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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 3420 ** Obsolete normative reference: RFC 5226 (ref. '3') (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 5246 (ref. '4') (Obsoleted by RFC 8446) ** Obsolete normative reference: RFC 6347 (ref. '5') (Obsoleted by RFC 9147) == Outdated reference: A later version (-27) exists of draft-ietf-bfcpbis-rfc4583bis-08 ** Obsolete normative reference: RFC 5389 (ref. '9') (Obsoleted by RFC 8489) -- Obsolete informational reference (is this intentional?): RFC 5245 (ref. '13') (Obsoleted by RFC 8445, RFC 8839) -- Obsolete informational reference (is this intentional?): RFC 4582 (ref. '15') (Obsoleted by RFC 8855) -- Obsolete informational reference (is this intentional?): RFC 1981 (ref. '20') (Obsoleted by RFC 8201) -- Obsolete informational reference (is this intentional?): RFC 5405 (ref. '24') (Obsoleted by RFC 8085) -- Obsolete informational reference (is this intentional?): RFC 4960 (ref. '26') (Obsoleted by RFC 9260) == Outdated reference: A later version (-07) exists of draft-ietf-mmusic-media-path-middleboxes-05 Summary: 4 errors (**), 0 flaws (~~), 4 warnings (==), 8 comments (--).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: May 8, 2014 T. Kristensen 7 Cisco 8 J. Ott 9 Aalto University 10 C. Eckel 11 Cisco 12 November 4, 2013 14 The Binary Floor Control Protocol (BFCP) 15 draft-ietf-bfcpbis-rfc4582bis-10 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 May 8, 2014. 50 Copyright Notice 52 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . 42 121 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 . . . . . . . . . . . . . . . . . . . . . 46 127 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 . . . . . . . . . . 47 131 8.3.3. Timer Values . . . . . . . . . . . . . . . . . . . . . 47 132 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 . . . . . . . . . . . . . . . . . . . . . . 78 183 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 78 184 18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 78 185 18.1. Normative References . . . . . . . . . . . . . . . . . . . 78 186 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 . . 84 190 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 [11] 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 [11]. 293 Floor control complements other functions defined in the XCON 294 conferencing framework [12]. 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 [12]. 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 [12]. 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 [17] can specify such floor- 355 related settings by editing the floor-information section of the 356 to-be created conference object provided in the body of a CCMP 357 confRequest/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. These data include 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 [10] exchange, which is described in [7]. How to 367 establish a connection to a BFCP floor control server outside the 368 context of an offer/answer exchange is described in [16]. Other 369 mechanisms are described in the XCON framework [12] (and other 370 related documents). 372 3.3. Obtaining Floor-Resource Associations 374 Floors are associated with resources. For example, a floor that 375 controls who talks at a given time has a particular audio session as 376 its associated resource. Associations between floors and resources 377 are part of the conference object. 379 Floor participants and floor chairs need to know which resources are 380 associated with which floors. They can obtain this information by 381 using different mechanisms, such as an SDP offer/answer [10] 382 exchange. How to use an SDP offer/answer exchange to obtain these 383 associations is described in [7]. 385 Note that floor participants perform SDP offer/answer exchanges 386 with the conference focus of the conference. So, the conference 387 focus needs to obtain information about associations between 388 floors and resources in order to be able to provide this 389 information to a floor participant in an SDP offer/answer 390 exchange. 392 Other mechanisms for obtaining this information, including discussion 393 of how the information is made available to a (SIP) Focus, are 394 described in the XCON framework [12] (and other related documents). 