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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BFCPbis Working Group G. Camarillo 3 Internet-Draft Ericsson 4 Obsoletes: 4583 (if approved) T. Kristensen 5 Intended status: Standards Track Cisco 6 Expires: August 19, 2014 February 15, 2014 8 Session Description Protocol (SDP) Format for Binary Floor Control 9 Protocol (BFCP) Streams 10 draft-ietf-bfcpbis-rfc4583bis-09 12 Abstract 14 This document specifies how to describe Binary Floor Control Protocol 15 (BFCP) streams in Session Description Protocol (SDP) descriptions. 16 User agents using the offer/answer model to establish BFCP streams 17 use this format in their offers and answers. 19 This document obsoletes RFC 4583. Changes from RFC 4583 are 20 summarized in Section 12. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on August 19, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Fields in the 'm' Line . . . . . . . . . . . . . . . . . . . . 3 59 4. Floor Control Server Determination . . . . . . . . . . . . . . 4 60 5. The 'confid' and 'userid' SDP Attributes . . . . . . . . . . . 6 61 6. Association between Streams and Floors . . . . . . . . . . . . 6 62 7. BFCP Version Negotiation . . . . . . . . . . . . . . . . . . . 7 63 8. BFCP Connection Management . . . . . . . . . . . . . . . . . . 8 64 8.1. TCP Connection Management . . . . . . . . . . . . . . . . 8 65 9. Authentication . . . . . . . . . . . . . . . . . . . . . . . . 8 66 10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 67 11. Security Considerations . . . . . . . . . . . . . . . . . . . 11 68 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 69 12.1. Registration of SDP 'proto' Values . . . . . . . . . . . . 12 70 12.2. Registration of the SDP 'floorctrl' Attribute . . . . . . 12 71 12.3. Registration of the SDP 'confid' Attribute . . . . . . . . 13 72 12.4. Registration of the SDP 'userid' Attribute . . . . . . . . 13 73 12.5. Registration of the SDP 'floorid' Attribute . . . . . . . 13 74 12.6. Registration of the SDP 'bfcpver' Attribute . . . . . . . 14 75 13. Changes from RFC 4583 . . . . . . . . . . . . . . . . . . . . 14 76 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 77 15. Normative References . . . . . . . . . . . . . . . . . . . . . 15 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 80 1. Introduction 82 As discussed in the BFCP (Binary Floor Control Protocol) 83 specification [8], a given BFCP client needs a set of data in order 84 to establish a BFCP connection to a floor control server. This data 85 include the transport address of the server, the conference 86 identifier, and the user identifier. 88 One way for clients to obtain this information is to use an offer/ 89 answer [4] exchange. This document specifies how to encode this 90 information in the SDP session descriptions that are part of such an 91 offer/answer exchange. 93 User agents typically use the offer/answer model to establish a 94 number of media streams of different types. Following this model, a 95 BFCP connection is described as any other media stream by using an 96 SDP 'm' line, possibly followed by a number of attributes encoded in 97 'a' lines. 99 2. Terminology 101 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 102 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 103 "OPTIONAL" in this document are to be interpreted as described in BCP 104 14, RFC 2119 [1] and indicate requirement levels for compliant 105 implementations. 107 3. Fields in the 'm' Line 109 This section describes how to generate an 'm' line for a BFCP stream. 111 According to the SDP specification [11], the 'm' line format is the 112 following: 114 m= ... 116 The media field MUST have a value of "application". 118 The port field is set depending on the value of the proto field, as 119 explained below. A port field value of zero has the standard SDP 120 meaning (i.e., rejection of the media stream) regardless of the proto 121 field. 123 When TCP is used as the transport, the port field is set following 124 the rules in [7]. Depending on the value of the 'setup' attribute 125 (discussed in Section 8.1), the port field contains the port to 126 which the remote endpoint will direct BFCP messages or is 127 irrelevant (i.e., the endpoint will initiate the connection 128 towards the remote endpoint) and should be set to a value of 9, 129 which is the discard port. 131 When UDP is used as the transport, the port field contains the 132 port to which the remote endpoint will direct BFCP messages 133 regardless of the value of the 'setup' attribute. 