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     advertisement, by applying in that way a piggibacking mechanism for
     simultaneously acknowledging and replying to the ADV message.  The <ack>
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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: October 24, 2015                                 April 22, 2015

7	                             CLUE protocol
8	                      draft-ietf-clue-protocol-04

10	Abstract

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

24	Status of This Memo

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

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

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

39	   This Internet-Draft will expire on October 24, 2015.

41	Copyright Notice

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

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

56	Table of Contents

58	   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
59	   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
60	   3.  Overview of the CLUE protocol  . . . . . . . . . . . . . . . .  5
61	   4.  Protocol messages  . . . . . . . . . . . . . . . . . . . . . .  7
62	     4.1.  OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . .  9
63	     4.2.  OPTIONS RESPONSE . . . . . . . . . . . . . . . . . . . . . 11
64	     4.3.  ADVERTISEMENT  . . . . . . . . . . . . . . . . . . . . . . 12
65	     4.4.  ADVERTISEMENT ACKNOWLEDGEMENT  . . . . . . . . . . . . . . 13
66	     4.5.  CONFIGURE  . . . . . . . . . . . . . . . . . . . . . . . . 14
67	     4.6.  CONFIGURE RESPONSE . . . . . . . . . . . . . . . . . . . . 14
68	     4.7.  Response codes and reason strings  . . . . . . . . . . . . 15
69	   5.  Protocol state machines  . . . . . . . . . . . . . . . . . . . 17
70	   6.  CLUE Participant's state machine . . . . . . . . . . . . . . . 17
71	     6.1.  Media Provider's state machine . . . . . . . . . . . . . . 19
72	     6.2.  Media Consumer's state machine . . . . . . . . . . . . . . 22
73	   7.  Versioning . . . . . . . . . . . . . . . . . . . . . . . . . . 25
74	   8.  Extensions and options . . . . . . . . . . . . . . . . . . . . 26
75	   9.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 27
76	   10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
77	     10.1. Simple ADV . . . . . . . . . . . . . . . . . . . . . . . . 31
78	     10.2. ADV with MCCs  . . . . . . . . . . . . . . . . . . . . . . 37
79	   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 44
80	     11.1. URN Sub-Namespace Registration . . . . . . . . . . . . . . 44
81	     11.2. XML Schema registration  . . . . . . . . . . . . . . . . . 45
82	     11.3. MIME Media Type Registration for 'application/clue+xml'  . 45
83	     11.4. DNS Registrations  . . . . . . . . . . . . . . . . . . . . 46
84	       11.4.1.  Application Service tag . . . . . . . . . . . . . . . 46
85	       11.4.2.  Application Protocol tag  . . . . . . . . . . . . . . 46
86	     11.5. CLUE Protocol Registry . . . . . . . . . . . . . . . . . . 47
87	       11.5.1.  CLUE Message Types  . . . . . . . . . . . . . . . . . 47
88	       11.5.2.  CLUE Response Codes . . . . . . . . . . . . . . . . . 48
89	   12. Diff with draft-ietf-clue-protocol-03  . . . . . . . . . . . . 49
90	   13. Diff with draft-ietf-clue-protocol-02  . . . . . . . . . . . . 49
91	   14. Diff with draft-ietf-clue-protocol-01  . . . . . . . . . . . . 50
92	   15. Diff with draft-ietf-clue-protocol-00  . . . . . . . . . . . . 50
93	   16. Diff with draft-presta-clue-protocol-04  . . . . . . . . . . . 51
94	   17. Diff with draft-presta-clue-protocol-03  . . . . . . . . . . . 51
95	   18. Diff with draft-presta-clue-protocol-02  . . . . . . . . . . . 51
96	   19. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 51
97	   20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
98	     20.1. Normative References . . . . . . . . . . . . . . . . . . . 51
99	     20.2. Informative References . . . . . . . . . . . . . . . . . . 52

101	1.  Introduction

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

107	   1.  enabling a MP to properly announce its current telepresence
108	       capabilities to a MC in terms of available media captures, groups
109	       of encodings, simultaneity constraints and other information
110	       envisioned in [I-D.ietf-clue-framework];

112	   2.  enabling a MC to request the desired multimedia streams from the
113	       offering MP.

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

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

128	2.  Terminology

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

136	   CLUE Participant:  An entity able to use the CLUE protocol within a
137	      telepresence session.  It can be an endpoint or an MCU able to use
138	      the CLUE protocol.

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

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

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

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

159	   Media Capture:  A "Media Capture", or simply "Capture", is a source
160	      of Media.

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

165	   Media Stream:  The term "Media Stream", or simply "Stream", is used
166	      as a synonymous of Capture Encoding.

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

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

174	3.  Overview of the CLUE protocol

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

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

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

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

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

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

237	   After that negotiation phase is completed, CLUE Participants describe
238	   and agree on the media flows to be exchanged.  Indeed, being CPs A
239	   and B both transmitting and receiving, it is possible to distinguish
240	   between two dialogues:

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

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

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

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

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

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

275	4.  Protocol messages

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

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

288	   The CLUE protocol messages are the following:

290	   o  OPTIONS

292	   o  OPTIONS RESPONSE
293	   o  ADVERTISEMENT (ADV)

295	   o  ADVERTISEMENT ACKNOWLEDGEMENT (ACK)

297	   o  CONFIGURE (CONF)

299	   o  CONFIGURE RESPONSE (CONF RESPONSE)

301	   While the OPTIONS and OPTIONS RESPONSE messages are exchanged in the
302	   initiation phase between the CPs, the other messages are involved in
303	   MP-MC dialogues.

305	   Each CLUE message inherits a basic structure depicted in the
306	   following excerpt:

308	<!-- CLUE MESSAGE TYPE -->
309	<xs:complexType name="clueMessageType" abstract="true">
310	<xs:sequence>
311	<xs:element name="clueId" type="xs:string"/>
312	<xs:element name="sequenceNr" type="xs:unsignedInt"/>
313	</xs:sequence>
314	<xs:attribute name="protocol" type="xs:string" fixed="CLUE" use="required"/>
315	<xs:attribute name="v" type="versionType" use="required"/>
316	</xs:complexType>

318	<!-- VERSION TYPE -->
319	<xs:simpleType name="versionType">
320	<xs:restriction base="xs:string">
321	<xs:pattern value="([0-9])+\.([0-9]+)"></xs:pattern>
322	</xs:restriction>
323	</xs:simpleType>

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

328	   o  clueId: an XML element containing the identifier of the CP within
329	      the telepresence system;

331	   o  sequenceNr: an XML element containing the local message sequence
332	      number;

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

337	   o  v: a mandatory attribute carrying the version of the protocol.
338	      The content of the "v" attribute is composed by the major version
339	      number followed by a dot and then by the minor version number of
340	      the CLUE protocol in use.  Allowed values are of this kind: "1.3",
341	      "2.45", etc.

343	   Each CP should manage up to three streams of sequence numbers: (i)
344	   one for the messages exchanged in the initiation phase, (ii) one for
345	   the messages exchanged as MP, and (iii) one for the messages
346	   exchanged as MC.

348	4.1.  OPTIONS

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

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

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

360	   o  supportedVersions: the list of the supported versions

362	   o  supportedOptions: the list of the supported options

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

366	<!-- CLUE OPTIONS -->
367	<xs:complexType name="optionsMessageType">
368	<xs:complexContent>
369	<xs:extension base="clueMessageType">
370	<xs:sequence>
371	<xs:element name="mediaProvider" type="xs:boolean"/>
372	<xs:element name="mediaConsumer" type="xs:boolean"/>
373	<xs:element name="supportedVersions" type="versionsListType" minOccurs="0"/>
374	<xs:element name="supportedOptions" type="optionsListType" minOccurs="0"/>
375	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
376	</xs:sequence>
377	<xs:anyAttribute namespace="##other" processContents="lax"/>
378	</xs:extension>
379	</xs:complexContent>
380	</xs:complexType>

382	<!-- VERSIONS LIST TYPE -->
383	<xs:complexType name="versionsListType">
384	<xs:sequence>
385	<xs:element name="version" type="versionType" minOccurs="1"
386	 maxOccurs="unbounded"/>
387	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
388	</xs:sequence>
389	<xs:anyAttribute namespace="##other" processContents="lax"/>
390	</xs:complexType>

392	<!-- OPTIONS LIST TYPE -->
393	<xs:complexType name="optionsListType">
394	<xs:sequence>
395	<xs:element name="option" type="optionType" minOccurs="1"
396	 maxOccurs="unbounded"/>
397	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
398	</xs:sequence>
399	<xs:anyAttribute namespace="##other" processContents="lax"/>
400	</xs:complexType>

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

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

438	4.2.  OPTIONS RESPONSE

440	   The OPTIONS RESPONSE is sent by a CR to a CI as a reply to the
441	   OPTIONS message.  As depicted in the figure below, the OPTIONS
442	   RESPONSE contains mandatorily a response code and a response string
443	   indicating the processing result of the OPTIONS message.  Following,
444	   the CR attaches two boolean tags, <mediaProvider> and
445	   <mediaConsumer>, expressing the supported roles in terms of
446	   respectively MP and MC, similarly to what the CI does in the OPTIONS
447	   message.  These two elements are optional in the OPTIONS RESPONSE
448	   since, in case of error response code, the CR might not want to add
449	   further information besides the response code and the reason string.
450	   In case of no errors, the CR MUST insert within the OPTIONS RESPONSE
451	   the <mediaProvider> and the <mediaConsumer> elements.  Finally, the
452	   highest commonly supported version number is expressed in the
453	   <version> field.  The content of the <version> element MUST be a
454	   string made by the major version number followed by a dot and then by
455	   the minor version number (e.g., 1.3 or 2.43).  The commonly supported
456	   options are copied in the the <commonOptions> field.

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

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

484	4.3.  ADVERTISEMENT

486	   The ADVERTISEMENT message (ADV) is used by the MP to advertise the
487	   available media captures and related information to the MC.  The MP
488	   sends to the MC an ADV as soon as it is ready after the successful
489	   completion of the initiation phase, i.e., as soon as the version and
490	   the options of the CLUE protocol are agreed between the CPs.  During
491	   the telepresence session, the ADV can be sent from the MP both
492	   periodically and on a per-event basis, i.e., each time there are
493	   changes in the MP's CLUE telepresence capabilities.

