XML
2318	                                      Registry", BCP 81, RFC 3688,
2319	                                      DOI 10.17487/RFC3688,
2320	                                      January 2004, <http://
2321	                                      www.rfc-editor.org/info/rfc3688>.

2323	   [RFC3958]                          Daigle, L. and A. Newton, "Domain-
2324	                                      Based Application Service Location
2325	                                      Using SRV RRs and the Dynamic
2326	                                      Delegation Discovery Service
2327	                                      (DDDS)", RFC 3958, DOI 10.17487/
2328	                                      RFC3958, January 2005, <http://
2329	                                      www.rfc-editor.org/info/rfc3958>.

2331	   [RFC5226]                          Narten, T. and H. Alvestrand,
2332	                                      "Guidelines for Writing an IANA
2333	                                      Considerations Section in RFCs",
2334	                                      BCP 26, RFC 5226, DOI 10.17487/
2335	                                      RFC5226, May 2008, <http://
2336	                                      www.rfc-editor.org/info/rfc5226>.

2338	22.2.  Informative References

2340	   [RFC4353]                          Rosenberg, J., "A Framework for
2341	                                      Conferencing with the Session
2342	                                      Initiation Protocol (SIP)",
2343	                                      RFC 4353, DOI 10.17487/RFC4353,
2344	                                      February 2006, <http://
2345	                                      www.rfc-editor.org/info/rfc4353>.

2347	   [RFC5117]                          Westerlund, M. and S. Wenger, "RTP
2348	                                      Topologies", RFC 5117,
2349	                                      DOI 10.17487/RFC5117,
2350	                                      January 2008, <http://
2351	                                      www.rfc-editor.org/info/rfc5117>.

2353	   [RFC6120]                          Saint-Andre, P., "Extensible
2354	                                      Messaging and Presence Protocol
2355	                                      (XMPP): Core", RFC 6120,
2356	                                      DOI 10.17487/RFC6120, March 2011,
2357	                                      <http://www.rfc-editor.org/info/
2358	                                      rfc6120>.

2360	   [RFC6502]                          Camarillo, G., Srinivasan, S.,
2361	                                      Even, R., and J. Urpalainen,
2362	                                      "Conference Event Package Data
2363	                                      Format Extension for Centralized
2364	                                      Conferencing (XCON)", RFC 6502,
2365	                                      DOI 10.17487/RFC6502, March 2012,
2366	                                      <http://www.rfc-editor.org/info/
2367	                                      rfc6502>.

2369	   [RFC6503]                          Barnes, M., Boulton, C., Romano,
2370	                                      S., and H. Schulzrinne,
2371	                                      "Centralized Conferencing
2372	                                      Manipulation Protocol", RFC 6503,
2373	                                      DOI 10.17487/RFC6503, March 2012,
2374	                                      <http://www.rfc-editor.org/info/
2375	                                      rfc6503>.

2377	   [RFC7262]                          Romanow, A., Botzko, S., and M.
2378	                                      Barnes, "Requirements for
2379	                                      Telepresence Multistreams",
2380	                                      RFC 7262, DOI 10.17487/RFC7262,
2381	                                      June 2014, <http://
2382	                                      www.rfc-editor.org/info/rfc7262>.

2384	Authors' Addresses

2386	   Roberta Presta
2387	   University of Napoli
2388	   Via Claudio 21
2389	   Napoli  80125
2390	   Italy

2392	   EMail: roberta.presta@unina.it

2394	   Simon Pietro Romano
2395	   University of Napoli
2396	   Via Claudio 21
2397	   Napoli  80125
2398	   Italy

2400	   EMail: spromano@unina.it