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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: July 6, 2017                                    January 2, 2017

7	                             CLUE protocol
8	                      draft-ietf-clue-protocol-11

10	Abstract

12	   The CLUE protocol is an application protocol conceived for the
13	   description and negotiation of a telepresence session.  The design of
14	   the CLUE protocol takes into account the requirements and the
15	   framework defined within the IETF CLUE working group.  A companion
16	   document delves into CLUE signaling details, as well as on the SIP/
17	   SDP session establishment phase.  CLUE messages flow over the CLUE
18	   data channel, based on reliable and ordered SCTP over DTLS transport.
19	   Message details, together with the behavior of CLUE Participants
20	   acting as Media Providers and/or Media Consumers, are herein
21	   discussed.

23	Status of This Memo

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

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

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

38	   This Internet-Draft will expire on July 6, 2017.

40	Copyright Notice

42	   Copyright (c) 2017 IETF Trust and the persons identified as the
43	   document authors.  All rights reserved.

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

55	Table of Contents

57	   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
58	   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
59	   3.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
60	   4.  Overview of the CLUE protocol . . . . . . . . . . . . . . . .   4
61	   5.  Protocol messages . . . . . . . . . . . . . . . . . . . . . .   6
62	     5.1.  OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . .   8
63	     5.2.  OPTIONS RESPONSE  . . . . . . . . . . . . . . . . . . . .  10
64	     5.3.  ADVERTISEMENT . . . . . . . . . . . . . . . . . . . . . .  11
65	     5.4.  ADVERTISEMENT ACKNOWLEDGEMENT . . . . . . . . . . . . . .  12
66	     5.5.  CONFIGURE . . . . . . . . . . . . . . . . . . . . . . . .  13
67	     5.6.  CONFIGURE RESPONSE  . . . . . . . . . . . . . . . . . . .  13
68	     5.7.  Response codes and reason strings . . . . . . . . . . . .  14
69	   6.  Protocol state machines . . . . . . . . . . . . . . . . . . .  16
70	     6.1.  Media Provider's state machine  . . . . . . . . . . . . .  18
71	     6.2.  Media Consumer's state machine  . . . . . . . . . . . . .  22
72	   7.  Versioning  . . . . . . . . . . . . . . . . . . . . . . . . .  25
73	   8.  Extensions and options  . . . . . . . . . . . . . . . . . . .  25
74	   9.  XML Schema  . . . . . . . . . . . . . . . . . . . . . . . . .  27
75	   10. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  31
76	     10.1.  Simple ADV . . . . . . . . . . . . . . . . . . . . . . .  31
77	     10.2.  ADV with MCCs  . . . . . . . . . . . . . . . . . . . . .  39
78	   11. Security Considerations . . . . . . . . . . . . . . . . . . .  49
79	   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  50
80	     12.1.  URN Sub-Namespace Registration . . . . . . . . . . . . .  50
81	     12.2.  XML Schema registration  . . . . . . . . . . . . . . . .  51
82	     12.3.  MIME Media Type Registration for 'application/clue+xml'   51
83	     12.4.  CLUE Protocol Registry . . . . . . . . . . . . . . . . .  52
84	       12.4.1.  CLUE Message Types . . . . . . . . . . . . . . . . .  52
85	       12.4.2.  CLUE Response Codes  . . . . . . . . . . . . . . . .  54
86	   13. Diff with draft-ietf-clue-protocol-06 . . . . . . . . . . . .  56
87	   14. Diff with draft-ietf-clue-protocol-05 . . . . . . . . . . . .  56
88	   15. Diff with draft-ietf-clue-protocol-04 . . . . . . . . . . . .  56
89	   16. Diff with draft-ietf-clue-protocol-03 . . . . . . . . . . . .  56
90	   17. Diff with draft-ietf-clue-protocol-02 . . . . . . . . . . . .  56
91	   18. Diff with draft-ietf-clue-protocol-01 . . . . . . . . . . . .  57
92	   19. Diff with draft-ietf-clue-protocol-00 . . . . . . . . . . . .  57
93	   20. Diff with draft-presta-clue-protocol-04 . . . . . . . . . . .  57
94	   21. Diff with draft-presta-clue-protocol-03 . . . . . . . . . . .  57
95	   22. Diff with draft-presta-clue-protocol-02 . . . . . . . . . . .  58
96	   23. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  58
97	   24. References  . . . . . . . . . . . . . . . . . . . . . . . . .  58
98	     24.1.  Normative References . . . . . . . . . . . . . . . . . .  58
99	     24.2.  Informative References . . . . . . . . . . . . . . . . .  59
100	   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  60

102	1.  Introduction

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

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

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

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

124	   In Section 4 we provide a general overview of the CLUE protocol.
125	   CLUE protocol messages are detailed in Section 5.  The CLUE Protocol
126	   state machines are introduced in Section 6.  Versioning and
127	   extensions are discussed in Section 7 and Section 8, respectively.
128	   The XML schema defining the CLUE messages is reported in Section 9.

130	2.  Terminology

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

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

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

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

154	   MCU:  Multipoint Control Unit (MCU) - a device that connects two or
155	      more endpoints together into one single multimedia conference
156	      [RFC7667].  An MCU may include a Mixer [RFC4353].

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

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

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

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

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

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

176	3.  Conventions

178	   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
179	   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
180	   document are to be interpreted as described in BCP 14, RFC 2119
181	   [RFC2119].

183	4.  Overview of the CLUE protocol

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

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

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

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

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

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

246	   After the negotiation phase is completed, CLUE Participants describe
247	   and agree on the media flows to be exchanged.  In many cases CPs will
248	   seek to both transmit and receive media.  Hence in a call between two
249	   CPs, A and B, there would be two separate dialogs, as follows:

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

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

259	   CLUE messages for the media session description and negotiation are
260	   designed by considering the MP side as the server side of the
261	   protocol, since it produces and provides media streams, and the MC
262	   side as the client side of the protocol, since it requests and
263	   receives media streams.  The messages that are exchanged to set up
264	   the telepresence media session are described by focusing on a single
265	   MP-MC dialogue.

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

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

279	   Besides ADVERTISEMENT and CONFIGURE, other messages have been
280	   conceived in order to provide all the needed mechanisms and
281	   operations.  Such messages are detailed in the following sections.

283	5.  Protocol messages

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

290	   The XML definitions of the CLUE information provided in
291	   [I-D.ietf-clue-data-model-schema] are included within some CLUE
292	   protocol messages (namely the ADVERTISEMENT and the CONFIGURE
293	   messages), in order to use the concepts defined in
294	   [I-D.ietf-clue-framework].

296	   The CLUE protocol messages are the following:

298	   o  OPTIONS

300	   o  OPTIONS RESPONSE

302	   o  ADVERTISEMENT (ADV)

304	   o  ADVERTISEMENT ACKNOWLEDGEMENT (ACK)

306	   o  CONFIGURE (CONF)

308	   o  CONFIGURE RESPONSE (CONF RESPONSE)

310	   While the OPTIONS and OPTIONS RESPONSE messages are exchanged in the
311	   initiation phase between the CPs, the other messages are involved in
312	   MP-MC dialogues.

314	   Each CLUE message inherits a basic structure depicted in the
315	   following excerpt:

317	   <!-- CLUE MESSAGE TYPE -->
318	   <xs:complexType name="clueMessageType" abstract="true">
319	   <xs:sequence>
320	   <xs:element name="clueId" type="xs:string"/>
321	   <xs:element name="sequenceNr" type="xs:positiveInteger"/>
322	   </xs:sequence>
323	   <xs:attribute name="protocol" type="xs:string" fixed="CLUE"
324	           use="required"/>
325	   <xs:attribute name="v" type="versionType" use="required"/>
326	   </xs:complexType>

328	   <!-- VERSION TYPE -->
329	   <xs:simpleType name="versionType">
330	   <xs:restriction base="xs:string">
331	   <xs:pattern value="[0-9]\.[0-9]"></xs:pattern>
332	   </xs:restriction>
333	   </xs:simpleType>

335	   The mandatory information contained in each CLUE message is:

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

340	   o  sequenceNr: an XML element containing the local message sequence
341	      number.  The sender must increment the sequence numbers by one for
342	      each new message sent, the receiver must remember the most recent
343	      sequence number received and send back a 402 error if it receives
344	      a message with an unexpected sequence number.  The initial
345	      sequence number can be chosen randomly by each party;

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

350	   o  v: a mandatory attribute carrying the version of the protocol.
351	      The content of the "v" attribute is composed by the major version
352	      number followed by a dot and then by the minor version number of
353	      the CLUE protocol in use.  Allowed values are of this kind are,
354	      e.g., "1.3", "2.4" etc.

356	   Each CP MUST be able to manage up to three (independent) streams of
357	   sequence numbers: (i) one for the messages exchanged in the
358	   initiation phase, (ii) one for the messages exchanged as MP, and
359	   (iii) one for the messages exchanged as MC.

361	5.1.  OPTIONS

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

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

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

373	   o  supportedVersions: the list of the supported versions

375	   o  supportedOptions: the list of the supported options

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

379	   <!-- CLUE OPTIONS -->
380	   <xs:complexType name="optionsMessageType">
381	   <xs:complexContent>
382	   <xs:extension base="clueMessageType">
383	   <xs:sequence>
384	   <xs:element name="mediaProvider" type="xs:boolean"/>
385	   <xs:element name="mediaConsumer" type="xs:boolean"/>
386	   <xs:element name="supportedVersions" type="versionsListType"
387	    minOccurs="0"/>
388	   <xs:element name="supportedOptions" type="optionsListType"
389	    minOccurs="0"/>
390	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
391	   </xs:sequence>
392	   <xs:anyAttribute namespace="##other" processContents="lax"/>
393	   </xs:extension>
394	   </xs:complexContent>
395	   </xs:complexType>

397	   <!-- VERSIONS LIST TYPE -->
398	   <xs:complexType name="versionsListType">
399	   <xs:sequence>
400	   <xs:element name="version" type="versionType" minOccurs="1"
401	    maxOccurs="unbounded"/>
402	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
403	   </xs:sequence>
404	   <xs:anyAttribute namespace="##other" processContents="lax"/>
405	   </xs:complexType>

407	   <!-- OPTIONS LIST TYPE -->
408	   <xs:complexType name="optionsListType">
409	   <xs:sequence>
410	   <xs:element name="option" type="optionType" minOccurs="1"
411	    maxOccurs="unbounded"/>
412	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
413	   </xs:sequence>
414	   <xs:anyAttribute namespace="##other" processContents="lax"/>
415	   </xs:complexType>

417	   <!-- OPTION TYPE -->
418	   <xs:complexType name="optionType">
419	   <xs:sequence>
420	   <xs:element name="name" type="xs:string" />
421	   <xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
422	   <xs:element name="version" type="versionType" minOccurs="0"/>
423	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
424	   </xs:sequence>
425	   <xs:anyAttribute namespace="##other" processContents="lax"/>
426	   </xs:complexType>

428	   <supportedVersions> contains the list of the versions that are
429	   supported by the CI, each one represented in a child <version>
430	   element.  The content of each <version> element is a string made by
431	   the major version number followed by a dot and then by the minor
432	   version number (e.g., 1.3 or 2.4).  Exactly one <version> element
433	   MUST be provided for each major version supported, containing the
434	   maximum minor version number of such a version, since all minor
435	   versions are backward compatible.  If no <supportedVersions> is
436	   carried within the OPTIONS message, the CI supports only the version
437	   declared in the "v" attribute and all the versions having the same
438	   major version number and lower minor version number.  For example, if
439	   the "v" attribute has a value of "3.4" and there is no
440	   <supportedVersions> tag in the OPTIONS message, it means the CI
441	   supports only major version 3 with all the minor versions comprised
442	   between 3.0 and 3.4, with version 3.4 included.  If a
443	   <supportedVersion> is provided, at least one <version> tag MUST be
444	   included.

446	   The <supportedOptions> element specifies the list of options
447	   supported by the CI.  If there is no <supportedOptions> in the
448	   OPTIONS message, the CI does not support anything other than what is
449	   envisioned in the versions it supports.  For each option, an <option>
450	   element is provided.  An option is characterized by a name, an XML
451	   schema of reference where the option is defined, and the version of
452	   the protocol which the option refers to.

454	5.2.  OPTIONS RESPONSE

456	   The OPTIONS RESPONSE is sent by a CR to a CI as a reply to the
457	   OPTIONS message.  As depicted in the figure below, the OPTIONS
458	   RESPONSE contains a mandatory response code and a reason string
459	   indicating the processing result of the OPTIONS message.  If the
460	   responseCode is of the type 2xx the response MUST also include
461	   <mediaProvider>, <mediaConsumer>, <version> and <commonOptions>
462	   elements; it MAY include them for any other response code.
463	   <mediaProvider> and <mediaConsumer> elements are associated with the
464	   supported roles (in terms of, respectively MP and MC), similarly to
465	   what the CI does in the OPTIONS message.  The <version> field
466	   indicates the highest commonly supported version number.  The content
467	   of the <version> element MUST be a string made of the major version
468	   number followed by a dot and then by the minor version number (e.g.,
469	   1.3 or 2.4).  Finally, the commonly supported options are copied in
470	   the <commonOptions> field.