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

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

526	4.4.  ADVERTISEMENT ACKNOWLEDGEMENT

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

535	   <!-- ADV ACK MESSAGE TYPE -->
536	   <xs:complexType name="advAcknowledgementMessageType">
537	   <xs:complexContent>
538	   <xs:extension base="clueMessageType">
539	   <xs:sequence>
540	   <xs:element name="responseCode" type="xs:short"/>
541	   <xs:element name="reasonString" type="xs:string"/>
542	   <xs:element name="advSequenceNr" type="xs:unsignedInt"/>
543	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
544	   </xs:sequence>
545	   <xs:anyAttribute namespace="##other" processContents="lax"/>
546	   </xs:extension>
547	   </xs:complexContent>
548	   </xs:complexType>

550	4.5.  CONFIGURE

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

558	    <!-- CLUE CONFIGURE MESSAGE TYPE -->
559	   <xs:complexType name="configureMessageType">
560	   <xs:complexContent>
561	   <xs:extension base="clueMessageType">
562	   <xs:sequence>
563	   <!-- mandatory fields -->
564	   <xs:element name="advSequenceNr" type="xs:unsignedInt"/>
565	   <xs:element name="ack" type="xs:boolean" minOccurs="0" fixed="true"/>
566	   <xs:element name="captureEncodings" type="dm:captureEncodingsType"
567	    minOccurs="0"/>
568	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
569	   </xs:sequence>
570	   <xs:anyAttribute namespace="##other" processContents="lax"/>
571	   </xs:extension>
572	   </xs:complexContent>
573	   </xs:complexType>

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

578	   The optional boolean <ack> element, set to "true", if present,
579	   indicates that the CONF message also acknowledge the referred
580	   advertisement, by applying in that way a piggibacking mechanism for
581	   simultaneously acknowledging and replying to the ADV message.  The
582	   <ack> element SHOULD not be present at all if an ACK message has been
583	   already sent back to the MP.

585	   The most important content of the CONFIGURE message is the list of
586	   the capture encodings provided in the <captureEncodings> element.
587	   Such an element contains a sequence of capture encodings,
588	   representing the streams to be instantiated.

590	4.6.  CONFIGURE RESPONSE
591	   <!-- CONFIGURE RESPONSE MESSAGE TYPE -->
592	   <xs:complexType name="configureResponseMessageType">
593	   <xs:complexContent>
594	   <xs:extension base="clueMessageType">
595	   <xs:sequence>
596	   <xs:element name="responseCode" type="xs:short"/>
597	   <xs:element name="reasonString" type="xs:string"/>
598	   <xs:element name="confSequenceNr" type="xs:unsignedInt"/>
599	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
600	   </xs:sequence>
601	   <xs:anyAttribute namespace="##other" processContents="lax"/>
602	   </xs:extension>
603	   </xs:complexContent>
604	   </xs:complexType>

606	   The CONFIGURE RESPONSE message (CONF RESPONSE) is sent from the MP to
607	   the MC to communicate the processing result of requests carried in
608	   the previously received CONF message.  It contains a response code
609	   with a reason string indicating either the success or the failure
610	   (along with failure details) of a CONF request processing.
611	   Following, the <confSequenceNr> field contains the sequence number of
612	   the CONF message the response refers to.

614	4.7.  Response codes and reason strings

616	   The response codes and strings defined for use with CLUE are as
617	   follows:

619	   +-----------------+----------------------+--------------------------+
620	   |                 |                      |                          |
621	   |  Response code  |  Response string     |       Description        |
622	   |                 |                      |                          |
623	   +-----------------+----------------------+--------------------------+
624	   |                 |                      |                          |
625	   |   200           |  Success             |  The request has been    |
626	   |                 |                      |  successfully processed. |
627	   |                 |                      |                          |
628	   +-----------------+----------------------+--------------------------+
629	   |                 |                      |                          |
630	   |   300           |  Bad syntax          |  The XML syntax of the   |
631	   |                 |                      |  message is not          |
632	   |                 |                      |  correct.                |
633	   +-----------------+----------------------+--------------------------+
634	   |                 |                      |                          |
635	   |   301           |  Invalid value       |  The message             |
636	   |                 |                      |  contains an invalid     |
637	   |                 |                      |  parameter value.        |
638	   +-----------------+----------------------+--------------------------+
639	   |                 |                      |                          |
640	   |   302           |  Conflicting values  |  The message             |
641	   |                 |                      |  contains values that    |
642	   |                 |                      |  cannot be used together.|
643	   +-----------------+----------------------+--------------------------+
644	   |                 |                      |                          |
645	   |   400           | Version not supported|  The protocol version    |
646	   |                 |                      |  used in the message     |
647	   |                 |                      |  is not supported.       |
648	   |                 |                      |                          |
649	   +-----------------+----------------------+--------------------------+
650	   |                 |                      |                          |
651	   |   401           |  Invalid sequencing  |  The sequence number of  |
652	   |                 |                      |  the message is out      |
653	   |                 |                      |  of date.                |
654	   +-----------------+----------------------+--------------------------+
655	   |                 |                      |                          |
656	   |   402           |  Invalid identifier  |  The identifier used in  |
657	   |                 |                      |  the message is          |
658	   |                 |                      |  not valid or unknown.   |
659	   +-----------------+----------------------+--------------------------+
660	   |                 |                      |                          |
661	   |   403           |  ADV Expired         |  The number of the ADV   |
662	   |                 |                      |  the CONF refers to is   |
663	   |                 |                      |  out of date.            |
664	   +-----------------+----------------------+--------------------------+
665	   |                 |                      |                          |
666	   |   404           |  Subset choice not   |  The subset choice is not|
667	   |                 |  allowed             | allowed for the specified|
668	   |                 |                      |  MCC                     |
669	   +-----------------+----------------------+--------------------------+

671	   Response codes are defined as a sequence of three digits.  A semantic
672	   is associated to the first digit.  Response codes that do not begin
673	   with "2" or "1" indicate an error response, i.e., that an error
674	   occurred while processing a CLUE request.  Response codes beginning
675	   with "3" indicate problems with the XML content of the message ("Bad
676	   syntax", "Invalid value", etc.), while response codes beginning with
677	   "4" refer to problems related to CLUE protocol semantics ("Invalid
678	   sequencing", "Version not supported", etc.).  Response codes
679	   beginning with "2" are associated to successful responses.  Response
680	   codes beginning with "1" could be associated to temporary responses.

682	   Further response codes can be designed in future version of the
683	   protocol, provided they do not overwrite the ones here defined and
684	   they respect the semantic of the first code digit.

686	5.  Protocol state machines

688	   The CLUE protocol is an application protocol used between two CPs in
689	   order to properly configure a multimedia telepresence session.  CLUE
690	   protocol messages flow upon the CLUE Data Channel, a DTLS/SCTP
691	   channel established as depicted in [I-D.ietf-clue-signaling].  Over
692	   such a channel there are typically two CLUE streams between the
693	   channel terminations flowing in opposite directions.  In other words,
694	   typically, both channel terminations act simultaneously as a MP and
695	   as a MC.  We herein discuss the state machines associated,
696	   respectively, with the CLUE Participant, with the MC process and with
697	   the MP process.  Only the CLUE application logic is considered.  The
698	   interaction of CLUE protocol and SDP negotiations for the media
699	   streams to be exchanged is treated in [I-D.ietf-clue-signaling],
700	   Section 5.

702	6.  CLUE Participant's state machine

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

707	   The initial state is the IDLE one.  When in the IDLE state, the CLUE
708	   data channel is not established and no CLUE-controlled media are
709	   exchanged between the two considered CLUE-capable devices (if there
710	   is an ongoing exchange of media streams, such media streams are not
711	   currently CLUE-controlled).

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

716	   If the CLUE data channel is successfully set up ("channel
717	   established"), the CP moves from the CHANNEL SETUP state to the
718	   OPTIONS state.  Otherwise ("channel error"), it moves back to the
719	   IDLE state.  The same transition happens if the CLUE-enabled
720	   telepresence session ends ("session ends"), i.e., when an SDP
721	   negotiation for removing the CLUE channel is performed.

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

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

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

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

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

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

758	                                  +----+
759	          +---------------------->|IDLE|<----------------------------+
760	          |                       +-+--+                             |
761	          |                         |                                |
762	          |                         |  start                         |
763	          |                         |  channel                       |
764	          |                         v                                |
765	          |  channel error/      +--------+                          |
766	          |  session ends        | CHANNEL|                          |
767	          +----------------------+ SETUP  |                          |
768	          |                      +--+-----+                          |
769	          |                         |                                |
770	          |                         |  channel                       |
771	          |                         |  established                   |
772	          |  channel error/         v                 OPTIONS phase  |
773	          |  session ends         +-------+           failure        |
774	          +-----------------------+OPTIONS+--------------------------+
775	          |                       +-+-----+                          |
776	          |                         |                                |
777	          |                         |  OPTIONS phase                 |
778	          |                         |  success                       |
779	          |                         v                                |
780	          |   channel error/     +---------+                         |
781	          |   session ends       | ACTIVE  |                         |
782	          +----------------------+         |                         |
783	                                 | +----+  +------------------+      |
784	                                 | | MP |  |    send/receive  |      |
785	                                 | +----+  |    CLUE messages |      |
786	                                 |         |<-----------------+      |
787	                                 | +----+  |                         |
788	                                 | | MC |  |both sub state machines  |
789	                                 | +----+  |terminated               |
790	                                 |         |                         |
791	                                 +---------+-------------------------+

793	6.1.  Media Provider's state machine

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

799	   After the ADV has been sent ("ADV sent"), the MP moves from the ADV
800	   state to the WAIT FOR ACK state.  If an ACK message with a successful
801	   response code arrives ("ACK received"), the MP moves to the WAIT FOR
802	   CONF state.  If a NACK arrives (i.e., an ACK message with an error
803	   response code), and the number of NACKs for the issued ADV is under
804	   the retry threshold ("NACK received && retry not expired"), the MP
805	   moves back to the ADV state for preparing a new ADV.  If a NACK
806	   arrives and the number of received NACKs for that ADV overcome the
807	   threshold ("NACK received and && retry expired"), the MP goes to the
808	   MP-TERMINATED state.  Similarly, if the waiting time for the ACK is
809	   fired a number of times under the retry threshold ("timeout && retry
810	   not expired"), the MP goes back to the ADV state to send a new copy
811	   of the ADV.  If the number of retries overcomes the threshold
812	   ("timeout && retry expired"), the MP moves from the WAIT FOR ACK
813	   state to the MP-TERMINATED state.  When in the WAIT FOR ACK state, if
814	   a CONF+ACK message arrives ("CONF+ACK received"), the MP goes
815	   directly to the CONF RESPONSE state.  CONF+ACK messages referring to
816	   out-of-date ADVs MUST be ignored, i.e., they do not trigger any state
817	   transition.  If the telepresence settings of the MP change while in
818	   the WAIT FOR ACK state ("changed telepresence settings"), the MP
819	   switches from the WAIT FOR ACK state to the ADV state to create a new
820	   ADV.

822	   When in the WAIT FOR CONF state, the MP listens to the channel for a
823	   CONF request coming from the MC.  If a CONF arrives ("CONF
824	   received"), the MP switches to the CONF RESPONSE state.  If the CONF
825	   does not arrive within the timeout interval and the retry threshold
826	   has not been overcome ("timeout && retry not expired"), the MP moves
827	   back to the ADV state.  When the retry expires ("timeout && retry
828	   expired") the MP moves to the MP TERMINATED state.  If the
829	   telepresence settings change in the meanwhile ("changed telepresence
830	   settings"), the MP moves from the WAIT FOR CONF back to the ADV state
831	   to create the new ADV to be sent to the MC.