395 According to the conferencing system policies, conference control 396 clients using CCMP [17] can modify the floor settings of a conference 397 by issuing CCMP confRequest/update messages providing the specific 398 updates to the section of the target conference 399 object. More information about CCMP and BFCP interaction can be 400 found in [18]. 402 3.4. Privileges of Floor Control 404 A participant whose floor request is granted has the right to use (in 405 a certain way) the resource or resources associated with the floor 406 that was requested. For example, the participant may have the right 407 to send media over a particular audio stream. 409 Nevertheless, holding a floor does not imply that others will not be 410 able to use its associated resources at the same time, even if they 411 do not have the right to do so. Determination of which media 412 participants can actually use the resources in the conference is 413 discussed in the XCON Framework [12]. 415 4. Overview of Operation 417 This section provides a non-normative description of BFCP operations. 418 Section 4.1 describes the interface between floor participants and 419 floor control servers, and Section 4.2 describes the interface 420 between floor chairs and floor control servers. 422 BFCP messages, which use a TLV (Type-Length-Value) binary encoding, 423 consist of a common header followed by a set of attributes. The 424 common header contains, among other information, a 32-bit conference 425 identifier. Floor participants, media participants, and floor chairs 426 are identified by 16-bit user identifiers. 428 BFCP supports nested attributes (i.e., attributes that contain 429 attributes). These are referred to as grouped attributes. 431 There are two types of transactions in BFCP: client-initiated 432 transactions and server-initiated transactions. Section 8 describes 433 both types of transactions in detail. 435 4.1. Floor Participant to Floor Control Server Interface 437 Floor participants request a floor by sending a FloorRequest message 438 to the floor control server. BFCP supports third-party floor 439 requests. That is, the floor participant sending the floor request 440 need not be colocated with the media participant that will get the 441 floor once the floor request is granted. FloorRequest messages carry 442 the identity of the requester in the User ID field of the common 443 header, and the identity of the beneficiary of the floor (in third- 444 party floor requests) in a BENEFICIARY-ID attribute. 446 Third-party floor requests can be sent, for example, by floor 447 participants that have a BFCP connection to the floor control 448 server but that are not media participants (i.e., they do not 449 handle any media). 451 FloorRequest messages identify the floor or floors being requested by 452 carrying their 16-bit floor identifiers in FLOOR-ID attributes. If a 453 FloorRequest message carries more than one floor identifier, the 454 floor control server treats all the floor requests as an atomic 455 package. That is, the floor control server either grants or denies 456 all the floors in the FloorRequest message. 458 Floor control servers respond to FloorRequest messages with 459 FloorRequestStatus messages, which provide information about the 460 status of the floor request. The first FloorRequestStatus message is 461 the response to the FloorRequest message from the client, and 462 therefore has the same Transaction ID as the FloorRequest. 464 Additionally, the first FloorRequestStatus message carries the Floor 465 Request ID in a FLOOR-REQUEST-INFORMATION attribute. Subsequent 466 FloorRequestStatus messages related to the same floor request will 467 carry the same Floor Request ID. This way, the floor participant can 468 associate them with the appropriate floor request. 470 Messages from the floor participant related to a particular floor 471 request also use the same Floor Request ID as the first 472 FloorRequestStatus Message from the floor control server. 474 Figures 2 and 3 below show examples of call flows where BFCP is used 475 over a reliable transport. Appendix A shows the same call flow 476 examples using an unreliable transport. 