idnits 2.17.1 draft-ietf-bfcpbis-rfc4582bis-14.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 1 instance of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 21, 2015) is 3139 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: 'RFC XXXX' on line 3426 ** Obsolete normative reference: RFC 4582 (ref. '2') (Obsoleted by RFC 8855) ** Obsolete normative reference: RFC 5226 (ref. '5') (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 5246 (ref. '6') (Obsoleted by RFC 8446) ** Obsolete normative reference: RFC 6347 (ref. '7') (Obsoleted by RFC 9147) == Outdated reference: A later version (-27) exists of draft-ietf-bfcpbis-rfc4583bis-12 ** Obsolete normative reference: RFC 5389 (ref. '11') (Obsoleted by RFC 8489) -- Obsolete informational reference (is this intentional?): RFC 5245 (ref. '15') (Obsoleted by RFC 8445, RFC 8839) -- Obsolete informational reference (is this intentional?): RFC 1981 (ref. '21') (Obsoleted by RFC 8201) == Outdated reference: A later version (-11) exists of draft-ietf-uta-tls-bcp-09 -- Obsolete informational reference (is this intentional?): RFC 5405 (ref. '26') (Obsoleted by RFC 8085) -- Obsolete informational reference (is this intentional?): RFC 4960 (ref. '28') (Obsoleted by RFC 9260) == Outdated reference: A later version (-07) exists of draft-ietf-mmusic-media-path-middleboxes-05 Summary: 5 errors (**), 0 flaws (~~), 5 warnings (==), 7 comments (--). 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: 4582 (if approved) K. Drage 5 Intended status: Standards Track Alcatel-Lucent 6 Expires: March 24, 2016 T. Kristensen 7 Cisco 8 J. Ott 9 Aalto University 10 C. Eckel 11 Cisco 12 September 21, 2015 14 The Binary Floor Control Protocol (BFCP) 15 draft-ietf-bfcpbis-rfc4582bis-14 17 Abstract 19 Floor control is a means to manage joint or exclusive access to 20 shared resources in a (multiparty) conferencing environment. 21 Thereby, floor control complements other functions -- such as 22 conference and media session setup, conference policy manipulation, 23 and media control -- that are realized by other protocols. 25 This document specifies the Binary Floor Control Protocol (BFCP). 26 BFCP is used between floor participants and floor control servers, 27 and between floor chairs (i.e., moderators) and floor control 28 servers. 30 This document obsoletes RFC 4582. Changes from RFC 4582 are 31 summarized in Section 16. 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on March 24, 2016. 50 Copyright Notice 52 Copyright (c) 2015 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 70 3.1. Floor Creation . . . . . . . . . . . . . . . . . . . . . . 9 71 3.2. Obtaining Information to Contact a Floor Control Server . 9 72 3.3. Obtaining Floor-Resource Associations . . . . . . . . . . 9 73 3.4. Privileges of Floor Control . . . . . . . . . . . . . . . 10 74 4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 10 75 4.1. Floor Participant to Floor Control Server Interface . . . 11 76 4.2. Floor Chair to Floor Control Server Interface . . . . . . 15 77 5. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . 16 78 5.1. COMMON-HEADER Format . . . . . . . . . . . . . . . . . . . 16 79 5.2. Attribute Format . . . . . . . . . . . . . . . . . . . . . 19 80 5.2.1. BENEFICIARY-ID . . . . . . . . . . . . . . . . . . . . 21 81 5.2.2. FLOOR-ID . . . . . . . . . . . . . . . . . . . . . . . 21 82 5.2.3. FLOOR-REQUEST-ID . . . . . . . . . . . . . . . . . . . 22 83 5.2.4. PRIORITY . . . . . . . . . . . . . . . . . . . . . . . 22 84 5.2.5. REQUEST-STATUS . . . . . . . . . . . . . . . . . . . . 23 85 5.2.6. ERROR-CODE . . . . . . . . . . . . . . . . . . . . . . 24 86 5.2.6.1. Error-Specific Details for Error Code 4 . . . . . 25 87 5.2.7. ERROR-INFO . . . . . . . . . . . . . . . . . . . . . . 25 88 5.2.8. PARTICIPANT-PROVIDED-INFO . . . . . . . . . . . . . . 26 89 5.2.9. STATUS-INFO . . . . . . . . . . . . . . . . . . . . . 27 90 5.2.10. SUPPORTED-ATTRIBUTES . . . . . . . . . . . . . . . . . 27 91 5.2.11. SUPPORTED-PRIMITIVES . . . . . . . . . . . . . . . . . 28 92 5.2.12. USER-DISPLAY-NAME . . . . . . . . . . . . . . . . . . 29 93 5.2.13. USER-URI . . . . . . . . . . . . . . . . . . . . . . . 29 94 5.2.14. BENEFICIARY-INFORMATION . . . . . . . . . . . . . . . 30 95 5.2.15. FLOOR-REQUEST-INFORMATION . . . . . . . . . . . . . . 31 96 5.2.16. REQUESTED-BY-INFORMATION . . . . . . . . . . . . . . . 32 97 5.2.17. FLOOR-REQUEST-STATUS . . . . . . . . . . . . . . . . . 32 98 5.2.18. OVERALL-REQUEST-STATUS . . . . . . . . . . . . . . . . 33 99 5.3. Message Format . . . . . . . . . . . . . . . . . . . . . . 34 100 5.3.1. FloorRequest . . . . . . . . . . . . . . . . . . . . . 34 101 5.3.2. FloorRelease . . . . . . . . . . . . . . . . . . . . . 34 102 5.3.3. FloorRequestQuery . . . . . . . . . . . . . . . . . . 34 103 5.3.4. FloorRequestStatus . . . . . . . . . . . . . . . . . . 35 104 5.3.5. UserQuery . . . . . . . . . . . . . . . . . . . . . . 35 105 5.3.6. UserStatus . . . . . . . . . . . . . . . . . . . . . . 35 106 5.3.7. FloorQuery . . . . . . . . . . . . . . . . . . . . . . 36 107 5.3.8. FloorStatus . . . . . . . . . . . . . . . . . . . . . 36 108 5.3.9. ChairAction . . . . . . . . . . . . . . . . . . . . . 36 109 5.3.10. ChairActionAck . . . . . . . . . . . . . . . . . . . . 36 110 5.3.11. Hello . . . . . . . . . . . . . . . . . . . . . . . . 37 111 5.3.12. HelloAck . . . . . . . . . . . . . . . . . . . . . . . 37 112 5.3.13. Error . . . . . . . . . . . . . . . . . . . . . . . . 37 113 5.3.14. FloorRequestStatusAck . . . . . . . . . . . . . . . . 38 114 5.3.15. FloorStatusAck . . . . . . . . . . . . . . . . . . . . 38 115 5.3.16. Goodbye . . . . . . . . . . . . . . . . . . . . . . . 38 116 5.3.17. GoodbyeAck . . . . . . . . . . . . . . . . . . . . . . 38 117 6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 39 118 6.1. Reliable Transport . . . . . . . . . . . . . . . . . . . . 39 119 6.2. Unreliable Transport . . . . . . . . . . . . . . . . . . . 40 120 6.2.1. Congestion Control . . . . . . . . . . . . . . . . . . 41 121 6.2.2. ICMP Error Handling . . . . . . . . . . . . . . . . . 42 122 6.2.3. Fragmentation Handling . . . . . . . . . . . . . . . . 42 123 6.2.4. NAT Traversal . . . . . . . . . . . . . . . . . . . . 44 124 7. Lower-Layer Security . . . . . . . . . . . . . . . . . . . . . 44 125 8. Protocol Transactions . . . . . . . . . . . . . . . . . . . . 45 126 8.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 45 127 8.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 46 128 8.3. Timers . . . . . . . . . . . . . . . . . . . . . . . . . . 46 129 8.3.1. Request Retransmission Timer, T1 . . . . . . . . . . . 46 130 8.3.2. Response Retransmission Timer, T2 . . . . . . . . . . 46 131 8.3.3. Timer Values . . . . . . . . . . . . . . . . . . . . . 46 132 9. Authentication and Authorization . . . . . . . . . . . . . . . 47 133 9.1. TLS/DTLS Based Mutual Authentication . . . . . . . . . . . 48 134 10. Floor Participant Operations . . . . . . . . . . . . . . . . . 48 135 10.1. Requesting a Floor . . . . . . . . . . . . . . . . . . . . 49 136 10.1.1. Sending a FloorRequest Message . . . . . . . . . . . . 49 137 10.1.2. Receiving a Response . . . . . . . . . . . . . . . . . 50 138 10.1.3. Reception of a Subsequent FloorRequestStatus 139 Message . . . . . . . . . . . . . . . . . . . . . . . 51 140 10.2. Cancelling a Floor Request and Releasing a Floor . . . . . 51 141 10.2.1. Sending a FloorRelease Message . . . . . . . . . . . . 51 142 10.2.2. Receiving a Response . . . . . . . . . . . . . . . . . 52 143 11. Chair Operations . . . . . . . . . . . . . . . . . . . . . . . 52 144 11.1. Sending a ChairAction Message . . . . . . . . . . . . . . 52 145 11.2. Receiving a Response . . . . . . . . . . . . . . . . . . . 54 146 12. General Client Operations . . . . . . . . . . . . . . . . . . 54 147 12.1. Requesting Information about Floors . . . . . . . . . . . 54 148 12.1.1. Sending a FloorQuery Message . . . . . . . . . . . . . 54 149 12.1.2. Receiving a Response . . . . . . . . . . . . . . . . . 55 150 12.1.3. Reception of a Subsequent FloorStatus Message . . . . 56 151 12.2. Requesting Information about Floor Requests . . . . . . . 56 152 12.2.1. Sending a FloorRequestQuery Message . . . . . . . . . 56 153 12.2.2. Receiving a Response . . . . . . . . . . . . . . . . . 56 154 12.3. Requesting Information about a User . . . . . . . . . . . 57 155 12.3.1. Sending a UserQuery Message . . . . . . . . . . . . . 57 156 12.3.2. Receiving a Response . . . . . . . . . . . . . . . . . 58 157 12.4. Obtaining the Capabilities of a Floor Control Server . . . 58 158 12.4.1. Sending a Hello Message . . . . . . . . . . . . . . . 58 159 12.4.2. Receiving Responses . . . . . . . . . . . . . . . . . 58 160 13. Floor Control Server Operations . . . . . . . . . . . . . . . 59 161 13.1. Reception of a FloorRequest Message . . . . . . . . . . . 59 162 13.1.1. Generating the First FloorRequestStatus Message . . . 60 163 13.1.2. Generation of Subsequent FloorRequestStatus 164 Messages . . . . . . . . . . . . . . . . . . . . . . . 61 165 13.2. Reception of a FloorRequestQuery Message . . . . . . . . . 62 166 13.3. Reception of a UserQuery Message . . . . . . . . . . . . . 64 167 13.4. Reception of a FloorRelease Message . . . . . . . . . . . 65 168 13.5. Reception of a FloorQuery Message . . . . . . . . . . . . 66 169 13.5.1. Generation of the First FloorStatus Message . . . . . 67 170 13.5.2. Generation of Subsequent FloorStatus Messages . . . . 68 171 13.6. Reception of a ChairAction Message . . . . . . . . . . . . 69 172 13.7. Reception of a Hello Message . . . . . . . . . . . . . . . 70 173 13.8. Error Message Generation . . . . . . . . . . . . . . . . . 70 174 14. Security Considerations . . . . . . . . . . . . . . . . . . . 71 175 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 72 176 15.1. Attribute Subregistry . . . . . . . . . . . . . . . . . . 72 177 15.2. Primitive Subregistry . . . . . . . . . . . . . . . . . . 73 178 15.3. Request Status Subregistry . . . . . . . . . . . . . . . . 74 179 15.4. Error Code Subregistry . . . . . . . . . . . . . . . . . . 75 180 16. Changes from RFC 4582 . . . . . . . . . . . . . . . . . . . . 76 181 16.1. Extensions for an unreliable transport . . . . . . . . . . 76 182 16.2. Other changes . . . . . . . . . . . . . . . . . . . . . . 77 183 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 78 184 18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 79 185 18.1. Normative References . . . . . . . . . . . . . . . . . . . 79 186 18.2. Informational References . . . . . . . . . . . . . . . . . 79 187 Appendix A. Example Call Flows for BFCP over an Unreliable 188 Transport . . . . . . . . . . . . . . . . . . . . . . 81 189 Appendix B. Motivation for Supporting an Unreliable Transport . . 85 190 B.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 85 191 B.1.1. Alternatives Considered . . . . . . . . . . . . . . . 86 192 B.1.1.1. ICE TCP . . . . . . . . . . . . . . . . . . . . . 86 193 B.1.1.2. Teredo . . . . . . . . . . . . . . . . . . . . . . 87 194 B.1.1.3. GUT . . . . . . . . . . . . . . . . . . . . . . . 87 195 B.1.1.4. UPnP IGD . . . . . . . . . . . . . . . . . . . . . 87 196 B.1.1.5. NAT PMP . . . . . . . . . . . . . . . . . . . . . 88 197 B.1.1.6. SCTP . . . . . . . . . . . . . . . . . . . . . . . 88 198 B.1.1.7. BFCP over UDP transport . . . . . . . . . . . . . 88 199 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 89 201 1. Introduction 203 Within a conference, some applications need to manage the access to a 204 set of shared resources, such as the right to send media to a 205 particular media session. Floor control enables such applications to 206 provide users with coordinated (shared or exclusive) access to these 207 resources. 209 The Requirements for Floor Control Protocol [13] list a set of 210 requirements that need to be met by floor control protocols. The 211 Binary Floor Control Protocol (BFCP), which is specified in this 212 document, meets these requirements. 214 In addition, BFCP has been designed so that it can be used in low- 215 bandwidth environments. The binary encoding used by BFCP achieves a 216 small message size (when message signatures are not used) that keeps 217 the time it takes to transmit delay-sensitive BFCP messages to a 218 minimum. Delay-sensitive BFCP messages include FloorRequest, 219 FloorRelease, FloorRequestStatus, and ChairAction. It is expected 220 that future extensions to these messages will not increase the size 221 of these messages in a significant way. 223 The remainder of this document is organized as follows: Section 2 224 defines the terminology used throughout this document, Section 3 225 discusses the scope of BFCP (i.e., which tasks fall within the scope 226 of BFCP and which ones are performed using different mechanisms), 227 Section 4 provides a non-normative overview of BFCP operation, and 228 subsequent sections provide the normative specification of BFCP. 230 2. Terminology 232 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 233 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 234 "OPTIONAL" in this document are to be interpreted as described in BCP 235 14, RFC 2119 [1] and indicate requirement levels for compliant 236 implementations. 238 Media Participant: An entity that has access to the media resources 239 of a conference (e.g., it can receive a media stream). In floor- 240 controlled conferences, a given media participant is typically 241 colocated with a floor participant, but it does not need to be. 242 Third-party floor requests consist of having a floor participant 243 request a floor for a media participant when they are not colocated. 244 The protocol between a floor participant and a media participant 245 (that are not colocated) is outside the scope of this document. 247 Client: A floor participant or a floor chair that communicates with a 248 floor control server using BFCP. 250 Floor: A temporary permission to access or manipulate a specific 251 shared resource or set of resources. 253 Floor Chair: A logical entity that manages one floor (grants, denies, 254 or revokes a floor). An entity that assumes the logical role of a 255 floor chair for a given transaction may assume a different role 256 (e.g., floor participant) for a different transaction. The roles of 257 floor chair and floor participant are defined on a transaction-by- 258 transaction basis. BFCP transactions are defined in Section 8. 260 Floor Control: A mechanism that enables applications or users to gain 261 safe and mutually exclusive or non-exclusive input access to the 262 shared object or resource. 264 Floor Control Server: A logical entity that maintains the state of 265 the floor(s), including which floors exists, who the floor chairs 266 are, who holds a floor, etc. Requests to manipulate a floor are 267 directed at the floor control server. The floor control server of a 268 conference may perform other logical roles (e.g., floor participant) 269 in another conference. 271 Floor Participant: A logical entity that requests floors, and 272 possibly information about them, from a floor control server. An 273 entity that assumes the logical role of a floor participant for a 274 given transaction may assume a different role (e.g., a floor chair) 275 for a different transaction. The roles of floor participant and 276 floor chair are defined on a transaction-by-transaction basis. BFCP 277 transactions are defined in Section 8. In floor-controlled 278 conferences, a given floor participant is typically colocated with a 279 media participant, but it does not need to be. Third-party floor 280 requests consist of having a floor participant request a floor for a 281 media participant when they are not colocated. 283 Participant: An entity that acts as a floor participant, as a media 284 participant, or as both. 286 BFCP Connection: A transport association between BFCP entities, used 287 to exchange BFCP messages. 289 3. Scope 291 As stated earlier, BFCP is a protocol to coordinate access to shared 292 resources in a conference following the requirements defined in [13]. 293 Floor control complements other functions defined in the XCON 294 conferencing framework [14]. The floor control protocol BFCP defined 295 in this document only specifies a means to arbitrate access to 296 floors. The rules and constraints for floor arbitration and the 297 results of floor assignments are outside the scope of this document 298 and are defined by other protocols [14]. 300 Figure 1 shows the tasks that BFCP can perform. 302 +---------+ 303 | Floor | 304 | Chair | 305 | | 306 +---------+ 307 ^ | 308 | | 309 Notification | | Decision 310 | | 311 | | 312 Floor | v 313 +-------------+ Request +---------+ +-------------+ 314 | Floor |----------->| Floor | Notification | Floor | 315 | Participant | | Control |------------->| Participant | 316 | |<-----------| Server | | | 317 +-------------+ Granted or +---------+ +-------------+ 318 Denied 320 Figure 1: Functionality provided by BFCP 322 BFCP provides a means: 324 o for floor participants to send floor requests to floor control 325 servers. 327 o for floor control servers to grant or deny requests to access a 328 given resource from floor participants. 330 o for floor chairs to send floor control servers decisions regarding 331 floor requests. 333 o for floor control servers to keep floor participants and floor 334 chairs informed about the status of a given floor or a given floor 335 request. 337 Even though tasks that do not belong to the previous list are outside 338 the scope of BFCP, some of these out-of-scope tasks relate to floor 339 control and are essential for creating floors and establishing BFCP 340 connections between different entities. In the following 341 subsections, we discuss some of these tasks and mechanisms to perform 342 them. 344 3.1. Floor Creation 346 The association of a given floor with a resource or a set of 347 resources (e.g., media streams) is out of the scope of BFCP as 348 described in [14]. Floor creation and termination are also outside 349 the scope of BFCP; these aspects are handled using the conference 350 control protocol for manipulating the conference object. 351 Consequently, the floor control server needs to stay up to date on 352 changes to the conference object (e.g., when a new floor is created). 354 Conference control clients using CCMP [18] can specify such floor- 355 related settings in the element [17] of the to-be 356 created conference object provided in the body of a CCMP confRequest/ 357 create message issued to the conference control server. 359 3.2. Obtaining Information to Contact a Floor Control Server 361 A client needs a set of data in order to establish a BFCP connection 362 to a floor control server. This data includes the transport address 363 of the server, the conference identifier, and a user identifier. 365 Clients can obtain this information in different ways. One is to use 366 an SDP offer/answer [12] exchange, which is described in [9]. How to 367 establish a connection to a BFCP floor control server outside the 368 context of an offer/answer exchange when using a reliable transport 369 is described in [3]. Other mechanisms are described in the XCON 370 framework [14] (and other related documents). For unreliable 371 transports, the use of an SDP offer/answer exchange is the only 372 specified mechanism. 374 3.3. Obtaining Floor-Resource Associations 376 Floors are associated with resources. For example, a floor that 377 controls who talks at a given time has a particular audio session as 378 its associated resource. Associations between floors and resources 379 are part of the conference object. 381 Floor participants and floor chairs need to know which resources are 382 associated with which floors. They can obtain this information by 383 using different mechanisms, such as an SDP offer/answer [12] 384 exchange. How to use an SDP offer/answer exchange to obtain these 385 associations is described in [9]. 387 Note that floor participants perform SDP offer/answer exchanges 388 with the conference focus of the conference. So, the conference 389 focus needs to obtain information about associations between 390 floors and resources in order to be able to provide this 391 information to a floor participant in an SDP offer/answer 392 exchange. 394 Other mechanisms for obtaining this information, including discussion 395 of how the information is made available to a (SIP) Focus, are 396 described in the XCON framework [14] (and other related documents). 397 According to the conferencing system policies, conference control 398 clients using CCMP [18] can modify the floor settings of a conference 399 by issuing CCMP confRequest/update messages providing the specific 400 updates to the element of the target conference 401 object. More information about CCMP and BFCP interaction can be 402 found in [19]. 404 3.4. Privileges of Floor Control 406 A participant whose floor request is granted has the right to use the 407 resource or resources associated with the floor that was requested. 408 For example, the participant may have the right to send media over a 409 particular audio stream. 411 Nevertheless, holding a floor does not imply that others will not be 412 able to use its associated resources at the same time, even if they 413 do not have the right to do so. Determination of which media 414 participants can actually use the resources in the conference is 415 discussed in the XCON Framework [14]. 417 4. Overview of Operation 419 This section provides a non-normative description of BFCP operations. 420 Section 4.1 describes the interface between floor participants and 421 floor control servers, and Section 4.2 describes the interface 422 between floor chairs and floor control servers. 424 BFCP messages, which use a TLV (Type-Length-Value) binary encoding, 425 consist of a common header followed by a set of attributes. The 426 common header contains, among other information, a 32-bit conference 427 identifier. Floor participants, media participants, and floor chairs 428 are identified by 16-bit user identifiers. 430 BFCP supports nested attributes (i.e., attributes that contain 431 attributes). These are referred to as grouped attributes. 433 There are two types of transactions in BFCP: client-initiated 434 transactions and server-initiated transactions. Section 8 describes 435 both types of transactions in detail. 