833	   The MP in the CONF RESPONSE state processes the received CONF in
834	   order to produce a CONF RESPONSE message.  If the MP is fine with the
835	   MC's configuration, then it sends a 200 CONF RESPONSE ("success CONF
836	   RESPONSE sent") and moves to the ESTABLISHED state.  If there are
837	   errors in the CONF processing, then the MP issues a CONF RESPONSE
838	   carrying an error response code and, if under the retry treshold
839	   ("error CONF RESPONSE sent && retry not expired"), it goes back to
840	   the WAIT FOR CONF state to wait for a new configuration request.  If
841	   the number of trials exceeds the retry threshold ("error CONF
842	   RESPONSE sent && retry expired"), the state MP TERMINATED is reached.
843	   Finally, if there are changes in the MP's telepresence settings
844	   ("changed telepresence settings"), the MP switches to the ADV state.

846	   The MP in the ESTABLISHED state has successfully negotiated the media
847	   streams with the MC by means of the CLUE messages.  If there are
848	   changes in the MP's telepresence settings ("changed telepresence
849	   settings"), the MP moves back to the ADV state.  In the ESTABLISHED
850	   state, the CLUE-controlled media streams of the session are those
851	   described in the last successfully processed CONF message.

853	+------------------------->+-----+<---------------------------+
854	|            +------------>| ADV |<-------------------+       |
855	|            |             +-+---+                    |       |timeout
856	|            |               |       NACK received    |       |&&
857	|            |       ADV sent|             &&         |       |retry
858	|            |               v       retry not expired|       |not
859	|     changed|             +--------+                 |       |expired
860	|telepresence+-------------+WAIT FOR+-----------------+       |
861	|    settings|   +---------+  ACK   +-------------------------+
862	|            |   |CONF+ACK +-+------+------------------------------------+
863	|            |   |received   |                          NACK received && |
864	|            |   |           |ACK received                 retry expired,|
865	|            |   |           v                   timeout && retry expired|
866	+------------|-------------+--------+                                    |
867	timeout      +-------------+WAIT FOR| timeout && retry expired           |
868	&&           |   |         |  CONF  +------------------------------------+
869	retry        |   |         +-+------+<-------------------------------+   |
870	not expired  |   |           |                                       |   |
871	             |   |           |CONF received                          |   |
872	             |   |           v               error CONF RESPONSE sent|   |
873	             |   +-------->+---------+        && retry not expired   |   |
874	             +-------------+CONF     |-------------------------------+   |
875	    +--------------------->|RESPONSE +-----------------------------------+
876	    |        |             +-+-------+           error CONF RESPONSE sent|
877	    |        |               |                           && retry expired|
878	    |        |               |  success                                  |
879	    |        |               |  CONF RESPONSE                            |
880	    |        |               |  sent                                     |
881	    |        |               |                                           |
882	    |        |               |                                           |
883	    |CONF    |               |                                           |
884	    |received|               v                                           |
885	    |        |             +------------+                                |
886	    |        +-------------+ESTABLISHED |                                |
887	    +----------------------+------------+                                |
888	                                                                         |
889	                                                                         |
890	                                                                         |
891	                           +-----------+                                 |
892	                           !    MP     |                                 |
893	                           |TERMINATED |                                 |
894	                           +-----------+<--------------------------------+

896	6.2.  Media Consumer's state machine

898	   As soon as the sub-state machine of the MC is activated, it is in the
899	   WAIT FOR ADV state.  An MC in the WAIT FOR ADV state is waiting for
900	   an ADV coming from the MP.  If the ADV arrives ("ADV received"), the
901	   MC reaches the ADV PROCESSING state.  Otherwise, the MC is stuck in
902	   the WAIT FOR ADV state.

904	   In the ADV PROCESSING state, the ADV is parsed by the MC.  If the ADV
905	   is successfully processed, there are two possibilities.  According to
906	   the first one, the MC issues a successful ACK message to the MP ("ACK
907	   sent") and moves to the CONF state.  In the second one, the MC
908	   prepares and sends a CONF message with the <ack> field set to "true"
909	   ("CONF+ACK sent") and goes directly to the WAIT FOR CONF RESPONSE
910	   state.

912	   If the ADV elaboration is unsuccessful (bad syntax, missing XML
913	   elements, etc.), and the number of times this condition has been
914	   verified is under the retry treshold, the MC sends a NACK message
915	   (i.e., an ACK with an error response code) to the MP describing the
916	   problem via a proper reason phrase.  By this way ("NACK sent && retry
917	   not expired"), the MC switches back to the WAIT FOR ADV state,
918	   waiting for a new ADV.  If the NACK retry expires ("NACK sent &&
919	   retry expired"), the MC moves to the MC TERMINATED state.

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

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

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

957	                           +----------+
958	                           | WAIT FOR |
959	                           |   ADV    |
960	                           +----+-----+<--------+
961	                                |               |
962	                        ADV     |      NACK sent|
963	                        received|      && retry |
964	                                v    not expired|    NACK sent &&
965	                           +-----------+--------+    retry expired
966	                           |  ADV      +---------------------------+
967	                           | PROCESSING|<-----------------------+  |
968	                           +-+-----+---+                        |  |
969	                             |     |                            |  |
970	                   CONF+ACK  |     |  ACK                       |  |
971	                     sent    |     |  sent                      |  |
972	                             |     v                            |  |
973	                             |  +-----+                         |  |
974	                             |  |CONF |            ADV received |  |
975	       +----------------------->|     +-------------------------+  |
976	       |                     |  +--+--+                         |  |
977	       |error CONF RESPONSE  |     |        error CONF RESPONSE |  |
978	       |received &&          |     | CONF   received &&         |  |
979	       |retry not expired,   |     | sent   retry expired       |  |
980	       |timeout &&           |     |      +------------------------+
981	       |retry not expired    v     v      |                     |  |
982	       +------------------+---------------+        ADV received |  |
983	               +--------->|   WAIT FOR    +---------------------+  |
984	               |          |  CONF RESPONSE+------------------------+
985	               |          +-------+-------+       timeout&&     |  |
986	               |                  |             retry expired   |  |
987	               |                  |                             |  |
988	               |                  |successful                   |  |
989	               |                  |CONF RESPONSE                |  |
990	               |                  |received                     |  |
991	               |                  v                             |  |
992	               |CONF sent   +-----------+           ADV received|  |
993	               +------------+ESTABLISHED+-----------------------+  |
994	                            +-----------+                          |
995	                                                                   |
996	                                                                   |
997	                                                                   |
998	                             +-----------+                         |
999	                             |   MC      |<------------------------+
1000	                             |TERMINATED |
1001	                             +-----------+

1003	7.  Versioning

1005	   CLUE protocol messages are XML messages compliant to the CLUE
1006	   protocol XML schema.  The version of the protocol corresponds to the
1007	   version of the schema.  Both client and server have to test the
1008	   compliance of the received messages with the XML schema of the CLUE
1009	   protocol.  If the compliance is not verified, the message cannot be
1010	   processed further.

1012	   Obviously, client and server cannot communicate if they do not share
1013	   exactly the same XML schema.  Such a schema is the one included in
1014	   the yet to come RFC, and associated with the CLUE URN
1015	   "urn:ietf:params:xml:ns:clue-protocol".  If all CLUE-enabled devices
1016	   use that schema there will be no interoperability problems due to
1017	   schema issues.

1019	   The version of the XML schema contained in the standard document
1020	   deriving from this draft will be 1.0.  The version usage is similar
1021	   in philosophy to XMPP ([RFC6120]).  A version number has major and
1022	   minor components, each a non-negative integer.  Major version changes
1023	   denote non-interoperable changes.  Minor version changes denote
1024	   schema changes that are backward compatible by ignoring unknown XML
1025	   elements, or other backward compatible changes.

1027	   The minor versions of the XML schema MUST be backward compatible, not
1028	   only in terms of schema but also semantically and procedurally as
1029	   well.  This means that they should define further features and
1030	   functionality besides those defined in the previous versions, in an
1031	   incremental way, without impacting the basic rules defined in the
1032	   previous version of the schema.  In this way, if a MP is able to
1033	   speak, e.g., version 1.5 of the protocol while the MC only
1034	   understands version 1.4, the MP should have no problem in reverting
1035	   the dialogue back to version 1.4 without exploiting 1.5 features and
1036	   functionality.

1038	   It is expected that, before the CLUE protocol XML schema reaches a
1039	   steady state, prototypes developed by different organizations will
1040	   conduct interoperability testing.  In that case, in order to
1041	   interoperate, they have to be compliant to the current version of the
1042	   XML schema, i.e., the one copied in the most up-to-date version of
1043	   the draft defining the CLUE protocol.  The versions of the non-
1044	   standard XML schema will be numbered as 0.01, 0.02, and so on.
1045	   During the standard development phase, the versions of the XML schema
1046	   will probably not be backward compatible so it is left to prototype
1047	   implementers the responsibility of keeping their products up to date.

1049	8.  Extensions and options

1051	   Although the standard version of the CLUE protocol XML schema is
1052	   designed to thoroughly cope with the requirements emerging from the
1053	   application domain, new needs might arise and extensions can be
1054	   designed.  Extensions specify information and behaviors that are not
1055	   described in a certain version of the protocol.  They can relate to:

1057	   1.  new information, to be carried in the existing messages.  For
1058	       example, we may want to add more fields within an existing
1059	       message;

1061	   2.  new messages.  This is the case if there is no proper message for
1062	       a certain task, so a brand new CLUE message needs to be defined.

1064	   As to the first type of extensions, it is possible to distinguish
1065	   between protocol-specific and data model information.  Indeed, CLUE
1066	   messages are envelopes carrying both:

1068	   o  (i) XML elements defined within the CLUE protocol XML schema
1069	      itself (protocol-specific information)

1071	   o  (ii) other XML elements compliant to the CLUE data model schema
1072	      (data model information)

1074	   When new protocol-specific information is needed somewhere in the
1075	   protocol messages, it can be added in place of the <any> elements and
1076	   <anyAttribute> elements envisioned by the protocol schema.  The
1077	   policy currently defined in the protocol schema for handling <any>
1078	   and <anyAttribute> elements is:

1080	   o  elementFormDefault="qualified"

1082	   o  attributeFormDefault="unqualified"

1084	   In that case, the new information must be qualified by namespaces
1085	   other than "urn:ietf:params:xml:ns:clue-protocol" (the protocol URN)
1086	   and "urn:ietf:params:xml:ns:clue-info" (the data model URN).
1087	   Elements or attributes from unknown namespaces MUST be ignored.

1089	   The other matter concerns data model information.  Data model
1090	   information is defined by the XML schema associated with the URN
1091	   "urn:ietf:params:xml:ns:clue-info".  Also for the XML elements
1092	   defined in such a schema there are extensibility issues.  Those
1093	   issues are overcome by using <any> and <anyAttribute> placeholders.
1094	   Similarly to what said before, new information within data model
1095	   elements can be added in place of <any> and <anyAttribute> schema
1096	   elements, as long as they are properly namespace qualified.