472	 <!-- CLUE OPTIONS RESPONSE -->
473	 <xs:complexType name="optionsResponseMessageType">
474	 <xs:complexContent>
475	 <xs:extension base="clueMessageType">
476	 <xs:sequence>
477	 <xs:element name="responseCode" type="responseCodeType"/>
478	 <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
479	 <xs:element name="mediaProvider" type="xs:boolean" minOccurs="0"/>
480	 <xs:element name="mediaConsumer" type="xs:boolean" minOccurs="0"/>
481	 <xs:element name="version" type="versionType" minOccurs="0"/>
482	 <xs:element name="commonOptions" type="optionsListType" minOccurs="0"/>
483	 <xs:any namespace="##other"
484	 processContents="lax" minOccurs="0"/>
485	 </xs:sequence>
486	 <xs:anyAttribute namespace="##other" processContents="lax"/>
487	 </xs:extension>
488	 </xs:complexContent>
489	 </xs:complexType>

491	   Upon reception of the OPTIONS RESPONSE the version to be used is
492	   provided in the <version> tag of the message.  The following CLUE
493	   messages MUST use such a version number in the "v" attribute.  The
494	   allowed options in the CLUE dialogue are those indicated in the
495	   <commonOptions> of the OPTIONS RESPONSE message.

497	5.3.  ADVERTISEMENT

499	   The ADVERTISEMENT message (ADV) is used by the MP to advertise the
500	   available media captures and related information to the MC.  The MP
501	   sends an ADV to the MC as soon as it is ready after the successful
502	   completion of the initiation phase, i.e., as soon as the version and
503	   the options of the CLUE protocol are agreed between the CPs.  During
504	   a single CLUE session, an MP may send new ADV messages to replace the
505	   previous advertisement, if, for instance, its CLUE telepresence media
506	   capabilities change mid-call.  A new ADV completely replaces the
507	   previous ADV.

509	   The ADV structure is defined in the schema excerpt below.  The ADV
510	   contains elements compliant with the CLUE data model that
511	   characterize the MP's telepresence offer.  Namely, such elements are:
512	   the list of the media captures (<mediaCaptures>), of the encoding
513	   groups (<encodingGroups>), of the capture scenes (<captureScenes>),
514	   of the simultaneous sets (<simultaneousSets>), of the global views
515	   (<globalViews>), and of the represented participants (<people>).
516	   Each of them is fully described in the CLUE framework document and
517	   formally defined in the CLUE data model document.

519	   <!-- CLUE ADVERTISEMENT MESSAGE TYPE -->
520	   <xs:complexType name="advertisementMessageType">
521	   <xs:complexContent>
522	   <xs:extension base="clueMessageType">
523	   <xs:sequence>
524	   <!-- mandatory -->
525	   <xs:element name="mediaCaptures" type="dm:mediaCapturesType"/>
526	   <xs:element name="encodingGroups" type="dm:encodingGroupsType"/>
527	   <xs:element name="captureScenes" type="dm:captureScenesType"/>
528	   <!-- optional -->
529	   <xs:element name="simultaneousSets" type="dm:simultaneousSetsType"
530	    minOccurs="0"/>
531	   <xs:element name="globalViews" type="dm:globalViewsType"
532	    minOccurs="0"/>
533	   <xs:element name="people" type="dm:peopleType" minOccurs="0"/>
534	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
535	   </xs:sequence>
536	   <xs:anyAttribute namespace="##other" processContents="lax"/>
537	   </xs:extension>
538	   </xs:complexContent>
539	   </xs:complexType>

541	5.4.  ADVERTISEMENT ACKNOWLEDGEMENT

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

550	   <!-- ADV ACK MESSAGE TYPE -->
551	   <xs:complexType name="advAcknowledgementMessageType">
552	   <xs:complexContent>
553	   <xs:extension base="clueMessageType">
554	   <xs:sequence>
555	   <xs:element name="responseCode" type="responseCodeType"/>
556	   <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
557	   <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
558	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
559	   </xs:sequence>
560	   <xs:anyAttribute namespace="##other" processContents="lax"/>
561	   </xs:extension>
562	   </xs:complexContent>
563	   </xs:complexType>

565	5.5.  CONFIGURE

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

573	    <!-- CLUE CONFIGURE MESSAGE TYPE -->
574	   <xs:complexType name="configureMessageType">
575	   <xs:complexContent>
576	   <xs:extension base="clueMessageType">
577	   <xs:sequence>
578	   <!-- mandatory fields -->
579	   <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
580	   <xs:element name="ack" type="xs:boolean" minOccurs="0" fixed="true"/>
581	   <xs:element name="captureEncodings" type="dm:captureEncodingsType"
582	    minOccurs="0"/>
583	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
584	   </xs:sequence>
585	   <xs:anyAttribute namespace="##other" processContents="lax"/>
586	   </xs:extension>
587	   </xs:complexContent>
588	   </xs:complexType>

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

593	   The optional boolean <ack> element, set to "true" when present,
594	   indicates that the CONF message also acknowledges with success the
595	   referred advertisement (CONF + ACK message), by applying in that way
596	   a piggybacking mechanism for simultaneously acknowledging and
597	   replying to the ADV message.  The <ack> element MUST NOT be present
598	   if an ACK message has been already sent back to the MP.

600	   The most important content of the CONFIGURE message is the list of
601	   the capture encodings provided in the <captureEncodings> element.
602	   Such an element contains a sequence of capture encodings,
603	   representing the streams to be instantiated.

605	5.6.  CONFIGURE RESPONSE
606	   <!-- CONFIGURE RESPONSE MESSAGE TYPE -->
607	   <xs:complexType name="configureResponseMessageType">
608	   <xs:complexContent>
609	   <xs:extension base="clueMessageType">
610	   <xs:sequence>
611	   <xs:element name="responseCode" type="responseCodeType"/>
612	   <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
613	   <xs:element name="confSequenceNr" type="xs:positiveInteger"/>
614	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
615	   </xs:sequence>
616	   <xs:anyAttribute namespace="##other" processContents="lax"/>
617	   </xs:extension>
618	   </xs:complexContent>
619	   </xs:complexType>

621	   The CONFIGURE RESPONSE message (CONF RESPONSE) is sent from the MP to
622	   the MC to communicate the processing result of requests carried in
623	   the previously received CONF message.  It contains a response code
624	   with a reason string indicating either the success or the failure
625	   (along with failure details) of a CONF request processing.
626	   Following, the <confSequenceNr> field contains the sequence number of
627	   the CONF message the response refers to.  We remark that there is no
628	   partial execution of commands.  As an example, if a MP is able to
629	   understand all the selected capture encodings except one, then the
630	   whole command fails and nothing is instantiated.

632	5.7.  Response codes and reason strings

634	   Response codes are defined as a sequence of three digits.  A well-
635	   defined meaning is associated with the first digit.  Response codes
636	   beginning with "2" are associated with successful responses.
637	   Response codes beginning with "1" will represent a delayed or
638	   incomplete response.  Response codes that do not begin with either
639	   "2" or "1" indicate an error response, i.e., that an error occurred
640	   while processing a CLUE request.  In particular, response codes
641	   beginning with "3" indicate problems with the XML content of the
642	   message (""Bad syntax", "Invalid value", etc.), while response codes
643	   beginning with "4" refer to problems related to CLUE protocol
644	   semantics ("Invalid sequencing", "Version not supported", etc.).
645	   100, 200, 300 and 400 codes are considered catch-alls.  Further
646	   response codes can be designed in future versions of the protocol,
647	   provided they do not overwrite the ones here defined and they respect
648	   the semantics of the first code digit.

650	   The response codes and strings defined for use with CLUE are as
651	   follows:

653	   +-----------------+----------------------+--------------------------+
654	   |                 |                      |                          |
655	   |  Response code  |  Reason string       |       Description        |
656	   |                 |                      |                          |
657	   +-----------------+----------------------+--------------------------+
658	   |                 |                      |                          |
659	   |   200           |  Success             |  The request has been    |
660	   |                 |                      |  successfully processed. |
661	   |                 |                      |                          |
662	   +-----------------+----------------------+--------------------------+
663	   |                 |                      |                          |
664	   |   300           |  Syntax errors or    |  The XML syntax of the   |
665	   |                 |  inconsistencies     |  message is not correct  |
666	   |                 |                      |  or there are invalid    |
667	   |                 |                      |  values.                 |
668	   +-----------------+----------------------+--------------------------+
669	   |                 |                      |                          |
670	   |   301           |  Bad syntax          |  The XML syntax of the   |
671	   |                 |                      |  message is not correct. |
672	   +-----------------+----------------------+--------------------------+
673	   |                 |                      |                          |
674	   |   302           |  Invalid value       |  The message             |
675	   |                 |                      |  contains an invalid     |
676	   |                 |                      |  parameter value.        |
677	   +-----------------+----------------------+--------------------------+
678	   |                 |                      |                          |
679	   |   303           |  Conflicting values  |  The message             |
680	   |                 |                      |  contains values that    |
681	   |                 |                      |  cannot be used together.|
682	   +-----------------+----------------------+--------------------------+
683	   |                 |                      |                          |
684	   |   400           | Semantic errors      |  Semantic errors in the  |
685	   |                 |                      |  received CLUE protocol  |
686	   |                 |                      |  message.                |
687	   |                 |                      |                          |
688	   +-----------------+----------------------+--------------------------+
689	   |                 |                      |                          |
690	   |   401           | Version not supported|  The protocol version    |
691	   |                 |                      |  used in the message     |
692	   |                 |                      |  is not supported.       |
693	   |                 |                      |                          |
694	   +-----------------+----------------------+--------------------------+
695	   |                 |                      |                          |
696	   |   402           |  Invalid sequencing  |  The sequence number of  |
697	   |                 |                      |  the message is out      |
698	   |                 |                      |  of date.                |
699	   +-----------------+----------------------+--------------------------+
700	   |                 |                      |                          |
701	   |   403           |  Invalid identifier  |  The identifier used in  |
702	   |                 |                      |  the message is          |
703	   |                 |                      |  not valid or unknown.   |
704	   +-----------------+----------------------+--------------------------+
705	   |                 |                      |                          |
706	   |   404           |  ADV Expired         |  The number of the ADV   |
707	   |                 |                      |  the CONF refers to is   |
708	   |                 |                      |  out of date.            |
709	   +-----------------+----------------------+--------------------------+
710	   |                 |                      |                          |
711	   |   405           |  Subset choice not   |  The subset choice is not|
712	   |                 |  allowed             | allowed for the specified|
713	   |                 |                      |  MCC                     |
714	   +-----------------+----------------------+--------------------------+

716	6.  Protocol state machines

718	   The CLUE protocol is an application protocol used between two CPs in
719	   order to properly configure a multimedia telepresence session.  CLUE
720	   protocol messages flow over the CLUE Data Channel, a DTLS/SCTP
721	   channel established as depicted in [I-D.ietf-clue-datachannel].  We
722	   herein discuss the state machines associated, respectively, with the
723	   CLUE Participant, with the MC process and with the MP process.
724	   Endpoints often wish to both send and receive media, i.e., act as
725	   both MP and MC.  As such there will often be two sets of messages
726	   flowing in opposite directions; the state machines of these two flows
727	   do not interact with each other.  Only the CLUE application logic is
728	   considered.  The interaction of CLUE protocol and SDP negotiations
729	   for the media streams exchanged is treated in
730	   [I-D.ietf-clue-signaling].

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

735	   The initial state is the IDLE one.  When in the IDLE state, the CLUE
736	   data channel is not established and no CLUE-controlled media are
737	   exchanged between the two considered CLUE-capable devices (if there
738	   is an ongoing exchange of media streams, such media streams are not
739	   currently CLUE-controlled).

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

744	   If the CLUE data channel is successfully set up ("channel
745	   established"), the CP moves from the CHANNEL SETUP state to the
746	   OPTIONS state.  Otherwise ("channel error"), it moves back to the
747	   IDLE state.  The same transition happens if the CLUE-enabled
748	   telepresence session ends ("session ends"), i.e., when an SDP
749	   negotiation for removing the CLUE channel is performed.

751	   When in the OPTIONS state, the CP addresses the initiation phase
752	   where both parts agree on the version and on the options to be used
753	   in the subsequent CLUE messages exchange phase.  If the CP is the
754	   Channel Initiator (CI), it sends an OPTIONS message and waits for the
755	   OPTIONS RESPONSE message.  If the CP is the Channel Receiver (CR), it
756	   waits for the OPTIONS message and, as soon as it arrives, replies
757	   with the OPTIONS RESPONSE message.  If the negotiation is
758	   successfully completed ("OPTIONS phase success"), the CP moves from
759	   the OPTIONS state to the ACTIVE state.  If the initiation phase fails
760	   ("OPTIONS phase failure"), the CP moves from the OPTIONS state to the
761	   IDLE state.  The initiation phase might fail because of one of the
762	   following reasons:

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

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

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

771	   When in the ACTIVE state, the CP starts the envisioned sub-state
772	   machines (i.e., the MP state machine and the MC state machine)
773	   according to the roles it plays in the telepresence sessions.  Such
774	   roles have been previously declared in the OPTIONS and OPTIONS
775	   RESPONSE messages involved in the initiation phase (see OPTIONS
776	   sections Section 5.1 and Section 5.2 for the details).  When in the
777	   ACTIVE state, the CP delegates the sending and the processing of the
778	   CLUE messages to the appropriate MP/MC sub-state machines.  If the CP
779	   receives a further OPTIONS/OPTIONS RESPONSE message, it MUST ignore
780	   the message and stay in the ACTIVE state.