437 4.1. Floor Participant to Floor Control Server Interface 439 Floor participants request a floor by sending a FloorRequest message 440 to the floor control server. BFCP supports third-party floor 441 requests. That is, the floor participant sending the floor request 442 need not be colocated with the media participant that will get the 443 floor once the floor request is granted. FloorRequest messages carry 444 the identity of the requester in the User ID field of the common 445 header, and the identity of the beneficiary of the floor (in third- 446 party floor requests) in a BENEFICIARY-ID attribute. 448 Third-party floor requests can be sent, for example, by floor 449 participants that have a BFCP connection to the floor control 450 server but that are not media participants (i.e., they do not 451 handle any media). 453 FloorRequest messages identify the floor or floors being requested by 454 carrying their 16-bit floor identifiers in FLOOR-ID attributes. If a 455 FloorRequest message carries more than one floor identifier, the 456 floor control server treats all the floor requests as an atomic 457 package. That is, the floor control server either grants or denies 458 all the floors in the FloorRequest message. 460 Floor control servers respond to FloorRequest messages with 461 FloorRequestStatus messages, which provide information about the 462 status of the floor request. The first FloorRequestStatus message is 463 the response to the FloorRequest message from the client, and 464 therefore has the same Transaction ID as the FloorRequest. 466 Additionally, the first FloorRequestStatus message carries the Floor 467 Request ID in a FLOOR-REQUEST-INFORMATION attribute. Subsequent 468 FloorRequestStatus messages related to the same floor request will 469 carry the same Floor Request ID. This way, the floor participant can 470 associate them with the appropriate floor request. 472 Messages from the floor participant related to a particular floor 473 request also use the same Floor Request ID as the first 474 FloorRequestStatus Message from the floor control server. 476 Figures 2 and 3 below show examples of call flows where BFCP is used 477 over a reliable transport. Appendix A shows the same call flow 478 examples using an unreliable transport. 480 Figure 2 shows how a floor participant requests a floor, obtains it, 481 and, at a later time, releases it. This figure illustrates the use, 482 among other things, of the Transaction ID and the FLOOR-REQUEST-ID 483 attribute. 485 Floor Participant Floor Control 486 Server 487 |(1) FloorRequest | 488 |Transaction ID: 123 | 489 |User ID: 234 | 490 |FLOOR-ID: 543 | 491 |---------------------------------------------->| 492 | | 493 |(2) FloorRequestStatus | 494 |Transaction ID: 123 | 495 |User ID: 234 | 496 |FLOOR-REQUEST-INFORMATION | 497 | Floor Request ID: 789 | 498 | OVERALL-REQUEST-STATUS | 499 | Request Status: Pending | 500 | FLOOR-REQUEST-STATUS | 501 | Floor ID: 543 | 502 |<----------------------------------------------| 503 | | 504 |(3) FloorRequestStatus | 505 |Transaction ID: 0 | 506 |User ID: 234 | 507 |FLOOR-REQUEST-INFORMATION | 508 | Floor Request ID: 789 | 509 | OVERALL-REQUEST-STATUS | 510 | Request Status: Accepted | 511 | Queue Position: 1st | 512 | FLOOR-REQUEST-STATUS | 513 | Floor ID: 543 | 514 |<----------------------------------------------| 515 | | 516 |(4) FloorRequestStatus | 517 |Transaction ID: 0 | 518 |User ID: 234 | 519 |FLOOR-REQUEST-INFORMATION | 520 | Floor Request ID: 789 | 521 | OVERALL-REQUEST-STATUS | 522 | Request Status: Granted | 523 | FLOOR-REQUEST-STATUS | 524 | Floor ID: 543 | 525 |<----------------------------------------------| 526 | | 527 |(5) FloorRelease | 528 |Transaction ID: 154 | 529 |User ID: 234 | 530 |FLOOR-REQUEST-ID: 789 | 531 |---------------------------------------------->| 532 | | 533 |(6) FloorRequestStatus | 534 |Transaction ID: 154 | 535 |User ID: 234 | 536 |FLOOR-REQUEST-INFORMATION | 537 | Floor Request ID: 789 | 538 | OVERALL-REQUEST-STATUS | 539 | Request Status: Released | 540 | FLOOR-REQUEST-STATUS | 541 | Floor ID: 543 | 542 |<----------------------------------------------| 544 Figure 2: Requesting and releasing a floor 546 Figure 3 shows how a floor participant requests to be informed on the 547 status of a floor. The first FloorStatus message from the floor 548 control server is the response to the FloorQuery message and, as 549 such, has the same Transaction ID as the FloorQuery message. 551 Subsequent FloorStatus messages consist of server-initiated 552 transactions, and therefore their Transaction ID is 0. FloorStatus 553 message (2) indicates that there are currently two floor requests for 554 the floor whose Floor ID is 543. FloorStatus message (3) indicates 555 that the floor requests with Floor Request ID 764 has been granted, 556 and the floor request with Floor Request ID 635 is the first in the 557 queue. FloorStatus message (4) indicates that the floor request with 558 Floor Request ID 635 has been granted. 560 Floor Participant Floor Control 561 Server 562 |(1) FloorQuery | 563 |Transaction ID: 257 | 564 |User ID: 234 | 565 |FLOOR-ID: 543 | 566 |---------------------------------------------->| 567 | | 568 |(2) FloorStatus | 569 |Transaction ID: 257 | 570 |User ID: 234 | 571 |FLOOR-ID:543 | 572 |FLOOR-REQUEST-INFORMATION | 573 | Floor Request ID: 764 | 574 | OVERALL-REQUEST-STATUS | 575 | Request Status: Accepted | 576 | Queue Position: 1st | 577 | FLOOR-REQUEST-STATUS | 578 | Floor ID: 543 | 579 | BENEFICIARY-INFORMATION | 580 | Beneficiary ID: 124 | 581 |FLOOR-REQUEST-INFORMATION | 582 | Floor Request ID: 635 | 583 | OVERALL-REQUEST-STATUS | 584 | Request Status: Accepted | 585 | Queue Position: 2nd | 586 | FLOOR-REQUEST-STATUS | 587 | Floor ID: 543 | 588 | BENEFICIARY-INFORMATION | 589 | Beneficiary ID: 154 | 590 |<----------------------------------------------| 591 | | 592 |(3) FloorStatus | 593 |Transaction ID: 0 | 594 |User ID: 234 | 595 |FLOOR-ID:543 | 596 |FLOOR-REQUEST-INFORMATION | 597 | Floor Request ID: 764 | 598 | OVERALL-REQUEST-STATUS | 599 | Request Status: Granted | 600 | FLOOR-REQUEST-STATUS | 601 | Floor ID: 543 | 602 | BENEFICIARY-INFORMATION | 603 | Beneficiary ID: 124 | 604 |FLOOR-REQUEST-INFORMATION | 605 | Floor Request ID: 635 | 606 | OVERALL-REQUEST-STATUS | 607 | Request Status: Accepted | 608 | Queue Position: 1st | 609 | FLOOR-REQUEST-STATUS | 610 | Floor ID: 543 | 611 | BENEFICIARY-INFORMATION | 612 | Beneficiary ID: 154 | 613 |<----------------------------------------------| 614 | | 615 |(4) FloorStatus | 616 |Transaction ID: 0 | 617 |User ID: 234 | 618 |FLOOR-ID:543 | 619 |FLOOR-REQUEST-INFORMATION | 620 | Floor Request ID: 635 | 621 | OVERALL-REQUEST-STATUS | 622 | Request Status: Granted | 623 | FLOOR-REQUEST-STATUS | 624 | Floor ID: 543 | 625 | BENEFICIARY-INFORMATION | 626 | Beneficiary ID: 154 | 627 |<----------------------------------------------| 629 Figure 3: Obtaining status information about a floor 631 FloorStatus messages contain information about the floor requests 632 they carry. For example, FloorStatus message (4) indicates that the 633 floor request with Floor Request ID 635 has as the beneficiary (i.e., 634 the participant that holds the floor when a particular floor request 635 is granted) the participant whose User ID is 154. The floor request 636 applies only to the floor whose Floor ID is 543. That is, this is 637 not a multi-floor floor request. 639 A multi-floor floor request applies to more than one floor (e.g., 640 a participant wants to be able to speak and write on the 641 whiteboard at the same time). The floor control server treats a 642 multi-floor floor request as an atomic package. That is, the 643 floor control server either grants the request for all floors or 644 denies the request for all floors. 646 4.2. Floor Chair to Floor Control Server Interface 648 Figure 4 shows a floor chair instructing a floor control server to 649 grant a floor. 651 Note, however, that although the floor control server needs to 652 take into consideration the instructions received in ChairAction 653 messages (e.g., granting a floor), it does not necessarily need to 654 perform them exactly as requested by the floor chair. The 655 operation that the floor control server performs depends on the 656 ChairAction message and on the internal state of the floor control 657 server. 659 For example, a floor chair may send a ChairAction message granting a 660 floor that was requested as part of an atomic floor request operation 661 that involved several floors. Even if the chair responsible for one 662 of the floors instructs the floor control server to grant the floor, 663 the floor control server will not grant it until the chairs 664 responsible for the other floors agree to grant them as well. In 665 another example, a floor chair may instruct the floor control server 666 to grant a floor to a participant. The floor control server needs to 667 revoke the floor from its current holder before granting it to the 668 new participant. 670 So, the floor control server is ultimately responsible for keeping a 671 coherent floor state using instructions from floor chairs as input to 672 this state. 674 Floor Chair Floor Control 675 Server 676 |(1) ChairAction | 677 |Transaction ID: 769 | 678 |User ID: 357 | 679 |FLOOR-REQUEST-INFORMATION | 680 | Floor Request ID: 635 | 681 | FLOOR-REQUEST-STATUS | 682 | Floor ID: 543 | 683 | Request Status: Granted | 684 |---------------------------------------------->| 685 | | 686 |(2) ChairActionAck | 687 |Transaction ID: 769 | 688 |User ID: 357 | 689 |<----------------------------------------------| 691 Figure 4: Chair instructing the floor control server 693 5. Packet Format 695 BFCP packets consist of a 12-octet common header followed by 696 attributes. All the protocol values MUST be sent in network byte 697 order. 699 5.1. COMMON-HEADER Format 701 The following is the format of the common header. 703 0 1 2 3 704 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 705 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 706 | Ver |R|F| Res | Primitive | Payload Length | 707 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 708 | Conference ID | 709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 | Transaction ID | User ID | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | Fragment Offset (if F is set) | Fragment Length (if F is set) | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 Figure 5: COMMON-HEADER format 717 Ver: This 3-bit field defines the version of BFCP that this message 718 adheres to. This specification defines two versions: 1 and 2. The 719 version field MUST be set to 1 when using BFCP over a reliable 720 transport. The version field MUST be set to 2 when using BFCP over 721 an unreliable transport. If a floor control server receives a 722 message with an unsupported version field value, and the extensions 723 in this document is supported, the receiving server MUST send an 724 Error message with parameter value 12 (Unsupported Version) to 725 indicate this. Note that BFCP entities supporting only the [2] 726 subset will not support this parameter value. 728 R: The Transaction Responder (R) flag-bit has relevance only for use 729 of BFCP over an unreliable transport. When cleared, it indicates 730 that this message is a request initiating a new transaction, and the 731 Transaction ID that follows has been generated for this transaction. 732 When set, it indicates that this message is a response to a previous 733 request, and the Transaction ID that follows is the one associated 734 with that request. When BFCP is used over a reliable transport, the 735 flag has no significance and MUST be cleared by the sender and MUST 736 be ignored by the receiver. 738 F: The Fragmentation (F) flag-bit has relevance only for use of BFCP 739 over an unreliable transport. When cleared, the message is not 740 fragmented. When set, it indicates that the message is a fragment of 741 a large fragmented BFCP message. (The optional fields Fragment 742 Offset and Fragment Length described below are present only if the F 743 flag is set). When BFCP is used over a reliable transport, the flag 744 has no significance and MUST be cleared by the sender and the flag 745 MUST be ignored by the receiver. In the latter case, the receiver 746 should also process the COMMON-HEADER as not having the Fragment 747 Offset and Fragment Length fields present. 749 Res: At this point, the 3 bits in the reserved field MUST be set to 750 zero by the sender of the message and MUST be ignored by the 751 receiver. 753 Primitive: This 8-bit field identifies the main purpose of the 754 message. The following primitive values are defined: 756 +-------+-----------------------+--------------------+ 757 | Value | Primitive | Direction | 758 +-------+-----------------------+--------------------+ 759 | 1 | FloorRequest | P -> S | 760 | 2 | FloorRelease | P -> S | 761 | 3 | FloorRequestQuery | P -> S ; Ch -> S | 762 | 4 | FloorRequestStatus | P <- S ; Ch <- S | 763 | 5 | UserQuery | P -> S ; Ch -> S | 764 | 6 | UserStatus | P <- S ; Ch <- S | 765 | 7 | FloorQuery | P -> S ; Ch -> S | 766 | 8 | FloorStatus | P <- S ; Ch <- S | 767 | 9 | ChairAction | Ch -> S | 768 | 10 | ChairActionAck | Ch <- S | 769 | 11 | Hello | P -> S ; Ch -> S | 770 | 12 | HelloAck | P <- S ; Ch <- S | 771 | 13 | Error | P <- S ; Ch <- S | 772 | 14 | FloorRequestStatusAck | P -> S ; Ch -> S | 773 | 15 | FloorStatusAck | P -> S ; Ch -> S | 774 | 16 | Goodbye | P -> S ; Ch -> S ; | 775 | | | P <- S ; Ch <- S | 776 | 17 | GoodbyeAck | P -> S ; Ch -> S ; | 777 | | | P <- S ; Ch <- S | 778 +-------+-----------------------+--------------------+ 780 S: Floor Control Server / P: Floor Participant / Ch: Floor Chair 782 Table 1: BFCP primitives 784 Payload Length: This 16-bit field contains the length of the message 785 in 4-octet units, excluding the common header. If a Floor Control 786 Server receives a message with an incorrect Payload Length field 787 value, the receiving server MUST send an Error message with parameter 788 value 13 (Incorrect Message Length) to indicate this. 790 Note: BFCP is designed to achieve small message size, as explained 791 in Section 1, and BFCP entities are REQUIRED to keep the BFCP 792 message size smaller than the size limited by the 16-bit Payload 793 Length field. To convey information not strictly related to floor 794 control, other protocols should be used such as the XCON framework 795 (cf. Section 3). 797 Conference ID: This 32-bit unsigned integer field identifies the 798 conference the message belongs to. 800 Transaction ID: This field contains a 16-bit value that allows users 801 to match a given message with its response (see Section 8). 803 User ID: This field contains a 16-bit unsigned integer that uniquely 804 identifies a participant within a conference. 806 The identity used by a participant in BFCP, which is carried in 807 the User ID field, is generally mapped to the identity used by the 808 same participant in the session establishment protocol (e.g., in 809 SIP). The way this mapping is performed is outside the scope of 810 this specification. 812 Fragment Offset: This optional field is present only if the F flag is 813 set and contains a 16-bit value that specifies the number of 4-octet 814 units contained in previous fragments, excluding the common header. 816 Fragment Length: This optional field is present only if the F flag is 817 set and contains a 16-bit value that specifies the number of 4-octet 818 units contained in this fragment, excluding the common header. 820 5.2. Attribute Format 822 BFCP attributes are encoded in TLV (Type-Length-Value) format. 823 Attributes are 32-bit aligned. 825 0 1 2 3 826 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 827 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 828 | Type |M| Length | | 829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 830 | | 831 / Attribute Contents / 832 / / 833 | | 834 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 836 Figure 6: Attribute format 838 Type: This 7-bit field contains the type of the attribute. Each 839 attribute, identified by its type, has a particular format. The 840 attribute formats defined are: 842 Unsigned16: The contents of the attribute consist of a 16-bit 843 unsigned integer. 845 OctetString16: The contents of the attribute consist of 16 bits of 846 arbitrary data. 848 OctetString: The contents of the attribute consist of arbitrary 849 data of variable length. 851 Grouped: The contents of the attribute consist of a sequence of 852 attributes. 854 Note that extension attributes defined in the future may define 855 new attribute formats. 857 The following attribute types are defined: 859 +------+---------------------------+---------------+ 860 | Type | Attribute | Format | 861 +------+---------------------------+---------------+ 862 | 1 | BENEFICIARY-ID | Unsigned16 | 863 | 2 | FLOOR-ID | Unsigned16 | 864 | 3 | FLOOR-REQUEST-ID | Unsigned16 | 865 | 4 | PRIORITY | OctetString16 | 866 | 5 | REQUEST-STATUS | OctetString16 | 867 | 6 | ERROR-CODE | OctetString | 868 | 7 | ERROR-INFO | OctetString | 869 | 8 | PARTICIPANT-PROVIDED-INFO | OctetString | 870 | 9 | STATUS-INFO | OctetString | 871 | 10 | SUPPORTED-ATTRIBUTES | OctetString | 872 | 11 | SUPPORTED-PRIMITIVES | OctetString | 873 | 12 | USER-DISPLAY-NAME | OctetString | 874 | 13 | USER-URI | OctetString | 875 | 14 | BENEFICIARY-INFORMATION | Grouped | 876 | 15 | FLOOR-REQUEST-INFORMATION | Grouped | 877 | 16 | REQUESTED-BY-INFORMATION | Grouped | 878 | 17 | FLOOR-REQUEST-STATUS | Grouped | 879 | 18 | OVERALL-REQUEST-STATUS | Grouped | 880 +------+---------------------------+---------------+ 882 Table 2: BFCP attributes 884 M: The 'M' bit, known as the Mandatory bit, indicates whether support 885 of the attribute is required. If a Floor Control Server receives an 886 unrecognized attribute with the 'M' bit set the server MUST send an 887 Error message with parameter value 4 (Unknown Mandatory Attribute) to 888 indicate this. The 'M' bit is significant for extension attributes 889 defined in other documents only. All attributes specified in this 890 document MUST be understood by the receiver so that the setting of 891 the 'M' bit is irrelevant for these. In all other cases, the 892 unrecognized attribute is ignored but the message is processed. 894 Length: This 8-bit field contains the length of the attribute in 895 octets, excluding any padding defined for specific attributes. The 896 length of attributes that are not grouped includes the Type, 'M' bit, 897 and Length fields. The Length in grouped attributes is the length of 898 the grouped attribute itself (including Type, 'M' bit, and Length 899 fields) plus the total length (including padding) of all the included 900 attributes. 902 Attribute Contents: The contents of the different attributes are 903 defined in the following sections. 905 5.2.1. BENEFICIARY-ID 907 The following is the format of the BENEFICIARY-ID attribute. 909 0 1 2 3 910 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 912 |0 0 0 0 0 0 1|M|0 0 0 0 0 1 0 0| Beneficiary ID | 913 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 915 Figure 7: BENEFICIARY-ID format 917 Beneficiary ID: This field contains a 16-bit value that uniquely 918 identifies a user within a conference. 920 Note that although the formats of the Beneficiary ID and of the 921 User ID field in the common header are similar, their semantics 922 are different. The Beneficiary ID is used in third-party floor 923 requests and to request information about a particular 924 participant. 926 5.2.2. FLOOR-ID 928 The following is the format of the FLOOR-ID attribute. 930 0 1 2 3 931 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 932 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 933 |0 0 0 0 0 1 0|M|0 0 0 0 0 1 0 0| Floor ID | 934 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 936 Figure 8: FLOOR-ID format 938 Floor ID: This field contains a 16-bit value that uniquely identifies 939 a floor within a conference. 941 5.2.3. FLOOR-REQUEST-ID 943 The following is the format of the FLOOR-REQUEST-ID attribute. 945 0 1 2 3 946 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 948 |0 0 0 0 0 1 1|M|0 0 0 0 0 1 0 0| Floor Request ID | 949 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 951 Figure 9: FLOOR-REQUEST-ID format 953 Floor Request ID: This field contains a 16-bit value that identifies 954 a floor request at the floor control server. 956 5.2.4. PRIORITY 958 The following is the format of the PRIORITY attribute. 960 0 1 2 3 961 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 962 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 963 |0 0 0 0 1 0 0|M|0 0 0 0 0 1 0 0|Prio | Reserved | 964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 966 Figure 10: PRIORITY format 968 Prio: This field contains a 3-bit priority value, as shown in 969 Table 3. Senders SHOULD NOT use values higher than 4 in this field. 970 Receivers MUST treat values higher than 4 as if the value received 971 were 4 (Highest). The default priority value when the PRIORITY 972 attribute is missing is 2 (Normal). 974 +-------+----------+ 975 | Value | Priority | 976 +-------+----------+ 977 | 0 | Lowest | 978 | 1 | Low | 979 | 2 | Normal | 980 | 3 | High | 981 | 4 | Highest | 982 +-------+----------+ 984 Table 3: Priority values 986 Reserved: At this point, the 13 bits in the reserved field MUST be 987 set to zero by the sender of the message and MUST be ignored by the 988 receiver. 990 5.2.5. REQUEST-STATUS 992 The following is the format of the REQUEST-STATUS attribute. 994 0 1 2 3 995 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 996 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 997 |0 0 0 0 1 0 1|M|0 0 0 0 0 1 0 0|Request Status |Queue Position | 998 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1000 Figure 11: REQUEST-STATUS format 1002 Request Status: This 8-bit field contains the status of the request, 1003 as described in the following table. 1005 +-------+-----------+ 1006 | Value | Status | 1007 +-------+-----------+ 1008 | 1 | Pending | 1009 | 2 | Accepted | 1010 | 3 | Granted | 1011 | 4 | Denied | 1012 | 5 | Cancelled | 1013 | 6 | Released | 1014 | 7 | Revoked | 1015 +-------+-----------+ 1017 Table 4: Request Status values 1019 Queue Position: This 8-bit field contains, when applicable, the 1020 position of the floor request in the floor request queue at the 1021 server. If the Request Status value is different from Accepted, if 1022 the floor control server does not implement a floor request queue, or 1023 if the floor control server does not want to provide the client with 1024 this information, all the bits of this field SHOULD be set to zero. 1026 A floor request is in Pending state if the floor control server needs 1027 to contact a floor chair in order to accept the floor request, but 1028 has not done it yet. Once the floor control chair accepts the floor 1029 request, the floor request is moved to the Accepted state. 