1098	   On the other hand (second type of extensions), "extra" CLUE protocol
1099	   messages, i.e., messages not envisioned in the latest standard
1100	   version of the schema, can be needed.  In that case, the messages and
1101	   the associated behavior should be defined in external documents that
1102	   both communication parties must be aware of.

1104	   Both types of extensions, i.e., new information and new messages, can
1105	   be characterized by:

1107	   o  a name;

1109	   o  an external XML Schema defining the XML information and/or the XML
1110	      messages representing the extension;

1112	   o  the standard version of the protocol the extension refers to.

1114	   For that reason, the extensions can be represented by means of the
1115	   <option> element as defined below, which is carried within the
1116	   OPTIONS and OPTIONS RESPONSE messages to represent the extensions
1117	   supported by the CI and by the CR.

1119	   <!-- OPTION TYPE -->
1120	   <xs:complexType name="optionType">
1121	   <xs:sequence>
1122	   <xs:element name="name" type="xs:string" />
1123	   <xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1124	   <xs:element name="version" type="versionType" minOccurs="0"/>
1125	   <xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1126	   </xs:sequence>
1127	   <xs:anyAttribute namespace="##other" processContents="lax"/>
1128	   </xs:complexType>

1130	9.  XML Schema

1132	   In this section, the XML schema defining the CLUE messages is
1133	   provided.

1135	<?xml version="1.0" encoding="UTF-8" ?>
1136	<xs:schema
1137	version="0.4"
1138	targetNamespace="urn:ietf:params:xml:ns:clue-protocol"
1139	xmlns:tns="urn:ietf:params:xml:ns:clue-protocol"
1140	xmlns:xs="http://www.w3.org/2001/XMLSchema"
1141	xmlns:dm="urn:ietf:params:xml:ns:clue-info"
1142	xmlns="urn:ietf:params:xml:ns:clue-protocol"
1143	elementFormDefault="qualified"
1144	attributeFormDefault="unqualified">

1146	<!-- Import data model schema -->
1147	<xs:import namespace="urn:ietf:params:xml:ns:clue-info"
1148	schemaLocation="data-model-schema-09.xsd"/>

1150	<!-- ELEMENT DEFINITIONS -->
1151	<xs:element name="options" type="optionsMessageType"/>
1152	<xs:element name="optionsResponse" type="optionsResponseMessageType"/>
1153	<xs:element name="advertisement" type="advertisementMessageType"/>
1154	<xs:element name="ack" type="advAcknowledgementMessageType"/>
1155	<xs:element name="configure" type="configureMessageType"/>
1156	<xs:element name="configureResponse" type="configureResponseMessageType"/>

1158	<!-- CLUE MESSAGE TYPE -->
1159	<xs:complexType name="clueMessageType" abstract="true">
1160	<xs:sequence>
1161	<xs:element name="clueId" type="xs:string"/>
1162	<xs:element name="sequenceNr" type="xs:unsignedInt"/>
1163	</xs:sequence>
1164	<xs:attribute name="protocol" type="xs:string" fixed="CLUE" use="required"/>
1165	<xs:attribute name="v" type="versionType" use="required"/>
1166	</xs:complexType>

1168	<!-- VERSION TYPE -->
1169	<xs:simpleType name="versionType">
1170	<xs:restriction base="xs:string">
1171	<xs:pattern value="([0-9])+\.([0-9]+)"></xs:pattern>
1172	</xs:restriction>
1173	</xs:simpleType>

1175	<!-- RESPONSE CODE TYPE -->
1176	<xs:simpleType name="responseCodeType">
1177	  <xs:restriction base="xs:integer">
1178	   <xs:pattern value="[1-9][0-9][0-9]"/>
1179	  </xs:restriction>
1180	</xs:simpleType>

1182	<!-- CLUE OPTIONS -->
1183	<xs:complexType name="optionsMessageType">
1184	<xs:complexContent>
1185	<xs:extension base="clueMessageType">
1186	<xs:sequence>
1187	<xs:element name="mediaProvider" type="xs:boolean"/>
1188	<xs:element name="mediaConsumer" type="xs:boolean"/>
1189	<xs:element name="supportedVersions" type="versionsListType" minOccurs="0"/>
1190	<xs:element name="supportedOptions" type="optionsListType" minOccurs="0"/>
1191	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1192	</xs:sequence>
1193	<xs:anyAttribute namespace="##other" processContents="lax"/>
1194	</xs:extension>
1195	</xs:complexContent>
1196	</xs:complexType>

1198	<!-- VERSIONS LIST TYPE -->
1199	<xs:complexType name="versionsListType">
1200	<xs:sequence>
1201	<xs:element name="version" type="versionType" minOccurs="1"
1202	 maxOccurs="unbounded"/>
1203	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1204	</xs:sequence>
1205	<xs:anyAttribute namespace="##other" processContents="lax"/>
1206	</xs:complexType>

1208	<!-- OPTIONS LIST TYPE -->
1209	<xs:complexType name="optionsListType">
1210	<xs:sequence>
1211	<xs:element name="option" type="optionType" minOccurs="1"
1212	 maxOccurs="unbounded"/>
1213	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1214	</xs:sequence>
1215	<xs:anyAttribute namespace="##other" processContents="lax"/>
1216	</xs:complexType>

1218	<!-- OPTION TYPE -->
1219	<xs:complexType name="optionType">
1220	<xs:sequence>
1221	<xs:element name="name" type="xs:string" />
1222	<xs:element name="schemaRef" type="xs:anyURI" minOccurs="0"/>
1223	<xs:element name="version" type="versionType" minOccurs="0"/>
1224	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1225	</xs:sequence>
1226	<xs:anyAttribute namespace="##other" processContents="lax"/>
1227	</xs:complexType>

1229	<!-- CLUE OPTIONS RESPONSE -->
1230	<xs:complexType name="optionsResponseMessageType">
1231	<xs:complexContent>
1232	<xs:extension base="clueMessageType">
1233	<xs:sequence>
1234	<xs:element name="responseCode" type="responseCodeType"/>
1235	<xs:element name="reasonString" type="xs:string"/>
1236	<xs:element name="mediaProvider" type="xs:boolean" minOccurs="0"/>
1237	<xs:element name="mediaConsumer" type="xs:boolean" minOccurs="0"/>
1238	<xs:element name="version" type="versionType" minOccurs="0"/>
1239	<xs:element name="commonOptions" type="optionsListType" minOccurs="0"/>
1240	<xs:any namespace="##other"
1241	processContents="lax" minOccurs="0"/>
1242	</xs:sequence>
1243	<xs:anyAttribute namespace="##other" processContents="lax"/>
1244	</xs:extension>
1245	</xs:complexContent>
1246	</xs:complexType>

1248	<!-- CLUE ADVERTISEMENT MESSAGE TYPE -->
1249	<xs:complexType name="advertisementMessageType">
1250	<xs:complexContent>
1251	<xs:extension base="clueMessageType">
1252	<xs:sequence>
1253	<!-- mandatory -->
1254	<xs:element name="mediaCaptures" type="dm:mediaCapturesType"/>
1255	<xs:element name="encodingGroups" type="dm:encodingGroupsType"/>
1256	<xs:element name="captureScenes" type="dm:captureScenesType"/>
1257	<!-- optional -->
1258	<xs:element name="simultaneousSets" type="dm:simultaneousSetsType"
1259	 minOccurs="0"/>
1260	<xs:element name="globalViews" type="dm:globalViewsType"
1261	 minOccurs="0"/>
1262	<xs:element name="people" type="dm:peopleType" minOccurs="0"/>
1263	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1264	</xs:sequence>
1265	<xs:anyAttribute namespace="##other" processContents="lax"/>
1266	</xs:extension>
1267	</xs:complexContent>
1268	</xs:complexType>

1270	<!-- ACK MESSAGE TYPE -->
1271	<xs:complexType name="advAcknowledgementMessageType">
1272	<xs:complexContent>
1273	<xs:extension base="clueMessageType">
1274	<xs:sequence>
1275	<xs:element name="responseCode" type="responseCodeType"/>
1276	<xs:element name="reasonString" type="xs:string"/>
1277	<xs:element name="advSequenceNr" type="xs:unsignedInt"/>
1278	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1279	</xs:sequence>
1280	<xs:anyAttribute namespace="##other" processContents="lax"/>
1281	</xs:extension>
1282	</xs:complexContent>
1283	</xs:complexType>

1285	<!-- CLUE CONFIGURE MESSAGE TYPE -->
1286	<xs:complexType name="configureMessageType">
1287	<xs:complexContent>
1288	<xs:extension base="clueMessageType">
1289	<xs:sequence>
1290	<xs:element name="advSequenceNr" type="xs:unsignedInt"/>
1291	<xs:element name="ack" type="xs:boolean"
1292	 minOccurs="0" fixed="true"/>
1293	<xs:element name="captureEncodings" type="dm:captureEncodingsType"
1294	 minOccurs="0"/>
1295	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1296	</xs:sequence>
1297	<xs:anyAttribute namespace="##other" processContents="lax"/>
1298	</xs:extension>
1299	</xs:complexContent>
1300	</xs:complexType>

1302	<!-- CONFIGURE RESPONSE MESSAGE TYPE -->
1303	<xs:complexType name="configureResponseMessageType">
1304	<xs:complexContent>
1305	<xs:extension base="clueMessageType">
1306	<xs:sequence>
1307	<xs:element name="responseCode" type="responseCodeType"/>
1308	<xs:element name="reasonString" type="xs:string"/>
1309	<xs:element name="confSequenceNr" type="xs:unsignedInt"/>
1310	<xs:any namespace="##other" processContents="lax" minOccurs="0"/>
1311	</xs:sequence>
1312	<xs:anyAttribute namespace="##other" processContents="lax"/>
1313	</xs:extension>
1314	</xs:complexContent>
1315	</xs:complexType>

1317	</xs:schema>

1319	10.  Examples

1321	   In the following we provide an example of ADVERTISEMENT representing
1322	   the telepresence environment described in
1323	   [I-D.ietf-clue-data-model-schema], Section "Sample XML file" and
1324	   Section "MCC example" respectively.

1326	10.1.  Simple ADV

1328	   The associated Media Provider's telepresence capabilities are
1329	   described in [I-D.ietf-clue-data-model-schema], Section "Sample XML
1330	   file".