135 This document defines four values for the proto field: TCP/BFCP, TCP/ 136 TLS/BFCP, UDP/BFCP, and UDP/TLS/BFCP. TCP/BFCP is used when BFCP 137 runs directly on top of TCP, TCP/TLS/BFCP is used when BFCP runs on 138 top of TLS, which in turn runs on top of TCP. Similarly, UDP/BFCP is 139 used when BFCP runs directly on top of UDP, and UDP/TLS/BFCP is used 140 when BFCP runs on top of DTLS [12], which in turn runs on top of UDP. 142 The fmt (format) list is not applicable to BFCP. The fmt list of 'm' 143 lines in the case of any proto field value related to BFCP SHOULD 144 contain a single "*" character. If the the fmt list contains any 145 other value it is ignored. 147 The following is an example of an 'm' line for a BFCP connection: 149 m=application 50000 TCP/TLS/BFCP * 151 4. Floor Control Server Determination 153 When two endpoints establish a BFCP stream, they need to determine 154 which of them acts as a floor control server. In the most common 155 scenario, a client establishes a BFCP stream with a conference server 156 that acts as the floor control server. Floor control server 157 determination is straight forward because one endpoint can only act 158 as a client and the other can only act as a floor control server. 160 However, there are scenarios where both endpoints could act as a 161 floor control server. For example, in a two-party session that 162 involves an audio stream and a shared whiteboard, the endpoints need 163 to decide which party will be acting as the floor control server. 165 Furthermore, there are situations where both the offerer and the 166 answerer act as both clients and floor control servers in the same 167 session. For example, in a two-party session that involves an audio 168 stream and a shared whiteboard, one party acts as the floor control 169 server for the audio stream and the other acts as the floor control 170 server for the shared whiteboard. 172 This document defines the 'floorctrl' SDP media-level attribute to 173 perform floor control determination. Its Augmented BNF syntax [2] 174 is: 176 floor-control-attribute = "a=floorctrl:" role *(SP role) 177 role = "c-only" / "s-only" / "c-s" 179 The offerer includes this attribute to state all the roles it would 180 be willing to perform: 182 c-only: The offerer would be willing to act as a floor control 183 client only. 185 s-only: The offerer would be willing to act as a floor control 186 server only. 188 c-s: The offerer would be willing to act both as a floor control 189 client and as a floor control server. 191 If an SDP media description in an offer contains a 'floorctrl' 192 attribute, the answerer accepting that media MUST include a 193 'floorctrl' attribute in the corresponding media description of the 194 answer. The answerer includes this attribute to state which role the 195 answerer will perform. That is, the answerer chooses one of the 196 roles the offerer is willing to perform and generates an answer with 197 the corresponding role for the answerer. Table 1 shows the 198 corresponding roles for an answerer, depending on the offerer's role. 200 +---------+----------+ 201 | Offerer | Answerer | 202 +---------+----------+ 203 | c-only | s-only | 204 | s-only | c-only | 205 | c-s | c-s | 206 +---------+----------+ 208 Table 1: Roles 210 The following are the descriptions of the roles when they are chosen 211 by an answerer: 213 c-only: The answerer will act as a floor control client. 214 Consequently, the offerer will act as a floor control server. 216 s-only: The answerer will act as a floor control server. 217 Consequently, the offerer will act as a floor control client. 219 c-s: The answerer will act both as a floor control client and as a 220 floor control server. Consequently, the offerer will also act 221 both as a floor control client and as a floor control server. 223 Endpoints that use the offer/answer model to establish BFCP 224 connections MUST support the 'floorctrl' attribute. A floor control 225 server acting as an offerer or as an answerer SHOULD include this 226 attribute in its session descriptions. 228 If the 'floorctrl' attribute is not used in an offer/answer exchange, 229 by default the offerer and the answerer will act as a floor control 230 client and as a floor control server, respectively. 232 The following is an example of a 'floorctrl' attribute in an offer. 233 When this attribute appears in an answer, it only carries one role: 235 a=floorctrl:c-only s-only c-s 237 5. The 'confid' and 'userid' SDP Attributes 239 This document defines the 'confid' and the 'userid' SDP media-level 240 attributes. These attributes are used by a floor control server to 241 provide a client with a conference ID and a user ID, respectively. 