1031 5.2.6. ERROR-CODE 1033 The following is the format of the ERROR-CODE attribute. 1035 0 1 2 3 1036 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1038 |0 0 0 0 1 1 0|M| Length | Error Code | | 1039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1040 | | 1041 | Error Specific Details | 1042 / / 1043 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 | | Padding | 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1047 Figure 12: ERROR-CODE format 1049 Error Code: This 8-bit field contains an error code from the 1050 following table. If an error code is not recognized by the receiver, 1051 then the receiver MUST assume that an error exists, and therefore 1052 that the original message that triggered the Error message to be sent 1053 is processed, but the nature of the error is unclear. 1055 +-------+-----------------------------------------------------------+ 1056 | Value | Meaning | 1057 +-------+-----------------------------------------------------------+ 1058 | 1 | Conference does not Exist | 1059 | 2 | User does not Exist | 1060 | 3 | Unknown Primitive | 1061 | 4 | Unknown Mandatory Attribute | 1062 | 5 | Unauthorized Operation | 1063 | 6 | Invalid Floor ID | 1064 | 7 | Floor Request ID Does Not Exist | 1065 | 8 | You have Already Reached the Maximum Number of Ongoing | 1066 | | Floor Requests for this Floor | 1067 | 9 | Use TLS | 1068 | 10 | Unable to Parse Message | 1069 | 11 | Use DTLS | 1070 | 12 | Unsupported Version | 1071 | 13 | Incorrect Message Length | 1072 | 14 | Generic Error | 1073 +-------+-----------------------------------------------------------+ 1075 Table 5: Error Code meaning 1077 Note: The Generic Error error code is intended to be used when an 1078 error occurs and the other specific error codes do not apply. 1080 Error Specific Details: Present only for certain Error Codes. In 1081 this document, only for Error Code 4 (Unknown Mandatory Attribute). 1082 See Section 5.2.6.1 for its definition. 1084 Padding: One, two, or three octets of padding added so that the 1085 contents of the ERROR-CODE attribute is 32-bit aligned. If the 1086 attribute is already 32-bit aligned, no padding is needed. 1088 The Padding bits MUST be set to zero by the sender and MUST be 1089 ignored by the receiver. 1091 5.2.6.1. Error-Specific Details for Error Code 4 1093 The following is the format of the Error-Specific Details field for 1094 Error Code 4. 1096 0 1 2 3 1097 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1099 | Unknown Type|R| Unknown Type|R| Unknown Type|R| Unknown Type|R| 1100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1101 | | 1102 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1103 | | Unknown Type|R| Unknown Type|R| 1104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1105 | Unknown Type|R| Unknown Type|R| 1106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1108 Figure 13: Unknown attributes format 1110 Unknown Type: These 7-bit fields contain the Types of the attributes 1111 (which were present in the message that triggered the Error message) 1112 that were unknown to the receiver. 1114 R: At this point, this bit is reserved. It MUST be set to zero by 1115 the sender of the message and MUST be ignored by the receiver. 1117 5.2.7. ERROR-INFO 1119 The following is the format of the ERROR-INFO attribute. 1121 0 1 2 3 1122 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1124 |0 0 0 0 1 1 1|M| Length | | 1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1126 | | 1127 / Text / 1128 / +-+-+-+-+-+-+-+-+ 1129 | | Padding | 1130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 Figure 14: ERROR-INFO format 1134 Text: This field contains UTF-8 [8] encoded text. 1136 In some situations, the contents of the Text field may be generated 1137 by an automaton. If this automaton has information about the 1138 preferred language of the receiver of a particular ERROR-INFO 1139 attribute, it MAY use this language to generate the Text field. 1141 Padding: One, two, or three octets of padding added so that the 1142 contents of the ERROR-INFO attribute is 32-bit aligned. The Padding 1143 bits MUST be set to zero by the sender and MUST be ignored by the 1144 receiver. If the attribute is already 32-bit aligned, no padding is 1145 needed. 1147 5.2.8. PARTICIPANT-PROVIDED-INFO 1149 The following is the format of the PARTICIPANT-PROVIDED-INFO 1150 attribute. 1152 0 1 2 3 1153 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1155 |0 0 0 1 0 0 0|M| Length | | 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1157 | | 1158 / Text / 1159 / +-+-+-+-+-+-+-+-+ 1160 | | Padding | 1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1163 Figure 15: PARTICIPANT-PROVIDED-INFO format 1165 Text: This field contains UTF-8 [8] encoded text. 1167 Padding: One, two, or three octets of padding added so that the 1168 contents of the PARTICIPANT-PROVIDED-INFO attribute is 32-bit 1169 aligned. The Padding bits MUST be set to zero by the sender and MUST 1170 be ignored by the receiver. If the attribute is already 32-bit 1171 aligned, no padding is needed. 1173 5.2.9. STATUS-INFO 1175 The following is the format of the STATUS-INFO attribute. 1177 0 1 2 3 1178 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1180 |0 0 0 1 0 0 1|M| Length | | 1181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1182 | | 1183 / Text / 1184 / +-+-+-+-+-+-+-+-+ 1185 | | Padding | 1186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1188 Figure 16: STATUS-INFO format 1190 Text: This field contains UTF-8 [8] encoded text. 1192 In some situations, the contents of the Text field may be generated 1193 by an automaton. If this automaton has information about the 1194 preferred language of the receiver of a particular STATUS-INFO 1195 attribute, it MAY use this language to generate the Text field. 1197 Padding: One, two, or three octets of padding added so that the 1198 contents of the STATUS-INFO attribute is 32-bit aligned. The Padding 1199 bits MUST be set to zero by the sender and MUST be ignored by the 1200 receiver. If the attribute is already 32-bit aligned, no padding is 1201 needed. 1203 5.2.10. SUPPORTED-ATTRIBUTES 1205 The following is the format of the SUPPORTED-ATTRIBUTES attribute. 1207 0 1 2 3 1208 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1210 |0 0 0 1 0 1 0|M| Length | Supp. Attr. |R| Supp. Attr. |R| 1211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1212 | Supp. Attr. |R| Supp. Attr. |R| Supp. Attr. |R| Supp. Attr. |R| 1213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1214 | | 1215 / / 1216 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1217 | | Padding | 1218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1220 Figure 17: SUPPORTED-ATTRIBUTES format 1222 Supp. Attr.: These fields contain the Types of the attributes that 1223 are supported by the floor control server in the following format: 1225 R: Reserved: This bit MUST be set to zero upon transmission and MUST 1226 be ignored upon reception. 1228 Padding: One, two, or three octets of padding added so that the 1229 contents of the SUPPORTED-ATTRIBUTES attribute is 32-bit aligned. If 1230 the attribute is already 32-bit aligned, no padding is needed. 1232 The Padding bits MUST be set to zero by the sender and MUST be 1233 ignored by the receiver. 1235 5.2.11. SUPPORTED-PRIMITIVES 1237 The following is the format of the SUPPORTED-PRIMITIVES attribute. 1239 0 1 2 3 1240 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1242 |0 0 0 1 0 1 1|M| Length | Primitive | Primitive | 1243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1244 | Primitive | Primitive | Primitive | Primitive | 1245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1246 | | 1247 / / 1248 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1249 | | Padding | 1250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1252 Figure 18: SUPPORTED-PRIMITIVES format 1254 Primitive: These fields contain the types of the BFCP messages that 1255 are supported by the floor control server. See Table 1 for the list 1256 of BFCP primitives. 1258 Padding: One, two, or three octets of padding added so that the 1259 contents of the SUPPORTED-PRIMITIVES attribute is 32-bit aligned. If 1260 the attribute is already 32-bit aligned, no padding is needed. 1262 The Padding bits MUST be set to zero by the sender and MUST be 1263 ignored by the receiver. 1265 5.2.12. USER-DISPLAY-NAME 1267 The following is the format of the USER-DISPLAY-NAME attribute. 1269 0 1 2 3 1270 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1272 |0 0 0 1 1 0 0|M| Length | | 1273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1274 | | 1275 / Text / 1276 / +-+-+-+-+-+-+-+-+ 1277 | | Padding | 1278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1280 Figure 19: USER-DISPLAY-NAME format 1282 Text: This field contains the UTF-8 encoded name of the user. 1284 Padding: One, two, or three octets of padding added so that the 1285 contents of the USER-DISPLAY-NAME attribute is 32-bit aligned. The 1286 Padding bits MUST be set to zero by the sender and MUST be ignored by 1287 the receiver. If the attribute is already 32-bit aligned, no padding 1288 is needed. 1290 5.2.13. USER-URI 1292 The following is the format of the USER-URI attribute. 1294 0 1 2 3 1295 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1297 |0 0 0 1 1 0 1|M| Length | | 1298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1299 | | 1300 / Text / 1301 / +-+-+-+-+-+-+-+-+ 1302 | | Padding | 1303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1305 Figure 20: USER-URI format 1307 Text: This field contains the UTF-8 encoded user's contact URI, that 1308 is, the URI used by the user to set up the resources (e.g., media 1309 streams) that are controlled by BFCP. For example, in the context of 1310 a conference set up by SIP, the USER-URI attribute would carry the 1311 SIP URI of the user. 1313 Messages containing a user's URI in a USER-URI attribute also 1314 contain the user's User ID. This way, a client receiving such a 1315 message can correlate the user's URI (e.g., the SIP URI the user 1316 used to join a conference) with the user's User ID. 1318 Padding: One, two, or three octets of padding added so that the 1319 contents of the USER-URI attribute is 32-bit aligned. The Padding 1320 bits MUST be set to zero by the sender and MUST be ignored by the 1321 receiver. If the attribute is already 32-bit aligned, no padding is 1322 needed. 1324 5.2.14. BENEFICIARY-INFORMATION 1326 The BENEFICIARY-INFORMATION attribute is a grouped attribute that 1327 consists of a header, which is referred to as BENEFICIARY- 1328 INFORMATION-HEADER, followed by a sequence of attributes. The 1329 following is the format of the BENEFICIARY-INFORMATION-HEADER: 1331 0 1 2 3 1332 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1334 |0 0 0 1 1 1 0|M| Length | Beneficiary ID | 1335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1337 Figure 21: BENEFICIARY-INFORMATION-HEADER format 1339 Beneficiary ID: This field contains a 16-bit value that uniquely 1340 identifies a user within a conference. 1342 The following is the ABNF (Augmented Backus-Naur Form) [4] of the 1343 BENEFICIARY-INFORMATION grouped attribute. (EXTENSION-ATTRIBUTE 1344 refers to extension attributes that may be defined in the future.) 1346 BENEFICIARY-INFORMATION = (BENEFICIARY-INFORMATION-HEADER) 1347 [USER-DISPLAY-NAME] 1348 [USER-URI] 1349 *(EXTENSION-ATTRIBUTE) 1351 Figure 22: BENEFICIARY-INFORMATION format 1353 5.2.15. FLOOR-REQUEST-INFORMATION 1355 The FLOOR-REQUEST-INFORMATION attribute is a grouped attribute that 1356 consists of a header, which is referred to as FLOOR-REQUEST- 1357 INFORMATION-HEADER, followed by a sequence of attributes. The 1358 following is the format of the FLOOR-REQUEST-INFORMATION-HEADER: 1360 0 1 2 3 1361 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1363 |0 0 0 1 1 1 1|M| Length | Floor Request ID | 1364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1366 Figure 23: FLOOR-REQUEST-INFORMATION-HEADER format 1368 Floor Request ID: This field contains a 16-bit value that identifies 1369 a floor request at the floor control server. 1371 The following is the ABNF of the FLOOR-REQUEST-INFORMATION grouped 1372 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1373 may be defined in the future.) 1375 FLOOR-REQUEST-INFORMATION = (FLOOR-REQUEST-INFORMATION-HEADER) 1376 [OVERALL-REQUEST-STATUS] 1377 1*(FLOOR-REQUEST-STATUS) 1378 [BENEFICIARY-INFORMATION] 1379 [REQUESTED-BY-INFORMATION] 1380 [PRIORITY] 1381 [PARTICIPANT-PROVIDED-INFO] 1382 *(EXTENSION-ATTRIBUTE) 1384 Figure 24: FLOOR-REQUEST-INFORMATION format 1386 5.2.16. REQUESTED-BY-INFORMATION 1388 The REQUESTED-BY-INFORMATION attribute is a grouped attribute that 1389 consists of a header, which is referred to as REQUESTED-BY- 1390 INFORMATION-HEADER, followed by a sequence of attributes. The 1391 following is the format of the REQUESTED-BY-INFORMATION-HEADER: 1393 0 1 2 3 1394 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1396 |0 0 1 0 0 0 0|M| Length | Requested-by ID | 1397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1399 Figure 25: REQUESTED-BY-INFORMATION-HEADER format 1401 Requested-by ID: This field contains a 16-bit value that uniquely 1402 identifies a user within a conference. 1404 The following is the ABNF of the REQUESTED-BY-INFORMATION grouped 1405 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1406 may be defined in the future.) 1408 REQUESTED-BY-INFORMATION = (REQUESTED-BY-INFORMATION-HEADER) 1409 [USER-DISPLAY-NAME] 1410 [USER-URI] 1411 *(EXTENSION-ATTRIBUTE) 1413 Figure 26: REQUESTED-BY-INFORMATION format 1415 5.2.17. FLOOR-REQUEST-STATUS 1417 The FLOOR-REQUEST-STATUS attribute is a grouped attribute that 1418 consists of a header, which is referred to as FLOOR-REQUEST-STATUS- 1419 HEADER, followed by a sequence of attributes. The following is the 1420 format of the FLOOR-REQUEST-STATUS-HEADER: 1422 0 1 2 3 1423 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1425 |0 0 1 0 0 0 1|M| Length | Floor ID | 1426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1428 Figure 27: FLOOR-REQUEST-STATUS-HEADER format 1430 Floor ID: this field contains a 16-bit value that uniquely identifies 1431 a floor within a conference. 1433 The following is the ABNF of the FLOOR-REQUEST-STATUS grouped 1434 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1435 may be defined in the future.) 1437 FLOOR-REQUEST-STATUS = (FLOOR-REQUEST-STATUS-HEADER) 1438 [REQUEST-STATUS] 1439 [STATUS-INFO] 1440 *(EXTENSION-ATTRIBUTE) 1442 Figure 28: FLOOR-REQUEST-STATUS format 1444 5.2.18. OVERALL-REQUEST-STATUS 1446 The OVERALL-REQUEST-STATUS attribute is a grouped attribute that 1447 consists of a header, which is referred to as OVERALL-REQUEST-STATUS- 1448 HEADER, followed by a sequence of attributes. The following is the 1449 format of the OVERALL-REQUEST-STATUS-HEADER: 1451 0 1 2 3 1452 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1454 |0 0 1 0 0 1 0|M| Length | Floor Request ID | 1455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1457 Figure 29: OVERALL-REQUEST-STATUS-HEADER format 1459 Floor Request ID: this field contains a 16-bit value that identifies 1460 a floor request at the floor control server. 1462 The following is the ABNF of the OVERALL-REQUEST-STATUS grouped 1463 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1464 may be defined in the future.) 1466 OVERALL-REQUEST-STATUS = (OVERALL-REQUEST-STATUS-HEADER) 1467 [REQUEST-STATUS] 1468 [STATUS-INFO] 1469 *(EXTENSION-ATTRIBUTE) 1471 Figure 30: OVERALL-REQUEST-STATUS format 1473 5.3. Message Format 1475 This section contains the normative ABNF (Augmented Backus-Naur Form) 1476 [4] of the BFCP messages. Extension attributes that may be defined 1477 in the future are referred to as EXTENSION-ATTRIBUTE in the ABNF. 1479 5.3.1. FloorRequest 1481 Floor participants request a floor by sending a FloorRequest message 1482 to the floor control server. The following is the format of the 1483 FloorRequest message: 1485 FloorRequest = (COMMON-HEADER) 1486 1*(FLOOR-ID) 1487 [BENEFICIARY-ID] 1488 [PARTICIPANT-PROVIDED-INFO] 1489 [PRIORITY] 1490 *(EXTENSION-ATTRIBUTE) 1492 Figure 31: FloorRequest format 1494 5.3.2. FloorRelease 1496 Floor participants release a floor by sending a FloorRelease message 1497 to the floor control server. Floor participants also use the 1498 FloorRelease message to cancel pending floor requests. The following 1499 is the format of the FloorRelease message: 1501 FloorRelease = (COMMON-HEADER) 1502 (FLOOR-REQUEST-ID) 1503 *(EXTENSION-ATTRIBUTE) 1505 Figure 32: FloorRelease format 1507 5.3.3. FloorRequestQuery 1509 Floor participants and floor chairs request information about a floor 1510 request by sending a FloorRequestQuery message to the floor control 1511 server. The following is the format of the FloorRequestQuery 1512 message: 1514 FloorRequestQuery = (COMMON-HEADER) 1515 (FLOOR-REQUEST-ID) 1516 *(EXTENSION-ATTRIBUTE) 1518 Figure 33: FloorRequestQuery format 1520 5.3.4. FloorRequestStatus 1522 The floor control server informs floor participants and floor chairs 1523 about the status of their floor requests by sending them 1524 FloorRequestStatus messages. The following is the format of the 1525 FloorRequestStatus message: 1527 FloorRequestStatus = (COMMON-HEADER) 1528 (FLOOR-REQUEST-INFORMATION) 1529 *(EXTENSION-ATTRIBUTE) 1531 Figure 34: FloorRequestStatus format 1533 5.3.5. UserQuery 1535 Floor participants and floor chairs request information about a 1536 participant and the floor requests related to this participant by 1537 sending a UserQuery message to the floor control server. The 1538 following is the format of the UserQuery message: 1540 UserQuery = (COMMON-HEADER) 1541 [BENEFICIARY-ID] 1542 *(EXTENSION-ATTRIBUTE) 1544 Figure 35: UserQuery format 1546 5.3.6. UserStatus 1548 The floor control server provides information about participants and 1549 their related floor requests to floor participants and floor chairs 1550 by sending them UserStatus messages. The following is the format of 1551 the UserStatus message: 1553 UserStatus = (COMMON-HEADER) 1554 [BENEFICIARY-INFORMATION] 1555 *(FLOOR-REQUEST-INFORMATION) 1556 *(EXTENSION-ATTRIBUTE) 1558 Figure 36: UserStatus format 1560 5.3.7. FloorQuery 1562 Floor participants and floor chairs request information about a floor 1563 or floors by sending a FloorQuery message to the floor control 1564 server. The following is the format of the FloorRequest message: 1566 FloorQuery = (COMMON-HEADER) 1567 *(FLOOR-ID) 1568 *(EXTENSION-ATTRIBUTE) 1570 Figure 37: FloorQuery format 1572 5.3.8. FloorStatus 1574 The floor control server informs floor participants and floor chairs 1575 about the status (e.g., the current holder) of a floor by sending 1576 them FloorStatus messages. The following is the format of the 1577 FloorStatus message: 1579 FloorStatus = (COMMON-HEADER) 1580 [FLOOR-ID] 1581 *(FLOOR-REQUEST-INFORMATION) 1582 *(EXTENSION-ATTRIBUTE) 1584 Figure 38: FloorStatus format 1586 5.3.9. ChairAction 1588 Floor chairs send instructions to floor control servers by sending 1589 them ChairAction messages. The following is the format of the 1590 ChairAction message: 1592 ChairAction = (COMMON-HEADER) 1593 (FLOOR-REQUEST-INFORMATION) 1594 *(EXTENSION-ATTRIBUTE) 1596 Figure 39: ChairAction format 1598 5.3.10. ChairActionAck 1600 Floor control servers confirm that they have accepted a ChairAction 1601 message by sending a ChairActionAck message. The following is the 1602 format of the ChairActionAck message: 1604 ChairActionAck = (COMMON-HEADER) 1605 *(EXTENSION-ATTRIBUTE) 1607 Figure 40: ChairActionAck format 1609 5.3.11. Hello 1611 Floor participants and floor chairs check the liveliness of floor 1612 control servers by sending a Hello message. The following is the 1613 format of the Hello message: 1615 Hello = (COMMON-HEADER) 1616 *(EXTENSION-ATTRIBUTE) 1618 Figure 41: Hello format 1620 5.3.12. HelloAck 1622 Floor control servers confirm that they are alive on reception of a 1623 Hello message by sending a HelloAck message. The following is the 1624 format of the HelloAck message: 1626 HelloAck = (COMMON-HEADER) 1627 (SUPPORTED-PRIMITIVES) 1628 (SUPPORTED-ATTRIBUTES) 1629 *(EXTENSION-ATTRIBUTE) 1631 Figure 42: HelloAck format 1633 5.3.13. Error 1635 Floor control servers inform floor participants and floor chairs 1636 about errors processing requests by sending them Error messages. The 1637 following is the format of the Error message: 1639 Error = (COMMON-HEADER) 1640 (ERROR-CODE) 1641 [ERROR-INFO] 1642 *(EXTENSION-ATTRIBUTE) 1644 Figure 43: Error format 1646 5.3.14. FloorRequestStatusAck 1648 When communicating over an unreliable transport, floor participants 1649 and chairs acknowledge the receipt of a subsequent FloorRequestStatus 1650 message from the floor control server (cf. Section 13.1.2) by sending 1651 a FloorRequestStatusAck message. The following is the format of the 1652 FloorRequestStatusAck message: 1654 FloorRequestStatusAck = (COMMON-HEADER) 1655 *(EXTENSION-ATTRIBUTE) 1657 Figure 44: FloorRequestStatusAck format 1659 5.3.15. FloorStatusAck 1661 When communicating over an unreliable transport, floor participants 1662 and chairs acknowledge the receipt of a subsequent FloorStatus 1663 message from the floor control server (cf. Section 13.5.2) by sending 1664 a FloorStatusAck message. The following is the format of the 1665 FloorStatusAck message: 1667 FloorStatusAck = (COMMON-HEADER) 1668 *(EXTENSION-ATTRIBUTE) 1670 Figure 45: FloorStatusAck format 1672 5.3.16. Goodbye 1674 BFCP entities communicating over an unreliable transport that wish to 1675 dissociate themselves from their remote participant do so through the 1676 transmission of a Goodbye. The following is the format of the 1677 Goodbye message: 1679 Goodbye = (COMMON-HEADER) 1680 *(EXTENSION-ATTRIBUTE) 1682 Figure 46: Goodbye format 1684 5.3.17. GoodbyeAck 1686 BFCP entities communicating over an unreliable transport acknowledge 1687 the receipt of a Goodbye message from a peer. The following is the 1688 format of the GoodbyeAck message: 1690 GoodbyeAck = (COMMON-HEADER) 1691 *(EXTENSION-ATTRIBUTE) 1693 Figure 47: GoodbyeAck format 1695 6. Transport 1697 The transport over which BFCP entities exchange messages depends on 1698 the information the clients obtain for how to to contact the floor 1699 control server, as described in Section 3.2. Two transports are 1700 supported: TCP, appropriate where connectivity is not impeded by 1701 network elements such as NAT devices or media relays; and UDP for 1702 those deployments where TCP may not be applicable or appropriate. 1704 Informational note: In practice, products are configured to try 1705 one transport first and use the other transport as a fallback. 