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

786	                                  +----+
787	          +---------------------->|IDLE|<----------------------------+
788	          |                       +-+--+                             |
789	          |                         |                                |
790	          |                         |  start                         |
791	          |                         |  channel                       |
792	          |                         v                                |
793	          |  channel error/      +--------+                          |
794	          |  session ends        | CHANNEL|                          |
795	          +----------------------+ SETUP  |                          |
796	          |                      +--+-----+                          |
797	          |                         |                                |
798	          |                         |  channel                       |
799	          |                         |  established                   |
800	          |  channel error/         v                 OPTIONS phase  |
801	          |  session ends         +-------+           failure        |
802	          +-----------------------+OPTIONS+--------------------------+
803	          |                       +-+-----+                          |
804	          |                         |                                |
805	          |                         |  OPTIONS phase                 |
806	          |                         |  success                       |
807	          |                         v                                |
808	          |   channel error/     +---------+                         |
809	          |   session ends       | ACTIVE  |                         |
810	          +----------------------+         |                         |
811	                                 | +----+  +------------------+      |
812	                                 | | MP |  |    send/receive  |      |
813	                                 | +----+  |    CLUE messages |      |
814	                                 |         |<-----------------+      |
815	                                 | +----+  |                         |
816	                                 | | MC |  |both sub state machines  |
817	                                 | +----+  |terminated               |
818	                                 |         |                         |
819	                                 +---------+-------------------------+

821	6.1.  Media Provider's state machine

823	   As soon as the sub-state machine of the MP is activated, it is in the
824	   ADV state.  In the ADV state, the MP prepares the ADV message
825	   reflecting its actual telepresence capabilities.

827	   After the ADV has been sent ("ADV sent"), the MP moves from the ADV
828	   state to the WAIT FOR ACK state.  If an ACK message with a successful
829	   response code arrives ("ACK received"), the MP moves to the WAIT FOR
830	   CONF state.  If a NACK arrives (i.e., an ACK message with an error
831	   response code), and the number of NACKs for the issued ADV is under
832	   the retry threshold ("NACK received && retry not expired"), the MP
833	   moves back to the ADV state for preparing a new ADV.  If a NACK
834	   arrives and the number of received NACKs for that ADV overcomes the
835	   threshold ("NACK received && retry expired"), the MP goes to the MP-
836	   TERMINATED state.  The same happens if the waiting time for the ACK
837	   is fired a number of times under the retry threshold ("timeout &&
838	   retry not expired"): also in this case, the MP goes back to the ADV
839	   state to send a new copy of the ADV.  If the number of retries
840	   overcomes the threshold ("timeout && retry expired"), the MP moves
841	   from the WAIT FOR ACK state to the MP-TERMINATED state.  When in the
842	   WAIT FOR ACK state, if a CONFIGURE message with the <ack> element set
843	   to TRUE arrives ("CONF+ACK received"), the MP goes directly to the
844	   CONF RESPONSE state.  CONF+ACK messages referring to out-of-date
845	   (i.e., having a sequence number equal to or less than the highest
846	   seen so far) ADVs MUST be ignored, i.e., they do not trigger any
847	   state transition.  If the telepresence settings of the MP change
848	   while in the WAIT FOR ACK state ("changed telepresence settings"),
849	   the MP switches from the WAIT FOR ACK state to the ADV state to
850	   create a new ADV.

852	   When in the WAIT FOR CONF state, the MP listens to the channel for a
853	   CONF request coming from the MC.  If a CONF arrives ("CONF
854	   received"), the MP switches to the CONF RESPONSE state.  If the CONF
855	   does not arrive within the timeout interval and the retry threshold
856	   has not been overcome ("timeout && retry not expired"), the MP moves
857	   back to the ADV state.  When the retry expires ("timeout && retry
858	   expired") the MP moves to the MP TERMINATED state.  If the
859	   telepresence settings change in the meanwhile ("changed telepresence
860	   settings"), the MP moves from the WAIT FOR CONF back to the ADV state
861	   to create the new ADV to be sent to the MC.

863	   The MP in the CONF RESPONSE state processes the received CONF in
864	   order to produce a CONF RESPONSE message.  If the MP successfully
865	   processes the MC's configuration, then it sends a 200 CONF RESPONSE
866	   ("success CONF RESPONSE sent") and moves to the ESTABLISHED state.
867	   If there are errors in the CONF processing, then the MP issues a CONF
868	   RESPONSE carrying an error response code and, if under the retry
869	   treshold ("error CONF RESPONSE sent && retry not expired"), it goes
870	   back to the WAIT FOR CONF state to wait for a new configuration
871	   request.  If the number of trials exceeds the retry threshold ("error
872	   CONF RESPONSE sent && retry expired"), the state MP TERMINATED is
873	   reached.  Finally, if there are changes in the MP's telepresence
874	   settings ("changed telepresence settings"), the MP switches to the
875	   ADV state.

877	   The MP in the ESTABLISHED state has successfully negotiated the media
878	   streams with the MC by means of the CLUE messages.  If there are
879	   changes in the MP's telepresence settings ("changed telepresence
880	   settings"), the MP moves back to the ADV state.  In the ESTABLISHED
881	   state, the CLUE-controlled media streams of the session are those
882	   described in the last successfully processed CONF message.

884	+------------------------->+-----+<---------------------------+
885	|            +------------>| ADV |<-------------------+       |
886	|            |             +-+---+                    |       |timeout
887	|            |               |       NACK received    |       |&&
888	|            |       ADV sent|             &&         |       |retry
889	|            |               v       retry not expired|       |not
890	|     changed|             +--------+                 |       |expired
891	|telepresence+-------------+WAIT FOR+-----------------+       |
892	|    settings|   +---------+  ACK   +-------------------------+
893	|            |   |CONF+ACK +-+------+----------------------------------+
894	|            |   |received   |                        NACK received && |
895	|            |   |           |ACK received               retry expired,|
896	|            |   |           v                 timeout && retry expired|
897	+------------|-------------+--------+                                  |
898	timeout      +-------------+WAIT FOR| timeout && retry expired         |
899	&&           |   |         |  CONF  +----------------------------------+
900	retry        |   |         +-+------+<-----------------------------+   |
901	not expired  |   |           |                                     |   |
902	             |   |           |CONF received                        |   |
903	             |   |           v             error CONF RESPONSE sent|   |
904	             |   +-------->+---------+      && retry not expired   |   |
905	             +-------------+CONF     |-----------------------------+   |
906	    +--------------------->|RESPONSE +---------------------------------+
907	    |        |             +-+-------+         error CONF RESPONSE sent|
908	    |        |               |                         && retry expired|
909	    |        |               |  success                                |
910	    |        |               |  CONF RESPONSE                          |
911	    |        |               |  sent                                   |
912	    |        |               |                                         |
913	    |        |               |                                         |
914	    |CONF    |               |                                         |
915	    |received|               v                                         |
916	    |        |             +------------+                              |
917	    |        +-------------+ESTABLISHED |                              |
918	    +----------------------+------------+                              |
919	                                                                       |
920	                                                                       |
921	                                                                       |
922	                           +-----------+                               |
923	                           !    MP     |                               |
924	                           |TERMINATED |                               |
925	                           +-----------+<------------------------------+

927	6.2.  Media Consumer's state machine

929	   As soon as the sub-state machine of the MC is activated, it is in the
930	   WAIT FOR ADV state.  An MC in the WAIT FOR ADV state is waiting for
931	   an ADV coming from the MP.  If the ADV arrives ("ADV received"), the
932	   MC reaches the ADV PROCESSING state.  Otherwise, the MC stays in the
933	   WAIT FOR ADV state.

935	   In the ADV PROCESSING state, the ADV is parsed by the MC.  If the ADV
936	   is successfully processed, there are two possibilities.  According to
937	   the first one, the MC issues a successful ACK message to the MP ("ACK
938	   sent") and moves to the CONF state.  In the second one, the MC
939	   prepares and sends a CONF message with the <ack> field set to "true"
940	   ("CONF+ACK sent") and goes directly to the WAIT FOR CONF RESPONSE
941	   state.

943	   If the ADV processing is unsuccessful (bad syntax, missing XML
944	   elements, etc.), and the number of times this has happened is under
945	   the retry threshold, the MC sends a NACK message (i.e., an ACK with
946	   an error response code) to the MP and optionally further describes
947	   the problem via a proper reason phrase.  In this way ("NACK sent &&
948	   retry not expired"), the MC switches back to the WAIT FOR ADV state,
949	   waiting for a new ADV.  If the NACK retry expires ("NACK sent &&
950	   retry expired"), the MC moves to the MC TERMINATED state.

952	   When in the CONF state, the MC prepares the CONF request to be issued
953	   to the MP on the basis of the previously ACK-ed ADV.  When the CONF
954	   has been sent ("CONF sent"), the MC moves to the WAIT FOR CONF
955	   RESPONSE state.  If a new ADV arrives in the meanwhile ("ADV
956	   received"), the MC goes back to the ADV PROCESSING state.

958	   In the WAIT FOR CONF RESPONSE state, the MC waits for the MP's
959	   response to the issued CONF or CONF+ACK.  If a 200 CONF RESPONSE
960	   message is received ("successful CONF RESPONSE received"), it means
961	   that the MP and the MC have successfully agreed on the media streams
962	   to be shared.  Then, the MC can move to the ESTABLISHED state.  On
963	   the other hand, if an error response is received and the associated
964	   retry counter does not overcome the threshold ("error CONF RESPONSE
965	   received && retry not expired"), the MC moves back to the CONF state
966	   to prepare a new CONF request.  In case of "error CONF RESPONSE
967	   received && retry expired", the MC moves to the MC TERMINATED state.
968	   If no CONF RESPONSE arrives and the number of timeouts is under the
969	   threshold ("timeout && retry not expired"), the MC moves to the CONF
970	   state and sends again the CONF message.  If no CONF RESPONSE arrives
971	   and the number of timeouts is over the threshold ("timeout && retry
972	   expired"), the MC moves to the MC TERMINATED state.  If a new ADV is
973	   received in the WAIT FOR CONF RESPONSE state, the MC switches to the
974	   ADV PROCESSING state.

976	   When the MC is in the ESTABLISHED state, the telepresence session
977	   configuration has been set up at the CLUE application level according
978	   to the MC's preferences.  Both the MP and the MC have agreed on (and
979	   are aware of) the CLUE-controlled media streams to be exchanged
980	   within the call.  While in the ESTABLISHED state, it might happen
981	   that the MC decides to change something in the call settings.  The MC
982	   then issues a new CONF ("CONF sent") and goes to wait for the new
983	   CONF RESPONSE in the WAIT FOR CONF RESPONSE state.  On the other
984	   hand, in the ESTABLISHED state, if a new ADV arrives from the MP
985	   ("ADV received"), it means that something has changed on the MP's
986	   side.  The MC then moves to the ADV PROCESSING state.

988	                           +----------+
989	                           | WAIT FOR |
990	                           |   ADV    |
991	                           +----+-----+<--------+
992	                                |               |
993	                        ADV     |      NACK sent|
994	                        received|      && retry |
995	                                v    not expired|    NACK sent &&
996	                           +-----------+--------+    retry expired
997	                           |  ADV      +---------------------------+
998	                           | PROCESSING|<-----------------------+  |
999	                           +-+-----+---+                        |  |
1000	                             |     |                            |  |
1001	                   CONF+ACK  |     |  ACK                       |  |
1002	                     sent    |     |  sent                      |  |
1003	                             |     v                            |  |
1004	                             |  +-----+                         |  |
1005	                             |  |CONF |            ADV received |  |
1006	       +----------------------->|     +-------------------------+  |
1007	       |                     |  +--+--+                         |  |
1008	       |error CONF RESPONSE  |     |        error CONF RESPONSE |  |
1009	       |received &&          |     | CONF   received &&         |  |
1010	       |retry not expired,   |     | sent   retry expired       |  |
1011	       |timeout &&           |     |      +------------------------+
1012	       |retry not expired    v     v      |                     |  |
1013	       +------------------+---------------+        ADV received |  |
1014	               +--------->|   WAIT FOR    +---------------------+  |
1015	               |          |  CONF RESPONSE+------------------------+
1016	               |          +-------+-------+       timeout&&     |  |
1017	               |                  |             retry expired   |  |
1018	               |                  |                             |  |
1019	               |                  |successful                   |  |
1020	               |                  |CONF RESPONSE                |  |
1021	               |                  |received                     |  |
1022	               |                  v                             |  |
1023	               |CONF sent   +-----------+           ADV received|  |
1024	               +------------+ESTABLISHED+-----------------------+  |
1025	                            +-----------+                          |
1026	                                                                   |
1027	                                                                   |
1028	                                                                   |
1029	                             +-----------+                         |
1030	                             |   MC      |<------------------------+
1031	                             |TERMINATED |
1032	                             +-----------+

1034	7.  Versioning

1036	   CLUE protocol messages are XML messages compliant to the CLUE
1037	   protocol XML schema [I-D.ietf-clue-data-model-schema].  The version
1038	   of the protocol corresponds to the version of the schema.  Both
1039	   client and server have to test the compliance of the received
1040	   messages with the XML schema of the CLUE protocol.  If the compliance
1041	   is not verified, the message cannot be processed further.