242 Their Augmented BNF syntax [2] is: 244 confid-attribute = "a=confid:" conference-id 245 conference-id = token 246 userid-attribute = "a=userid:" user-id 247 user-id = token 249 The 'confid' and the 'userid' attributes carry the decimal integer 250 representation of a conference ID and a user ID, respectively. 252 Endpoints that use the offer/answer model to establish BFCP 253 connections MUST support the 'confid' and the 'userid' attributes. A 254 floor control server acting as an offerer or as an answerer MUST 255 include these attributes in its session descriptions. 257 6. Association between Streams and Floors 259 This document defines the 'floorid' SDP media-level attribute. Its 260 Augmented BNF syntax [2] is: 262 floor-id-attribute = "a=floorid:" token [" mstrm:" token *(SP token)] 264 The 'floorid' attribute is used in the SDP media description for BFCP 265 media. It defines a floor identifier and, possibly, associates it 266 with one or more media streams. The token representing the floor ID 267 is the integer representation of the Floor ID to be used in BFCP. 268 The token representing the media stream is a pointer to the media 269 stream, which is identified by an SDP label attribute [9]. 271 Endpoints that use the offer/answer model to establish BFCP 272 connections MUST support the 'floorid' and the 'label' attributes. A 273 floor control server acting as an offerer or as an answerer MUST 274 include these attributes in its session descriptions. 276 Note: In [15] 'm-stream' was erroneously used in Section 10. 277 Although the example was non-normative, it is implemented by some 278 vendors and occurs in cases where the endpoint is willing to act as 279 an server. Therefore, it is RECOMMENDED to support parsing and 280 interpreting 'm-stream' the same way as 'mstrm' when receiving. 282 7. BFCP Version Negotiation 284 This document defines the 'bfcpver' SDP media-level attribute. Its 285 Augmented BNF syntax [2] is: 287 bfcp-version-attribute = "a=bfcpver:" bfcp-version *(SP bfcp-version) 288 bfcp-version = token 290 The 'bfcpver' attribute defines the list of the versions of BFCP 291 supported by the endpoint. Tokens representing versions MUST be 292 integers matching the "Version" field that would be presented in the 293 BFCP COMMON-HEADER [8]. The version of BFCP to be used will then be 294 confirmed with a BFCP-level Hello/HelloAck. 296 Endpoints that use the offer/answer model to establish BFCP 297 connections SHOULD support the 'bfcpver' attribute. A floor control 298 server acting as an offerer or as an answerer SHOULD include this 299 attribute in its session descriptions. However, endpoints that 300 support RFCXXXX, and not only the RFC 4583 subset, are REQUIRED to 301 support and, when acting as a floor control server to use the 302 'bfcpver' attribute. 304 If a 'bfcpver' attribute is not present, default values are inferred 305 from the transport specified in the m-line (Section 3). In 306 accordance with definition of the Version field in [8], when used 307 over a reliable transport the default value is "1", and when used 308 over an unreliable transport the default value is "2". 310 8. BFCP Connection Management 312 BFCP connections can use TCP or UDP as the underlying transport. 313 BFCP entities exchanging BFCP messages over UDP will direct the BFCP 314 messages to the peer side connection address and port provided in the 315 SDP 'm' line. TCP connection management is more complicated and is 316 described below. 318 8.1. TCP Connection Management 320 The management of the TCP connection used to transport BFCP is 321 performed using the 'setup' and 'connection' attributes, as defined 322 in [7]. 324 The 'setup' attribute indicates which of the endpoints (client or 325 floor control server) initiates the TCP connection. The 'connection' 326 attribute handles TCP connection reestablishment. 328 The BFCP specification [8] describes a number of situations when the 329 TCP connection between a client and the floor control server needs to 330 be reestablished. However, that specification does not describe the 331 reestablishment process because this process depends on how the 332 connection was established in the first place. BFCP entities using 333 the offer/answer model follow the following rules. 335 When the existing TCP connection is reset following the rules in [8], 336 the client MUST generate an offer towards the floor control server in 337 order to reestablish the connection. If a TCP connection cannot 338 deliver a BFCP message and times out, the entity that attempted to 339 send the message (i.e., the one that detected the TCP timeout) MUST 340 generate an offer in order to reestablish the TCP connection. 