1706 Whether TCP or UDP is chosen as underlying transport depends on 1707 the type of product and the deployment environment. See 1708 Appendix B for additional considerations. 1710 6.1. Reliable Transport 1712 BFCP entities may elect to exchange BFCP messages using TCP 1713 connections. TCP provides an in-order reliable delivery of a stream 1714 of bytes. Consequently, message framing needs to be implemented in 1715 the application layer. BFCP implements application-layer framing 1716 using TLV-encoded attributes. 1718 A client MUST NOT use more than one TCP connection to communicate 1719 with a given floor control server within a conference. Nevertheless, 1720 if the same physical box handles different clients (e.g., a floor 1721 chair and a floor participant), which are identified by different 1722 User IDs, a separate connection per client is allowed. 1724 If a BFCP entity (a client or a floor control server) receives data 1725 that cannot be parsed, the entity MUST close the TCP connection, and 1726 the connection SHOULD be reestablished. Similarly, if a TCP 1727 connection cannot deliver a BFCP message and times out or receives an 1728 ICMP port unreachable message mid-connection, the TCP connection 1729 SHOULD be reestablished. 1731 The way connection reestablishment is handled depends on how the 1732 client obtains information to contact the floor control server. Once 1733 the TCP connection is reestablished, the client MAY resend those 1734 messages for which it did not get a response from the floor control 1735 server. 1737 If a floor control server detects that the TCP connection towards one 1738 of the floor participants is lost, it is up to the local policy of 1739 the floor control server what to do with the pending floor requests 1740 of the floor participant. In any case, it is RECOMMENDED that the 1741 floor control server keep the floor requests (i.e., that it does not 1742 cancel them) while the TCP connection is reestablished. 1744 If a client wishes to end its BFCP connection with a floor control 1745 server, the client closes (i.e., a graceful close) the TCP connection 1746 towards the floor control server. If a floor control server wishes 1747 to end its BFCP connection with a client (e.g., the Focus of the 1748 conference informs the floor control server that the client has been 1749 kicked out from the conference), the floor control server closes 1750 (i.e., a graceful close) the TCP connection towards the client. 1752 6.2. Unreliable Transport 1754 BFCP entities may elect to exchange BFCP messages using UDP 1755 datagrams. UDP is an unreliable transport where neither delivery nor 1756 ordering is assured. Each BFCP UDP datagram MUST contain exactly one 1757 BFCP message or message fragment. To keep large BFCP messages from 1758 being fragmented at the IP layer, the fragmentation of BFCP messages 1759 that exceed the path MTU size is performed at the BFCP level. 1760 Considerations related to fragmentation are covered in Section 6.2.3. 1761 The message format for BFCP messages is the same regardless of 1762 whether the messages are sent in UDP datagrams or over a TCP stream. 1764 Clients MUST announce their presence to the floor control server by 1765 sending a Hello message. The floor control server responds to the 1766 Hello message with a HelloAck message. The client considers the 1767 floor control service as present and available only upon receiving 1768 the HelloAck message. Situations where the floor control service is 1769 considered to have become unavailable due to ICMP messages are 1770 described in Section 6.2.2 and the behavior when timers fire is 1771 described in Section 8.3. 1773 As described in Section 8, each request sent by a floor participant 1774 or chair forms a client transaction that expects an acknowledgement 1775 message back from the floor control server within a retransmission 1776 window. Concordantly, messages sent by the floor control server that 1777 initiate new transactions (e.g., FloorStatus announcements as part of 1778 a FloorQuery subscription) require acknowledgement messages from the 1779 floor participant and chair entities to which they were sent. 1781 If a Floor Control Server receives data that cannot be parsed, the 1782 receiving server MUST send an Error message with parameter value 10 1783 (Unable to parse message) indicating receipt of a malformed message, 1784 given that it is possible to parse the received message to such an 1785 extent that an Error message may be built. 1787 Entities MUST have at most one outstanding request transaction per 1788 peer at any one time. Implicit subscriptions occur for a client- 1789 initiated request transaction whose acknowledgement is implied by the 1790 first server-initiated response for that transaction, followed by 1791 zero of more subsequent server-initiated messages corresponding to 1792 the same transaction. An example is a FloorRequest message for which 1793 there are potentially multiple responses from the floor control 1794 server as it processes intermediate states until a terminal state 1795 (e.g., Granted or Denied) is attained. The subsequent changes in 1796 state for the request are new transactions whose Transaction ID is 1797 determined by the floor control server and whose receipt by the 1798 client participant is acknowledged with a FloorRequestStatusAck 1799 message. 1801 By restricting entities to having at most one pending transaction 1802 open in a BFCP connection, both the out-of-order receipt of messages 1803 as well as the possibility for congestion are mitigated. Additional 1804 details regarding congestion control are provided in Section 6.2.1. 1805 A server-initiated request (e.g., a FloorStatus with an update from 1806 the floor control server) received by a participant before the 1807 initial FloorRequestStatus message that closes the client-initiated 1808 transaction that was instigated by the FloorRequest MUST be treated 1809 as superseding the information conveyed in any such late arriving 1810 response. As the floor control server cannot send a second update to 1811 the implicit floor status subscription until the first is 1812 acknowledged, ordinality is maintained. 1814 If a client wishes to end its BFCP connection with a floor control 1815 server, it is REQUIRED that the client send a Goodbye message to 1816 dissociate itself from any allocated resources. If a floor control 1817 server wishes to end its BFCP connection with a client (e.g., the 1818 Focus of the conference informs the floor control server that the 1819 client has been kicked out from the conference), it is REQUIRED that 1820 the floor control server send a Goodbye message towards the client. 1822 6.2.1. Congestion Control 1824 BFCP may be characterized to generate "low data-volume" traffic, per 1825 the classification in [26]. Nevertheless is it necessary to ensure 1826 suitable and necessary congestion control mechanisms are used for 1827 BFCP over UDP. As described in Section 6.2, within the same BFCP 1828 connection, every entity - client or server - is only allowed to send 1829 one request at a time, and await the acknowledging response. This 1830 way at most one datagram is sent per RTT given the message is not 1831 lost during transmission. In case the message is lost, the request 1832 retransmission timer T1 specified in Section 8.3.1 will fire and the 1833 message is retransmitted up to three times, in addition to the 1834 original transmission of the message. The default initial interval 1835 MUST be set to 500ms and the interval MUST be doubled after each 1836 retransmission attempt. This is identical to the specification of 1837 the timer A and its initial value T1 in SIP as described in Section 1838 17.1.1.2 of [16]. 1840 6.2.2. ICMP Error Handling 1842 If a BFCP entity receives an ICMP port unreachable message mid- 1843 connection, the entity MUST treat the BFCP connection as closed 1844 (e.g., an implicit Goodbye message from the peer). The entity MAY 1845 attempt to re-establish the BFCP connection afresh. The new BFCP 1846 connection will appear as originating from a wholly new floor 1847 participant, chair or floor control server with all state previously 1848 held about that participant lost. 1850 Informational note: The recommendation to treat the connection as 1851 closed in this case, stems from the fact that the peer entities 1852 cannot rely on IP and port tuple to uniquely identify the 1853 participant, nor would extending Hello to include an attribute 1854 that advertised what identity the entity previously was assigned 1855 (i.e., a User ID) be acceptable due to session hijacking. 1857 In deployments where NAT appliances or other such devices are present 1858 and affecting port reachability for each entity, one possibility is 1859 to utilize the peer connectivity checks, relay use and NAT pinhole 1860 maintenance mechanisms defined in ICE [15]. 1862 6.2.3. Fragmentation Handling 1864 When using UDP, a single BFCP message could be fragmented at the IP 1865 layer if its overall size exceeds the path MTU of the network. To 1866 avoid this happening at the IP layer, a fragmentation scheme for BFCP 1867 is defined below. 1869 BFCP is designed for achieving small message size, due to the binary 1870 encoding as described in Section 1. The fragmentation scheme is 1871 therefore deliberately kept simple and straightforward, since the 1872 probability of fragmentation of BFCP messages being required is 1873 small. By design, the fragmentation scheme does not acknowledge 1874 individual BFCP message fragments. The whole BFCP message is 1875 acknowledged if received completely. 1877 BFCP entities should consider the MTU size available between the 1878 sender and the receiver and MAY run MTU discovery, such as 1879 [20][21][22], for this purpose. 1881 When transmitting a BFCP message with size greater than the path MTU, 1882 the sender MUST fragment the message into a series of N contiguous 1883 data ranges. The value for N is defined as ceil(message size - 1884 COMMON-HEADER size / MTU size - COMMON-HEADER size), where ceil is 1885 the integer ceiling function and the COMMON-HEADER size includes the 1886 Fragment Offset and Fragment Length fields. The sender then creates 1887 N BFCP fragment messages (one for each data range) with the same 1888 Transaction ID. The size of each of these N messages, with the 1889 COMMON-HEADER included, MUST be smaller than the path MTU. The F 1890 flag in the COMMON-HEADER in all the fragments is set to indicate 1891 fragmentation of the BFCP message. 1893 For each of these fragments the Fragment Offset and Fragment Length 1894 fields are included in the COMMON-HEADER. The Fragment Offset field 1895 denotes the number of bytes contained in the previous fragments. The 1896 Fragment Length contains the length of the fragment itself. Note 1897 that the Payload Length field contains the length of the entire, 1898 unfragmented message. 1900 When a BFCP implementation receives a BFCP message fragment, it MUST 1901 buffer the fragment until either it has received the entire BFCP 1902 message, or until the Response Retransmission Timer expires. The 1903 state machine should handle the BFCP message only after all the 1904 fragments for the message have been received. 1906 If a fragment of a BFCP message is lost, the sender will not receive 1907 an acknowledgement for the message. Therefore the sender will 1908 retransmit the message with same transaction ID as specified in 1909 Section 8.3. If the acknowledgement message sent by the receiver is 1910 lost, then the entire message will be resent by the sender. The 1911 receiver MUST then retransmit the acknowledgement. The receiver MAY 1912 discard an incomplete buffer utilizing the Response Retransmission 1913 Timer, starting the timer after the receipt of the first fragment. 1915 A Denial of Service (DoS) attack utilizing the fragmentation 1916 scheme described above is mitigated by the fact that the Response 1917 Retransmission Timer is started after receipt of the first BFCP 1918 message fragment. In addition, the Payload Length field can be 1919 compared with the Fragment Offset and Fragment Length fields to 1920 verify the message fragments as they arrive. To make DoS attacks 1921 with spoofed IP addresses difficult, BFCP entities SHOULD use the 1922 cookie exchange mechanism in DTLS [7]. 1924 When deciding message fragment size based on path MTU, the BFCP 1925 fragmentation handling should take into account how the DTLS record 1926 framing expands the datagram size as described in Section 4.1.1.1 of 1927 [7]. 1929 6.2.4. NAT Traversal 1931 One of the key benefits when using UDP for BFCP communication is the 1932 ability to leverage the existing NAT traversal infrastructure and 1933 strategies deployed to facilitate transport of the media associated 1934 with the video conferencing sessions. Depending on the given 1935 deployment, this infrastructure typically includes some subset of ICE 1936 [15]. 1938 In order to facilitate the initial establishment of NAT bindings, and 1939 to maintain those bindings once established, BFCP entities using an 1940 unreliable transport are RECOMMENDED to use STUN [11] Binding 1941 Indication for keep-alives, as described for ICE [15]. Section 6.7 1942 of [23] provides useful recommendations for middlebox interaction 1943 when DTLS is used. 1945 Informational note: Since the version number is set to 2 when BFCP 1946 is used over an unreliable transport, cf. the Ver field in 1947 Section 5.1, it is straight forward to distinguish between STUN 1948 and BFCP packets even without checking the STUN magic cookie [11]. 1950 In order to facilitate traversal of BFCP packets through NATs, BFCP 1951 entities using an unreliable transport are RECOMMENDED to use 1952 symmetric ports for sending and receiving BFCP packets, as 1953 recommended for RTP/RTCP [10]. 1955 7. Lower-Layer Security 1957 BFCP relies on lower-layer security mechanisms to provide replay and 1958 integrity protection and confidentiality. BFCP floor control servers 1959 and clients (which include both floor participants and floor chairs) 1960 MUST support TLS for transport over TCP [6] and MUST support DTLS [7] 1961 for transport over UDP. Any BFCP entity MAY support other security 1962 mechanisms. 1964 BFCP entities MUST support, at a minimum, the 1965 TLS_RSA_WITH_AES_128_CBC_SHA cipher suite [6] for backwards 1966 compatibility with existing implementations of RFC 4582. In 1967 accordance with the recommendations and guidelines in [24], BFCP 1968 entities SHOULD support the following cipher suites: 1970 o TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 1972 o TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 1974 o TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 1975 o TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 1977 8. Protocol Transactions 1979 In BFCP, there are two types of transactions: client-initiated 1980 transactions and server-initiated transactions. 1982 Client-initiated transactions consist of a request from a client to a 1983 floor control server and a response from the floor control server to 1984 the client. 1986 Server-initiated transactions have different requirements and 1987 behavior depending on underlying transport: 1989 When using a reliable transport, server-initiated transactions 1990 consist of a single message from a floor control server to a 1991 client (notifications). They do not trigger any response. 1993 When using an unreliable transport, server-initiated transactions 1994 consist of a request from a floor control server to a client and a 1995 response from the client to the floor control server. 1997 When using BFCP over an unreliable transport, retransmission timer T1 1998 (see Section 8.3) MUST be used for all requests until the transaction 1999 is completed. 2001 8.1. Client Behavior 2003 A client starting a client-initiated transaction MUST set the 2004 Conference ID in the common header of the message to the Conference 2005 ID for the conference that the client obtained previously. 2007 The client MUST set the Transaction ID value in the common header to 2008 a number that is different from 0 and that MUST NOT be reused in 2009 another message from the client until a response from the server is 2010 received for the transaction. The client uses the Transaction ID 2011 value to match this message with the response from the floor control 2012 server. When using BFCP over an unreliable transport, it is 2013 important to choose a Transaction ID value that lets the receiver 2014 distinguish the reception of the next message in a sequence of BFCP 2015 messages from a retransmission of a previous message. Therefore, 2016 BFCP entities using an unreliable transport MUST use monotonically 2017 increasing Transaction ID values (except for wrap-around). 2019 A client receiving a server-initiated transaction over an unreliable 2020 transport MUST copy the Transaction ID from the request received from 2021 the server into the response. 2023 8.2. Server Behavior 2025 A floor control server sending a response within a client-initiated 2026 transaction MUST copy the Conference ID, the Transaction ID, and the 2027 User ID from the request received from the client into the response. 2029 Server-initiated transactions MUST contain a Transaction ID equal to 2030 0 when BFCP is used over a reliable transport. Over an unreliable 2031 transport, the Transaction ID shall have the same properties as for 2032 client-initiated transactions. The server uses the Transaction ID 2033 value to match this message with the response from the floor 2034 participant or floor chair. 2036 8.3. Timers 2038 When BFCP entities are communicating over an unreliable transport, 2039 two retransmission timers are employed to help mitigate against loss 2040 of datagrams. Retransmission and response caching are not required 2041 when BFCP entities communicate over a reliable transport. 2043 8.3.1. Request Retransmission Timer, T1 2045 T1 is a timer that schedules retransmission of a request until an 2046 appropriate response is received or until the maximum number of 2047 retransmissions have occurred. The timer doubles on each re- 2048 transmit, failing after three unacknowledged retransmission attempts. 2050 If a valid response is not received for a client- or server-initiated 2051 transaction, the implementation MUST consider the BFCP connection as 2052 failed. Implementations SHOULD follow the reestablishment procedure 2053 described in section 6. 2055 8.3.2. Response Retransmission Timer, T2 2057 T2 is a timer that, when fired, signals that the BFCP entity can 2058 release knowledge of the transaction against which it is running. It 2059 is started upon the first transmission of the response to a request 2060 and is the only mechanism by which that response is released by the 2061 BFCP entity. Any subsequent retransmissions of the same request can 2062 be responded to by replaying the cached response, whilst that value 2063 is retained until the timer has fired. Refer to Section 6.2.3 for 2064 the role this timer has in the fragmentation handling scheme. 2066 8.3.3. Timer Values 2068 The table below defines the different timers required when BFCP 2069 entities communicate over an unreliable transport. 2071 +-------+--------------------------------------+---------+ 2072 | Timer | Description | Value/s | 2073 +-------+--------------------------------------+---------+ 2074 | T1 | Initial request retransmission timer | 0.5s | 2075 | T2 | Response retransmission timer | 10s | 2076 +-------+--------------------------------------+---------+ 2078 Table 6: Timers 2080 The default value for T1 is 500 ms, this is an estimate of the RTT 2081 for completing the transaction. T1 MAY be chosen larger, and this is 2082 RECOMMENDED if it is known in advance that the RTT is larger. 2083 Regardless of the value of T1, the exponential backoffs on 2084 retransmissions described in Section 8.3.1 MUST be used. 2086 T2 SHALL be set such that it encompasses all legal retransmissions 2087 per T1 plus a factor to accommodate network latency between BFCP 2088 entities. The default value is based on the sum of the three 2089 retransmissions related to T1 using its default value (7.5s) and an 2090 extra 2.5s is added to take into account potential messages in 2091 transit due to latency. 2093 9. Authentication and Authorization 2095 BFCP clients SHOULD authenticate the floor control server before 2096 sending any BFCP message to it or accepting any BFCP message from it. 2097 Similarly, floor control servers SHOULD authenticate a client before 2098 accepting any BFCP message from it or sending any BFCP message to it. 2100 If the signaling or control protocol traffic used to set up the 2101 conference is authenticated and confidentiality and integrity 2102 protected, and the extensions in this document are supported, the 2103 BFCP clients MUST authenticate the floor control server and the floor 2104 control servers MUST authenticate the client before communicating as 2105 described above. Note that BFCP entities supporting only the [2] 2106 subset may not comply with this mandatory authentication requirement. 2108 BFCP supports TLS/DTLS mutual authentication between clients and 2109 floor control servers, as specified in Section 9.1. This is the 2110 RECOMMENDED authentication mechanism in BFCP. 2112 Note that future extensions may define additional authentication 2113 mechanisms. 2115 In addition to authenticating BFCP messages, floor control servers 2116 need to authorize them. On receiving an authenticated BFCP message, 2117 the floor control server checks whether the client sending the 2118 message is authorized. If the client is not authorized to perform 2119 the operation being requested, the floor control server generates an 2120 Error message, as described in Section 13.8, with an Error code with 2121 a value of 5 (Unauthorized Operation). Messages from a client that 2122 cannot be authorized MUST NOT be processed further. 2124 9.1. TLS/DTLS Based Mutual Authentication 2126 BFCP supports TLS/DTLS based mutual authentication between clients 2127 and floor control servers. If TLS/DTLS is used, an initial 2128 integrity-protected channel is REQUIRED between the client and the 2129 floor control server that can be used to exchange their self-signed 2130 certificates or, more commonly, the fingerprints of these 2131 certificates. These certificates are used at TLS/DTLS establishment 2132 time. 2134 The implementation of such an integrity-protected channel using 2135 SIP and the SDP offer/answer model is described in [9]. 