1332	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1333	<advertisement xmlns="urn:ietf:params:xml:ns:clue-protocol"
1334	               xmlns:ns2="urn:ietf:params:xml:ns:clue-info"
1335	               xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0"
1336	               protocol="CLUE" v="0.4">
1337	    <clueId>Napoli</clueId>
1338	    <sequenceNr>45</sequenceNr>
1339	    <mediaCaptures>
1340	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1341	         xsi:type="ns2:videoCaptureType"  captureID="AC0" mediaType="video">
1342	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1343	            <ns2:encGroupIDREF>EG1</ns2:encGroupIDREF>
1344	            <ns2:spatialInformation>
1345	                <ns2:capturePoint>
1346	                    <ns2:x>0.5</ns2:x>
1347	                    <ns2:y>1.0</ns2:y>
1348	                    <ns2:z>0.5</ns2:z>
1349	                    <ns2:lineOfCapturePoint>
1350	                        <ns2:x>0.5</ns2:x>
1351	                        <ns2:y>0.0</ns2:y>
1352	                        <ns2:z>0.5</ns2:z>
1353	                    </ns2:lineOfCapturePoint>
1354	                </ns2:capturePoint>
1355	            </ns2:spatialInformation>
1356	            <ns2:individual>true</ns2:individual>
1357	            <ns2:description lang="en">main audio from the room</ns2:description>
1358	            <ns2:priority>1</ns2:priority>
1359	            <ns2:lang>it</ns2:lang>
1360	            <ns2:mobility>static</ns2:mobility>
1361	            <ns2:view>room</ns2:view>
1362	            <ns2:capturedPeople>
1363	                <ns2:personIDREF>alice</ns2:personIDREF>
1364	                <ns2:personIDREF>bob</ns2:personIDREF>
1365	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1366	            </ns2:capturedPeople>
1367	        </ns2:mediaCapture>
1368	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1369	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC0">
1370	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1371	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1372	            <ns2:spatialInformation>
1373	                <ns2:capturePoint>
1374	                    <ns2:x>0.5</ns2:x>
1375	                    <ns2:y>1.0</ns2:y>
1376	                    <ns2:z>0.5</ns2:z>
1377	                    <ns2:lineOfCapturePoint>
1378	                        <ns2:x>0.5</ns2:x>
1379	                        <ns2:y>0.0</ns2:y>
1380	                        <ns2:z>0.5</ns2:z>
1381	                    </ns2:lineOfCapturePoint>
1382	                </ns2:capturePoint>
1383	            </ns2:spatialInformation>
1384	            <ns2:individual>true</ns2:individual>
1385	            <ns2:description lang="en">left camera video capture
1386	            </ns2:description>
1387	            <ns2:priority>1</ns2:priority>
1388	            <ns2:lang>it</ns2:lang>
1389	            <ns2:mobility>static</ns2:mobility>
1390	            <ns2:view>individual</ns2:view>
1391	            <ns2:capturedPeople>
1392	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1393	            </ns2:capturedPeople>
1394	        </ns2:mediaCapture>
1395	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1396	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC1">
1397	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1398	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1399	            <ns2:spatialInformation>
1400	                <ns2:capturePoint>
1401	                    <ns2:x>0.5</ns2:x>
1402	                    <ns2:y>1.0</ns2:y>
1403	                    <ns2:z>0.5</ns2:z>
1404	                    <ns2:lineOfCapturePoint>
1405	                        <ns2:x>0.5</ns2:x>
1406	                        <ns2:y>0.0</ns2:y>
1407	                        <ns2:z>0.5</ns2:z>
1408	                    </ns2:lineOfCapturePoint>
1409	                </ns2:capturePoint>
1410	            </ns2:spatialInformation>
1411	            <ns2:individual>true</ns2:individual>
1412	            <ns2:description lang="en">central camera video capture
1413	            </ns2:description>
1414	            <ns2:priority>1</ns2:priority>
1415	            <ns2:lang>it</ns2:lang>
1416	            <ns2:mobility>static</ns2:mobility>
1417	            <ns2:view>individual</ns2:view>
1418	            <ns2:capturedPeople>
1419	                <ns2:personIDREF>alice</ns2:personIDREF>
1420	            </ns2:capturedPeople>
1421	        </ns2:mediaCapture>
1422	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1423	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC2">
1424	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1425	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1426	            <ns2:spatialInformation>
1427	                <ns2:capturePoint>
1428	                    <ns2:x>0.5</ns2:x>
1429	                    <ns2:y>1.0</ns2:y>
1430	                    <ns2:z>0.5</ns2:z>
1431	                    <ns2:lineOfCapturePoint>
1432	                        <ns2:x>0.5</ns2:x>
1433	                        <ns2:y>0.0</ns2:y>
1434	                        <ns2:z>0.5</ns2:z>
1435	                    </ns2:lineOfCapturePoint>
1436	                </ns2:capturePoint>
1437	            </ns2:spatialInformation>
1438	            <ns2:individual>true</ns2:individual>
1439	            <ns2:description lang="en">right camera video capture
1440	            </ns2:description>
1441	            <ns2:priority>1</ns2:priority>
1442	            <ns2:lang>it</ns2:lang>
1443	            <ns2:mobility>static</ns2:mobility>
1444	            <ns2:view>individual</ns2:view>
1445	            <ns2:capturedPeople>
1446	                <ns2:personIDREF>bob</ns2:personIDREF>
1447	            </ns2:capturedPeople>
1448	        </ns2:mediaCapture>
1449	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1450	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC3">
1451	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1452	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1453	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1454	            <ns2:composed>false</ns2:composed>
1455	            <ns2:switched>true</ns2:switched>
1456	            <ns2:policy>Soundlevel:0</ns2:policy>
1457	            <ns2:maxCaptures>1</ns2:maxCaptures>
1458	            <ns2:description lang="en">loudest room segment</ns2:description>
1459	            <ns2:priority>1</ns2:priority>
1460	            <ns2:lang>it</ns2:lang>
1461	            <ns2:mobility>static</ns2:mobility>
1462	            <ns2:view>individual</ns2:view>
1463	        </ns2:mediaCapture>
1464	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1465	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="VC4">
1466	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1467	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1468	            <ns2:spatialInformation>
1469	                <ns2:capturePoint>
1470	                    <ns2:x>0.5</ns2:x>
1471	                    <ns2:y>1.0</ns2:y>
1472	                    <ns2:z>0.5</ns2:z>
1473	                    <ns2:lineOfCapturePoint>
1474	                        <ns2:x>0.5</ns2:x>
1475	                        <ns2:y>0.0</ns2:y>
1476	                        <ns2:z>0.5</ns2:z>
1477	                    </ns2:lineOfCapturePoint>
1478	                </ns2:capturePoint>
1479	            </ns2:spatialInformation>
1480	            <ns2:individual>true</ns2:individual>
1481	            <ns2:description lang="en">zoomed out view of all people in
1482	            the room
1483	            </ns2:description>
1484	            <ns2:priority>1</ns2:priority>
1485	            <ns2:lang>it</ns2:lang>
1486	            <ns2:mobility>static</ns2:mobility>
1487	            <ns2:view>room</ns2:view>
1488	            <ns2:capturedPeople>
1489	                <ns2:personIDREF>alice</ns2:personIDREF>
1490	                <ns2:personIDREF>bob</ns2:personIDREF>
1491	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1492	            </ns2:capturedPeople>
1493	        </ns2:mediaCapture>
1494	    </mediaCaptures>
1495	    <encodingGroups>
1496	        <ns2:encodingGroup encodingGroupID="EG0">
1497	            <ns2:maxGroupBandwidth>600000</ns2:maxGroupBandwidth>
1498	            <ns2:encodingIDList>
1499	                <ns2:encID>ENC1</ns2:encID>
1500	                <ns2:encID>ENC2</ns2:encID>
1501	                <ns2:encID>ENC3</ns2:encID>
1502	            </ns2:encodingIDList>
1503	        </ns2:encodingGroup>
1504	        <ns2:encodingGroup encodingGroupID="EG1">
1505	            <ns2:maxGroupBandwidth>300000</ns2:maxGroupBandwidth>
1506	            <ns2:encodingIDList>
1507	                <ns2:encID>ENC4</ns2:encID>
1508	                <ns2:encID>ENC5</ns2:encID>
1509	            </ns2:encodingIDList>
1510	        </ns2:encodingGroup>
1511	    </encodingGroups>
1512	    <captureScenes>
1513	        <ns2:captureScene scale="unknown" sceneID="CS1">
1514	            <ns2:sceneViews>
1515	                <ns2:sceneView sceneViewID="SE1">
1516	                    <ns2:mediaCaptureIDs>
1517	                        <ns2:captureIDREF>VC0</ns2:captureIDREF>
1518	                        <ns2:captureIDREF>VC1</ns2:captureIDREF>
1519	                        <ns2:captureIDREF>VC2</ns2:captureIDREF>

1521	                    </ns2:mediaCaptureIDs>
1522	                </ns2:sceneView>
1523	                <ns2:sceneView sceneViewID="SE2">
1524	                    <ns2:mediaCaptureIDs>
1525	                        <ns2:captureIDREF>VC3</ns2:captureIDREF>
1526	                    </ns2:mediaCaptureIDs>
1527	                </ns2:sceneView>
1528	                <ns2:sceneView sceneViewID="SE3">
1529	                    <ns2:mediaCaptureIDs>
1530	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1531	                    </ns2:mediaCaptureIDs>
1532	                </ns2:sceneView>
1533	                <ns2:sceneView sceneViewID="SE4">
1534	                    <ns2:mediaCaptureIDs>
1535	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1536	                    </ns2:mediaCaptureIDs>
1537	                </ns2:sceneView>
1538	            </ns2:sceneViews>
1539	        </ns2:captureScene>
1540	    </captureScenes>
1541	    <simultaneousSets>
1542	        <ns2:simultaneousSet setID="SS1">
1543	            <ns2:mediaCaptureIDREF>VC3</ns2:mediaCaptureIDREF>
1544	            <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1545	        </ns2:simultaneousSet>
1546	        <ns2:simultaneousSet setID="SS2">
1547	            <ns2:mediaCaptureIDREF>VC0</ns2:mediaCaptureIDREF>
1548	            <ns2:mediaCaptureIDREF>VC2</ns2:mediaCaptureIDREF>
1549	            <ns2:mediaCaptureIDREF>VC4</ns2:mediaCaptureIDREF>
1550	            <ns2:mediaCaptureIDREF>VC3</ns2:mediaCaptureIDREF>
1551	        </ns2:simultaneousSet>
1552	    </simultaneousSets>
1553	    <people>
1554	        <ns2:person personID="bob">
1555	            <ns2:personInfo>
1556	                <ns3:fn>
1557	                    <ns3:text>Bob</ns3:text>
1558	                </ns3:fn>
1559	            </ns2:personInfo>
1560	            <ns2:personType>minute taker</ns2:personType>
1561	        </ns2:person>
1562	        <ns2:person personID="alice">
1563	            <ns2:personInfo>
1564	                <ns3:fn>
1565	                    <ns3:text>Alice</ns3:text>
1566	                </ns3:fn>
1567	            </ns2:personInfo>
1568	            <ns2:personType>presenter</ns2:personType>

1570	        </ns2:person>
1571	        <ns2:person personID="ciccio">
1572	            <ns2:personInfo>
1573	                <ns3:fn>
1574	                    <ns3:text>Ciccio</ns3:text>
1575	                </ns3:fn>
1576	            </ns2:personInfo>
1577	            <ns2:personType>chairman</ns2:personType>
1578	            <ns2:personType>timekeeper</ns2:personType>
1579	        </ns2:person>
1580	    </people>
1581	</advertisement>

1583	10.2.  ADV with MCCs

1585	   The associated Media Provider's telepresence capabilities are
1586	   described in [I-D.ietf-clue-data-model-schema], Section "MCC
1587	   example".