342 Endpoints that use the offer/answer model to establish TCP 343 connections MUST support the 'setup' and 'connection' attributes. 345 9. Authentication 347 When a BFCP connection is established using the offer/answer model, 348 it is assumed that the offerer and the answerer authenticate each 349 other using some mechanism. TLS/DTLS is the preferred mechanism, but 350 other mechanisms are possible and outside the scope of this document. 351 Once this mutual authentication takes place, all the offerer and the 352 answerer need to ensure is that the entity they are receiving BFCP 353 messages from is the same as the one that generated the previous 354 offer or answer. 356 When SIP is used to perform an offer/answer exchange, the initial 357 mutual authentication takes place at the SIP level. Additionally, 358 SIP uses S/MIME [6] to provide an integrity-protected channel with 359 optional confidentiality for the offer/answer exchange. BFCP takes 360 advantage of this integrity-protected offer/answer exchange to 361 perform authentication. Within the offer/answer exchange, the 362 offerer and answerer exchange the fingerprints of their self-signed 363 certificates. These self-signed certificates are then used to 364 establish the TLS/DTLS connection that will carry BFCP traffic 365 between the offerer and the answerer. 367 BFCP clients and floor control servers follow the rules in [10] 368 regarding certificate choice and presentation. This implies that 369 unless a 'fingerprint' attribute is included in the session 370 description, the certificate provided at the TLS-/DTLS-level MUST 371 either be directly signed by one of the other party's trust anchors 372 or be validated using a certification path that terminates at one of 373 the other party's trust anchors [5]. Endpoints that use the offer/ 374 answer model to establish BFCP connections MUST support the 375 'fingerprint' attribute and MUST include it in their session 376 descriptions. 378 When TLS is used with TCP, once the underlying connection is 379 established, the answerer acts as the TLS server regardless of its 380 role (passive or active) in the TCP establishment procedure. 382 Endpoints that use the offer/answer model to establish a DTLS 383 association MUST support the 'setup' attribute, as defined in [7]. 384 When DTLS is used with UDP, the 'setup' attribute indicates which of 385 the endpoints (client or floor control server) initiates the DTLS 386 association setup. The requirements for the offer/answer exchange 387 specified in [13], Section 5 MUST be followed when using DTLS. 389 Informational note: How to determine which endpoint to initiate 390 the TLS/DTLS association depends on the selected underlying 391 transport. It was decided to keep the original semantics in [15] 392 for TCP to retain backwards compatibility. When using UDP, the 393 procedure above was preferred since it adheres to [13] as used for 394 DTLS-SRTP, it does not overload offer/answer semantics, and it 395 works for offerless INVITE in scenarios with B2BUAs. 397 10. Examples 399 For the purpose of brevity, the main portion of the session 400 description is omitted in the examples, which only show 'm' lines and 401 their attributes. 403 The following is an example of an offer sent by a conference server 404 to a client. 406 m=application 50000 TCP/TLS/BFCP * 407 a=setup:passive 408 a=connection:new 409 a=fingerprint:SHA-1 \ 410 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 411 a=floorctrl:s-only 412 a=confid:4321 413 a=userid:1234 414 a=floorid:1 mstrm:10 415 a=floorid:2 mstrm:11 416 a=bfcpver:1 417 m=audio 50002 RTP/AVP 0 418 a=label:10 419 m=video 50004 RTP/AVP 31 420 a=label:11 422 Note that due to RFC formatting conventions, this document splits SDP 423 across lines whose content would exceed 72 characters. A backslash 424 character marks where this line folding has taken place. This 425 backslash and its trailing CRLF and whitespace would not appear in 426 actual SDP content. 428 The following is the answer returned by the client. 430 m=application 9 TCP/TLS/BFCP * 431 a=setup:active 432 a=connection:new 433 a=fingerprint:SHA-1 \ 434 3D:B4:7B:E3:CC:FC:0D:1B:5D:31:33:9E:48:9B:67:FE:68:40:E8:21 435 a=floorctrl:c-only 436 a=bfcpver:1 437 m=audio 55000 RTP/AVP 0 438 m=video 55002 RTP/AVP 31 440 A similar example using unreliable transport and DTLS is shown below, 441 where the offer is sent from a client. 443 m=application 50000 UDP/TLS/BFCP * 444 a=setup:actpass 445 a=fingerprint:SHA-1 \ 446 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 447 a=floorctrl:c-only s-only 448 a=confid:4321 449 a=userid:1234 450 a=floorid:1 mstrm:10 451 a=floorid:2 mstrm:11 452 a=bfcpver:2 453 m=audio 50002 RTP/AVP 0 454 a=label:10 455 m=video 50004 RTP/AVP 31 456 a=label:11 458 The following is the answer returned by the server. 