2137 BFCP messages received over an authenticated TLS/DTLS connection are 2138 considered authenticated. A floor control server that receives a 2139 BFCP message over TCP/UDP (no TLS/DTLS) MAY request the use of TLS/ 2140 DTLS by generating an Error message, as described in Section 13.8, 2141 with an Error code with a value of 9 (Use TLS) or a value of 11 (Use 2142 DTLS) respectively. Clients configured to require the use of TLS/ 2143 DTLS MUST ignore unauthenticated messages. 2145 Note that future extensions may define additional authentication 2146 mechanisms that may not require an initial integrity-protected 2147 channel (e.g., authentication based on certificates signed by a 2148 certificate authority). 2150 As described in Section 9, floor control servers need to perform 2151 authorization before processing any message. In particular, the 2152 floor control server MUST check that messages arriving over a given 2153 authenticated TLS/DTLS connection use an authorized User ID (i.e., a 2154 User ID that the user that established the authenticated TLS/DTLS 2155 connection is allowed to use). 2157 10. Floor Participant Operations 2159 This section specifies how floor participants can perform different 2160 operations, such as requesting a floor, using the protocol elements 2161 described in earlier sections. Section 11 specifies operations that 2162 are specific to floor chairs, such as instructing the floor control 2163 server to grant or revoke a floor, and Section 12 specifies 2164 operations that can be performed by any client (i.e., both floor 2165 participants and floor chairs). 2167 10.1. Requesting a Floor 2169 A floor participant that wishes to request one or more floors does so 2170 by sending a FloorRequest message to the floor control server. 2172 10.1.1. Sending a FloorRequest Message 2174 The ABNF in Section 5.3.1 describes the attributes that a 2175 FloorRequest message can contain. In addition, the ABNF specifies 2176 normatively which of these attributes are mandatory, and which ones 2177 are optional. 2179 The floor participant sets the Conference ID and the Transaction ID 2180 in the common header following the rules given in Section 8.1. 2182 The floor participant sets the User ID in the common header to the 2183 floor participant's identifier. This User ID will be used by the 2184 floor control server to authenticate and authorize the request. If 2185 the sender of the FloorRequest message (identified by the User ID) is 2186 not the participant that would eventually get the floor (i.e., a 2187 third-party floor request), the sender SHOULD add a BENEFICIARY-ID 2188 attribute to the message identifying the beneficiary of the floor. 2190 Note that the name space for both the User ID and the Beneficiary 2191 ID is the same. That is, a given participant is identified by a 2192 single 16-bit value that can be used in the User ID in the common 2193 header and in several attributes: BENEFICIARY-ID, BENEFICIARY- 2194 INFORMATION, and REQUESTED-BY-INFORMATION. 2196 The floor participant MUST insert at least one FLOOR-ID attribute in 2197 the FloorRequest message. If the client inserts more than one 2198 FLOOR-ID attribute, the floor control server will treat all the floor 2199 requests as an atomic package. That is, the floor control server 2200 will either grant or deny all the floors in the FloorRequest message. 2202 The floor participant may use a PARTICIPANT-PROVIDED-INFO attribute 2203 to state the reason why the floor or floors are being requested. The 2204 Text field in the PARTICIPANT-PROVIDED-INFO attribute is intended for 2205 human consumption. 2207 The floor participant may request that the server handle the floor 2208 request with a certain priority using a PRIORITY attribute. 2210 10.1.2. Receiving a Response 2212 A message from the floor control server is considered a response to 2213 the FloorRequest message if the message from the floor control server 2214 has the same Conference ID, Transaction ID, and User ID as the 2215 FloorRequest message, as described in Section 8.1. On receiving such 2216 a response, the floor participant follows the rules in Section 9 that 2217 relate to floor control server authentication. 2219 The successful processing of a FloorRequest message at the floor 2220 control server involves generating one or several FloorRequestStatus 2221 messages. The floor participant obtains a Floor Request ID in the 2222 Floor Request ID field of a FLOOR-REQUEST-INFORMATION attribute in 2223 the first FloorRequestStatus message from the floor control server. 2224 Subsequent FloorRequestStatus messages from the floor control server 2225 regarding the same floor request will carry the same Floor Request ID 2226 in a FLOOR-REQUEST-INFORMATION attribute as the initial 2227 FloorRequestStatus message. This way, the floor participant can 2228 associate subsequent incoming FloorRequestStatus messages with the 2229 ongoing floor request. 2231 The floor participant obtains information about the status of the 2232 floor request in the FLOOR-REQUEST-INFORMATION attribute of each of 2233 the FloorRequestStatus messages received from the floor control 2234 server. This attribute is a grouped attribute, and as such it 2235 includes a number of attributes that provide information about the 2236 floor request. 2238 The OVERALL-REQUEST-STATUS attribute provides information about the 2239 overall status of the floor request. If the Request Status value is 2240 Granted, all the floors that were requested in the FloorRequest 2241 message have been granted. If the Request Status value is Denied, 2242 all the floors that were requested in the FloorRequest message have 2243 been denied. A floor request is considered to be ongoing while it is 2244 in the Pending, Accepted, or Granted states. If the floor request 2245 value is unknown, then the response is still processed. However, no 2246 meaningful value can be reported to the user. 2248 The STATUS-INFO attribute, if present, provides extra information 2249 that the floor participant can display to the user. 2251 The FLOOR-REQUEST-STATUS attributes provide information about the 2252 status of the floor request as it relates to a particular floor. The 2253 STATUS-INFO attribute, if present, provides extra information that 2254 the floor participant can display to the user. 2256 The BENEFICIARY-INFORMATION attribute identifies the beneficiary of 2257 the floor request in third-party floor requests. The REQUESTED-BY- 2258 INFORMATION attribute need not be present in FloorRequestStatus 2259 messages received by the floor participant that requested the floor, 2260 as this floor participant is already identified by the User ID in the 2261 common header. 2263 The PRIORITY attribute, when present, contains the priority that was 2264 requested by the generator of the FloorRequest message. 2266 If the response is an Error message, the floor control server could 2267 not process the FloorRequest message for some reason, which is 2268 described in the Error message. 2270 10.1.3. Reception of a Subsequent FloorRequestStatus Message 2272 When communicating over an unreliable transport and upon receiving a 2273 FloorRequestStatus message from a floor control server, the 2274 participant MUST respond with a FloorRequestStatusAck message within 2275 the transaction failure window to complete the transaction. 2277 10.2. Cancelling a Floor Request and Releasing a Floor 2279 A floor participant that wishes to cancel an ongoing floor request 2280 does so by sending a FloorRelease message to the floor control 2281 server. The FloorRelease message is also used by floor participants 2282 that hold a floor and would like to release it. 2284 10.2.1. Sending a FloorRelease Message 2286 The ABNF in Section 5.3.2 describes the attributes that a 2287 FloorRelease message can contain. In addition, the ABNF specifies 2288 normatively which of these attributes are mandatory, and which ones 2289 are optional. 2291 The floor participant sets the Conference ID and the Transaction ID 2292 in the common header following the rules given in Section 8.1. The 2293 floor participant sets the User ID in the common header to the floor 2294 participant's identifier. This User ID will be used by the floor 2295 control server to authenticate and authorize the request. 2297 Note that the FloorRelease message is used to release a floor or 2298 floors that were granted and to cancel ongoing floor requests 2299 (from the protocol perspective, both are ongoing floor requests). 2300 Using the same message in both situations helps resolve the race 2301 condition that occurs when the FloorRelease message and the 2302 FloorGrant message cross each other on the wire. 2304 The floor participant uses the FLOOR-REQUEST-ID that was received in 2305 the response to the FloorRequest message that the FloorRelease 2306 message is cancelling. 2308 Note that if the floor participant requested several floors as an 2309 atomic operation (i.e., in a single FloorRequest message), all the 2310 floors are released as an atomic operation as well (i.e., all are 2311 released at the same time). 2313 10.2.2. Receiving a Response 2315 A message from the floor control server is considered a response to 2316 the FloorRelease message if the message from the floor control server 2317 has the same Conference ID, Transaction ID, and User ID as the 2318 FloorRequest message, as described in Section 8.1. On receiving such 2319 a response, the floor participant follows the rules in Section 9 that 2320 relate to floor control server authentication. 2322 If the response is a FloorRequestStatus message, the Request Status 2323 value in the OVERALL-REQUEST-STATUS attribute (within the FLOOR- 2324 REQUEST-INFORMATION grouped attribute) will be Cancelled or Released. 2326 If the response is an Error message, the floor control server could 2327 not process the FloorRequest message for some reason, which is 2328 described in the Error message. 2330 It is possible that the FloorRelease message crosses on the wire with 2331 a FloorRequestStatus message from the server with a Request Status 2332 different from Cancelled or Released. In any case, such a 2333 FloorRequestStatus message will not be a response to the FloorRelease 2334 message, as its Transaction ID will not match that of the 2335 FloorRelease. 2337 11. Chair Operations 2339 This section specifies how floor chairs can instruct the floor 2340 control server to grant or revoke a floor using the protocol elements 2341 described in earlier sections. 2343 Floor chairs that wish to send instructions to a floor control server 2344 do so by sending a ChairAction message. 2346 11.1. Sending a ChairAction Message 2348 The ABNF in Section 5.3.9 describes the attributes that a ChairAction 2349 message can contain. In addition, the ABNF specifies normatively 2350 which of these attributes are mandatory, and which ones are optional. 2352 The floor chair sets the Conference ID and the Transaction ID in the 2353 common header following the rules given in Section 8.1. The floor 2354 chair sets the User ID in the common header to the floor chair's 2355 identifier. This User ID will be used by the floor control server to 2356 authenticate and authorize the request. 2358 The ChairAction message contains instructions that apply to one or 2359 more floors within a particular floor request. The floor or floors 2360 are identified by the FLOOR-REQUEST-STATUS attributes and the floor 2361 request is identified by the FLOOR-REQUEST-INFORMATION-HEADER, which 2362 are carried in the ChairAction message. 2364 For example, if a floor request consists of two floors that depend on 2365 different floor chairs, each floor chair will grant its floor within 2366 the floor request. Once both chairs have granted their floor, the 2367 floor control server will grant the floor request as a whole. On the 2368 other hand, if one of the floor chairs denies its floor, the floor 2369 control server will deny the floor request as a whole, regardless of 2370 the other floor chair's decision. 2372 The floor chair provides the new status of the floor request as it 2373 relates to a particular floor using a FLOOR-REQUEST-STATUS attribute. 2374 If the new status of the floor request is Accepted, the floor chair 2375 MAY use the Queue Position field to provide a queue position for the 2376 floor request. If the floor chair does not wish to provide a queue 2377 position, all the bits of the Queue Position field MUST be set to 2378 zero. The floor chair MUST use the Status Revoked to revoke a floor 2379 that was granted (i.e., Granted status) and MUST use the Status 2380 Denied to reject floor requests in any other status (e.g., Pending 2381 and Accepted). 2383 The floor chair MAY add an OVERALL-REQUEST-STATUS attribute to the 2384 ChairAction message to provide a new overall status for the floor 2385 request. If the new overall status of the floor request is Accepted, 2386 the floor chair can use the Queue Position field to provide a queue 2387 position for the floor request. 2389 Note that a particular floor control server can implement a 2390 different queue for each floor containing all the floor requests 2391 that relate to that particular floor, a general queue for all 2392 floor requests, or both. Also note that a floor request can 2393 involve several floors and that a ChairAction message can only 2394 deal with a subset of these floors (e.g., if a single floor chair 2395 is not authorized to manage all the floors). In this case, the 2396 floor control server will combine the instructions received from 2397 the different floor chairs in FLOOR-REQUEST-STATUS attributes to 2398 come up with the overall status of the floor request. 2400 Note that, while the action of a floor chair may communicate 2401 information in the OVERALL-REQUEST-STATUS attribute, the floor 2402 control server may override, modify, or ignore this field's 2403 content. 2405 The floor chair MAY include STATUS-INFO attributes to state the 2406 reason why the floor or floors are being accepted, granted, or 2407 revoked. The Text in the STATUS-INFO attribute is intended for human 2408 consumption. 2410 11.2. Receiving a Response 2412 A message from the floor control server is considered a response to 2413 the ChairAction message if the message from the server has the same 2414 Conference ID, Transaction ID, and User ID as the ChairAction 2415 message, as described in Section 8.1. On receiving such a response, 2416 the floor chair follows the rules in Section 9 that relate to floor 2417 control server authentication. 2419 A ChairActionAck message from the floor control server confirms that 2420 the floor control server has accepted the ChairAction message. An 2421 Error message indicates that the floor control server could not 2422 process the ChairAction message for some reason, which is described 2423 in the Error message. 2425 12. General Client Operations 2427 This section specifies operations that can be performed by any 2428 client. That is, they are not specific to floor participants or 2429 floor chairs. They can be performed by both. 2431 12.1. Requesting Information about Floors 2433 A client can obtain information about the status of a floor or floors 2434 in different ways, which include using BFCP and using out-of-band 2435 mechanisms. Clients using BFCP to obtain such information use the 2436 procedures described in this section. 2438 Clients request information about the status of one or several floors 2439 by sending a FloorQuery message to the floor control server. 2441 12.1.1. Sending a FloorQuery Message 2443 The ABNF in Section 5.3.7 describes the attributes that a FloorQuery 2444 message can contain. In addition, the ABNF specifies normatively 2445 which of these attributes are mandatory, and which ones are optional. 2447 The client sets the Conference ID and the Transaction ID in the 2448 common header following the rules given in Section 8.1. The client 2449 sets the User ID in the common header to the client's identifier. 2450 This User ID will be used by the floor control server to authenticate 2451 and authorize the request. 2453 The client inserts in the message all the Floor IDs it wants to 2454 receive information about. The floor control server will send 2455 periodic information about all of these floors. If the client does 2456 not want to receive information about a particular floor any longer, 2457 it sends a new FloorQuery message removing the FLOOR-ID of this 2458 floor. If the client does not want to receive information about any 2459 floor any longer, it sends a FloorQuery message with no FLOOR-ID 2460 attribute. 2462 12.1.2. Receiving a Response 2464 A message from the floor control server is considered a response to 2465 the FloorQuery message if the message from the floor control server 2466 has the same Conference ID, Transaction ID, and User ID as the 2467 FloorRequest message, as described in Section 8.1. On receiving such 2468 a response, the client follows the rules in Section 9 that relate to 2469 floor control server authentication. 2471 On reception of the FloorQuery message, the floor control server MUST 2472 respond with a FloorStatus message or with an Error message. If the 2473 response is a FloorStatus message, it will contain information about 2474 one of the floors the client requested information about. If the 2475 client did not include any FLOOR-ID attribute in its FloorQuery 2476 message (i.e., the client does not want to receive information about 2477 any floor any longer), the FloorStatus message from the floor control 2478 server will not include any FLOOR-ID attribute either. 2480 FloorStatus messages that carry information about a floor contain a 2481 FLOOR-ID attribute that identifies the floor. After this attribute, 2482 FloorStatus messages contain information about existing (one or more) 2483 floor requests that relate to that floor. The information about each 2484 particular floor request is encoded in a FLOOR-REQUEST-INFORMATION 2485 attribute. This grouped attribute carries a Floor Request ID that 2486 identifies the floor request, followed by a set of attributes that 2487 provide information about the floor request. 2489 After the first FloorStatus, the floor control server will continue 2490 sending FloorStatus messages, periodically informing the client about 2491 changes on the floors the client requested information about. 2493 12.1.3. Reception of a Subsequent FloorStatus Message 2495 When communicating over an unreliable transport and upon receiving a 2496 FloorStatus message from a floor control server, the participant MUST 2497 respond with a FloorStatusAck message within the transaction failure 2498 window to complete the transaction. 2500 12.2. Requesting Information about Floor Requests 2502 A client can obtain information about the status of one or several 2503 floor requests in different ways, which include using BFCP and using 2504 out-of-band mechanisms. Clients using BFCP to obtain such 2505 information use the procedures described in this section. 2507 Clients request information about the current status of a floor 2508 request by sending a FloorRequestQuery message to the floor control 2509 server. 2511 Requesting information about a particular floor request is useful in 2512 a number of situations. For example, on reception of a FloorRequest 2513 message, a floor control server may choose to return 2514 FloorRequestStatus messages only when the floor request changes its 2515 state (e.g., from Accepted to Granted), but not when the floor 2516 request advances in its queue. In this situation, if the user 2517 requests it, the floor participant can use a FloorRequestQuery 2518 message to poll the floor control server for the status of the floor 2519 request. 2521 12.2.1. Sending a FloorRequestQuery Message 2523 The ABNF in Section 5.3.3 describes the attributes that a 2524 FloorRequestQuery message can contain. In addition, the ABNF 2525 specifies normatively which of these attributes are mandatory, and 2526 which ones are optional. 2528 The client sets the Conference ID and the Transaction ID in the 2529 common header following the rules given in Section 8.1. The client 2530 sets the User ID in the common header to the client's identifier. 2531 This User ID will be used by the floor control server to authenticate 2532 and authorize the request. 2534 The client MUST insert a FLOOR-REQUEST-ID attribute that identifies 2535 the floor request at the floor control server. 2537 12.2.2. Receiving a Response 2539 A message from the floor control server is considered a response to 2540 the FloorRequestQuery message if the message from the floor control 2541 server has the same Conference ID, Transaction ID, and User ID as the 2542 FloorRequestQuery message, as described in Section 8.1. On receiving 2543 such a response, the client follows the rules in Section 9 that 2544 relate to floor control server authentication. 2546 If the response is a FloorRequestStatus message, the client obtains 2547 information about the status of the FloorRequest the client requested 2548 information about in a FLOOR-REQUEST-INFORMATION attribute. 2550 If the response is an Error message, the floor control server could 2551 not process the FloorRequestQuery message for some reason, which is 2552 described in the Error message. 2554 12.3. Requesting Information about a User 2556 A client can obtain information about a participant and the floor 2557 requests related to this participant in different ways, which include 2558 using BFCP and using out-of-band mechanisms. Clients using BFCP to 2559 obtain such information use the procedures described in this section. 2561 Clients request information about a participant and the floor 2562 requests related to this participant by sending a UserQuery message 2563 to the floor control server. 2565 This functionality may be useful for floor chairs or floor 2566 participants interested in the display name and the URI of a 2567 particular floor participant. In addition, a floor participant may 2568 find it useful to request information about itself. For example, a 2569 floor participant, after experiencing connectivity problems (e.g., 2570 its TCP connection with the floor control server was down for a while 2571 and eventually was re-established), may need to request information 2572 about all the floor requests associated to itself that still exist. 2574 12.3.1. Sending a UserQuery Message 2576 The ABNF in Section 5.3.5 describes the attributes that a UserQuery 2577 message can contain. In addition, the ABNF specifies normatively 2578 which of these attributes are mandatory, and which ones are optional. 