1589	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
1590	<advertisement xmlns="urn:ietf:params:xml:ns:clue-protocol"
1591	 xmlns:ns2="urn:ietf:params:xml:ns:clue-info"
1592	 xmlns:ns3="urn:ietf:params:xml:ns:vcard-4.0" protocol="CLUE" v="0.4">
1593	    <clueId>Napoli CLUE Endpoint</clueId>
1594	    <sequenceNr>34</sequenceNr>
1595	    <mediaCaptures>
1596	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1597	         xsi:type="ns2:videoCaptureType" mediaType="video" captureID="AC0">
1598	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1599	            <ns2:encGroupIDREF>EG1</ns2:encGroupIDREF>
1600	            <ns2:spatialInformation>
1601	                <ns2:capturePoint>
1602	                    <ns2:x>0.5</ns2:x>
1603	                    <ns2:y>1.0</ns2:y>
1604	                    <ns2:z>0.5</ns2:z>
1605	                    <ns2:lineOfCapturePoint>
1606	                        <ns2:x>0.5</ns2:x>
1607	                        <ns2:y>0.0</ns2:y>
1608	                        <ns2:z>0.5</ns2:z>
1609	                    </ns2:lineOfCapturePoint>
1610	                </ns2:capturePoint>
1611	            </ns2:spatialInformation>
1612	            <ns2:individual>true</ns2:individual>
1613	            <ns2:description lang="en">main audio from the room</ns2:description>
1614	            <ns2:priority>1</ns2:priority>
1615	            <ns2:lang>it</ns2:lang>
1616	            <ns2:mobility>static</ns2:mobility>
1617	            <ns2:view>room</ns2:view>
1618	            <ns2:capturedPeople>
1619	                <ns2:personIDREF>alice</ns2:personIDREF>
1620	                <ns2:personIDREF>bob</ns2:personIDREF>
1621	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1622	            </ns2:capturedPeople>
1623	        </ns2:mediaCapture>
1624	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1625	         xsi:type="ns2:videoCaptureType" captureID="VC0" mediaType="video" >
1626	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1627	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1628	            <ns2:spatialInformation>
1629	                <ns2:capturePoint>
1630	                    <ns2:x>0.5</ns2:x>
1631	                    <ns2:y>1.0</ns2:y>
1632	                    <ns2:z>0.5</ns2:z>
1633	                    <ns2:lineOfCapturePoint>
1634	                        <ns2:x>0.5</ns2:x>
1635	                        <ns2:y>0.0</ns2:y>
1636	                        <ns2:z>0.5</ns2:z>
1637	                    </ns2:lineOfCapturePoint>
1638	                </ns2:capturePoint>
1639	            </ns2:spatialInformation>
1640	            <ns2:individual>true</ns2:individual>
1641	            <ns2:description lang="en">left camera video capture</ns2:description>
1642	            <ns2:priority>1</ns2:priority>
1643	            <ns2:lang>it</ns2:lang>
1644	            <ns2:mobility>static</ns2:mobility>
1645	            <ns2:view>individual</ns2:view>
1646	            <ns2:capturedPeople>
1647	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1648	            </ns2:capturedPeople>
1649	        </ns2:mediaCapture>
1650	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1651	        xsi:type="ns2:videoCaptureType" captureID="VC1" mediaType="video">
1652	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1653	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1654	            <ns2:spatialInformation>
1655	                <ns2:capturePoint>
1656	                    <ns2:x>0.5</ns2:x>
1657	                    <ns2:y>1.0</ns2:y>
1658	                    <ns2:z>0.5</ns2:z>
1659	                    <ns2:lineOfCapturePoint>
1660	                        <ns2:x>0.5</ns2:x>
1661	                        <ns2:y>0.0</ns2:y>
1662	                        <ns2:z>0.5</ns2:z>
1663	                    </ns2:lineOfCapturePoint>
1664	                </ns2:capturePoint>
1665	            </ns2:spatialInformation>
1666	            <ns2:individual>true</ns2:individual>
1667	            <ns2:description lang="en">central camera video capture
1668	            </ns2:description>
1669	            <ns2:priority>1</ns2:priority>
1670	            <ns2:lang>it</ns2:lang>
1671	            <ns2:mobility>static</ns2:mobility>
1672	            <ns2:view>individual</ns2:view>
1673	            <ns2:capturedPeople>
1674	                <ns2:personIDREF>alice</ns2:personIDREF>
1675	            </ns2:capturedPeople>
1676	        </ns2:mediaCapture>
1677	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1678	        xsi:type="ns2:videoCaptureType" captureID="VC2" mediaType="video" >
1679	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1680	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1681	            <ns2:spatialInformation>
1682	                <ns2:capturePoint>
1683	                    <ns2:x>0.5</ns2:x>
1684	                    <ns2:y>1.0</ns2:y>
1685	                    <ns2:z>0.5</ns2:z>
1686	                    <ns2:lineOfCapturePoint>
1687	                        <ns2:x>0.5</ns2:x>
1688	                        <ns2:y>0.0</ns2:y>
1689	                        <ns2:z>0.5</ns2:z>
1690	                    </ns2:lineOfCapturePoint>
1691	                </ns2:capturePoint>
1692	            </ns2:spatialInformation>
1693	            <ns2:individual>true</ns2:individual>
1694	            <ns2:description lang="en">right camera video capture
1695	            </ns2:description>
1696	            <ns2:priority>1</ns2:priority>
1697	            <ns2:lang>it</ns2:lang>
1698	            <ns2:mobility>static</ns2:mobility>
1699	            <ns2:view>individual</ns2:view>
1700	            <ns2:capturedPeople>
1701	                <ns2:personIDREF>bob</ns2:personIDREF>
1702	            </ns2:capturedPeople>
1703	        </ns2:mediaCapture>
1704	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1705	        xsi:type="ns2:videoCaptureType" captureID="VC3" mediaType="video" >
1706	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1707	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1708	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1709	            <ns2:content>
1710	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1711	            </ns2:content>
1712	            <ns2:policy>Soundlevel:0</ns2:policy>
1713	            <ns2:maxCaptures>1</ns2:maxCaptures>
1714	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1715	            <ns2:description lang="en">loudest room segment</ns2:description>
1716	            <ns2:priority>1</ns2:priority>
1717	            <ns2:lang>it</ns2:lang>
1718	            <ns2:mobility>static</ns2:mobility>
1719	            <ns2:view>individual</ns2:view>
1720	        </ns2:mediaCapture>
1721	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1722	        xsi:type="ns2:videoCaptureType"  captureID="VC4" mediaType="video">
1723	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1724	            <ns2:encGroupIDREF>EG0</ns2:encGroupIDREF>
1725	            <ns2:spatialInformation>
1726	                <ns2:capturePoint>
1727	                    <ns2:x>0.5</ns2:x>
1728	                    <ns2:y>1.0</ns2:y>
1729	                    <ns2:z>0.5</ns2:z>
1730	                    <ns2:lineOfCapturePoint>
1731	                        <ns2:x>0.5</ns2:x>
1732	                        <ns2:y>0.0</ns2:y>
1733	                        <ns2:z>0.5</ns2:z>
1734	                    </ns2:lineOfCapturePoint>
1735	                </ns2:capturePoint>
1736	            </ns2:spatialInformation>
1737	            <ns2:individual>true</ns2:individual>
1738	            <ns2:description lang="en">zoomed out view of all people in the room
1739	            </ns2:description>
1740	            <ns2:priority>1</ns2:priority>
1741	            <ns2:lang>it</ns2:lang>
1742	            <ns2:mobility>static</ns2:mobility>
1743	            <ns2:view>room</ns2:view>
1744	            <ns2:capturedPeople>
1745	                <ns2:personIDREF>alice</ns2:personIDREF>
1746	                <ns2:personIDREF>bob</ns2:personIDREF>
1747	                <ns2:personIDREF>ciccio</ns2:personIDREF>
1748	            </ns2:capturedPeople>
1749	        </ns2:mediaCapture>
1750	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1751	        xsi:type="ns2:videoCaptureType"  captureID="VC5" mediaType="video">
1752	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1753	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1754	            <ns2:content>
1755	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1756	            </ns2:content>
1757	            <ns2:policy>Soundlevel:1</ns2:policy>
1758	            <ns2:maxCaptures>1</ns2:maxCaptures>
1759	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1760	            <ns2:description lang="en">penultimate loudest room segment
1761	            </ns2:description>
1762	            <ns2:priority>1</ns2:priority>
1763	            <ns2:lang>it</ns2:lang>
1764	            <ns2:mobility>static</ns2:mobility>
1765	            <ns2:view>individual</ns2:view>
1766	        </ns2:mediaCapture>
1767	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1768	        xsi:type="ns2:videoCaptureType"  captureID="VC6" mediaType="video">
1769	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1770	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1771	            <ns2:content>
1772	                <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1773	            </ns2:content>
1774	            <ns2:composed>false</ns2:composed>
1775	            <ns2:switched>true</ns2:switched>
1776	            <ns2:policy>Soundlevel:2</ns2:policy>
1777	            <ns2:maxCaptures>1</ns2:maxCaptures>
1778	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1779	            <ns2:description lang="en">last but two loudest room segment
1780	            </ns2:description>
1781	            <ns2:priority>1</ns2:priority>
1782	            <ns2:lang>it</ns2:lang>
1783	            <ns2:mobility>static</ns2:mobility>
1784	            <ns2:view>individual</ns2:view>
1785	        </ns2:mediaCapture>
1786	        <ns2:mediaCapture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1787	        xsi:type="ns2:videoCaptureType" captureID="VC7" mediaType="video">
1788	            <ns2:captureSceneIDREF>CS1</ns2:captureSceneIDREF>
1789	            <ns2:nonSpatiallyDefinable>true</ns2:nonSpatiallyDefinable>
1790	            <ns2:content>
1791	                <ns2:captureIDREF>VC3</ns2:captureIDREF>
1792	                <ns2:captureIDREF>VC5</ns2:captureIDREF>
1793	                <ns2:captureIDREF>VC6</ns2:captureIDREF>
1794	            </ns2:content>
1795	            <ns2:composed>true</ns2:composed>
1796	            <ns2:switched>true</ns2:switched>
1797	            <ns2:maxCaptures>1</ns2:maxCaptures>
1798	            <ns2:allowSubsetChoice>false</ns2:allowSubsetChoice>
1799	            <ns2:description lang="en">big picture of the current speaker +
1800	            pips about previous speakers</ns2:description>
1801	            <ns2:priority>1</ns2:priority>
1802	            <ns2:lang>it</ns2:lang>
1803	            <ns2:mobility>static</ns2:mobility>
1804	            <ns2:view>individual</ns2:view>
1805	        </ns2:mediaCapture>