460 m=application 55000 UDP/TLS/BFCP * 461 a=setup:active 462 a=fingerprint:SHA-1 \ 463 3D:B4:7B:E3:CC:FC:0D:1B:5D:31:33:9E:48:9B:67:FE:68:40:E8:21 464 a=floorctrl:s-only 465 a=confid:4321 466 a=userid:1234 467 a=floorid:1 mstrm:10 468 a=floorid:2 mstrm:11 469 a=bfcpver:2 470 m=audio 55002 RTP/AVP 0 471 m=video 55004 RTP/AVP 31 473 11. Security Considerations 475 The BFCP [8], SDP [11], and offer/answer [4] specifications discuss 476 security issues related to BFCP, SDP, and offer/answer, respectively. 477 In addition, [7] and [10] discuss security issues related to the 478 establishment of TCP and TLS connections using an offer/answer model. 479 Furthermore, when using DTLS over UDP, considerations for its use 480 with RTP and RTCP are presented in [13]. The requirements for the 481 offer/answer exchange, as listed in Section 5 of that document, MUST 482 be followed. 484 An initial integrity-protected channel is REQUIRED for BFCP to 485 exchange self-signed certificates between a client and the floor 486 control server. For session descriptions carried in SIP [3], S/MIME 487 [6] is the natural choice to provide such a channel. 489 12. IANA Considerations 491 [Editorial note: The changes in Section 12.1 instruct the IANA to 492 register the two new values UDP/BFCP and UDP/TLS/BFCP for the SDP 493 'proto' field. The new section Section 12.6 registers a new SDP 494 "bfcpver" attribute. The rest is unchanged from [14].] 496 12.1. Registration of SDP 'proto' Values 498 The IANA has registered the following values for the SDP 'proto' 499 field under the Session Description Protocol (SDP) Parameters 500 registry: 502 +--------------+------------+ 503 | Value | Reference | 504 +--------------+------------+ 505 | TCP/BFCP | [RFC XXXX] | 506 | TCP/TLS/BFCP | [RFC XXXX] | 507 | UDP/BFCP | [RFC XXXX] | 508 | UDP/TLS/BFCP | [RFC XXXX] | 509 +--------------+------------+ 511 Table 2: Values for the SDP 'proto' field 513 12.2. Registration of the SDP 'floorctrl' Attribute 515 The IANA has registered the following SDP att-field under the Session 516 Description Protocol (SDP) Parameters registry: 518 Contact name: Gonzalo.Camarillo@ericsson.com 520 Attribute name: floorctrl 522 Long-form attribute name: Floor Control 524 Type of attribute: Media level 526 Subject to charset: No 528 Purpose of attribute: The 'floorctrl' attribute is used to perform 529 floor control server determination. 531 Allowed attribute values: 1*("c-only" / "s-only" / "c-s") 533 12.3. Registration of the SDP 'confid' Attribute 535 The IANA has registered the following SDP att-field under the Session 536 Description Protocol (SDP) Parameters registry: 538 Contact name: Gonzalo.Camarillo@ericsson.com 540 Attribute name: confid 542 Long-form attribute name: Conference Identifier 544 Type of attribute: Media level 546 Subject to charset: No 548 Purpose of attribute: The 'confid' attribute carries the integer 549 representation of a Conference ID. 551 Allowed attribute values: A token 553 12.4. Registration of the SDP 'userid' Attribute 555 The IANA has registered the following SDP att-field under the Session 556 Description Protocol (SDP) Parameters registry: 558 Contact name: Gonzalo.Camarillo@ericsson.com 560 Attribute name: userid 562 Long-form attribute name: User Identifier 564 Type of attribute: Media level 566 Subject to charset: No 568 Purpose of attribute: The 'userid' attribute carries the integer 569 representation of a User ID. 571 Allowed attribute values: A token 573 12.5. Registration of the SDP 'floorid' Attribute 575 The IANA has registered the following SDP att-field under the Session 576 Description Protocol (SDP) Parameters registry: 578 Contact name: Gonzalo.Camarillo@ericsson.com 580 Attribute name: floorid 582 Long-form attribute name: Floor Identifier 584 Type of attribute: Media level 586 Subject to charset: No 588 Purpose of attribute: The 'floorid' attribute associates a floor 589 with one or more media streams. 591 Allowed attribute values: Tokens 593 12.6. Registration of the SDP 'bfcpver' Attribute 595 The IANA has registered the following SDP att-field under the Session 596 Description Protocol (SDP) Parameters registry: 598 Contact name: Gonzalo.Camarillo@ericsson.com 600 Attribute name: bfcpver 602 Long-form attribute name: BFCP Version 604 Type of attribute: Media level 606 Subject to charset: No 608 Purpose of attribute: The 'bfcpver' attribute lists supported BFCP 609 versions. 611 Allowed attribute values: Tokens 613 13. Changes from RFC 4583 615 Following is the list of technical changes and other fixes from [15]. 