2580 The client sets the Conference ID and the Transaction ID in the 2581 common header following the rules given in Section 8.1. The client 2582 sets the User ID in the common header to the client's identifier. 2583 This User ID will be used by the floor control server to authenticate 2584 and authorize the request. 2586 If the floor participant the client is requesting information about 2587 is not the client issuing the UserQuery message (which is identified 2588 by the User ID in the common header of the message), the client MUST 2589 insert a BENEFICIARY-ID attribute. 2591 12.3.2. Receiving a Response 2593 A message from the floor control server is considered a response to 2594 the UserQuery message if the message from the floor control server 2595 has the same Conference ID, Transaction ID, and User ID as the 2596 UserQuery message, as described in Section 8.1. On receiving such a 2597 response, the client follows the rules in Section 9 that relate to 2598 floor control server authentication. 2600 If the response is a UserStatus message, the client obtains 2601 information about the floor participant in a BENEFICIARY-INFORMATION 2602 grouped attribute and about the status of the floor requests 2603 associated with the floor participant in FLOOR-REQUEST-INFORMATION 2604 attributes. 2606 If the response is an Error message, the floor control server could 2607 not process the UserQuery message for some reason, which is described 2608 in the Error message. 2610 12.4. Obtaining the Capabilities of a Floor Control Server 2612 A client that wishes to obtain the capabilities of a floor control 2613 server does so by sending a Hello message to the floor control 2614 server. 2616 12.4.1. Sending a Hello Message 2618 The ABNF in Section 5.3.11 describes the attributes that a Hello 2619 message can contain. In addition, the ABNF specifies normatively 2620 which of these attributes are mandatory, and which ones are optional. 2622 The client sets the Conference ID and the Transaction ID in the 2623 common header following the rules given in Section 8.1. The client 2624 sets the User ID in the common header to the client's identifier. 2625 This User ID will be used by the floor control server to authenticate 2626 and authorize the request. 2628 12.4.2. Receiving Responses 2630 A message from the floor control server is considered a response to 2631 the Hello message by the client if the message from the floor control 2632 server has the same Conference ID, Transaction ID, and User ID as the 2633 Hello message, as described in Section 8.1. On receiving such a 2634 response, the client follows the rules in Section 9 that relate to 2635 floor control server authentication. 2637 If the response is a HelloAck message, the floor control server could 2638 process the Hello message successfully. The SUPPORTED-PRIMITIVES and 2639 SUPPORTED-ATTRIBUTES attributes indicate which primitives and 2640 attributes, respectively, are supported by the server. 2642 If the response is an Error message, the floor control server could 2643 not process the Hello message for some reason, which is described in 2644 the Error message. 2646 13. Floor Control Server Operations 2648 This section specifies how floor control servers can perform 2649 different operations, such as granting a floor, using the protocol 2650 elements described in earlier sections. 2652 On reception of a message from a client, the floor control server 2653 MUST check whether the value of the Primitive is supported. If it is 2654 not, the floor control server MUST send an Error message, as 2655 described in Section 13.8, with Error code 3 (Unknown Primitive). 2657 On reception of a message from a client, the floor control server 2658 MUST check whether the value of the Conference ID matched an existing 2659 conference. If it does not, the floor control server MUST send an 2660 Error message, as described in Section 13.8, with Error code 1 2661 (Conference does not Exist). 2663 On reception of a message from a client, the floor control server 2664 follows the rules in Section 9 that relate to the authentication of 2665 the message. 2667 On reception of a message from a client, the floor control server 2668 MUST check whether it understands all the mandatory ('M' bit set) 2669 attributes in the message. If the floor control server does not 2670 understand all of them, the floor control server MUST send an Error 2671 message, as described in Section 13.8, with Error code 4 (Unknown 2672 Mandatory Attribute). The Error message SHOULD list the attributes 2673 that were not understood. 2675 13.1. Reception of a FloorRequest Message 2677 On reception of a FloorRequest message, the floor control server 2678 follows the rules in Section 9 that relate to client authentication 2679 and authorization. If while processing the FloorRequest message, the 2680 floor control server encounters an error, it MUST generate an Error 2681 response following the procedures described in Section 13.8. 2683 BFCP allows floor participants to have several ongoing floor 2684 requests for the same floor (e.g., the same floor participant can 2685 occupy more than one position in a queue at the same time). A 2686 floor control server that only supports a certain number of 2687 ongoing floor requests per floor participant (e.g., one) can use 2688 Error Code 8 (You have Already Reached the Maximum Number of 2689 Ongoing Floor Requests for this Floor) to inform the floor 2690 participant. 2692 When communicating over an unreliable transport and upon receiving a 2693 FloorRequest from a participant, the floor control server MUST 2694 respond with a FloorRequestStatus message within the transaction 2695 failure window to complete the transaction. 2697 13.1.1. Generating the First FloorRequestStatus Message 2699 The successful processing of a FloorRequest message by a floor 2700 control server involves generating one or several FloorRequestStatus 2701 messages, the first of which SHOULD be generated as soon as possible. 2702 If the floor control server cannot accept, grant, or deny the floor 2703 request right away (e.g., a decision from a chair is needed), it 2704 SHOULD use a Request Status value of Pending in the OVERALL-REQUEST- 2705 STATUS attribute (within the FLOOR-REQUEST-INFORMATION grouped 2706 attribute) of the first FloorRequestStatus message it generates. 2708 The policy that a floor control server follows to grant or deny 2709 floors is outside the scope of this document. A given floor 2710 control server may perform these decisions automatically while 2711 another may contact a human acting as a chair every time a 2712 decision needs to be made. 2714 The floor control server MUST copy the Conference ID, the Transaction 2715 ID, and the User ID from the FloorRequest into the 2716 FloorRequestStatus, as described in Section 8.2. Additionally, the 2717 floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped 2718 attribute to the FloorRequestStatus. The attributes contained in 2719 this grouped attribute carry information about the floor request. 2721 The floor control server MUST assign an identifier that is unique 2722 within the conference to this floor request, and MUST insert it in 2723 the Floor Request ID field of the FLOOR-REQUEST-INFORMATION 2724 attribute. This identifier will be used by the floor participant (or 2725 by a chair or chairs) to refer to this specific floor request in the 2726 future. 2728 The floor control server MUST copy the Floor IDs in the FLOOR-ID 2729 attributes of the FloorRequest into the FLOOR-REQUEST-STATUS 2730 attributes in the FLOOR-REQUEST-INFORMATION grouped attribute. These 2731 Floor IDs identify the floors being requested (i.e., the floors 2732 associated with this particular floor request). 2734 The floor control server SHOULD copy (if present) the contents of the 2735 BENEFICIARY-ID attribute from the FloorRequest into a BENEFICIARY- 2736 INFORMATION attribute inside the FLOOR-REQUEST-INFORMATION grouped 2737 attribute. Additionally, the floor control server MAY provide the 2738 display name and the URI of the beneficiary in this BENEFICIARY- 2739 INFORMATION attribute. 2741 The floor control server MAY provide information about the requester 2742 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2743 FLOOR-REQUEST-INFORMATION grouped attribute. 2745 The floor control server MAY copy (if present) the PRIORITY attribute 2746 from the FloorRequest into the FLOOR-REQUEST-INFORMATION grouped 2747 attribute. 2749 Note that this attribute carries the priority requested by the 2750 participant. The priority that the floor control server assigns 2751 to the floor request depends on the priority requested by the 2752 participant and the rights the participant has according to the 2753 policy of the conference. For example, a participant that is only 2754 allowed to use the Normal priority may request Highest priority 2755 for a floor request. In that case, the floor control server would 2756 ignore the priority requested by the participant. 2758 The floor control server MAY copy (if present) the PARTICIPANT- 2759 PROVIDED-INFO attribute from the FloorRequest into the FLOOR-REQUEST- 2760 INFORMATION grouped attribute. 2762 13.1.2. Generation of Subsequent FloorRequestStatus Messages 2764 A floor request is considered to be ongoing as long as it is not in 2765 the Cancelled, Released, or Revoked states. If the OVERALL-REQUEST- 2766 STATUS attribute (inside the FLOOR-REQUEST-INFORMATION grouped 2767 attribute) of the first FloorRequestStatus message generated by the 2768 floor control server did not indicate any of these states, the floor 2769 control server will need to send subsequent FloorRequestStatus 2770 messages. 2772 When the status of the floor request changes, the floor control 2773 server SHOULD send new FloorRequestStatus messages with the 2774 appropriate Request Status. The floor control server MUST add a 2775 FLOOR-REQUEST-INFORMATION attribute with a Floor Request ID equal to 2776 the one sent in the first FloorRequestStatus message to any new 2777 FloorRequestStatus related to the same floor request. (The Floor 2778 Request ID identifies the floor request to which the 2779 FloorRequestStatus applies.) 2781 When using BFCP over a reliable transport, the floor control server 2782 MUST set the Transaction ID of subsequent FloorRequestStatus messages 2783 to 0. When using BFCP over an unreliable transport, the Transaction 2784 ID MUST be non-zero and unique in the context of outstanding 2785 transactions over an unreliable transport as described in Section 8. 2787 The rate at which the floor control server sends 2788 FloorRequestStatus messages is a matter of local policy. A floor 2789 control server may choose to send a new FloorRequestStatus message 2790 every time the floor request moves in the floor request queue, 2791 while another may choose only to send a new FloorRequestStatus 2792 message when the floor request is Granted or Denied. 2794 The floor control server may add a STATUS-INFO attribute to any of 2795 the FloorRequestStatus messages it generates to provide extra 2796 information about its decisions regarding the floor request (e.g., 2797 why it was denied). 2799 Floor participants and floor chairs may request to be informed 2800 about the status of a floor following the procedures in 2801 Section 12.1. If the processing of a floor request changes the 2802 status of a floor (e.g., the floor request is granted and 2803 consequently the floor has a new holder), the floor control server 2804 needs to follow the procedures in Section 13.5 to inform the 2805 clients that have requested that information. 2807 The common header and the rest of the attributes are the same as in 2808 the first FloorRequestStatus message. 2810 The floor control server can discard the state information about a 2811 particular floor request when this reaches a status of Cancelled, 2812 Released, or Revoked. 2814 When communicating over an unreliable transport and a 2815 FloorRequestStatusAck message is not received within the transaction 2816 failure window, the floor control server MUST retransmit the 2817 FloorRequestStatus message according to Section 6.2. 2819 13.2. Reception of a FloorRequestQuery Message 2821 On reception of a FloorRequestQuery message, the floor control server 2822 follows the rules in Section 9 that relate to client authentication 2823 and authorization. If while processing the FloorRequestQuery 2824 message, the floor control server encounters an error, it MUST 2825 generate an Error response following the procedures described in 2826 Section 13.8. 2828 The successful processing of a FloorRequestQuery message by a floor 2829 control server involves generating a FloorRequestStatus message, 2830 which SHOULD be generated as soon as possible. 2832 When communicating over an unreliable transport and upon receiving a 2833 FloorRequestQuery from a participant, the floor control server MUST 2834 respond with a FloorRequestStatus message within the transaction 2835 failure window to complete the transaction. 2837 The floor control server MUST copy the Conference ID, the Transaction 2838 ID, and the User ID from the FloorRequestQuery message into the 2839 FloorRequestStatus message, as described in Section 8.2. 2840 Additionally, the floor control server MUST include information about 2841 the floor request in the FLOOR-REQUEST-INFORMATION grouped attribute 2842 to the FloorRequestStatus. 2844 The floor control server MUST copy the contents of the 2845 FLOOR-REQUEST-ID attribute from the FloorRequestQuery message into 2846 the Floor Request ID field of the FLOOR-REQUEST-INFORMATION 2847 attribute. 2849 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 2850 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2851 floors being requested (i.e., the floors associated with the floor 2852 request identified by the FLOOR-REQUEST-ID attribute). 2854 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 2855 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2856 beneficiary of the floor request. Additionally, the floor control 2857 server MAY provide the display name and the URI of the beneficiary in 2858 this BENEFICIARY-INFORMATION attribute. 2860 The floor control server MAY provide information about the requester 2861 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2862 FLOOR-REQUEST-INFORMATION grouped attribute. 2864 The floor control server MAY provide the reason why the floor 2865 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 2867 The floor control server MAY also add to the FLOOR-REQUEST- 2868 INFORMATION grouped attribute a PRIORITY attribute with the Priority 2869 value requested for the floor request and a STATUS-INFO attribute 2870 with extra information about the floor request. 2872 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 2873 to the FLOOR-REQUEST-INFORMATION grouped attribute with the current 2874 status of the floor request. The floor control server MAY provide 2875 information about the status of the floor request as it relates to 2876 each of the floors being requested in the FLOOR-REQUEST-STATUS 2877 attributes. 2879 13.3. Reception of a UserQuery Message 2881 On reception of a UserQuery message, the floor control server follows 2882 the rules in Section 9 that relate to client authentication and 2883 authorization. If while processing the UserQuery message, the floor 2884 control server encounters an error, it MUST generate an Error 2885 response following the procedures described in Section 13.8. 2887 The successful processing of a UserQuery message by a floor control 2888 server involves generating a UserStatus message, which SHOULD be 2889 generated as soon as possible. 2891 When communicating over an unreliable transport and upon receiving a 2892 UserQuery from a participant, the floor control server MUST respond 2893 with a UserStatus message within the transaction failure window to 2894 complete the transaction. 2896 The floor control server MUST copy the Conference ID, the Transaction 2897 ID, and the User ID from the UserQuery message into the USerStatus 2898 message, as described in Section 8.2. 2900 The sender of the UserQuery message is requesting information about 2901 all the floor requests associated with a given participant (i.e., the 2902 floor requests where the participant is either the beneficiary or the 2903 requester). This participant is identified by a BENEFICIARY-ID 2904 attribute or, in the absence of a BENEFICIARY-ID attribute, by a the 2905 User ID in the common header of the UserQuery message. 2907 The floor control server MUST copy, if present, the contents of the 2908 BENEFICIARY-ID attribute from the UserQuery message into a 2909 BENEFICIARY-INFORMATION attribute in the UserStatus message. 2910 Additionally, the floor control server MAY provide the display name 2911 and the URI of the participant about which the UserStatus message 2912 provides information in this BENEFICIARY-INFORMATION attribute. 2914 The floor control server SHOULD add to the UserStatus message a 2915 FLOOR-REQUEST-INFORMATION grouped attribute for each floor request 2916 related to the participant about which the message provides 2917 information (i.e., the floor requests where the participant is either 2918 the beneficiary or the requester). For each FLOOR-REQUEST- 2919 INFORMATION attribute, the floor control server follows the following 2920 steps. 2922 The floor control server MUST identify the floor request the FLOOR- 2923 REQUEST-INFORMATION attribute applies to by filling the Floor Request 2924 ID field of the FLOOR-REQUEST-INFORMATION attribute. 2926 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 2927 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2928 floors being requested (i.e., the floors associated with the floor 2929 request identified by the FLOOR-REQUEST-ID attribute). 2931 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 2932 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2933 beneficiary of the floor request. Additionally, the floor control 2934 server MAY provide the display name and the URI of the beneficiary in 2935 this BENEFICIARY-INFORMATION attribute. 2937 The floor control server MAY provide information about the requester 2938 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2939 FLOOR-REQUEST-INFORMATION grouped attribute. 2941 The floor control server MAY provide the reason why the floor 2942 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 2944 The floor control server MAY also add to the FLOOR-REQUEST- 2945 INFORMATION grouped attribute a PRIORITY attribute with the Priority 2946 value requested for the floor request. 2948 The floor control server MUST include the current status of the floor 2949 request in an OVERALL-REQUEST-STATUS attribute to the FLOOR-REQUEST- 2950 INFORMATION grouped attribute. The floor control server MAY add a 2951 STATUS-INFO attribute with extra information about the floor request. 2953 The floor control server MAY provide information about the status of 2954 the floor request as it relates to each of the floors being requested 2955 in the FLOOR-REQUEST-STATUS attributes. 2957 13.4. Reception of a FloorRelease Message 2959 On reception of a FloorRelease message, the floor control server 2960 follows the rules in Section 9 that relate to client authentication 2961 and authorization. If while processing the FloorRelease message, the 2962 floor control server encounters an error, it MUST generate an Error 2963 response following the procedures described in Section 13.8. 2965 The successful processing of a FloorRelease message by a floor 2966 control server involves generating a FloorRequestStatus message, 2967 which SHOULD be generated as soon as possible. 2969 When communicating over an unreliable transport and upon receiving a 2970 FloorRelease from a participant, the floor control server MUST 2971 respond with a FloorRequestStatus message within the transaction 2972 failure window to complete the transaction. 2974 The floor control server MUST copy the Conference ID, the Transaction 2975 ID, and the User ID from the FloorRelease message into the 2976 FloorRequestStatus message, as described in Section 8.2. 2978 The floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped 2979 attribute to the FloorRequestStatus. The attributes contained in 2980 this grouped attribute carry information about the floor request. 2982 The FloorRelease message identifies the floor request it applies to 2983 using a FLOOR-REQUEST-ID. The floor control server MUST copy the 2984 contents of the FLOOR-REQUEST-ID attribute from the FloorRelease 2985 message into the Floor Request ID field of the FLOOR-REQUEST- 2986 INFORMATION attribute. 2988 The floor control server MUST identify the floors being released 2989 (i.e., the floors associated with the floor request identified by the 2990 FLOOR-REQUEST-ID attribute) in FLOOR-REQUEST-STATUS attributes to the 2991 FLOOR-REQUEST-INFORMATION grouped attribute. 2993 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 2994 to the FLOOR-REQUEST-INFORMATION grouped attribute. The Request 2995 Status value SHOULD be Released, if the floor (or floors) had been 2996 previously granted, or Cancelled, if the floor (or floors) had not 2997 been previously granted. The floor control server MAY add a STATUS- 2998 INFO attribute with extra information about the floor request. 3000 13.5. Reception of a FloorQuery Message 3002 On reception of a FloorQuery message, the floor control server 3003 follows the rules in Section 9 that relate to client authentication. 3004 If while processing the FloorQuery message, the floor control server 3005 encounters an error, it MUST generate an Error response following the 3006 procedures described in Section 13.8. 3008 When communicating over an unreliable transport and upon receiving a 3009 FloorQuery from a participant, the floor control server MUST respond 3010 with a FloorStatus message within the transaction failure window to 3011 complete the transaction. 3013 A floor control server receiving a FloorQuery message from a client 3014 SHOULD keep this client informed about the status of the floors 3015 identified by FLOOR-ID attributes in the FloorQuery message. Floor 3016 Control Servers keep clients informed by using FloorStatus messages. 3018 An individual FloorStatus message carries information about a single 3019 floor. So, when a FloorQuery message requests information about more 3020 than one floor, the floor control server needs to send separate 3021 FloorStatus messages for different floors. 