1807	    </mediaCaptures>
1808	    <encodingGroups>
1809	        <ns2:encodingGroup encodingGroupID="EG0">
1810	            <ns2:maxGroupBandwidth>600000</ns2:maxGroupBandwidth>
1811	            <ns2:encodingIDList>
1812	                <ns2:encID>ENC1</ns2:encID>
1813	                <ns2:encID>ENC2</ns2:encID>
1814	                <ns2:encID>ENC3</ns2:encID>
1815	            </ns2:encodingIDList>
1816	        </ns2:encodingGroup>
1817	        <ns2:encodingGroup encodingGroupID="EG1">
1818	            <ns2:maxGroupBandwidth>300000</ns2:maxGroupBandwidth>
1819	            <ns2:encodingIDList>
1820	                <ns2:encID>ENC4</ns2:encID>
1821	                <ns2:encID>ENC5</ns2:encID>
1822	            </ns2:encodingIDList>
1823	        </ns2:encodingGroup>
1824	    </encodingGroups>
1825	    <captureScenes>
1826	        <ns2:captureScene scale="unknown" sceneID="CS1">
1827	            <ns2:sceneViews>
1828	                <ns2:sceneView sceneViewID="SE1">
1829	                    <ns2:description lang="en">participants' individual videos
1830	                    </ns2:description>
1831	                    <ns2:mediaCaptureIDs>
1832	                        <ns2:captureIDREF>VC0</ns2:captureIDREF>
1833	                        <ns2:captureIDREF>VC1</ns2:captureIDREF>
1834	                        <ns2:captureIDREF>VC2</ns2:captureIDREF>
1835	                    </ns2:mediaCaptureIDs>
1836	                </ns2:sceneView>
1837	                <ns2:sceneView sceneViewID="SE2">
1838	                    <ns2:description lang="en">loudest segment of the room
1839	                    </ns2:description>
1840	                    <ns2:mediaCaptureIDs>
1841	                        <ns2:captureIDREF>VC3</ns2:captureIDREF>
1842	                    </ns2:mediaCaptureIDs>
1843	                </ns2:sceneView>
1844	                <ns2:sceneView sceneViewID="SE5">
1845	                    <ns2:description lang="en">loudest segment
1846	                    of the room + pips</ns2:description>
1847	                    <ns2:mediaCaptureIDs>
1848	                        <ns2:captureIDREF>VC7</ns2:captureIDREF>
1849	                    </ns2:mediaCaptureIDs>
1850	                </ns2:sceneView>
1851	                <ns2:sceneView sceneViewID="SE4">
1852	                    <ns2:description lang="en">room audio</ns2:description>
1853	                    <ns2:mediaCaptureIDs>
1854	                        <ns2:captureIDREF>AC0</ns2:captureIDREF>

1856	                    </ns2:mediaCaptureIDs>
1857	                </ns2:sceneView>
1858	                <ns2:sceneView sceneViewID="SE3">
1859	                    <ns2:description lang="en">room video</ns2:description>
1860	                    <ns2:mediaCaptureIDs>
1861	                        <ns2:captureIDREF>VC4</ns2:captureIDREF>
1862	                    </ns2:mediaCaptureIDs>
1863	                </ns2:sceneView>
1864	            </ns2:sceneViews>
1865	        </ns2:captureScene>
1866	    </captureScenes>
1867	    <simultaneousSets>
1868	        <ns2:simultaneousSet setID="SS1">
1869	            <ns2:mediaCaptureIDREF>VC7</ns2:mediaCaptureIDREF>
1870	            <ns2:sceneViewIDREF>SE1</ns2:sceneViewIDREF>
1871	        </ns2:simultaneousSet>
1872	        <ns2:simultaneousSet setID="SS2">
1873	            <ns2:mediaCaptureIDREF>VC0</ns2:mediaCaptureIDREF>
1874	            <ns2:mediaCaptureIDREF>VC2</ns2:mediaCaptureIDREF>
1875	            <ns2:mediaCaptureIDREF>VC4</ns2:mediaCaptureIDREF>
1876	            <ns2:mediaCaptureIDREF>VC7</ns2:mediaCaptureIDREF>
1877	        </ns2:simultaneousSet>
1878	    </simultaneousSets>
1879	    <people>
1880	        <ns2:person personID="bob">
1881	            <ns2:personInfo>
1882	                <ns3:fn>
1883	                    <ns3:text>Bob</ns3:text>
1884	                </ns3:fn>
1885	            </ns2:personInfo>
1886	            <ns2:personType>minute taker</ns2:personType>
1887	        </ns2:person>
1888	        <ns2:person personID="alice">
1889	            <ns2:personInfo>
1890	                <ns3:fn>
1891	                    <ns3:text>Alice</ns3:text>
1892	                </ns3:fn>
1893	            </ns2:personInfo>
1894	            <ns2:personType>presenter</ns2:personType>
1895	        </ns2:person>
1896	        <ns2:person personID="ciccio">
1897	            <ns2:personInfo>
1898	                <ns3:fn>
1899	                    <ns3:text>Ciccio</ns3:text>
1900	                </ns3:fn>
1901	            </ns2:personInfo>
1902	            <ns2:personType>chairman</ns2:personType>
1903	            <ns2:personType>timekeeper</ns2:personType>

1905	        </ns2:person>
1906	    </people>
1907	</advertisement>

1909	11.  IANA Considerations

1911	   This document registers a new XML namespace, a new XML schema and the
1912	   MIME type for the schema.  This document also registers the "CLUE"
1913	   Application Service tag and the "CLUE" Application Protocol tag and
1914	   defines registries for the CLUE messages and response codes.

1916	11.1.  URN Sub-Namespace Registration

1918	   This section registers a new XML namespace,
1919	   ""urn:ietf:params:xml:ns:clue-protocol"".

1921	   URI: urn:ietf:params:xml:ns:clue-protocol

1923	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
1924	   Pietro Romano (spromano@unina.it).

1926	   XML:

1928	   BEGIN
1929	    <?xml version="1.0"?>
1930	    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
1931	      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1932	    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
1933	      <head>
1934	        <title>CLUE Messages</title>
1935	      </head>
1936	      <body>
1937	        <h1>Namespace for CLUE Messages</h1>
1938	        <h2>urn:ietf:params:xml:ns:clue-protocol</h2>
1939	   [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
1940	       with the RFC number for this specification.]]
1941	        <p>See <a href="[[RFC URL]]">
1942	           RFCXXXX</a>.</p>
1943	      </body>
1944	    </html>
1945	   END

1947	11.2.  XML Schema registration

1949	   This section registers an XML schema per the guidelines in [RFC3688].

1951	   URI: urn:ietf:params:xml:schema:clue-protocol

1953	   Registrant Contact: CLUE working group (clue@ietf.org), Simon Pietro
1954	   Romano (spromano@unina.it).

1956	   Schema: The XML for this schema can be found as the entirety of
1957	   Section 9 of this document.

1959	11.3.  MIME Media Type Registration for 'application/clue+xml'

1961	   This section registers the " "application/clue+xml"" MIME type.

1963	   To: ietf-types@iana.org

1965	   Subject: Registration of MIME media type application/clue+xml

1967	   MIME media type name: application

1969	   MIME subtype name: clue+xml

1971	   Required parameters: (none)

1973	   Optional parameters: charset
1974	   Same as the charset parameter of "application/xml" as specified in
1975	   [RFC3023], Section 3.2.

1977	   Encoding considerations: Same as the encoding considerations of
1978	   "application/xml" as specified in [RFC3023], Section 3.2.

1980	   Security considerations: This content type is designed to carry
1981	   protocol data related to telepresence session control.  Some of the
1982	   data could be considered private.  This media type does not provide
1983	   any protection and thus other mechanisms such as those described in
1984	   Section Security are required to protect the data.  This media type
1985	   does not contain executable content.

1987	   Interoperability considerations: None.

1989	   Published specification: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
1990	   replace XXXX with the RFC number for this specification.]]

1992	   Applications that use this media type: CLUE participants.

1994	   Additional Information: Magic Number(s): (none),
1995	   File extension(s): .clue,
1996	   Macintosh File Type Code(s): TEXT.

1998	   Person & email address to contact for further information: Simon
1999	   Pietro Romano (spromano@unina.it).

2001	   Intended usage: LIMITED USE

2003	   Author/Change controller: The IETF

2005	   Other information: This media type is a specialization of
2006	   application/xml [RFC3023], and many of the considerations described
2007	   there also apply to application/clue+xml.

2009	11.4.  DNS Registrations

2011	   Section 11.4.1 defines an Application Service tag of "CLUE", which is
2012	   used to identify the CLUE service.  The Application Protocol tag
2013	   "CLUE", defined in Section 11.4.2, is used to identify a CLUE
2014	   Participant that understands CLUE.

2016	11.4.1.  Application Service tag

2018	   This section registers a new S-NAPTR/U-NAPTR Application Service tag
2019	   for CLUE, as mandated by [RFC3958].

2021	   Application Service Tag: CLUE

2023	   Intended usage: Identifies a server that supports CLUE telepresence
2024	   conferencing.

2026	   Defining publication: RFCXXXX [[NOTE TO IANA/RFC-EDITOR: Please
2027	   replace XXXX with the RFC number for this specification.]]

2029	   Contact information: The authors of this document

2031	   Author/Change controller: The IESG

2033	11.4.2.  Application Protocol tag

2035	   This section registers a new S-NAPTR/U-NAPTR Application Protocol tag
2036	   for CLUE, as mandated by [RFC3958].

2038	   Application Service Tag: CLUE

2040	   Intended Usage: Identifies the CLUE Protocol.

2042	   Applicable Service Tag(s): CLUE
2043	   Terminal NAPTR Record Type(s): U

2045	   Defining Publication: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
2046	   replace XXXX with the RFC number for this specification.]]

2048	   Contact Information: The authors of this document

2050	   Author/Change Controller: The IESG

2052	11.5.  CLUE Protocol Registry

2054	   The document requests that the IANA creates new registries for CLUE
2055	   messages and response codes.

2057	11.5.1.  CLUE Message Types

2059	   The following summarizes the registry for CLUE messages:

2061	   Related Registry: CLUE Message Types Registry

2063	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2064	   with the RFC number for this specification.]]

2066	   Registration/Assignment Procedures: Following the policies outlined
2067	   in [RFC5226], the IANA policy for assigning new values for the CLUE
2068	   message types for the CLUE protocol is Specification Required.

2070	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2071	   Pietro Romano (spromano@unina.it).

2073	   The initial Message table is populated using the CLUE messages
2074	   described in Section 4 and defined in the XML schema in Section 9.