1043	   Obviously, client and server cannot communicate if they do not share
1044	   exactly the same XML schema.  Such a schema associated with the CLUE
1045	   URN "urn:ietf:params:xml:ns:clue-protocol".  If all CLUE-enabled
1046	   devices use that schema there will be no interoperability problems
1047	   due to schema issues.

1049	   This document defines XML schema version 1.0.  The version usage is
1050	   similar in philosophy to XMPP ([RFC6120]).  A version number has
1051	   major and minor components, each a non-negative integer.  Major
1052	   version changes denote non-interoperable changes.  Minor version
1053	   changes denote schema changes that are backward compatible by
1054	   ignoring unknown XML elements, or other backward compatible changes.

1056	   The minor versions of the XML schema MUST be backward compatible, not
1057	   only in terms of schema but also semantically and procedurally as
1058	   well.  This means that they should define further features and
1059	   functionality besides those defined in the previous versions, in an
1060	   incremental way, without impacting the basic rules defined in the
1061	   previous version of the schema.  In this way, if a MP is able to
1062	   speak, e.g., version 1.5 of the protocol while the MC only
1063	   understands version 1.4, the MP should have no problem in reverting
1064	   the dialogue back to version 1.4 without exploiting 1.5 features and
1065	   functionality.  Version 1.4 is the one to be spoken and has to appear
1066	   in the "v" attribute of the subsequent CLUE messages.  In other
1067	   words, in this example, the MP MUST use version 1.4 and downgrade to
1068	   the lower version.  This said, and coherently with the general IETF
1069	   "protocol robustness principle" stating that "an implementation must
1070	   be conservative in its sending behavior, and liberal in its receiving
1071	   behavior" [RFC1122], Clue Participants MUST ignore unknown elements
1072	   or attributes that are not envisioned in the negotiated protocol
1073	   version and related options.

1075	8.  Extensions and options

1077	   Although the standard version of the CLUE protocol XML schema is
1078	   designed to thoroughly cope with the requirements emerging from the
1079	   application domain, new needs might arise and extensions can be
1080	   designed.  Extensions specify information and behaviors that are not
1081	   described in a certain version of the protocol.  They can relate to:

1083	   1.  new information, to be carried in the existing messages.  For
1084	       example, more fields may be added within an existing message;

1086	   2.  new messages.  This is the case if there is no proper message for
1087	       a certain task, so a brand new CLUE message needs to be defined.

1089	   As to the first type of extensions, it is possible to distinguish
1090	   between protocol-specific and data model information.  Indeed, CLUE
1091	   messages are envelopes carrying both:

1093	   o  (i) XML elements defined within the CLUE protocol XML schema
1094	      itself (protocol-specific information)

1096	   o  (ii) other XML elements compliant to the CLUE data model schema
1097	      (data model information)

1099	   When new protocol-specific information is needed somewhere in the
1100	   protocol messages, it can be added in place of the <any> elements and
1101	   <anyAttribute> elements envisioned by the protocol schema.  The
1102	   policy currently defined in the protocol schema for handling <any>
1103	   and <anyAttribute> elements is:

1105	   o  elementFormDefault="qualified"

1107	   o  attributeFormDefault="unqualified"

1109	   In that case, the new information must be qualified by namespaces
1110	   other than "urn:ietf:params:xml:ns:clue-protocol" (the protocol URN)
1111	   and "urn:ietf:params:xml:ns:clue-info" (the data model URN).
1112	   Elements or attributes from unknown namespaces MUST be ignored.

1114	   The other matter concerns data model information.  Data model
1115	   information is defined by the XML schema associated with the URN
1116	   "urn:ietf:params:xml:ns:clue-info".  Also for the XML elements
1117	   defined in such a schema there are extensibility issues.  Those
1118	   issues are overcome by using <any> and <anyAttribute> placeholders.
1119	   Similarly to what said before, new information within data model
1120	   elements can be added in place of <any> and <anyAttribute> schema
1121	   elements, as long as they are properly namespace qualified.

1123	   On the other hand (second type of extensions), "extra" CLUE protocol
1124	   messages, i.e., messages not envisioned in the latest standard
1125	   version of the schema, can be needed.  In that case, the messages and
1126	   the associated behavior should be defined in external documents that
1127	   both communication parties must be aware of.

1129	   Both types of extensions, i.e., new information and new messages, can
1130	   be characterized by:

1132	   o  a name;

1134	   o  an external XML Schema defining the XML information and/or the XML
1135	      messages representing the extension;

1137	   o  the standard version of the protocol the extension refers to.

1139	   For that reason, the extensions can be represented by means of the
1140	   <option> element as defined below, which is carried within the
1141	   OPTIONS and OPTIONS RESPONSE messages to represent the extensions
1142	   supported by the CI and by the CR.

1144	   <!-- OPTION TYPE -->
1145	   <xs:complexType name="optionType">
1146	   <xs:sequence>
1147	   <xs:element name="name" type="xs:string" />
1148	   <xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1149	   <xs:element name="version" type="versionType" minOccurs="0"/>
1150	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1151	   </xs:sequence>
1152	   <xs:anyAttribute namespace="##other" processContents="lax"/>
1153	   </xs:complexType>

1155	9.  XML Schema

1157	   In this section, the XML schema defining the CLUE messages is
1158	   provided.

1160	 <?xml version="1.0" encoding="UTF-8" ?>
1161	 <xs:schema
1162	 version="1.0"
1163	 targetNamespace="urn:ietf:params:xml:ns:clue-protocol"
1164	 xmlns:tns="urn:ietf:params:xml:ns:clue-protocol"
1165	 xmlns:xs="http://www.w3.org/2001/XMLSchema"
1166	 xmlns:dm="urn:ietf:params:xml:ns:clue-info"
1167	 xmlns="urn:ietf:params:xml:ns:clue-protocol"
1168	 elementFormDefault="qualified"
1169	 attributeFormDefault="unqualified">

1171	 <!-- Import data model schema -->
1172	 <xs:import namespace="urn:ietf:params:xml:ns:clue-info"
1173	 schemaLocation="data-model-schema-17.xsd"/>

1175	 <!-- ELEMENT DEFINITIONS -->
1176	 <xs:element name="options" type="optionsMessageType"/>
1177	 <xs:element name="optionsResponse" type="optionsResponseMessageType"/>
1178	 <xs:element name="advertisement" type="advertisementMessageType"/>
1179	 <xs:element name="ack" type="advAcknowledgementMessageType"/>
1180	 <xs:element name="configure" type="configureMessageType"/>
1181	 <xs:element name="configureResponse"
1182	  type="configureResponseMessageType"/>

1184	 <!-- CLUE MESSAGE TYPE -->
1185	 <xs:complexType name="clueMessageType" abstract="true">
1186	 <xs:sequence>
1187	 <xs:element name="clueId" type="xs:string"/>
1188	 <xs:element name="sequenceNr" type="xs:positiveInteger"/>
1189	 </xs:sequence>
1190	 <xs:attribute name="protocol" type="xs:string" fixed="CLUE"
1191	  use="required"/>
1192	 <xs:attribute name="v" type="versionType" use="required"/>
1193	 </xs:complexType>

1195	 <!-- VERSION TYPE -->
1196	 <xs:simpleType name="versionType">
1197	 <xs:restriction base="xs:string">
1198	 <xs:pattern value="[0-9]\.[0-9]"></xs:pattern>
1199	 </xs:restriction>
1200	 </xs:simpleType>

1202	 <!-- RESPONSE CODE TYPE -->
1203	 <xs:simpleType name="responseCodeType">
1204	   <xs:restriction base="xs:integer">
1205	    <xs:pattern value="[1-9][0-9][0-9]"/>
1206	   </xs:restriction>
1207	 </xs:simpleType>

1209	 <!-- CLUE OPTIONS -->
1210	 <xs:complexType name="optionsMessageType">
1211	 <xs:complexContent>
1212	 <xs:extension base="clueMessageType">
1213	 <xs:sequence>
1214	 <xs:element name="mediaProvider" type="xs:boolean"/>
1215	 <xs:element name="mediaConsumer" type="xs:boolean"/>
1216	 <xs:element name="supportedVersions" type="versionsListType"
1217	  minOccurs="0"/>
1218	 <xs:element name="supportedOptions" type="optionsListType"
1219	  minOccurs="0"/>
1220	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1221	 </xs:sequence>
1222	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1223	 </xs:extension>
1224	 </xs:complexContent>
1225	 </xs:complexType>

1227	 <!-- VERSIONS LIST TYPE -->
1228	 <xs:complexType name="versionsListType">
1229	 <xs:sequence>
1230	 <xs:element name="version" type="versionType" minOccurs="1"
1231	  maxOccurs="unbounded"/>
1232	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1233	 </xs:sequence>
1234	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1235	 </xs:complexType>

1237	 <!-- OPTIONS LIST TYPE -->
1238	 <xs:complexType name="optionsListType">
1239	 <xs:sequence>
1240	 <xs:element name="option" type="optionType" minOccurs="1"
1241	  maxOccurs="unbounded"/>
1242	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1243	 </xs:sequence>
1244	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1245	 </xs:complexType>

1247	 <!-- OPTION TYPE -->
1248	 <xs:complexType name="optionType">
1249	 <xs:sequence>
1250	 <xs:element name="name" type="xs:string" />
1251	 <xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1252	 <xs:element name="version" type="versionType" minOccurs="0"/>
1253	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1254	 </xs:sequence>
1255	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1256	 </xs:complexType>

1258	 <!-- CLUE OPTIONS RESPONSE -->
1259	 <xs:complexType name="optionsResponseMessageType">
1260	 <xs:complexContent>
1261	 <xs:extension base="clueMessageType">
1262	 <xs:sequence>
1263	 <xs:element name="responseCode" type="responseCodeType"/>
1264	 <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
1265	 <xs:element name="mediaProvider" type="xs:boolean" minOccurs="0"/>
1266	 <xs:element name="mediaConsumer" type="xs:boolean" minOccurs="0"/>
1267	 <xs:element name="version" type="versionType" minOccurs="0"/>
1268	 <xs:element name="commonOptions" type="optionsListType" minOccurs="0"/>
1269	 <xs:any namespace="##other"
1270	 processContents="lax" minOccurs="0"/>
1271	 </xs:sequence>
1272	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1273	 </xs:extension>
1274	 </xs:complexContent>
1275	 </xs:complexType>

1277	 <!-- CLUE ADVERTISEMENT MESSAGE TYPE -->
1278	 <xs:complexType name="advertisementMessageType">
1279	 <xs:complexContent>
1280	 <xs:extension base="clueMessageType">
1281	 <xs:sequence>
1282	 <!-- mandatory -->
1283	 <xs:element name="mediaCaptures" type="dm:mediaCapturesType"/>
1284	 <xs:element name="encodingGroups" type="dm:encodingGroupsType"/>
1285	 <xs:element name="captureScenes" type="dm:captureScenesType"/>
1286	 <!-- optional -->
1287	 <xs:element name="simultaneousSets" type="dm:simultaneousSetsType"
1288	  minOccurs="0"/>
1289	 <xs:element name="globalViews" type="dm:globalViewsType"
1290	  minOccurs="0"/>
1291	 <xs:element name="people" type="dm:peopleType" minOccurs="0"/>
1292	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1293	 </xs:sequence>
1294	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1295	 </xs:extension>
1296	 </xs:complexContent>
1297	 </xs:complexType>

1299	 <!-- ACK MESSAGE TYPE -->
1300	 <xs:complexType name="advAcknowledgementMessageType">
1301	 <xs:complexContent>
1302	 <xs:extension base="clueMessageType">
1303	 <xs:sequence>
1304	 <xs:element name="responseCode" type="responseCodeType"/>
1305	 <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
1306	 <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
1307	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1308	 </xs:sequence>
1309	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1310	 </xs:extension>
1311	 </xs:complexContent>
1312	 </xs:complexType>

1314	 <!-- CLUE CONFIGURE MESSAGE TYPE -->
1315	 <xs:complexType name="configureMessageType">
1316	 <xs:complexContent>
1317	 <xs:extension base="clueMessageType">
1318	 <xs:sequence>
1319	 <xs:element name="advSequenceNr" type="xs:positiveInteger"/>
1320	 <xs:element name="ack" type="xs:boolean"
1321	  minOccurs="0" fixed="true"/>
1322	 <xs:element name="captureEncodings" type="dm:captureEncodingsType"
1323	  minOccurs="0"/>
1324	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1325	 </xs:sequence>
1326	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1327	 </xs:extension>
1328	 </xs:complexContent>
1329	 </xs:complexType>

1331	 <!-- CONFIGURE RESPONSE MESSAGE TYPE -->
1332	 <xs:complexType name="configureResponseMessageType">
1333	 <xs:complexContent>
1334	 <xs:extension base="clueMessageType">
1335	 <xs:sequence>
1336	 <xs:element name="responseCode" type="responseCodeType"/>
1337	 <xs:element name="reasonString" type="xs:string" minOccurs="0"/>
1338	 <xs:element name="confSequenceNr" type="xs:positiveInteger"/>
1339	 <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1340	 </xs:sequence>
1341	 <xs:anyAttribute namespace="##other" processContents="lax"/>
1342	 </xs:extension>
1343	 </xs:complexContent>
1344	 </xs:complexType>

1346	 </xs:schema>

1348	10.  Examples

1350	   In the following we provide an example of ADVERTISEMENT representing
1351	   the telepresence environment described in
1352	   [I-D.ietf-clue-data-model-schema], Section "Sample XML file" and
1353	   Section "MCC example" respectively.