3023 The information FloorQuery messages carry may depend on the user 3024 requesting the information. For example, a chair may be able to 3025 receive information about pending requests, while a regular user may 3026 not be authorized to do so. 3028 13.5.1. Generation of the First FloorStatus Message 3030 The successful processing of a FloorQuery message by a floor control 3031 server involves generating one or several FloorStatus messages, the 3032 first of which SHOULD be generated as soon as possible. 3034 The floor control server MUST copy the Conference ID, the Transaction 3035 ID, and the User ID from the FloorQuery message into the FloorStatus 3036 message, as described in Section 8.2. 3038 If the FloorQuery message did not contain any FLOOR-ID attribute, the 3039 floor control server sends the FloorStatus message without adding any 3040 additional attribute and does not send any subsequent FloorStatus 3041 message to the floor participant. 3043 If the FloorQuery message contained one or more FLOOR-ID attributes, 3044 the floor control server chooses one from among them and adds this 3045 FLOOR-ID attribute to the FloorStatus message. The floor control 3046 server SHOULD add a FLOOR-REQUEST-INFORMATION grouped attribute for 3047 each floor request associated to the floor. Each FLOOR-REQUEST- 3048 INFORMATION grouped attribute contains a number of attributes that 3049 provide information about the floor request. For each FLOOR-REQUEST- 3050 INFORMATION attribute, the floor control server follows the following 3051 steps. 3053 The floor control server MUST identify the floor request the FLOOR- 3054 REQUEST-INFORMATION attribute applies to by filling the Floor Request 3055 ID field of the FLOOR-REQUEST-INFORMATION attribute. 3057 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 3058 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 3059 floors being requested (i.e., the floors associated with the floor 3060 request identified by the FLOOR-REQUEST-ID attribute). 3062 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 3063 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 3064 beneficiary of the floor request. Additionally, the floor control 3065 server MAY provide the display name and the URI of the beneficiary in 3066 this BENEFICIARY-INFORMATION attribute. 3068 The floor control server MAY provide information about the requester 3069 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 3070 FLOOR-REQUEST-INFORMATION grouped attribute. 3072 The floor control server MAY provide the reason why the floor 3073 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 3075 The floor control server MAY also add to the FLOOR-REQUEST- 3076 INFORMATION grouped attribute a PRIORITY attribute with the Priority 3077 value requested for the floor request. 3079 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 3080 to the FLOOR-REQUEST-INFORMATION grouped attribute with the current 3081 status of the floor request. The floor control server MAY add a 3082 STATUS-INFO attribute with extra information about the floor request. 3084 The floor control server MAY provide information about the status of 3085 the floor request as it relates to each of the floors being requested 3086 in the FLOOR-REQUEST-STATUS attributes. 3088 13.5.2. Generation of Subsequent FloorStatus Messages 3090 If the FloorQuery message carried more than one FLOOR-ID attribute, 3091 the floor control server SHOULD generate a FloorStatus message for 3092 each of them (except for the FLOOR-ID attribute chosen for the first 3093 FloorStatus message) as soon as possible. These FloorStatus messages 3094 are generated following the same rules as those for the first 3095 FloorStatus message (see Section 13.5.1), but their Transaction ID is 3096 0 when using a reliable transport and non-zero and unique in the 3097 context of outstanding transactions when using an unreliable 3098 transport (cf. Section 8). 3100 After generating these messages, the floor control server sends 3101 FloorStatus messages, periodically keeping the client informed about 3102 all the floors for which the client requested information. The 3103 Transaction ID of these messages MUST be 0 when using a reliable 3104 transport and non-zero and unique in the context of outstanding 3105 transactions when using an unreliable transport (cf. Section 8). 3107 The rate at which the floor control server sends FloorStatus 3108 messages is a matter of local policy. A floor control server may 3109 choose to send a new FloorStatus message every time a new floor 3110 request arrives, while another may choose to only send a new 3111 FloorStatus message when a new floor request is Granted. 3113 When communicating over an unreliable transport and a FloorStatusAck 3114 message is not received within the transaction failure window, the 3115 floor control server MUST retransmit the FloorStatus message 3116 according to Section 6.2. 3118 13.6. Reception of a ChairAction Message 3120 On reception of a ChairAction message, the floor control server 3121 follows the rules in Section 9 that relate to client authentication 3122 and authorization. If while processing the ChairAction message, the 3123 floor control server encounters an error, it MUST generate an Error 3124 response following the procedures described in Section 13.8. 3126 The successful processing of a ChairAction message by a floor control 3127 server involves generating a ChairActionAck message, which SHOULD be 3128 generated as soon as possible. 3130 When communicating over an unreliable transport and upon receiving a 3131 ChairAction from a chair, the floor control server MUST respond with 3132 a ChairActionAck message within the transaction failure window to 3133 complete the transaction. 3135 The floor control server MUST copy the Conference ID, the Transaction 3136 ID, and the User ID from the ChairAction message into the 3137 ChairActionAck message, as described in Section 8.2. 3139 The floor control server needs to take into consideration the 3140 operation requested in the ChairAction message (e.g., granting a 3141 floor) but does not necessarily need to perform it as requested by 3142 the floor chair. The operation that the floor control server 3143 performs depends on the ChairAction message and on the internal state 3144 of the floor control server. 3146 For example, a floor chair may send a ChairAction message granting a 3147 floor that was requested as part of an atomic floor request operation 3148 that involved several floors. Even if the chair responsible for one 3149 of the floors instructs the floor control server to grant the floor, 3150 the floor control server will not grant it until the chairs 3151 responsible for the other floors agree to grant them as well. 3153 So, the floor control server is ultimately responsible for keeping a 3154 coherent floor state using instructions from floor chairs as input to 3155 this state. 3157 If the new Status in the ChairAction message is Accepted and all the 3158 bits of the Queue Position field are zero, the floor chair is 3159 requesting that the floor control server assign a queue position 3160 (e.g., the last in the queue) to the floor request based on the local 3161 policy of the floor control server. (Of course, such a request only 3162 applies if the floor control server implements a queue.) 3164 13.7. Reception of a Hello Message 3166 On reception of a Hello message, the floor control server follows the 3167 rules in Section 9 that relate to client authentication. If while 3168 processing the Hello message, the floor control server encounters an 3169 error, it MUST generate an Error response following the procedures 3170 described in Section 13.8. 3172 If the version of BFCP specified in the Version field of the COMMON- 3173 HEADER is supported by the floor control server, it MUST respond with 3174 the same version number in the HelloAck; this defines the version for 3175 all subsequent BFCP messages within this BFCP Connection. If the 3176 version given in the Hello message is not supported, and the 3177 extensions in this document is supported, the receiving server MUST 3178 instead send an Error message with parameter value 12 (Unsupported 3179 Version). Note that BFCP entities supporting only the [2] subset 3180 will not support this parameter value. 3182 When communicating over an unreliable transport and upon receiving a 3183 Hello from a participant, the floor control server MUST respond with 3184 a HelloAck message within the transaction failure window to complete 3185 the transaction. 3187 The successful processing of a Hello message by a floor control 3188 server involves generating a HelloAck message, which SHOULD be 3189 generated as soon as possible. The floor control server MUST copy 3190 the Conference ID, the Transaction ID, and the User ID from the Hello 3191 into the HelloAck, as described in Section 8.2. 3193 The floor control server MUST add a SUPPORTED-PRIMITIVES attribute to 3194 the HelloAck message listing all the primitives (i.e., BFCP messages) 3195 supported by the floor control server. 3197 The floor control server MUST add a SUPPORTED-ATTRIBUTES attribute to 3198 the HelloAck message listing all the attributes supported by the 3199 floor control server. 3201 13.8. Error Message Generation 3203 Error messages are always sent in response to a previous message from 3204 the client as part of a client-initiated transaction. The ABNF in 3205 Section 5.3.13 describes the attributes that an Error message can 3206 contain. In addition, the ABNF specifies normatively which of these 3207 attributes are mandatory and which ones are optional. 3209 The floor control server MUST copy the Conference ID, the Transaction 3210 ID, and the User ID from the message from the client into the Error 3211 message, as described in Section 8.2. 3213 The floor control server MUST add an ERROR-CODE attribute to the 3214 Error message. The ERROR-CODE attribute contains an Error Code from 3215 Table 5. Additionally, the floor control server may add an ERROR- 3216 INFO attribute with extra information about the error. 3218 14. Security Considerations 3220 BFCP uses TLS/DTLS to provide mutual authentication between clients 3221 and servers. TLS/DTLS also provides replay and integrity protection 3222 and confidentiality. It is RECOMMENDED that TLS/DTLS with an 3223 encryption algorithm according to Section 7 always be used. In cases 3224 where signaling/control traffic is properly protected, as described 3225 in Section 9 it is REQUIRED to use a mandated encryption algorithm. 3226 BFCP entities MAY use other security mechanisms as long as they 3227 provide similar security properties. 3229 The remainder of this section analyzes some of the threats against 3230 BFCP and how they are addressed. 3232 An attacker may attempt to impersonate a client (a floor participant 3233 or a floor chair) in order to generate forged floor requests or to 3234 grant or deny existing floor requests. Client impersonation is 3235 avoided by having servers only accept BFCP messages over 3236 authenticated TLS/DTLS connections. The floor control server assumes 3237 that attackers cannot hijack the TLS/DTLS connection and, therefore, 3238 that messages over the TLS/DTLS connection come from the client that 3239 was initially authenticated. 3241 An attacker may attempt to impersonate a floor control server. A 3242 successful attacker would be able to make clients think that they 3243 hold a particular floor so that they would try to access a resource 3244 (e.g., sending media) without having legitimate rights to access it. 3245 Floor control server impersonation is avoided by having servers only 3246 accept BFCP messages over authenticated TLS/DTLS connections, as well 3247 as ensuring clients only send and accept messages over authenticated 3248 TLS/DTLS connections. 3250 Attackers may attempt to modify messages exchanged by a client and a 3251 floor control server. The integrity protection provided by TLS/DTLS 3252 connections prevents this attack. 3254 An attacker may attempt to fetch a valid message sent by a client to 3255 a floor control server and replay it over a connection between the 3256 attacker and the floor control server. This attack is prevented by 3257 having floor control servers check that messages arriving over a 3258 given authenticated TLS/DTLS connection use an authorized user ID 3259 (i.e., a user ID that the user that established the authenticated 3260 TLS/DTLS connection is allowed to use). 3262 Attackers may attempt to pick messages from the network to get access 3263 to confidential information between the floor control server and a 3264 client (e.g., why a floor request was denied). TLS/DTLS 3265 confidentiality prevents this attack. Therefore, it is REQUIRED that 3266 TLS/DTLS be used with an encryption algorithm according to Section 7. 3268 15. IANA Considerations 3270 [Editorial note: This section instructs the IANA to register new 3271 entries in the BFCP Primitive subregistry in Section 15.2 and for 3272 the BFCP Error Code subregistry in Section 15.4.] 3274 The IANA has created a registry for BFCP parameters called "Binary 3275 Floor Control Protocol (BFCP) Parameters". This registry has a 3276 number of subregistries, which are described in the following 3277 sections. 3279 15.1. Attribute Subregistry 3281 This section establishes the Attribute subregistry under the BFCP 3282 Parameters registry. As per the terminology in RFC 5226 [5], the 3283 registration policy for BFCP attributes shall be "Specification 3284 Required". For the purposes of this subregistry, the BFCP attributes 3285 for which IANA registration is requested MUST be defined by a 3286 standards-track RFC. Such an RFC MUST specify the attribute's type, 3287 name, format, and semantics. 3289 For each BFCP attribute, the IANA registers its type, its name, and 3290 the reference to the RFC where the attribute is defined. The 3291 following table contains the initial values of this subregistry. 3293 +------+---------------------------+------------+ 3294 | Type | Attribute | Reference | 3295 +------+---------------------------+------------+ 3296 | 1 | BENEFICIARY-ID | [RFC XXXX] | 3297 | 2 | FLOOR-ID | [RFC XXXX] | 3298 | 3 | FLOOR-REQUEST-ID | [RFC XXXX] | 3299 | 4 | PRIORITY | [RFC XXXX] | 3300 | 5 | REQUEST-STATUS | [RFC XXXX] | 3301 | 6 | ERROR-CODE | [RFC XXXX] | 3302 | 7 | ERROR-INFO | [RFC XXXX] | 3303 | 8 | PARTICIPANT-PROVIDED-INFO | [RFC XXXX] | 3304 | 9 | STATUS-INFO | [RFC XXXX] | 3305 | 10 | SUPPORTED-ATTRIBUTES | [RFC XXXX] | 3306 | 11 | SUPPORTED-PRIMITIVES | [RFC XXXX] | 3307 | 12 | USER-DISPLAY-NAME | [RFC XXXX] | 3308 | 13 | USER-URI | [RFC XXXX] | 3309 | 14 | BENEFICIARY-INFORMATION | [RFC XXXX] | 3310 | 15 | FLOOR-REQUEST-INFORMATION | [RFC XXXX] | 3311 | 16 | REQUESTED-BY-INFORMATION | [RFC XXXX] | 3312 | 17 | FLOOR-REQUEST-STATUS | [RFC XXXX] | 3313 | 18 | OVERALL-REQUEST-STATUS | [RFC XXXX] | 3314 +------+---------------------------+------------+ 3316 Table 7: Initial values of the BFCP Attribute subregistry 3318 15.2. Primitive Subregistry 3320 [Editorial note: This section instructs the IANA to register the 3321 following new values for the BFCP Primitive subregistry: 3322 FloorRequestStatusAck, FloorStatusAck, Goodbye, and GoodbyeAck.] 3324 This section establishes the Primitive subregistry under the BFCP 3325 Parameters registry. As per the terminology in RFC 5226 [5], the 3326 registration policy for BFCP primitives shall be "Specification 3327 Required". For the purposes of this subregistry, the BFCP primitives 3328 for which IANA registration is requested MUST be defined by a 3329 standards-track RFC. Such an RFC MUST specify the primitive's value, 3330 name, format, and semantics. 3332 For each BFCP primitive, the IANA registers its value, its name, and 3333 the reference to the RFC where the primitive is defined. The 3334 following table contains the initial values of this subregistry. 3336 +-------+-----------------------+------------+ 3337 | Value | Primitive | Reference | 3338 +-------+-----------------------+------------+ 3339 | 1 | FloorRequest | [RFC XXXX] | 3340 | 2 | FloorRelease | [RFC XXXX] | 3341 | 3 | FloorRequestQuery | [RFC XXXX] | 3342 | 4 | FloorRequestStatus | [RFC XXXX] | 3343 | 5 | UserQuery | [RFC XXXX] | 3344 | 6 | UserStatus | [RFC XXXX] | 3345 | 7 | FloorQuery | [RFC XXXX] | 3346 | 8 | FloorStatus | [RFC XXXX] | 3347 | 9 | ChairAction | [RFC XXXX] | 3348 | 10 | ChairActionAck | [RFC XXXX] | 3349 | 11 | Hello | [RFC XXXX] | 3350 | 12 | HelloAck | [RFC XXXX] | 3351 | 13 | Error | [RFC XXXX] | 3352 | 14 | FloorRequestStatusAck | [RFC XXXX] | 3353 | 15 | FloorStatusAck | [RFC XXXX] | 3354 | 16 | Goodbye | [RFC XXXX] | 3355 | 17 | GoodbyeAck | [RFC XXXX] | 3356 +-------+-----------------------+------------+ 3358 Table 8: Initial values of the BFCP primitive subregistry 3360 15.3. Request Status Subregistry 3362 This section establishes the Request Status subregistry under the 3363 BFCP Parameters registry. As per the terminology in RFC 5226 [5], 3364 the registration policy for BFCP request status shall be 3365 "Specification Required". For the purposes of this subregistry, the 3366 BFCP request status for which IANA registration is requested MUST be 3367 defined by a standards-track RFC. Such an RFC MUST specify the value 3368 and the semantics of the request status. 3370 For each BFCP request status, the IANA registers its value, its 3371 meaning, and the reference to the RFC where the request status is 3372 defined. The following table contains the initial values of this 3373 subregistry. 3375 +-------+-----------+------------+ 3376 | Value | Status | Reference | 3377 +-------+-----------+------------+ 3378 | 1 | Pending | [RFC XXXX] | 3379 | 2 | Accepted | [RFC XXXX] | 3380 | 3 | Granted | [RFC XXXX] | 3381 | 4 | Denied | [RFC XXXX] | 3382 | 5 | Cancelled | [RFC XXXX] | 3383 | 6 | Released | [RFC XXXX] | 3384 | 7 | Revoked | [RFC XXXX] | 3385 +-------+-----------+------------+ 3387 Table 9: Initial values of the Request Status subregistry 3389 15.4. Error Code Subregistry 3391 [Editorial note: This section instructs the IANA to register the 3392 following new values for the BFCP Error Code subregistry: 10, 11, 3393 12, 13 and 14.] 3395 This section establishes the Error Code subregistry under the BFCP 3396 Parameters registry. As per the terminology in RFC 5226 [5], the 3397 registration policy for BFCP error codes shall be "Specification 3398 Required". For the purposes of this subregistry, the BFCP error 3399 codes for which IANA registration is requested MUST be defined by a 3400 standards-track RFC. Such an RFC MUST specify the value and the 3401 semantics of the error code, and any Error Specific Details that 3402 apply to it. 3404 For each BFCP primitive, the IANA registers its value, its meaning, 3405 and the reference to the RFC where the primitive is defined. The 3406 following table contains the initial values of this subregistry. 3408 +-------+--------------------------------------+------------+ 3409 | Value | Meaning | Reference | 3410 +-------+--------------------------------------+------------+ 3411 | 1 | Conference does not Exist | [RFC XXXX] | 3412 | 2 | User does not Exist | [RFC XXXX] | 3413 | 3 | Unknown Primitive | [RFC XXXX] | 3414 | 4 | Unknown Mandatory Attribute | [RFC XXXX] | 3415 | 5 | Unauthorized Operation | [RFC XXXX] | 3416 | 6 | Invalid Floor ID | [RFC XXXX] | 3417 | 7 | Floor Request ID Does Not Exist | [RFC XXXX] | 3418 | 8 | You have Already Reached the Maximum | [RFC XXXX] | 3419 | | Number of Ongoing Floor Requests for | | 3420 | | this Floor | | 3421 | 9 | Use TLS | [RFC XXXX] | 3422 | 10 | Unable to parse message | [RFC XXXX] | 3423 | 11 | Use DTLS | [RFC XXXX] | 3424 | 12 | Unsupported Version | [RFC XXXX] | 3425 | 13 | Incorrect Message Length | [RFC XXXX] | 3426 | 14 | Generic Error | [RFC XXXX] | 3427 +-------+--------------------------------------+------------+ 3429 Table 10: Initial Values of the Error Code subregistry 3431 16. Changes from RFC 4582 3433 Following is the list of technical changes and other non-trivial 3434 fixes from [2]. 3436 16.1. Extensions for an unreliable transport 3438 Main purpose of this work was to revise the specification to support 3439 BFCP over an unreliable transport, resulting in the following 3440 changes: 3442 1. Overview of Operation (Section 4): 3443 Changed the description of client-initiated and server-initiated 3444 transactions, referring to Section 8. 3446 2. COMMON-HEADER Format (Section 5.1): 3447 Ver(sion) field, where the value 2 is used for the extensions 3448 for an unreliable transport. Added new R and F flag-bits for an 3449 unreliable transport. Res(erved) field is now 3 bit. New 3450 optional Fragment Offset and Fragment Length fields. 3452 3. New primitives (Section 5.1): 3453 Added four new primitives: FloorRequestStatusAck, 3454 FloorStatusAck, Goodbye, and GoodbyeAck. 3456 4. New error codes (Section 5.2.6): 3457 Added three new error codes: "Unable to Parse Message", "Use 3458 DTLS" and "Unsupported Version". Note that two additional error 3459 codes were added, see Section 16.2. 3461 5. ABNF for new primitives (Section 5.3): 3462 New subsections with normative ABNF for the new primitives. 3464 6. Transport split in two (Section 6): 3465 Section 6 specifying the transport was split in two subsections; 3466 Section 6.1 for a reliable transport and Section 6.2 for an 3467 unreliable transport. Where the specification for an unreliable 3468 transport amongst other issues deals with reliability, 3469 congestion control, fragmentation and ICMP. 3471 7. Mandate DTLS (Section 7 and Section 9): 3472 Mandate DTLS support when transport over UDP is used. 3474 8. Transaction changes (Section 8): 3475 Server-initiated transactions over an unreliable transport has 3476 non-zero and unique Transaction ID. Over an unreliable 3477 transport, the retransmit timers T1 and T2 described in 3478 Section 8.3 apply. 3480 9. Requiring timely response (Section 8.3, Section 10.1.2, 3481 Section 10.2.2, Section 11.2, Section 12.1.2, Section 12.2.2, 3482 Section 12.3.2, Section 12.4.2, Section 10.1.3 and 3483 Section 12.1.3): 3484 Describing that a given response must be sent within the 3485 transaction failure window to complete the transaction. 3487 10. Updated IANA Considerations (Section 15): 3488 Added the new primitives and error codes to Section 15.2 and 3489 Section 15.4 respectively. 3491 11. Examples over an unreliable transport (Appendix A): 3492 Added sample interactions over an unreliable transport for the 3493 scenarios in Figure 2 and Figure 3 3495 12. Motivation for an unreliable transport (Appendix B): 3496 Introduction to and motivation for extending BFCP to support an 3497 unreliable transport. 