2076	   o  OPTIONS

2078	   o  OPTIONS RESPONSE

2080	   o  ADVERTISEMENT (ADV)

2082	   o  ADVERTISEMENT ACKNOWLEDGEMENT (ACK)

2084	   o  CONFIGURE (CONF)

2086	   o  CONFIGURE RESPONSE (CONF RESPONSE)

2088	11.5.2.  CLUE Response Codes

2090	   The following summarizes the requested registry for CLUE response
2091	   codes:

2093	   Related Registry: CLUE Response Code Registry

2095	   Defining RFC: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please replace XXXX
2096	   with the RFC number for this specification.]]

2098	   Registration/Assignment Procedures: Following the policies outlined
2099	   in [RFC5226], the IANA policy for assigning new values for the
2100	   Response codes for CLUE shall be Specification Required.

2102	   Registrant Contact: IETF CLUE working group (clue@ietf.org), Simon
2103	   Pietro Romano (spromano@unina.it).

2105	   The initial Response-code table is populated using the Response codes
2106	   defined in Section 4.7 as follows:

2108	   +-----------------+----------------------+--------------------------+
2109	   |                 |                      |                          |
2110	   |  Response code  |  Response string     |       Description        |
2111	   |                 |                      |                          |
2112	   +-----------------+----------------------+--------------------------+
2113	   |                 |                      |                          |
2114	   |   200           |  Success             |  The request has been    |
2115	   |                 |                      |  successfully processed. |
2116	   |                 |                      |                          |
2117	   +-----------------+----------------------+--------------------------+
2118	   |                 |                      |                          |
2119	   |   300           |  Bad syntax          |  The XML syntax of the   |
2120	   |                 |                      |  message is not          |
2121	   |                 |                      |  correct.                |
2122	   +-----------------+----------------------+--------------------------+
2123	   |                 |                      |                          |
2124	   |   301           |  Invalid value       |  The message             |
2125	   |                 |                      |  contains an invalid     |
2126	   |                 |                      |  parameter value.        |
2127	   +-----------------+----------------------+--------------------------+
2128	   |                 |                      |                          |
2129	   |   302           |  Conflicting values  |  The message             |
2130	   |                 |                      |  contains values that    |
2131	   |                 |                      |  cannot be used together.|
2132	   +-----------------+----------------------+--------------------------+
2133	   |                 |                      |                          |
2134	   |   400           | Version not supported|  The protocol version    |
2135	   |                 |                      |  used in the message     |
2136	   |                 |                      |  is not supported.       |
2137	   |                 |                      |                          |
2138	   +-----------------+----------------------+--------------------------+
2139	   |                 |                      |                          |
2140	   |   401           |  Invalid sequencing  |  The sequence number of  |
2141	   |                 |                      |  the message is out      |
2142	   |                 |                      |  of date.                |
2143	   +-----------------+----------------------+--------------------------+
2144	   |                 |                      |                          |
2145	   |   402           |  Invalid identifier  |  The identifier used in  |
2146	   |                 |                      |  the message is          |
2147	   |                 |                      |  not valid or unknown.   |
2148	   +-----------------+----------------------+--------------------------+
2149	   |                 |                      |                          |
2150	   |   403           |  ADV Expired         |  The number of the ADV   |
2151	   |                 |                      |  the CONF refers to is   |
2152	   |                 |                      |  out of date.            |
2153	   +-----------------+----------------------+--------------------------+
2154	   |                 |                      |                          |
2155	   |   404           |  Subset choice not   |  The subset choice is not|
2156	   |                 |  allowed             | allowed for the specified|
2157	   |                 |                      |  MCC                     |
2158	   +-----------------+----------------------+--------------------------+

2160	12.  Diff with draft-ietf-clue-protocol-03

2162	   o  Response codes section updated.

2164	   o  maxCaptureEncodings removed from examples, allowSubsetChoice
2165	      added.

2167	   o  State machines reviewed and related descriptions aligned with the
2168	      diagrams.

2170	   o  Applied recommended updates indicated in Christian's review (2015-
2171	      03-19).

2173	13.  Diff with draft-ietf-clue-protocol-02

2175	   o  CLUE Participant state machine: TERMINATED state replaced with
2176	      IDLE.

2178	   o  MP and MC state machines: SDP O/A state removed.

2180	   o  Diff mechanism (and related example) removed.

2182	   o  Schema updates: versionType used as the data type for all versions
2183	      fields, xs:unsignedInt used as the data type for all sequence
2184	      number fields, diff support removed from the ADV definition.

2186	14.  Diff with draft-ietf-clue-protocol-01

2188	   o  The diff mechanism for the ADV message has been introduced.

2190	   o  READV and READV RESPONSE message have been both removed.

2192	   o  The state machines have been deeply reviewed and changed.

2194	   o  References: references have been updated and splitted into
2195	      Informative references and Normative references as in framework
2196	      v17.

2198	   o  Schema: <globalSceneEntries> changed in <globalViews>,
2199	      <participants> in <people>

2201	   o  Terminology: many definitions added.

2203	   o  Response codes updated.

2205	15.  Diff with draft-ietf-clue-protocol-00

2207	   1.  The XML schema of the ADVERTISEMENT and of the READV have been
2208	       aligned with the current definitions in
2209	       [I-D.ietf-clue-data-model-schema] (example of updates:
2210	       <participants> --> <people>, <globalCaptureEntries> -->
2211	       <globalSceneEntries>)

2213	   2.  Text has been added to clarify that, in the OPTIONS RESPONSE,
2214	       when the response code is not an error response code, both
2215	       <mediaProvider> and <mediaConsumer> are mandatory.

2217	   3.  The content of the "v" attribute and of the <version> elements
2218	       carried in the OPTIONS and OPTIONS RESPONSE messages has been
2219	       described more precisely.

2221	   4.  Advertisement examples have been added.

2223	16.  Diff with draft-presta-clue-protocol-04

2225	   1.  The response code type error in the OPTIONS response (and in
2226	       other parts) has been corrected.

2228	17.  Diff with draft-presta-clue-protocol-03

2230	   1.  The XML Schema has been deeply revised and completed.

2232	   2.  The descriptions of the CLUE messages have been added.

2234	   3.  The distinction between major version numbers and minor version
2235	       numbers has been cut and pasted from [I-D.ietf-clue-signaling].

2237	   4.  Besides the two way one, a three way mechanism for the options
2238	       negotiation has been proposed and provided to foster discussion.

2240	18.  Diff with draft-presta-clue-protocol-02

2242	   1.  "Terminology" section added.

2244	   2.  Introduced the concept of "CLUE Participant" - an Endpoint or a
2245	       MCU able to use the CLUE protocol within a telepresence session.
2246	       A CLUE Participant can act as a Media Provider and/or as a Media
2247	       Consumer.

2249	   3.  Introduced the ACK/NACK mechanism for the ADVERTISEMENT.

2251	   4.  MP and MC state machines have been updated.  The CP state machine
2252	       has been added.

2254	19.  Acknowledgments

2256	   The authors thank all the CLUErs for their precious feedbacks and
2257	   support, in particular Paul Kyzivat, Christian Groves and Scarlett
2258	   Liuyan.

2260	20.  References

2262	20.1.  Normative References

2264	   [I-D.ietf-clue-data-model-schema]  Presta, R. and S. Romano, "An XML
2265	                                      Schema for the CLUE data model", d
2266	                                      raft-ietf-clue-data-model-schema-
2267	                                      09 (work in progress), April 2015.

2269	   [I-D.ietf-clue-datachannel]        Holmberg, C., "CLUE Protocol data
2270	                                      channel",
2271	                                      (work in progress), March 2015.

2273	   [I-D.ietf-clue-framework]          Duckworth, M., Pepperell, A., and
2274	                                      S. Wenger, "Framework for
2275	                                      Telepresence Multi-Streams",
2276	                                      draft-ietf-clue-framework-22 (work
2277	                                      in progress), April 2015.

2279	   [I-D.ietf-clue-signaling]          Kyzivat, P., Xiao, L., Groves, C.,
2280	                                      and R. Hansen, "CLUE Signaling",
2281	                                      draft-ietf-clue-signaling-05 (work
2282	                                      in progress), March 2015.

2284	   [RFC3023]                          Murata, M., St. Laurent, S., and
2285	                                      D. Kohn, "XML Media Types",
2286	                                      RFC 3023, January 2001.

2288	   [RFC3550]                          Schulzrinne, H., Casner, S.,
2289	                                      Frederick, R., and V. Jacobson,
2290	                                      "RTP: A Transport Protocol for
2291	                                      Real-Time Applications", STD 64,
2292	                                      RFC 3550, July 2003.

2294	   [RFC3688]                          Mealling, M., "The IETF XML
2295	                                      Registry", BCP 81, RFC 3688,
2296	                                      January 2004.

2298	   [RFC3958]                          Daigle, L. and A. Newton, "Domain-
2299	                                      Based Application Service Location
2300	                                      Using SRV RRs and the Dynamic
2301	                                      Delegation Discovery Service
2302	                                      (DDDS)", RFC 3958, January 2005.

2304	   [RFC5226]                          Narten, T. and H. Alvestrand,
2305	                                      "Guidelines for Writing an IANA
2306	                                      Considerations Section in RFCs",
2307	                                      BCP 26, RFC 5226, May 2008.

2309	20.2.  Informative References

2311	   [RFC4353]                          Rosenberg, J., "A Framework for
2312	                                      Conferencing with the Session
2313	                                      Initiation Protocol (SIP)",
2314	                                      RFC 4353, February 2006.

2316	   [RFC5117]                          Westerlund, M. and S. Wenger, "RTP
2317	                                      Topologies", RFC 5117,
2318	                                      January 2008.

2320	   [RFC6120]                          Saint-Andre, P., "Extensible
2321	                                      Messaging and Presence Protocol
2322	                                      (XMPP): Core", RFC 6120,
2323	                                      March 2011.

2325	   [RFC6502]                          Camarillo, G., Srinivasan, S.,
2326	                                      Even, R., and J. Urpalainen,
2327	                                      "Conference Event Package Data
2328	                                      Format Extension for Centralized
2329	                                      Conferencing (XCON)", RFC 6502,
2330	                                      March 2012.

2332	   [RFC6503]                          Barnes, M., Boulton, C., Romano,
2333	                                      S., and H. Schulzrinne,
2334	                                      "Centralized Conferencing
2335	                                      Manipulation Protocol", RFC 6503,
2336	                                      March 2012.

2338	   [RFC7262]                          Romanow, A., Botzko, S., and M.
2339	                                      Barnes, "Requirements for
2340	                                      Telepresence Multistreams",
2341	                                      RFC 7262, June 2014.

2343	Authors' Addresses

2345	   Roberta Presta
2346	   University of Napoli
2347	   Via Claudio 21
2348	   Napoli  80125
2349	   Italy

2351	   EMail: roberta.presta@unina.it

2353	   Simon Pietro Romano
2354	   University of Napoli
2355	   Via Claudio 21
2356	   Napoli  80125
2357	   Italy

2359	   EMail: spromano@unina.it