1355	10.1.  Simple ADV

1357	   The associated Media Provider's telepresence capabilities are
1358	   described in [I-D.ietf-clue-data-model-schema], Section "Sample XML
1359	   file".

1361	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1362	<ns2:advertisement xmlns="urn:ietf:params:xml:ns:clue-info"
1363	 xmlns:ns2="urn:ietf:params:xml:ns:clue-protocol"
1364	 xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0" protocol="CLUE" v="1.0">
1365	    <ns2:clueId>Napoli CLUE Endpoint</ns2:clueId>
1366	    <ns2:sequenceNr>34</ns2:sequenceNr>
1367	        <mediaCaptures>
1368	                <mediaCapture
1369	                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1370	                xsi:type="audioCaptureType" captureID="AC0" mediaType="audio">
1371	                        <captureSceneIDREF>CS1</captureSceneIDREF>
1372	                        <spatialInformation>
1373	                                <captureOrigin>
1374	                                        <capturePoint>
1375	                                                <x>0.0</x>
1376	                                                <y>0.0</y>
1377	                                                <z>10.0</z>
1378	                                        </capturePoint>
1379	                                        <lineOfCapturePoint>
1380	                                                <x>0.0</x>
1381	                                                <y>1.0</y>
1382	                                                <z>10.0</z>
1383	                                        </lineOfCapturePoint>
1384	                                </captureOrigin>
1385	                        </spatialInformation>
1386	                        <individual>true</individual>
1387	                        <encGroupIDREF>EG1</encGroupIDREF>
1388	             <description lang="en">main audio from the room
1389	             </description>
1390	             <priority>1</priority>
1391	             <lang>it</lang>
1392	             <mobility>static</mobility>
1393	             <view>room</view>
1394	             <capturedPeople>
1395	                 <personIDREF>alice</personIDREF>
1396	                 <personIDREF>bob</personIDREF>
1397	                 <personIDREF>ciccio</personIDREF>
1398	             </capturedPeople>
1399	         </mediaCapture>
1400	         <mediaCapture
1401	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1402	          xsi:type="videoCaptureType" captureID="VC0" mediaType="video">
1403	             <captureSceneIDREF>CS1</captureSceneIDREF>
1404	             <spatialInformation>
1405	                 <captureOrigin>
1406	                         <capturePoint>
1407	                         <x>-2.0</x>
1408	                         <y>0.0</y>
1409	                         <z>10.0</z>
1410	                     </capturePoint>
1411	                 </captureOrigin>
1412	                 <captureArea>
1413	                         <bottomLeft>
1414	                         <x>-3.0</x>
1415	                         <y>20.0</y>
1416	                         <z>9.0</z>
1417	                         </bottomLeft>
1418	                         <bottomRight>
1419	                         <x>-1.0</x>
1420	                         <y>20.0</y>
1421	                         <z>9.0</z>
1422	                         </bottomRight>
1423	                         <topLeft>
1424	                         <x>-3.0</x>
1425	                         <y>20.0</y>
1426	                         <z>11.0</z>
1427	                         </topLeft>
1428	                         <topRight>
1429	                         <x>-1.0</x>
1430	                         <y>20.0</y>
1431	                         <z>11.0</z>
1432	                         </topRight>
1433	                 </captureArea>
1434	             </spatialInformation>
1435	             <individual>true</individual>
1436	             <encGroupIDREF>EG0</encGroupIDREF>
1437	             <description lang="en">left camera video capture
1438	             </description>
1439	             <priority>1</priority>
1440	             <lang>it</lang>
1441	             <mobility>static</mobility>
1442	             <view>individual</view>
1443	             <capturedPeople>
1444	                 <personIDREF>ciccio</personIDREF>
1445	             </capturedPeople>
1446	         </mediaCapture>
1447	         <mediaCapture
1448	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1449	          xsi:type="videoCaptureType" captureID="VC1" mediaType="video">
1450	             <captureSceneIDREF>CS1</captureSceneIDREF>
1451	             <spatialInformation>
1452	                 <captureOrigin>
1453	                         <capturePoint>
1454	                         <x>0.0</x>
1455	                         <y>0.0</y>
1456	                         <z>10.0</z>
1457	                     </capturePoint>
1458	                 </captureOrigin>
1459	                 <captureArea>
1460	                         <bottomLeft>
1461	                         <x>-1.0</x>
1462	                         <y>20.0</y>
1463	                         <z>9.0</z>
1464	                         </bottomLeft>
1465	                         <bottomRight>
1466	                         <x>1.0</x>
1467	                         <y>20.0</y>
1468	                         <z>9.0</z>
1469	                         </bottomRight>
1470	                         <topLeft>
1471	                         <x>-1.0</x>
1472	                         <y>20.0</y>
1473	                         <z>11.0</z>
1474	                         </topLeft>
1475	                         <topRight>
1476	                         <x>1.0</x>
1477	                         <y>20.0</y>
1478	                         <z>11.0</z>
1479	                         </topRight>
1480	                 </captureArea>
1481	             </spatialInformation>
1482	             <individual>true</individual>
1483	             <encGroupIDREF>EG0</encGroupIDREF>
1484	             <description lang="en">central camera video capture
1485	             </description>
1486	             <priority>1</priority>
1487	             <lang>it</lang>
1488	             <mobility>static</mobility>
1489	             <view>individual</view>
1490	             <capturedPeople>
1491	                 <personIDREF>alice</personIDREF>
1492	             </capturedPeople>
1493	         </mediaCapture>
1494	         <mediaCapture
1495	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1496	          xsi:type="videoCaptureType" captureID="VC2" mediaType="video">
1497	             <captureSceneIDREF>CS1</captureSceneIDREF>
1498	             <spatialInformation>
1499	                 <captureOrigin>
1500	                         <capturePoint>
1501	                         <x>2.0</x>
1502	                         <y>0.0</y>
1503	                         <z>10.0</z>
1504	                     </capturePoint>
1505	                 </captureOrigin>
1506	                 <captureArea>
1507	                         <bottomLeft>
1508	                         <x>1.0</x>
1509	                         <y>20.0</y>
1510	                         <z>9.0</z>
1511	                         </bottomLeft>
1512	                         <bottomRight>
1513	                         <x>3.0</x>
1514	                         <y>20.0</y>
1515	                         <z>9.0</z>
1516	                         </bottomRight>
1517	                         <topLeft>
1518	                         <x>1.0</x>
1519	                         <y>20.0</y>
1520	                         <z>11.0</z>
1521	                         </topLeft>
1522	                         <topRight>
1523	                         <x>3.0</x>
1524	                         <y>20.0</y>
1525	                         <z>11.0</z>
1526	                         </topRight>
1527	                 </captureArea>
1528	             </spatialInformation>
1529	             <individual>true</individual>
1530	             <encGroupIDREF>EG0</encGroupIDREF>
1531	             <description lang="en">right camera video capture
1532	             </description>
1533	             <priority>1</priority>
1534	             <lang>it</lang>
1535	             <mobility>static</mobility>
1536	             <view>individual</view>
1537	             <capturedPeople>
1538	                 <personIDREF>bob</personIDREF>
1539	             </capturedPeople>
1540	         </mediaCapture>
1541	         <mediaCapture
1542	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1543	          xsi:type="videoCaptureType" captureID="VC3" mediaType="video">
1544	             <captureSceneIDREF>CS1</captureSceneIDREF>
1545	             <spatialInformation>
1546	                 <captureArea>
1547	                         <bottomLeft>
1548	                         <x>-3.0</x>
1549	                         <y>20.0</y>
1550	                         <z>9.0</z>
1551	                         </bottomLeft>
1552	                         <bottomRight>
1553	                         <x>3.0</x>
1554	                         <y>20.0</y>
1555	                         <z>9.0</z>
1556	                         </bottomRight>
1557	                         <topLeft>
1558	                         <x>-3.0</x>
1559	                         <y>20.0</y>
1560	                         <z>11.0</z>
1561	                         </topLeft>
1562	                         <topRight>
1563	                         <x>3.0</x>
1564	                         <y>20.0</y>
1565	                         <z>11.0</z>
1566	                         </topRight>
1567	                 </captureArea>
1568	             </spatialInformation>
1569	             <content>
1570	                 <sceneViewIDREF>SE1</sceneViewIDREF>
1571	             </content>
1572	             <policy>SoundLevel:0</policy>
1573	             <encGroupIDREF>EG0</encGroupIDREF>
1574	             <description lang="en">loudest room segment</description>
1575	             <priority>2</priority>
1576	             <lang>it</lang>
1577	             <mobility>static</mobility>
1578	             <view>individual</view>
1579	             </mediaCapture>
1580	         <mediaCapture
1581	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1582	          xsi:type="videoCaptureType" captureID="VC4" mediaType="video">
1583	             <captureSceneIDREF>CS1</captureSceneIDREF>
1584	             <spatialInformation>
1585	                 <captureOrigin>
1586	                         <capturePoint>
1587	                         <x>0.0</x>
1588	                         <y>0.0</y>
1589	                         <z>10.0</z>
1590	                     </capturePoint>
1591	                 </captureOrigin>
1592	                 <captureArea>
1593	                         <bottomLeft>
1594	                         <x>-3.0</x>
1595	                         <y>20.0</y>
1596	                         <z>7.0</z>
1597	                         </bottomLeft>
1598	                         <bottomRight>
1599	                         <x>3.0</x>
1600	                         <y>20.0</y>
1601	                         <z>7.0</z>
1602	                         </bottomRight>
1603	                         <topLeft>
1604	                         <x>-3.0</x>
1605	                         <y>20.0</y>
1606	                         <z>13.0</z>
1607	                         </topLeft>
1608	                         <topRight>
1609	                         <x>3.0</x>
1610	                         <y>20.0</y>
1611	                         <z>13.0</z>
1612	                         </topRight>
1613	                 </captureArea>
1614	             </spatialInformation>
1615	             <individual>true</individual>
1616	             <encGroupIDREF>EG0</encGroupIDREF>
1617	             <description lang="en">zoomed out view of all people in the
1618	             room</description>
1619	             <priority>2</priority>
1620	             <lang>it</lang>
1621	             <mobility>static</mobility>
1622	             <view>room</view>
1623	             <capturedPeople>
1624	                 <personIDREF>alice</personIDREF>
1625	                 <personIDREF>bob</personIDREF>
1626	                 <personIDREF>ciccio</personIDREF>
1627	                 </capturedPeople>
1628	         </mediaCapture>
1629	     </mediaCaptures>
1630	     <encodingGroups>
1631	         <encodingGroup encodingGroupID="EG0">
1632	             <maxGroupBandwidth>600000</maxGroupBandwidth>
1633	             <encodingIDList>
1634	                 <encodingID>ENC1</encodingID>
1635	                 <encodingID>ENC2</encodingID>
1636	                 <encodingID>ENC3</encodingID>
1637	             </encodingIDList>
1638	         </encodingGroup>
1639	         <encodingGroup encodingGroupID="EG1">
1640	             <maxGroupBandwidth>300000</maxGroupBandwidth>
1641	             <encodingIDList>
1642	                 <encodingID>ENC4</encodingID>
1643	                 <encodingID>ENC5</encodingID>
1644	             </encodingIDList>
1645	         </encodingGroup>
1646	     </encodingGroups>
1647	     <captureScenes>
1648	         <captureScene scale="unknown" sceneID="CS1">
1649	             <sceneViews>
1650	                 <sceneView sceneViewID="SE1">
1651	                     <mediaCaptureIDs>
1652	                         <mediaCaptureIDREF>VC0</mediaCaptureIDREF>
1653	                         <mediaCaptureIDREF>VC1</mediaCaptureIDREF>
1654	                         <mediaCaptureIDREF>VC2</mediaCaptureIDREF>
1655	                     </mediaCaptureIDs>
1656	                 </sceneView>
1657	                 <sceneView sceneViewID="SE2">
1658	                     <mediaCaptureIDs>
1659	                         <mediaCaptureIDREF>VC3</mediaCaptureIDREF>
1660	                     </mediaCaptureIDs>
1661	                 </sceneView>
1662	                 <sceneView sceneViewID="SE3">
1663	                     <mediaCaptureIDs>
1664	                         <mediaCaptureIDREF>VC4</mediaCaptureIDREF>
1665	                     </mediaCaptureIDs>
1666	                 </sceneView>
1667	                 <sceneView sceneViewID="SE4">
1668	                     <mediaCaptureIDs>
1669	                         <mediaCaptureIDREF>AC0</mediaCaptureIDREF>
1670	                     </mediaCaptureIDs>
1671	                 </sceneView>
1672	             </sceneViews>
1673	         </captureScene>
1674	     </captureScenes>
1675	     <simultaneousSets>
1676	         <simultaneousSet setID="SS1">
1677	             <mediaCaptureIDREF>VC3</mediaCaptureIDREF>
1678	             <sceneViewIDREF>SE1</sceneViewIDREF>
1679	         </simultaneousSet>
1680	         <simultaneousSet setID="SS2">
1681	             <mediaCaptureIDREF>VC0</mediaCaptureIDREF>
1682	             <mediaCaptureIDREF>VC2</mediaCaptureIDREF>
1683	             <mediaCaptureIDREF>VC4</mediaCaptureIDREF>
1684	         </simultaneousSet>
1685	     </simultaneousSets>
1686	     <people>
1687	         <person personID="bob">
1688	             <personInfo>
1689	                 <ns2:fn>
1690	                     <ns2:text>Bob</ns2:text>
1691	                 </ns2:fn>
1692	             </personInfo>
1693	             <personType>minute taker</personType>
1694	         </person>
1695	         <person personID="alice">
1696	             <personInfo>
1697	                 <ns3:fn>
1698	                     <ns3:text>Alice</ns3:text>
1699	                 </ns3:fn>
1700	             </personInfo>
1701	             <personType>presenter</personType>
1702	         </person>
1703	         <person personID="ciccio">
1704	             <personInfo>
1705	                 <ns3:fn>
1706	                     <ns3:text>Ciccio</ns3:text>
1707	                 </ns3:fn>
1708	             </personInfo>
1709	             <personType>chairman</personType>
1710	             <personType>timekeeper</personType>
1711	         </person>
1712	     </people>
1713	</ns2:advertisement>

1715	10.2.  ADV with MCCs

1717	   The associated Media Provider's telepresence capabilities are
1718	   described in [I-D.ietf-clue-data-model-schema], Section "MCC
1719	   example".