617 Main purpose of this work was to add signaling support necessary to 618 support BFCP over unreliable transport, as described in [8], 619 resulting in the following changes: 621 1. Fields in the 'm' Line (Section 3): 622 The section is re-written to remove reference to the exclusivity 623 of TCP as a transport for BFCP streams. The proto field values 624 UDP/BFCP and UDP/TLS/BFCP added. 626 2. Authentication (Section 9): 627 In last paragraph, made clear that a TCP connection was 628 described. 630 3. Security Considerations (Section 11): 631 For the DTLS over UDP case, mention existing considerations and 632 requirements for the offer/answer exchange in [13]. 634 4. Registration of SDP 'proto' Values (Section 12.1): 635 Register the two new values UDP/BFCP and UDP/TLS/BFCP in the SDP 636 parameters registry. 638 5. BFCP Version Negotiation (Section 7): 639 A new 'bfcpver' SDP media-level attribute is added in order to 640 signal supported version number. 642 The clarification and bug fixes: 644 1. Errata ID: 712 (Section 4 and Section 6): 645 Language clarification. Don't use terms like an SDP attribute is 646 "used in an 'm' line", instead make clear that the attribute is a 647 media-level attribute. 649 2. Fix typo in example (Section 10): 650 Do not use 'm-stream' in the SDP example, use the correct 'mstrm' 651 as specified in Section 10. Recommend interpreting 'm-stream' if 652 it is received, since it is present in some implementations. 654 3. Assorted clarifications (Across the document): 655 Non-functional language clarifications and some corrections in 656 the normative language as a result of reviews. 658 14. Acknowledgements 660 Joerg Ott, Keith Drage, Alan Johnston, Eric Rescorla, Roni Even, and 661 Oscar Novo provided useful ideas for the original [15]. The authors 662 also acknowledge contributions to the revision of BFCP for use over 663 an unreliable transport from Geir Arne Sandbakken, Charles Eckel, 664 Alan Ford, Eoin McLeod and Mark Thompson. Useful and important final 665 reviews were done by Ali C. Begen, Mary Barnes and Charles Eckel. 667 15. Normative References 669 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 670 Levels", BCP 14, RFC 2119, March 1997. 672 [2] Crocker, D. and P. Overell, "Augmented BNF for Syntax 673 Specifications: ABNF", STD 68, RFC 5234, January 2008. 675 [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 676 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 677 Session Initiation Protocol", RFC 3261, June 2002. 679 [4] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with 680 Session Description Protocol (SDP)", RFC 3264, June 2002. 682 [5] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, 683 R., and W. Polk, "Internet X.509 Public Key Infrastructure 684 Certificate and Certificate Revocation List (CRL) Profile", 685 RFC 5280, May 2008. 687 [6] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail 688 Extensions (S/MIME) Version 3.2 Certificate Handling", 689 RFC 5750, January 2010. 691 [7] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the 692 Session Description Protocol (SDP)", RFC 4145, September 2005. 694 [8] Camarillo, G., Drage, K., Kristensen, T., Ott, J., and C. 695 Eckel, "The Binary Floor Control Protocol (BFCP)", 696 draft-ietf-bfcpbis-rfc4582bis-11 (work in progress), 697 February 2014. 699 [9] Levin, O. and G. Camarillo, "The Session Description Protocol 700 (SDP) Label Attribute", RFC 4574, August 2006. 702 [10] Lennox, J., "Connection-Oriented Media Transport over the 703 Transport Layer Security (TLS) Protocol in the Session 704 Description Protocol (SDP)", RFC 4572, July 2006. 706 [11] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 707 Description Protocol", RFC 4566, July 2006. 709 [12] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 710 Security Version 1.2", RFC 6347, January 2012. 712 [13] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework for 713 Establishing a Secure Real-time Transport Protocol (SRTP) 714 Security Context Using Datagram Transport Layer Security 715 (DTLS)", RFC 5763, May 2010. 717 [14] Camarillo, G., Ott, J., and K. Drage, "The Binary Floor Control 718 Protocol (BFCP)", RFC 4582, November 2006. 720 [15] Camarillo, G., "Session Description Protocol (SDP) Format for 721 Binary Floor Control Protocol (BFCP) Streams", RFC 4583, 722 November 2006. 724 Authors' Addresses 726 Gonzalo Camarillo 727 Ericsson 728 Hirsalantie 11 729 Jorvas 02420 730 Finland 732 Email: Gonzalo.Camarillo@ericsson.com 734 Tom Kristensen 735 Cisco 736 Philip Pedersens vei 22 737 N-1366 Lysaker 738 Norway 740 Email: tomkrist@cisco.com, tomkri@ifi.uio.no