3499 16.2. Other changes 3501 Clarifications and bug fixes: 3503 1. ABNF fixes (Figure 22, Figure 24, ="fig:reqby-information"/>, 3504 Figure 28, Figure 30, and the ABNF figures in Section 5.3): 3505 Although formally correct in [2], the notation has changed in a 3506 number of Figures to an equivalent form for clarity, e.g., 3507 s/*1(FLOOR-ID)/[FLOOR-ID]/ in Figure 38 and s/*[XXX]/*(XXX)/ in 3508 the other figures. 3510 2. Typo (Section 12.4.2): 3511 Change from SUPPORTED-PRIMITVIES to SUPPORTED-PRIMITIVES in the 3512 second paragraph. 3514 3. Corrected attribute type (Section 13.1.1): 3515 Change from PARTICIPANT-PROVIDED-INFO to PRIORITY attributed in 3516 the eighth paragraph, since the note below describes priority and 3517 that the last paragraph deals with PARTICIPANT-PROVIDED-INFO. 3519 4. New error codes (Section 5.2.6): 3520 Added two additional error codes: "Incorrect Message Length" and 3521 "Generic Error". 3523 5. Assorted clarifications (Across the document): 3524 Language clarifications as a result of reviews. Also, the 3525 normative language where tightened where appropriate, i.e. 3526 changed from SHOULD strength to MUST in a number of places. 3528 17. Acknowledgements 3530 The XCON WG chairs, Adam Roach and Alan Johnston, provided useful 3531 ideas for RFC 4582 [2]. Additionally, Xiaotao Wu, Paul Kyzivat, 3532 Jonathan Rosenberg, Miguel A. Garcia-Martin, Mary Barnes, Ben 3533 Campbell, Dave Morgan, and Oscar Novo provided useful comments during 3534 the work with RFC 4582. The authors also acknowledge contributions 3535 to the revision of BFCP for use over an unreliable transport from 3536 Geir Arne Sandbakken who had the initial idea, Alfred E. Heggestad, 3537 Trond G. Andersen, Gonzalo Camarillo, Roni Even, Lorenzo Miniero, 3538 Joerg Ott, Eoin McLeod, Mark K. Thompson, Hadriel Kaplan, Dan Wing, 3539 Cullen Jennings, David Benham, Nivedita Melinkeri, Woo Johnman, 3540 Vijaya Mandava and Alan Ford. In the final phase Ernst Horvath did a 3541 thorough review revealing issues that needed clarification and 3542 changes. Useful and important final reviews were done by Mary 3543 Barnes. 3545 18. References 3546 18.1. Normative References 3548 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 3549 Levels", BCP 14, RFC 2119, March 1997. 3551 [2] Camarillo, G., Ott, J., and K. Drage, "The Binary Floor Control 3552 Protocol (BFCP)", RFC 4582, November 2006. 3554 [3] Camarillo, G., "Connection Establishment in the Binary Floor 3555 Control Protocol (BFCP)", RFC 5018, September 2007. 3557 [4] Crocker, D. and P. Overell, "Augmented BNF for Syntax 3558 Specifications: ABNF", STD 68, RFC 5234, January 2008. 3560 [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 3561 Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. 3563 [6] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) 3564 Protocol Version 1.2", RFC 5246, August 2008. 3566 [7] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 3567 Security Version 1.2", RFC 6347, January 2012. 3569 [8] Yergeau, F., "UTF-8, a transformation format of ISO 10646", 3570 STD 63, RFC 3629, November 2003. 3572 [9] Camarillo, G., Kristensen, T., and P. Jones, "Session 3573 Description Protocol (SDP) Format for Binary Floor Control 3574 Protocol (BFCP) Streams", draft-ietf-bfcpbis-rfc4583bis-12 3575 (work in progress), Semptember 2015. 3577 [10] Wing, D., "Symmetric RTP / RTP Control Protocol (RTCP)", 3578 BCP 131, RFC 4961, July 2007. 3580 [11] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session 3581 Traversal Utilities for NAT (STUN)", RFC 5389, October 2008. 3583 18.2. Informational References 3585 [12] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with 3586 Session Description Protocol (SDP)", RFC 3264, June 2002. 3588 [13] Koskelainen, P., Ott, J., Schulzrinne, H., and X. Wu, 3589 "Requirements for Floor Control Protocols", RFC 4376, 3590 February 2006. 3592 [14] Barnes, M., Boulton, C., and O. Levin, "A Framework for 3593 Centralized Conferencing", RFC 5239, June 2008. 3595 [15] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A 3596 Protocol for Network Address Translator (NAT) Traversal for 3597 Offer/Answer Protocols", RFC 5245, April 2010. 3599 [16] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 3600 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 3601 Session Initiation Protocol", RFC 3261, June 2002. 3603 [17] Novo, O., Camarillo, G., Morgan, D., and J. Urpalainen, 3604 "Conference Information Data Model for Centralized Conferencing 3605 (XCON)", RFC 6501, March 2012. 3607 [18] Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne, 3608 "Centralized Conferencing Manipulation Protocol", RFC 6503, 3609 March 2012. 3611 [19] Barnes, M., Miniero, L., Presta, R., and SP. Romano, 3612 "Centralized Conferencing Manipulation Protocol (CCMP) Call 3613 Flow Examples", RFC 6504, March 2012. 3615 [20] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 3616 November 1990. 3618 [21] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery for 3619 IP version 6", RFC 1981, August 1996. 3621 [22] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3622 Discovery", RFC 4821, March 2007. 3624 [23] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework for 3625 Establishing a Secure Real-time Transport Protocol (SRTP) 3626 Security Context Using Datagram Transport Layer Security 3627 (DTLS)", RFC 5763, May 2010. 3629 [24] Sheffer, Y., Holz, R., and P. Saint-Andre, "Recommendations for 3630 Secure Use of TLS and DTLS", draft-ietf-uta-tls-bcp-09 (work in 3631 progress), February 2015. 3633 [25] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network 3634 Address Translations (NATs)", RFC 4380, February 2006. 3636 [26] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines for 3637 Application Designers", BCP 145, RFC 5405, November 2008. 3639 [27] Thaler, D., "Teredo Extensions", RFC 6081, January 2011. 3641 [28] Stewart, R., "Stream Control Transmission Protocol", RFC 4960, 3642 September 2007. 3644 [29] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach, "TCP 3645 Candidates with Interactive Connectivity Establishment (ICE)", 3646 RFC 6544, March 2012. 3648 [30] Manner, J., Varis, N., and B. Briscoe, "Generic UDP Tunnelling 3649 (GUT)", draft-manner-tsvwg-gut-02 (work in progress), 3650 July 2010. 3652 [31] Stucker, B., Tschofenig, H., and G. Salgueiro, "Analysis of 3653 Middlebox Interactions for Signaling Protocol Communication 3654 along the Media Path", 3655 draft-ietf-mmusic-media-path-middleboxes-05 (work in progress), 3656 July 2012. 3658 [32] Guha, S. and P. Francis, "Characterization and Measurement of 3659 TCP Traversal through NATs and Firewalls", 2005, 3660 . 3662 [33] Ford, B., Srisuresh, P., and D. Kegel, "Peer-to-Peer 3663 Communication Across Network Address Translators", April 2005, 3664 . 3666 Appendix A. Example Call Flows for BFCP over an Unreliable Transport 3668 With reference to Section 4.1, the following figures show 3669 representative call-flows for requesting and releasing a floor, and 3670 obtaining status information about a floor when BFCP is deployed over 3671 an unreliable transport. The figures here show a loss-less 3672 interaction. 3674 Floor Participant Floor Control 3675 Server 3676 |(1) FloorRequest | 3677 |Transaction ID: 123 | 3678 |User ID: 234 | 3679 |FLOOR-ID: 543 | 3680 |---------------------------------------------->| 3681 | | 3682 |(2) FloorRequestStatus | 3683 |Transaction ID: 123 | 3684 |User ID: 234 | 3685 |FLOOR-REQUEST-INFORMATION | 3686 | Floor Request ID: 789 | 3687 | OVERALL-REQUEST-STATUS | 3688 | Request Status: Pending | 3689 | FLOOR-REQUEST-STATUS | 3690 | Floor ID: 543 | 3691 |<----------------------------------------------| 3692 | | 3693 |(3) FloorRequestStatus | 3694 |Transaction ID: 124 | 3695 |User ID: 234 | 3696 |FLOOR-REQUEST-INFORMATION | 3697 | Floor Request ID: 789 | 3698 | OVERALL-REQUEST-STATUS | 3699 | Request Status: Accepted | 3700 | Queue Position: 1st | 3701 | FLOOR-REQUEST-STATUS | 3702 | Floor ID: 543 | 3703 |<----------------------------------------------| 3704 | | 3705 |(4) FloorRequestStatusAck | 3706 |Transaction ID: 124 | 3707 |User ID: 234 | 3708 |---------------------------------------------->| 3709 | | 3710 |(5) FloorRequestStatus | 3711 |Transaction ID: 125 | 3712 |User ID: 234 | 3713 |FLOOR-REQUEST-INFORMATION | 3714 | Floor Request ID: 789 | 3715 | OVERALL-REQUEST-STATUS | 3716 | Request Status: Granted | 3717 | FLOOR-REQUEST-STATUS | 3718 | Floor ID: 543 | 3719 |<----------------------------------------------| 3720 | | 3721 |(6) FloorRequestStatusAck | 3722 |Transaction ID: 125 | 3723 |User ID: 234 | 3724 |---------------------------------------------->| 3725 | | 3726 |(7) FloorRelease | 3727 |Transaction ID: 126 | 3728 |User ID: 234 | 3729 |FLOOR-REQUEST-ID: 789 | 3730 |---------------------------------------------->| 3731 | | 3732 |(8) FloorRequestStatus | 3733 |Transaction ID: 126 | 3734 |User ID: 234 | 3735 |FLOOR-REQUEST-INFORMATION | 3736 | Floor Request ID: 789 | 3737 | OVERALL-REQUEST-STATUS | 3738 | Request Status: Released | 3739 | FLOOR-REQUEST-STATUS | 3740 | Floor ID: 543 | 3741 |<----------------------------------------------| 3743 Figure 48: Requesting and releasing a floor 3745 Note that in Figure 48, the FloorRequestStatus message from the floor 3746 control server to the floor participant is a transaction-closing 3747 message as a response to the client-initiated transaction with 3748 Transaction ID 154. It does not and SHOULD NOT be followed by a 3749 FloorRequestStatusAck message from the floor participant to the floor 3750 control server. 3752 Floor Participant Floor Control 3753 Server 3754 |(1) FloorQuery | 3755 |Transaction ID: 257 | 3756 |User ID: 234 | 3757 |FLOOR-ID: 543 | 3758 |---------------------------------------------->| 3759 | | 3760 |(2) FloorStatus | 3761 |Transaction ID: 257 | 3762 |User ID: 234 | 3763 |FLOOR-ID:543 | 3764 |FLOOR-REQUEST-INFORMATION | 3765 | Floor Request ID: 764 | 3766 | OVERALL-REQUEST-STATUS | 3767 | Request Status: Accepted | 3768 | Queue Position: 1st | 3769 | FLOOR-REQUEST-STATUS | 3770 | Floor ID: 543 | 3771 | BENEFICIARY-INFORMATION | 3772 | Beneficiary ID: 124 | 3773 |FLOOR-REQUEST-INFORMATION | 3774 | Floor Request ID: 635 | 3775 | OVERALL-REQUEST-STATUS | 3776 | Request Status: Accepted | 3777 | Queue Position: 2nd | 3778 | FLOOR-REQUEST-STATUS | 3779 | Floor ID: 543 | 3780 | BENEFICIARY-INFORMATION | 3781 | Beneficiary ID: 154 | 3782 |<----------------------------------------------| 3783 | | 3784 |(3) FloorStatus | 3785 |Transaction ID: 258 | 3786 |User ID: 234 | 3787 |FLOOR-ID:543 | 3788 |FLOOR-REQUEST-INFORMATION | 3789 | Floor Request ID: 764 | 3790 | OVERALL-REQUEST-STATUS | 3791 | Request Status: Granted | 3792 | FLOOR-REQUEST-STATUS | 3793 | Floor ID: 543 | 3794 | BENEFICIARY-INFORMATION | 3795 | Beneficiary ID: 124 | 3796 |FLOOR-REQUEST-INFORMATION | 3797 | Floor Request ID: 635 | 3798 | OVERALL-REQUEST-STATUS | 3799 | Request Status: Accepted | 3800 | Queue Position: 1st | 3801 | FLOOR-REQUEST-STATUS | 3802 | Floor ID: 543 | 3803 | BENEFICIARY-INFORMATION | 3804 | Beneficiary ID: 154 | 3805 |<----------------------------------------------| 3806 | | 3807 |(4) FloorStatusAck | 3808 |Transaction ID: 258 | 3809 |User ID: 234 | 3810 |---------------------------------------------->| 3811 | | 3812 |(5) FloorStatus | 3813 |Transaction ID: 259 | 3814 |User ID: 234 | 3815 |FLOOR-ID:543 | 3816 |FLOOR-REQUEST-INFORMATION | 3817 | Floor Request ID: 635 | 3818 | OVERALL-REQUEST-STATUS | 3819 | Request Status: Granted | 3820 | FLOOR-REQUEST-STATUS | 3821 | Floor ID: 543 | 3822 | BENEFICIARY-INFORMATION | 3823 | Beneficiary ID: 154 | 3824 |<----------------------------------------------| 3825 | | 3826 |(6) FloorStatusAck | 3827 |Transaction ID: 259 | 3828 |User ID: 234 | 3829 |---------------------------------------------->| 3831 Figure 49: Obtaining status information about a floor 3833 Appendix B. Motivation for Supporting an Unreliable Transport 3835 This appendix is contained in this document as an aid to understand 3836 the background and rationale for adding support for unreliable 3837 transport. 3839 B.1. Motivation 3841 In existing video conferencing deployments, BFCP is used to manage 3842 the floor for the content sharing associated with the conference. 3843 For peer to peer scenarios, including business to business 3844 conferences and point to point conferences in general, it is 3845 frequently the case that one or both endpoints exists behind a NAT. 3846 BFCP roles are negotiated in the offer/answer exchange as specified 3847 in [9], resulting in one endpoint being responsible for opening the 3848 TCP connection used for the BFCP communication. 3850 +---------+ 3851 | Network | 3852 +---------+ 3853 +-----+ / \ +-----+ 3854 | NAT |/ \| NAT | 3855 +-----+ +-----+ 3856 +----+ / \ +----+ 3857 |BFCP|/ \|BFCP| 3858 | UA | | UA | 3859 +----+ +----+ 3861 Figure 50: Use Case 3863 The communication session between the video conferencing endpoints 3864 typically consists of a number of RTP over UDP media streams, for 3865 audio and video, and a BFCP connection for floor control. Existing 3866 deployments are most common in, but not limited to, enterprise 3867 networks. In existing deployments, NAT traversal for the RTP streams 3868 works using ICE and/or other methods, including those described in 3869 [31]. 3871 When enhancing an existing SIP based video conferencing deployment 3872 with support for content sharing, the BFCP connection often poses a 3873 problem. The reasons for this fall into two general classes. First, 3874 there may be a strong preference for UDP based signaling in general. 3875 On high capacity endpoints (e.g., PSTN gateways or SIP/H.323 inter- 3876 working gateways), TCP can suffer from head of line blocking, and it 3877 uses many kernel buffers. Network operators view UDP as a way to 3878 avoid both of these. Second, establishment and traversal of the TCP 3879 connection involving ephemeral ports, as is typically the case with 3880 BFCP over TCP, can be problematic, as described in Appendix A of 3881 [29]. A broad study of NAT behavior and peer-to-peer TCP 3882 establishment for a comprehensive set of TCP NAT traversal techniques 3883 over a wide range of commercial NAT products concluded it was not 3884 possible to establish a TCP connection in 11% of the cases [32]. The 3885 results are worse when focusing on enterprise NATs. A study of hole 3886 punching as a NAT traversal technique across a wide variety of 3887 deployed NATs reported consistently higher success rates when using 3888 UDP than when using TCP [33]. 3890 It is worth noticing that BFCP over UDP is already being used in real 3891 deployments, underlining the necessity to specify a common way to 3892 exchange BFCP messages where TCP is not appropriate, to avoid a 3893 situation where multiple different and non-interoperable 3894 implementations would co-exist in the market. The purpose of this 3895 draft is to formalize and publish the extension from the standard 3896 specification to facilitate complete interoperability between 3897 implementations. 3899 B.1.1. Alternatives Considered 3901 In selecting the approach of defining UDP as an alternate transport 3902 for BFCP, several alternatives were considered and explored to some 3903 degree. Each of these is discussed briefly in the following 3904 subsections. In summary, while the not chosen alternatives work in a 3905 number of scenarios, they are not sufficient, in and of themselves, 3906 to address the use case targeted by this draft. The last 3907 alternative, presented in Appendix B.1.1.7, is the selected one and 3908 is specified in this draft. 3910 It is also worth noting that the IETF Transport Area were asked for a 3911 way to tunnel TCP over UDP, but at that point there was no consensus 3912 on how to achieve that. 3914 B.1.1.1. ICE TCP 3916 ICE TCP [29] extends ICE to TCP based media, including the ability to 3917 offer a mix of TCP and UDP based candidates for a single stream. ICE 3918 TCP has, in general, a lower success probability for enabling TCP 3919 connectivity without a relay if both of the hosts are behind a NAT 3920 (see Appendix A of [29]) than enabling UDP connectivity in the same 3921 scenarios. The happens because many of the currently deployed NATs 3922 in video conferencing networks do not support the flow of TCP hand 3923 shake packets seen in case of TCP simultaneous-open, either because 3924 they do not allow incoming TCP SYN packets from an address to which a 3925 SYN packet has been sent to recently, or because they do not properly 3926 process the subsequent SYNACK. Implementing various techniques 3927 advocated for candidate collection in [29] should increase the 3928 success probability, but many of these techniques require support 3929 from some network elements (e.g., from the NATs). Such support is 3930 not common in enterprise NATs. 3932 B.1.1.2. Teredo 3934 Teredo [25] enables nodes located behind one or more IPv4 NATs to 3935 obtain IPv6 connectivity by tunneling packets over UDP. Teredo 3936 extensions [27] provide additional capabilities to Teredo, including 3937 support for more types of NATs and support for more efficient 3938 communication. 3940 As defined, Teredo could be used to make BFCP work for the video 3941 conferencing use cases addressed in this draft. However, running the 3942 service requires the help of "Teredo servers" and "Teredo relays" 3943 [25]. These servers and relays generally do not exist in the 3944 existing video conferencing deployments. It also requires IPv6 3945 awareness on the endpoints. It should also be noted that ICMP6, as 3946 used with Teredo to complete an initial protocol exchange and confirm 3947 that the appropriate NAT bindings have been set up, is not a 3948 conventional feature of IPv4 or even IPv6, and some currently 3949 deployed IPv6 firewalls discard ICMP messages. As these networks 3950 continue to evolve and tackle the transaction to IPv6, Teredo servers 3951 and relays may be deployed, making Teredo available as a suitable 3952 alternative to BFCP over UDP. 3954 B.1.1.3. GUT 3956 GUT [30] attempts to facilitate tunneling over UDP by encapsulating 3957 the native transport protocol and its payload (in general the whole 3958 IP payload) within a UDP packet destined to the well-known port 3959 GUT_P. Unfortunately, it requires user-space TCP, for which there is 3960 not a readily available implementation, and creating one is a large 3961 project in itself. This draft has expired and its future is still 3962 not clear as it has not yet been adopted by a working group. 3964 B.1.1.4. UPnP IGD 3966 Universal Plug and Play Internet Gateway Devices (UPnP IGD) sit on 3967 the edge of the network, providing connectivity to the Internet for 3968 computers internal to the LAN, but do not allow Internet devices to 3969 connect to computers on the internal LAN. IGDs enable a computer on 3970 an internal LAN to create port mappings on their NAT, through which 3971 hosts on the Internet can send data that will be forwarded to the 3972 computer on the internal LAN. IGDs may be self-contained hardware 3973 devices or may be software components provided within an operating 3974 system. 3976 In considering UPnP IGD, several issues exist. Not all NATs support 3977 UPnP, and many that do support it are configured with it turned off 3978 by default. NATs are often multilayered, and UPnP does not work well 3979 with such NATs. For example, a typical DSL modems acts as a NAT, and 3980 the user plugs in a wireless access point behind that, which adds 3981 another layer NAT. The client can discover the first layer of NAT 3982 using multicast but it is harder to figure out how to discover and 3983 control NATs in the next layer up. 3985 B.1.1.5. NAT PMP 3987 The NAT Port Mapping Protocol (NAT PMP) allows a computer in a 3988 private network (behind a NAT router) to automatically configure the 3989 router to allow parties outside the private network to contact it. 3990 NAT PMP runs over UDP. It essentially automates the process of port 3991 forwarding. Included in the protocol is a method for retrieving the 3992 public IP address of a NAT gateway, thus allowing a client to make 3993 this public IP address and port number known to peers that may wish 3994 to communicate with it. 3996 Many NATs do not support PMP. In those that do support it, it has 3997 similar issues with negotiation of multilayer NATs as UPnP. Video 3998 conferencing is used extensively in enterprise networks, and NAT PMP 3999 is not generally available in enterprise-class routers. 4001 B.1.1.6. SCTP 4003 It would be quite straight forward to specify a BFCP binding for SCTP 4004 [28], and then tunnel SCTP over UDP in the use case described in 4005 Appendix B.1. SCTP is gaining some momentum currently. There is 4006 ongoing discussion in the RTCWeb WG regarding this approach. 4007 However, this approach for tunneling over UDP was not mature enough 4008 when considered and not even fully specified. 4010 B.1.1.7. BFCP over UDP transport 4012 To overcome the problems with establishing TCP flows between BFCP 4013 entities, an alternative is to define UDP as an alternate transport 4014 for BFCP, leveraging the same mechanisms in place for the RTP over 4015 UDP media streams for the BFCP communication. When using UDP as the 4016 transport, it is recommended to follow the guidelines provided in 4017 [26]. 4019 Minor changes to the transaction model are introduced in that all 4020 requests now have an appropriate response to complete the 4021 transaction. The requests are sent with a retransmit timer 4022 associated with the response to achieve reliability. This 4023 alternative does not change the semantics of BFCP. It permits UDP as 4024 an alternate transport. 4026 Existing implementations, in the spirit of the approach detailed in 4027 earlier versions of this draft, have demonstrated this approach to be 4028 feasible. Initial compatibility among implementations has been 4029 achieved at previous interoperability events. The authors view this 4030 extension as a pragmatic solution to an existing deployment 4031 challenge. This is the chosen approach, and the extensions is 4032 specified in this document. 4034 Authors' Addresses 4036 Gonzalo Camarillo 4037 Ericsson 4038 Hirsalantie 11 4039 FI-02420 Jorvas 4040 Finland 4042 Email: gonzalo.camarillo@ericsson.com 4044 Keith Drage 4045 Alcatel-Lucent 4046 Quadrant, StoneHill Green, Westlea 4047 Swindon, Wilts 4048 UK 4050 Email: drage@alcatel-lucent.com 4052 Tom Kristensen 4053 Cisco 4054 Philip Pedersens vei 1 4055 NO-1366 Lysaker 4056 Norway 4058 Email: tomkrist@cisco.com, tomkri@ifi.uio.no 4060 Joerg Ott 4061 Aalto University 4062 Otakaari 5 A 4063 FI-02150 Espoo 4064 Finland 4066 Email: jo@comnet.tkk.fi 4067 Charles Eckel 4068 Cisco 4069 707 Tasman Drive 4070 California, CA 95035 4071 United States 4073 Email: eckelcu@cisco.com