1721	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1722	<ns2:advertisement xmlns="urn:ietf:params:xml:ns:clue-info"
1723	 xmlns:ns2="urn:ietf:params:xml:ns:clue-protocol"
1724	 xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0" protocol="CLUE" v="1.0">
1725	    <ns2:clueId>Napoli CLUE Endpoint</ns2:clueId>
1726	    <ns2:sequenceNr>34</ns2:sequenceNr>
1727	     <mediaCaptures>
1728	         <mediaCapture
1729	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1730	          xsi:type="audioCaptureType" captureID="AC0" mediaType="audio">
1731	             <captureSceneIDREF>CS1</captureSceneIDREF>
1732	             <spatialInformation>
1733	                 <captureOrigin>
1734	                         <capturePoint>
1735	                         <x>0.0</x>
1736	                         <y>0.0</y>
1737	                         <z>10.0</z>
1738	                     </capturePoint>
1739	                     <lineOfCapturePoint>
1740	                         <x>0.0</x>
1741	                         <y>1.0</y>
1742	                         <z>10.0</z>
1743	                     </lineOfCapturePoint>
1744	                 </captureOrigin>
1745	             </spatialInformation>
1746	             <individual>true</individual>
1747	             <encGroupIDREF>EG1</encGroupIDREF>
1748	             <description lang="en">main audio from the room
1749	             </description>
1750	             <priority>1</priority>
1751	             <lang>it</lang>
1752	             <mobility>static</mobility>
1753	             <view>room</view>
1754	             <capturedPeople>
1755	                 <personIDREF>alice</personIDREF>
1756	                 <personIDREF>bob</personIDREF>
1757	                 <personIDREF>ciccio</personIDREF>
1758	             </capturedPeople>
1759	         </mediaCapture>
1760	         <mediaCapture
1761	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1762	          xsi:type="videoCaptureType" captureID="VC0" mediaType="video">
1763	             <captureSceneIDREF>CS1</captureSceneIDREF>
1764	             <spatialInformation>
1765	                 <captureOrigin>
1766	                         <capturePoint>
1767	                         <x>0.5</x>
1768	                         <y>1.0</y>
1769	                         <z>0.5</z>
1770	                     </capturePoint>
1771	                     <lineOfCapturePoint>
1772	                         <x>0.5</x>
1773	                         <y>0.0</y>
1774	                         <z>0.5</z>
1775	                     </lineOfCapturePoint>
1776	                 </captureOrigin>
1777	             </spatialInformation>
1778	             <individual>true</individual>
1779	             <encGroupIDREF>EG0</encGroupIDREF>
1780	             <description lang="en">left camera video capture
1781	             </description>
1782	             <priority>1</priority>
1783	             <lang>it</lang>
1784	             <mobility>static</mobility>
1785	             <view>individual</view>
1786	             <capturedPeople>
1787	                 <personIDREF>ciccio</personIDREF>
1788	             </capturedPeople>
1789	         </mediaCapture>
1790	         <mediaCapture
1791	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1792	          xsi:type="videoCaptureType" captureID="VC1" mediaType="video">
1793	             <captureSceneIDREF>CS1</captureSceneIDREF>
1794	             <spatialInformation>
1795	                 <captureOrigin>
1796	                         <capturePoint>
1797	                         <x>0.0</x>
1798	                         <y>0.0</y>
1799	                         <z>10.0</z>
1800	                     </capturePoint>
1801	                 </captureOrigin>
1802	                 <captureArea>
1803	                         <bottomLeft>
1804	                         <x>-1.0</x>
1805	                         <y>20.0</y>
1806	                         <z>9.0</z>
1807	                         </bottomLeft>
1808	                         <bottomRight>
1809	                         <x>1.0</x>
1810	                         <y>20.0</y>
1811	                         <z>9.0</z>
1812	                         </bottomRight>
1813	                         <topLeft>
1814	                         <x>-1.0</x>
1815	                         <y>20.0</y>
1816	                         <z>11.0</z>
1817	                         </topLeft>
1818	                         <topRight>
1819	                         <x>1.0</x>
1820	                         <y>20.0</y>
1821	                         <z>11.0</z>
1822	                         </topRight>
1823	                 </captureArea>
1824	             </spatialInformation>
1825	             <individual>true</individual>
1826	             <encGroupIDREF>EG0</encGroupIDREF>
1827	             <description lang="en">central camera video capture
1828	             </description>
1829	             <priority>1</priority>
1830	             <lang>it</lang>
1831	             <mobility>static</mobility>
1832	             <view>individual</view>
1833	             <capturedPeople>
1834	                 <personIDREF>alice</personIDREF>
1835	             </capturedPeople>
1836	         </mediaCapture>
1837	         <mediaCapture
1838	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1839	          xsi:type="videoCaptureType" captureID="VC2" mediaType="video">
1840	             <captureSceneIDREF>CS1</captureSceneIDREF>
1841	             <spatialInformation>
1842	                 <captureOrigin>
1843	                         <capturePoint>
1844	                         <x>2.0</x>
1845	                         <y>0.0</y>
1846	                         <z>10.0</z>
1847	                     </capturePoint>
1848	                 </captureOrigin>
1849	                 <captureArea>
1850	                         <bottomLeft>
1851	                         <x>1.0</x>
1852	                         <y>20.0</y>
1853	                         <z>9.0</z>
1854	                         </bottomLeft>
1855	                         <bottomRight>
1856	                         <x>3.0</x>
1857	                         <y>20.0</y>
1858	                         <z>9.0</z>
1859	                         </bottomRight>
1860	                         <topLeft>
1861	                         <x>1.0</x>
1862	                         <y>20.0</y>
1863	                         <z>11.0</z>
1864	                         </topLeft>
1865	                         <topRight>
1866	                         <x>3.0</x>
1867	                         <y>20.0</y>
1868	                         <z>11.0</z>
1869	                         </topRight>
1870	                 </captureArea>
1871	             </spatialInformation>
1872	             <individual>true</individual>
1873	             <encGroupIDREF>EG0</encGroupIDREF>
1874	             <description lang="en">right camera video capture
1875	             </description>
1876	             <priority>1</priority>
1877	             <lang>it</lang>
1878	             <mobility>static</mobility>
1879	             <view>individual</view>
1880	             <capturedPeople>
1881	                 <personIDREF>bob</personIDREF>
1882	             </capturedPeople>
1883	         </mediaCapture>
1884	         <mediaCapture
1885	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1886	          xsi:type="videoCaptureType" captureID="VC3" mediaType="video">
1887	             <captureSceneIDREF>CS1</captureSceneIDREF>
1888	             <spatialInformation>
1889	                 <captureArea>
1890	                         <bottomLeft>
1891	                         <x>-3.0</x>
1892	                         <y>20.0</y>
1893	                         <z>9.0</z>
1894	                         </bottomLeft>
1895	                         <bottomRight>
1896	                         <x>3.0</x>
1897	                         <y>20.0</y>
1898	                         <z>9.0</z>
1899	                         </bottomRight>
1900	                         <topLeft>
1901	                         <x>-3.0</x>
1902	                         <y>20.0</y>
1903	                         <z>11.0</z>
1904	                         </topLeft>
1905	                         <topRight>
1906	                         <x>3.0</x>
1907	                         <y>20.0</y>
1908	                         <z>11.0</z>
1909	                         </topRight>
1910	                 </captureArea>
1911	             </spatialInformation>
1912	             <content>
1913	                 <sceneViewIDREF>SE1</sceneViewIDREF>
1914	             </content>
1915	             <policy>SoundLevel:0</policy>
1916	             <encGroupIDREF>EG0</encGroupIDREF>
1917	             <description lang="en">loudest room segment</description>
1918	             <priority>2</priority>
1919	             <lang>it</lang>
1920	             <mobility>static</mobility>
1921	             <view>individual</view>
1922	         </mediaCapture>
1923	         <mediaCapture
1924	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1925	          xsi:type="videoCaptureType" captureID="VC4" mediaType="video">
1926	             <captureSceneIDREF>CS1</captureSceneIDREF>
1927	             <spatialInformation>
1928	                 <captureOrigin>
1929	                         <capturePoint>
1930	                         <x>0.0</x>
1931	                         <y>0.0</y>
1932	                         <z>10.0</z>
1933	                     </capturePoint>
1934	                 </captureOrigin>
1935	                 <captureArea>
1936	                         <bottomLeft>
1937	                         <x>-3.0</x>
1938	                         <y>20.0</y>
1939	                         <z>7.0</z>
1940	                         </bottomLeft>
1941	                         <bottomRight>
1942	                         <x>3.0</x>
1943	                         <y>20.0</y>
1944	                         <z>7.0</z>
1945	                         </bottomRight>
1946	                         <topLeft>
1947	                         <x>-3.0</x>
1948	                         <y>20.0</y>
1949	                         <z>13.0</z>
1950	                         </topLeft>
1951	                         <topRight>
1952	                         <x>3.0</x>
1953	                         <y>20.0</y>
1954	                         <z>13.0</z>
1955	                         </topRight>
1956	                 </captureArea>
1957	             </spatialInformation>
1958	             <individual>true</individual>
1959	             <encGroupIDREF>EG0</encGroupIDREF>
1960	             <description lang="en">
1961	               zoomed out view of all people in the room
1962	             </description>
1963	             <priority>2</priority>
1964	             <lang>it</lang>
1965	             <mobility>static</mobility>
1966	             <view>room</view>
1967	             <capturedPeople>
1968	                 <personIDREF>alice</personIDREF>
1969	                 <personIDREF>bob</personIDREF>
1970	                 <personIDREF>ciccio</personIDREF>
1971	             </capturedPeople>
1972	         </mediaCapture>
1973	         <mediaCapture
1974	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1975	          xsi:type="videoCaptureType" captureID="VC5" mediaType="video">
1976	             <captureSceneIDREF>CS1</captureSceneIDREF>
1977	             <spatialInformation>
1978	                 <captureArea>
1979	                         <bottomLeft>
1980	                         <x>-3.0</x>
1981	                         <y>20.0</y>
1982	                         <z>9.0</z>
1983	                         </bottomLeft>
1984	                         <bottomRight>
1985	                         <x>3.0</x>
1986	                         <y>20.0</y>
1987	                         <z>9.0</z>
1988	                         </bottomRight>
1989	                         <topLeft>
1990	                         <x>-3.0</x>
1991	                         <y>20.0</y>
1992	                         <z>11.0</z>
1993	                         </topLeft>
1994	                         <topRight>
1995	                         <x>3.0</x>
1996	                         <y>20.0</y>
1997	                         <z>11.0</z>
1998	                         </topRight>
1999	                 </captureArea>
2000	             </spatialInformation>
2001	             <content>
2002	                 <sceneViewIDREF>SE1</sceneViewIDREF>
2003	             </content>
2004	             <policy>SoundLevel:1</policy>
2005	             <description lang="en">penultimate loudest room segment
2006	             </description>
2007	             <lang>it</lang>
2008	             <mobility>static</mobility>
2009	             <view>individual</view>
2010	         </mediaCapture>
2011	         <mediaCapture
2012	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
2013	          xsi:type="videoCaptureType" captureID="VC6" mediaType="video">
2014	             <captureSceneIDREF>CS1</captureSceneIDREF>
2015	             <spatialInformation>
2016	                 <captureArea>
2017	                         <bottomLeft>
2018	                         <x>-3.0</x>
2019	                         <y>20.0</y>
2020	                         <z>9.0</z>
2021	                         </bottomLeft>
2022	                         <bottomRight>
2023	                         <x>3.0</x>
2024	                         <y>20.0</y>
2025	                         <z>9.0</z>
2026	                         </bottomRight>
2027	                         <topLeft>
2028	                         <x>-3.0</x>
2029	                         <y>20.0</y>
2030	                         <z>11.0</z>
2031	                         </topLeft>
2032	                         <topRight>
2033	                         <x>3.0</x>
2034	                         <y>20.0</y>
2035	                         <z>11.0</z>
2036	                         </topRight>
2037	                 </captureArea>
2038	             </spatialInformation>
2039	             <content>
2040	                 <sceneViewIDREF>SE1</sceneViewIDREF>
2041	             </content>
2042	             <policy>SoundLevel:2</policy>
2043	             <description lang="en">last but two loudest room segment
2044	             </description>
2045	             <lang>it</lang>
2046	             <mobility>static</mobility>
2047	             <view>individual</view>
2048	         </mediaCapture>
2049	         <mediaCapture
2050	          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
2051	          xsi:type="videoCaptureType" captureID="VC7" mediaType="video">
2052	             <captureSceneIDREF>CS1</captureSceneIDREF>
2053	             <spatialInformation>
2054	                 <captureArea>
2055	                         <bottomLeft>
2056	                         <x>-3.0</x>
2057	                         <y>20.0</y>
2058	                         <z>9.0</z>
2059	                         </bottomLeft>
2060	                         <bottomRight>
2061	                         <x>3.0</x>
2062	                         <y>20.0</y>
2063	                         <z>9.0</z>
2064	                         </bottomRight>
2065	                         <topLeft>
2066	                         <x>-3.0</x>
2067	                         <y>20.0</y>
2068	                         <z>11.0</z>
2069	                         </topLeft>
2070	                         <topRight>
2071	                         <x>3.0</x>
2072	                         <y>20.0</y>
2073	                         <z>11.0</z>
2074	                         </topRight>
2075	                 </captureArea>
2076	             </spatialInformation>
2077	             <content>
2078	                 <mediaCaptureIDREF>VC3</mediaCaptureIDREF>
2079	                 <mediaCaptureIDREF>VC5</mediaCaptureIDREF>
2080	                 <mediaCaptureIDREF>VC6</mediaCaptureIDREF>
2081	             </content>
2082	             <maxCaptures exactNumber="true">3</maxCaptures>
2083	             <encGroupIDREF>EG0</encGroupIDREF>
2084	             <description lang="en">big picture of the current speaker +
2085	             pips about previous speakers</description>
2086	             <priority>3</priority>
2087	             <lang>it</lang>
2088	             <mobility>static</mobility>
2089	             <view>individual</view>
2090	         </mediaCapture>
2091	     </mediaCaptures>
2092	     <encodingGroups>
2093	         <encodingGroup encodingGroupID="EG0">
2094	             <maxGroupBandwidth>600000</maxGroupBandwidth>
2095	             <encodingIDList>
2096	                 <encodingID>ENC1</encodingID>
2097	                 <encodingID>ENC2</encodingID>
2098	                 <encodingID>ENC3</encodingID>
2099	             </encodingIDList>
2100	         </encodingGroup>
2101	         <encodingGroup encodingGroupID="EG1">
2102	             <maxGroupBandwidth>300000</maxGroupBandwidth>
2103	             <encodingIDList>
2104	                 <encodingID>ENC4</encodingID>
2105	                 <encodingID>ENC5</encodingID>
2106	             </encodingIDList>
2107	         </encodingGroup>
2108	     </encodingGroups>
2109	     <captureScenes>
2110	         <captureScene scale="unknown" sceneID="CS1">
2111	             <sceneViews>
2112	                 <sceneView sceneViewID="SE1">
2113	                     <description lang="en">participants' individual
2114	                     videos</description>
2115	                     <mediaCaptureIDs>
2116	                         <mediaCaptureIDREF>VC0</mediaCaptureIDREF>
2117	                         <mediaCaptureIDREF>VC1</mediaCaptureIDREF>
2118	                         <mediaCaptureIDREF>VC2</mediaCaptureIDREF>
2119	                     </mediaCaptureIDs>
2120	                 </sceneView>
2121	                 <sceneView sceneViewID="SE2">
2122	                     <description lang="en">loudest segment of the
2123	                     room</description>
2124	                     <mediaCaptureIDs>
2125	                         <mediaCaptureIDREF>VC3</mediaCaptureIDREF>
2126	                     </mediaCaptureIDs>
2127	                 </sceneView>
2128	                 <sceneView sceneViewID="SE5">
2129	                     <description lang="en">loudest segment of the
2130	                     room + pips</description>
2131	                     <mediaCaptureIDs>
2132	                         <mediaCaptureIDREF>VC7</mediaCaptureIDREF>
2133	                     </mediaCaptureIDs>
2134	                 </sceneView>
2135	                 <sceneView sceneViewID="SE4">
2136	                     <description lang="en">room audio</description>
2137	                     <mediaCaptureIDs>
2138	                         <mediaCaptureIDREF>AC0</mediaCaptureIDREF>
2139	                     </mediaCaptureIDs>
2140	                 </sceneView>
2141	                 <sceneView sceneViewID="SE3">
2142	                     <description lang="en">room video</description>
2143	                     <mediaCaptureIDs>
2144	                         <mediaCaptureIDREF>VC4</mediaCaptureIDREF>
2145	                     </mediaCaptureIDs>
2146	                 </sceneView>
2147	             </sceneViews>
2148	         </captureScene>
2149	     </captureScenes>
2150	     <simultaneousSets>
2151	         <simultaneousSet setID="SS1">
2152	             <mediaCaptureIDREF>VC3</mediaCaptureIDREF>
2153	             <mediaCaptureIDREF>VC7</mediaCaptureIDREF>
2154	             <sceneViewIDREF>SE1</sceneViewIDREF>
2155	         </simultaneousSet>
2156	         <simultaneousSet setID="SS2">
2157	             <mediaCaptureIDREF>VC0</mediaCaptureIDREF>
2158	             <mediaCaptureIDREF>VC2</mediaCaptureIDREF>
2159	             <mediaCaptureIDREF>VC4</mediaCaptureIDREF>
2160	         </simultaneousSet>
2161	     </simultaneousSets>
2162	     <people>
2163	         <person personID="bob">
2164	             <personInfo>
2165	                 <ns3:fn>
2166	                     <ns3:text>Bob</ns2:text>
2167	                 </ns3:fn>
2168	             </personInfo>
2169	             <personType>minute taker</personType>
2170	         </person>
2171	         <person personID="alice">
2172	             <personInfo>
2173	                 <ns3:fn>
2174	                     <ns3:text>Alice</ns2:text>
2175	                 </ns3:fn>
2176	             </personInfo>
2177	             <personType>presenter</personType>
2178	         </person>
2179	         <person personID="ciccio">
2180	             <personInfo>
2181	                 <ns3:fn>
2182	                     <ns3:text>Ciccio</ns2:text>
2183	                 </ns3:fn>
2184	             </personInfo>
2185	             <personType>chairman</personType>
2186	             <personType>timekeeper</personType>
2187	         </person>
2188	     </people>
2189	</ns2:advertisement>

2191	11.  Security Considerations

2193	   As a general consideration, we remark that the CLUE framework (and
2194	   related protocol) has been conceived at the outset by embracing the
2195	   security-by-design paradigm.  This entails that a number of
2196	   requirements have been identified and properly standardized as
2197	   mandatory within the entire set of documents associated with the CLUE
2198	   architecture.  Requirements include: (i) the use of cryptography and
2199	   authentication; (ii) protection of all sensitive fields; (iii) mutual
2200	   authentication between CLUE endpoints; (iv) the presence of
2201	   authorization mechanisms; (v) the presence of native defence
2202	   mechanisms against malicious activities such as eavesdropping,
2203	   selective modification, deletion, replay (and related combinations
2204	   thereof).  Hence, security of the single components of the CLUE
2205	   solution cannot be evaluated independently of the integrated view of
2206	   the final architecture.

2208	   The CLUE protocol is an application-level protocol allowing a Media
2209	   Producer and a Media Consumer to negotiate a variegated set of
2210	   parameters associated with the establishment of a telepresence
2211	   session.  This unavoidably exposes a CLUE-enabled telepresence system
2212	   to a number of potential threats, most of which are extensively
2213	   discussed in the framework document [I-D.ietf-clue-framework].  The
2214	   security considerations section of the mentioned document actually
2215	   discusses issues associated with the setup and management of a
2216	   telepresence session both in the basic case involving two CLUE
2217	   endpoints acting, respectively, as MP and MC, and in the more
2218	   advanced scenario envisaging the presence of an MCU.

2220	   The framework document also mentions that the information carried
2221	   within CLUE protocol messages might contain sensitive data, which
2222	   SHOULD hence be accessed only by authenticated endpoints.  Security
2223	   issues associated with the CLUE data model schema are discussed in
2224	   [I-D.ietf-clue-data-model-schema].

2226	   There is extra information carried by the CLUE protocol which is not
2227	   associated with the CLUE data model schema and which exposes
2228	   information that might be of concern.  This information is primarily
2229	   exchanged during the options negotiation phase.  In the Clue
2230	   Participant state machine OPTIONS state, both parties agree on the
2231	   version and on the options to be used in the subsequent CLUE messages
2232	   exchange phase.  A malicious participant might either try to retrieve
2233	   a detailed footprint of a specific CLUE protocol implementation
2234	   during this initial setup phase, or force the communicating party to
2235	   use a non-up-to-date version of the protocol which they know how to
2236	   break.  Indeed, exposing all of the supported versions and options
2237	   could conceivably leak information about the specific implementation
2238	   of the protocol.  In theory an implementation could choose not to
2239	   announce all of the versions it supports if it wants to avoid such
2240	   leakage, though at the expenses of interoperability.  With respect to
2241	   the above considerations, it is noted that the OPTIONS state is only
2242	   reached after the CLUE data channel has been successfully set up.
2243	   This ensures that only authenticated parties can exchange OPTIONS and
2244	   related OPTIONS RESPONSE messages and hence drastically reduces the
2245	   attack surface which is exposed to malicious parties.

2247	   The CLUE framework clearly states the requirement to protect CLUE
2248	   protocol messages against threats deriving from the presence of a
2249	   malicious agent capable to gain access to the CLUE data channel.
2250	   Such a requirement is met by the CLUE data channel solution described
2251	   in [I-D.ietf-clue-datachannel], which ensures protection from both
2252	   message recovery and message tampering.  With respect to this last
2253	   point, any implementation of the CLUE protocol compliant with the
2254	   CLUE specification MUST rely on the exchange of messages which flow
2255	   on top of a reliable and ordered SCTP over DTLS transport channel
2256	   connecting two CLUE Participants.

2258	12.  IANA Considerations

2260	   This document registers a new XML namespace, a new XML schema and the
2261	   MIME type for the schema.  This document also registers the "CLUE"
2262	   Application Service tag and the "CLUE" Application Protocol tag and
2263	   defines registries for the CLUE messages and response codes.

2265	12.1.  URN Sub-Namespace Registration

2267	   This section registers a new XML namespace,
2268	   ""urn:ietf:params:xml:ns:clue-protocol"".

2270	   URI: urn:ietf:params:xml:ns:clue-protocol

2272	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2273	   Pietro Romano (spromano@unina.it).

2275	   XML:

2277	   BEGIN
2278	    <?xml version="1.0"?>
2279	    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
2280	      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
2281	    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
2282	      <head>
2283	        <title>CLUE Messages</title>
2284	      </head>
2285	      <body>
2286	        <h1>Namespace for CLUE Messages</h1>
2287	        <h2>urn:ietf:params:xml:ns:clue-protocol</h2>
2288	   [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
2289	       with the RFC number for this specification.]]
2290	        <p>See <a href="[[RFC URL]]">
2291	           RFCXXXX</a>.</p>
2292	      </body>
2293	    </html>
2294	   END

2296	12.2.  XML Schema registration

2298	   This section registers an XML schema per the guidelines in [RFC3688].

2300	   URI: urn:ietf:params:xml:schema:clue-protocol

2302	   Registrant Contact: CLUE working group (clue@ietf.org), Simon Pietro
2303	   Romano (spromano@unina.it).

2305	   Schema: The XML for this schema can be found as the entirety of
2306	   Section 9 of this document.

2308	12.3.  MIME Media Type Registration for 'application/clue+xml'

2310	   This section registers the ""application/clue+xml"" MIME type.

2312	   To: ietf-types@iana.org

2314	   Subject: Registration of MIME media type application/clue+xml

2316	   MIME media type name: application

2318	   MIME subtype name: clue+xml

2320	   Required parameters: (none)
2321	   Optional parameters: charset
2322	   Same as the charset parameter of "application/xml" as specified in
2323	   [RFC7303], Section 3.2.

2325	   Encoding considerations: Same as the encoding considerations of
2326	   "application/xml" as specified in [RFC7303], Section 3.2.

2328	   Security considerations: This content type is designed to carry
2329	   protocol data related to telepresence session control.  Some of the
2330	   data could be considered private.  This media type does not provide
2331	   any protection and thus other mechanisms such as those described in
2332	   Section Security are required to protect the data.  This media type
2333	   does not contain executable content.

2335	   Interoperability considerations: None.

2337	   Published specification: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
2338	   replace XXXX with the RFC number for this specification.]]

2340	   Applications that use this media type: CLUE participants.

2342	   Additional Information: Magic Number(s): (none),
2343	   File extension(s): .xml,
2344	   Macintosh File Type Code(s): TEXT.

2346	   Person & email address to contact for further information: Simon
2347	   Pietro Romano (spromano@unina.it).

2349	   Intended usage: LIMITED USE

2351	   Author/Change controller: The IETF

2353	   Other information: This media type is a specialization of
2354	   application/xml [RFC7303], and many of the considerations described
2355	   there also apply to application/clue+xml.

2357	12.4.  CLUE Protocol Registry

2359	   The document requests that the IANA creates new registries for CLUE
2360	   messages and response codes.

2362	12.4.1.  CLUE Message Types

2364	   The following summarizes the registry for CLUE messages:

2366	   Related Registry: CLUE Message Types Registry
2367	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2368	   with the RFC number for this specification.]]

2370	   Registration/Assignment Procedures: Following the policies outlined
2371	   in [RFC5226], the IANA policy for assigning new values for the CLUE
2372	   message types for the CLUE protocol is Specification Required.

2374	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2375	   Pietro Romano (spromano@unina.it).

2377	   The initial Message table is populated using the CLUE messages
2378	   described in Section 5 and defined in the XML schema in Section 9.

2380	   +-------------------+-----------------------------------+-----------+
2381	   | Message           | Description                       | Reference |
2382	   +-------------------+-----------------------------------+-----------+
2383	   | options           | "OPTIONS" in this document. Sent  | RFCXXXX   |
2384	   |                   | by the CI to the CR  in the       |           |
2385	   |                   | initiation phase to specify the   |           |
2386	   |                   | roles played by the CI, the       |           |
2387	   |                   | supported versions and the        |           |
2388	   |                   | supported protocol options.       |           |
2389	   | optionsResponse   | "OPTIONS RESPONSE" in this        | RFCXXXX   |
2390	   |                   | document. Sent by the CI to the   |           |
2391	   |                   | CR in reply to an OPTIONS message |           |
2392	   |                   | to finally estabilsh the version  |           |
2393	   |                   | and the options to be used in the |           |
2394	   |                   | following CLUE messages exchange. |           |
2395	   | advertisement     | "ADVERTISEMENT" or "ADV" in this  | RFCXXXX   |
2396	   |                   | document. Sent by the MP to the   |           |
2397	   |                   | MC to specify the telepresence    |           |
2398	   |                   | capabilities of the MP expressed  |           |
2399	   |                   | according to the CLUE framework.  |           |
2400	   | ack               | "ACK" in this document. Sent by   | RFCXXXX   |
2401	   |                   | the MC to the MP to acknowledge   |           |
2402	   |                   | the reception of an ADVERTISEMENT |           |
2403	   |                   | message.                          |           |
2404	   | configure         | "CONFIGURE" or "CONF" in this     | RFCXXXX   |
2405	   |                   | document. Sent by the MC to the   |           |
2406	   |                   | MP to specify the desired media   |           |
2407	   |                   | captures among those specified in |           |
2408	   |                   | the ADVERTISEMENT.                |           |
2409	   | configureResponse | "CONFIGURE RESPONSE" or "CONF     | RFCXXXX   |
2410	   |                   | RESPONSE" in this document. Sent  |           |
2411	   |                   | by the MP to the MC in reply to a |           |
2412	   |                   | CONFIGURE message to communicate  |           |
2413	   |                   | if the configuration request has  |           |
2414	   |                   | been successfully processed or    |           |
2415	   |                   | not.                              |           |
2416	   +-------------------+-----------------------------------+-----------+

2418	                                 IANA-CLUE

2420	12.4.2.  CLUE Response Codes

2422	   The following summarizes the requested registry for CLUE response
2423	   codes:

2425	   Related Registry: CLUE Response Code Registry
2426	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2427	   with the RFC number for this specification.]]

2429	   Registration/Assignment Procedures: Following the policies outlined
2430	   in [RFC5226], the IANA policy for assigning new values for the
2431	   Response codes for CLUE shall be Specification Required.

2433	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2434	   Pietro Romano (spromano@unina.it).

2436	   The initial Response-code table is populated using the Response codes
2437	   defined in Section 5.7 as follows:

2439	   +--------+-----------------+----------------------------+-----------+
2440	   | Number | Default         | Description                | Reference |
2441	   |        | Response String |                            |           |
2442	   +--------+-----------------+----------------------------+-----------+
2443	   | 200    | Success         | The request has been       | RFCXXXX   |
2444	   |        |                 | successfully processed.    |           |
2445	   | 300    | Syntax errors   | The XML syntax of the      | RFCXXXX   |
2446	   |        | and             | message is not correct or  |           |
2447	   |        | inconsistencies | there are invalid values.  |           |
2448	   | 301    | Bad syntax      | The XML syntax of the      | RFCXXXX   |
2449	   |        |                 | message is not correct.    |           |
2450	   | 302    | Invalid value   | The message contains an    | RFCXXXX   |
2451	   |        |                 | invalid parameter value.   |           |
2452	   | 303    | Conficting      | The message contains       | RFCXXXX   |
2453	   |        | values          | values that cannot be used |           |
2454	   |        |                 | together.                  |           |
2455	   | 400    | Semantic errors | Semantic errors in the     | RFCXXXX   |
2456	   |        |                 | received CLUE protocol     |           |
2457	   |        |                 | message.                   |           |
2458	   | 401    | Version not     | The protocol version used  | RFCXXXX   |
2459	   |        | supported       | in the message is not      |           |
2460	   |        |                 | supported.                 |           |
2461	   | 402    | Invalid         | The sequence number of the | RFCXXXX   |
2462	   |        | sequencing      | message is out of date.    |           |
2463	   | 403    | Invalid         | The identifier used in the | RFCXXXX   |
2464	   |        | identifier      | message is no valid or     |           |
2465	   |        |                 | unknown.                   |           |
2466	   | 404    | ADV Expired     | The number of the ADV the  | RFCXXXX   |
2467	   |        |                 | CONF refers to is out of   |           |
2468	   |        |                 | date.                      |           |
2469	   | 405    | Subset choice   | The subset choice is not   | RFCXXXX   |
2470	   |        | not allowed     | allowed for the specified  |           |
2471	   |        |                 | MCC.                       |           |
2472	   +--------+-----------------+----------------------------+-----------+

2474	13.  Diff with draft-ietf-clue-protocol-06

2476	   o  XML schema definition of <version> has been changed to match
2477	      pattern "X.Y", where X and Y are single digits.

2479	   o  100, 200, 300, 400 defined as catch-all response codes.

2481	   o  Updates in IANA section.

2483	14.  Diff with draft-ietf-clue-protocol-05

2485	   o  This document corrects some versioning errors of draft-ietf-clue-
2486	      protocol-05.

2488	15.  Diff with draft-ietf-clue-protocol-04

2490	   o  The document has been revised based on feedback recevied on the
2491	      ML.  No major modification is included in this version.

2493	16.  Diff with draft-ietf-clue-protocol-03

2495	   o  Response codes section updated.

2497	   o  maxCaptureEncodings removed from examples, allowSubsetChoice
2498	      added.

2500	   o  State machines descriptions aligned with pictures.

2502	   o  Applied recommended updates indicated in Christian's review
2503	      (2015-03-19).

2505	17.  Diff with draft-ietf-clue-protocol-02

2507	   o  CLUE Participant state machine: TERMINATED state replaced with
2508	      IDLE.

2510	   o  MP and MC state machines: SDP O/A state removed.

2512	   o  Diff mechanism (and related example) removed.

2514	   o  Schema updates: versionType used as the data type for all versions
2515	      fields, xs:unsignedInt used as the data type for all sequence
2516	      number fields, diff support removed from the ADV definition.

2518	18.  Diff with draft-ietf-clue-protocol-01

2520	   o  The diff mechanism for the ADV message has been introduced.

2522	   o  READV and READV RESPONSE message have been both removed.

2524	   o  The state machines have been deeply reviewed and changed.

2526	   o  References: references have been updated and splitted into
2527	      Informative references and Normative references as in framework
2528	      v17.

2530	   o  Schema: <globalSceneEntries> changed in <globalViews>,
2531	      <participants> in <people>

2533	   o  Terminology: many definitions added.

2535	   o  Response codes updated.

2537	19.  Diff with draft-ietf-clue-protocol-00

2539	   1.  The XML schema of the ADVERTISEMENT and of the READV have been
2540	       aligned with the current definitions in
2541	       [I-D.ietf-clue-data-model-schema] (example of updates:
2542	       <participants> --> <people>, <globalCaptureEntries> -->
2543	       <globalSceneEntries>)

2545	   2.  Text has been added to clarify that, in the OPTIONS RESPONSE,
2546	       when the response code is not an error response code, both
2547	       <mediaProvider> and <mediaConsumer> are mandatory.

2549	   3.  The content of the "v" attribute and of the <version> elements
2550	       carried in the OPTIONS and OPTIONS RESPONSE messages has been
2551	       described more precisely.

2553	   4.  Advertisement examples have been added.

2555	20.  Diff with draft-presta-clue-protocol-04

2557	   1.  The response code type error in the OPTIONS response (and in
2558	       other parts) has been corrected.

2560	21.  Diff with draft-presta-clue-protocol-03

2562	   1.  The XML Schema has been deeply revised and completed.

2564	   2.  The descriptions of the CLUE messages have been added.

2566	   3.  The distinction between major version numbers and minor version
2567	       numbers has been cut and pasted from [I-D.ietf-clue-signaling].

2569	   4.  Besides the two way one, a three way mechanism for the options
2570	       negotiation has been proposed and provided to foster discussion.

2572	22.  Diff with draft-presta-clue-protocol-02

2574	   1.  "Terminology" section added.

2576	   2.  Introduced the concept of "CLUE Participant" - an Endpoint or a
2577	       MCU able to use the CLUE protocol within a telepresence session.
2578	       A CLUE Participant can act as a Media Provider and/or as a Media
2579	       Consumer.

2581	   3.  Introduced the ACK/NACK mechanism for the ADVERTISEMENT.

2583	   4.  MP and MC state machines have been updated.  The CP state machine
2584	       has been added.

2586	23.  Acknowledgments

2588	   The authors thank all the CLUErs for their precious feedbacks and
2589	   support, in particular Paul Kyzivat, Christian Groves and Scarlett
2590	   Liuyan.

2592	24.  References

2594	24.1.  Normative References

2596	   [I-D.ietf-clue-data-model-schema]
2597	              Presta, R. and S. Romano, "An XML Schema for the CLUE data
2598	              model", draft-ietf-clue-data-model-schema-17 (work in
2599	              progress), August 2016.

2601	   [I-D.ietf-clue-datachannel]
2602	              Holmberg, C., "CLUE Protocol data channel", draft-ietf-
2603	              clue-datachannel-14 (work in progress), August 2016.

2605	   [I-D.ietf-clue-framework]
2606	              Duckworth, M., Pepperell, A., and S. Wenger, "Framework
2607	              for Telepresence Multi-Streams", draft-ietf-clue-
2608	              framework-25 (work in progress), January 2016.

2610	   [I-D.ietf-clue-signaling]
2611	              Kyzivat, P., Xiao, L., Groves, C., and R. Hansen, "CLUE
2612	              Signaling", draft-ietf-clue-signaling-09 (work in
2613	              progress), March 2016.

2615	   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
2616	              Requirement Levels", BCP 14, RFC 2119,
2617	              DOI 10.17487/RFC2119, March 1997,
2618	              <http://www.rfc-editor.org/info/rfc2119>.

2620	   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
2621	              Jacobson, "RTP: A Transport Protocol for Real-Time
2622	              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
2623	              July 2003, <http://www.rfc-editor.org/info/rfc3550>.

2625	   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
2626	              DOI 10.17487/RFC3688, January 2004,
2627	              <http://www.rfc-editor.org/info/rfc3688>.

2629	   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
2630	              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
2631	              DOI 10.17487/RFC5226, May 2008,
2632	              <http://www.rfc-editor.org/info/rfc5226>.

2634	   [RFC7303]  Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
2635	              DOI 10.17487/RFC7303, July 2014,
2636	              <http://www.rfc-editor.org/info/rfc7303>.

2638	24.2.  Informative References

2640	   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
2641	              Communication Layers", STD 3, RFC 1122,
2642	              DOI 10.17487/RFC1122, October 1989,
2643	              <http://www.rfc-editor.org/info/rfc1122>.

2645	   [RFC4353]  Rosenberg, J., "A Framework for Conferencing with the
2646	              Session Initiation Protocol (SIP)", RFC 4353,
2647	              DOI 10.17487/RFC4353, February 2006,
2648	              <http://www.rfc-editor.org/info/rfc4353>.

2650	   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
2651	              Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
2652	              March 2011, <http://www.rfc-editor.org/info/rfc6120>.

2654	   [RFC7262]  Romanow, A., Botzko, S., and M. Barnes, "Requirements for
2655	              Telepresence Multistreams", RFC 7262,
2656	              DOI 10.17487/RFC7262, June 2014,
2657	              <http://www.rfc-editor.org/info/rfc7262>.

2659	   [RFC7667]  Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
2660	              DOI 10.17487/RFC7667, November 2015,
2661	              <http://www.rfc-editor.org/info/rfc7667>.

2663	Authors' Addresses

2665	   Roberta Presta
2666	   University of Napoli
2667	   Via Claudio 21
2668	   Napoli  80125
2669	   Italy

2671	   EMail: roberta.presta@unina.it

2673	   Simon Pietro Romano
2674	   University of Napoli
2675	   Via Claudio 21
2676	   Napoli  80125
2677	   Italy

2679	   EMail: spromano@unina.it