478 Figure 2 shows how a floor participant requests a floor, obtains it, 479 and, at a later time, releases it. This figure illustrates the use, 480 among other things, of the Transaction ID and the FLOOR-REQUEST-ID 481 attribute. 483 Floor Participant Floor Control 484 Server 485 |(1) FloorRequest | 486 |Transaction ID: 123 | 487 |User ID: 234 | 488 |FLOOR-ID: 543 | 489 |---------------------------------------------->| 490 | | 491 |(2) FloorRequestStatus | 492 |Transaction ID: 123 | 493 |User ID: 234 | 494 |FLOOR-REQUEST-INFORMATION | 495 | Floor Request ID: 789 | 496 | OVERALL-REQUEST-STATUS | 497 | Request Status: Pending | 498 | FLOOR-REQUEST-STATUS | 499 | Floor ID: 543 | 500 |<----------------------------------------------| 501 | | 502 |(3) FloorRequestStatus | 503 |Transaction ID: 0 | 504 |User ID: 234 | 505 |FLOOR-REQUEST-INFORMATION | 506 | Floor Request ID: 789 | 507 | OVERALL-REQUEST-STATUS | 508 | Request Status: Accepted | 509 | Queue Position: 1st | 510 | FLOOR-REQUEST-STATUS | 511 | Floor ID: 543 | 512 |<----------------------------------------------| 513 | | 514 |(4) FloorRequestStatus | 515 |Transaction ID: 0 | 516 |User ID: 234 | 517 |FLOOR-REQUEST-INFORMATION | 518 | Floor Request ID: 789 | 519 | OVERALL-REQUEST-STATUS | 520 | Request Status: Granted | 521 | FLOOR-REQUEST-STATUS | 522 | Floor ID: 543 | 523 |<----------------------------------------------| 524 | | 525 |(5) FloorRelease | 526 |Transaction ID: 154 | 527 |User ID: 234 | 528 |FLOOR-REQUEST-ID: 789 | 529 |---------------------------------------------->| 530 | | 531 |(6) FloorRequestStatus | 532 |Transaction ID: 154 | 533 |User ID: 234 | 534 |FLOOR-REQUEST-INFORMATION | 535 | Floor Request ID: 789 | 536 | OVERALL-REQUEST-STATUS | 537 | Request Status: Released | 538 | FLOOR-REQUEST-STATUS | 539 | Floor ID: 543 | 540 |<----------------------------------------------| 542 Figure 2: Requesting and releasing a floor 544 Figure 3 shows how a floor participant requests to be informed on the 545 status of a floor. The first FloorStatus message from the floor 546 control server is the response to the FloorQuery message and, as 547 such, has the same Transaction ID as the FloorQuery message. 549 Subsequent FloorStatus messages consist of server-initiated 550 transactions, and therefore their Transaction ID is 0. FloorStatus 551 message (2) indicates that there are currently two floor requests for 552 the floor whose Floor ID is 543. FloorStatus message (3) indicates 553 that the floor requests with Floor Request ID 764 has been granted, 554 and the floor request with Floor Request ID 635 is the first in the 555 queue. FloorStatus message (4) indicates that the floor request with 556 Floor Request ID 635 has been granted. 558 Floor Participant Floor Control 559 Server 560 |(1) FloorQuery | 561 |Transaction ID: 257 | 562 |User ID: 234 | 563 |FLOOR-ID: 543 | 564 |---------------------------------------------->| 565 | | 566 |(2) FloorStatus | 567 |Transaction ID: 257 | 568 |User ID: 234 | 569 |FLOOR-ID:543 | 570 |FLOOR-REQUEST-INFORMATION | 571 | Floor Request ID: 764 | 572 | OVERALL-REQUEST-STATUS | 573 | Request Status: Accepted | 574 | Queue Position: 1st | 575 | FLOOR-REQUEST-STATUS | 576 | Floor ID: 543 | 577 | BENEFICIARY-INFORMATION | 578 | Beneficiary ID: 124 | 579 |FLOOR-REQUEST-INFORMATION | 580 | Floor Request ID: 635 | 581 | OVERALL-REQUEST-STATUS | 582 | Request Status: Accepted | 583 | Queue Position: 2nd | 584 | FLOOR-REQUEST-STATUS | 585 | Floor ID: 543 | 586 | BENEFICIARY-INFORMATION | 587 | Beneficiary ID: 154 | 588 |<----------------------------------------------| 589 | | 590 |(3) FloorStatus | 591 |Transaction ID: 0 | 592 |User ID: 234 | 593 |FLOOR-ID:543 | 594 |FLOOR-REQUEST-INFORMATION | 595 | Floor Request ID: 764 | 596 | OVERALL-REQUEST-STATUS | 597 | Request Status: Granted | 598 | FLOOR-REQUEST-STATUS | 599 | Floor ID: 543 | 600 | BENEFICIARY-INFORMATION | 601 | Beneficiary ID: 124 | 602 |FLOOR-REQUEST-INFORMATION | 603 | Floor Request ID: 635 | 604 | OVERALL-REQUEST-STATUS | 605 | Request Status: Accepted | 606 | Queue Position: 1st | 607 | FLOOR-REQUEST-STATUS | 608 | Floor ID: 543 | 609 | BENEFICIARY-INFORMATION | 610 | Beneficiary ID: 154 | 611 |<----------------------------------------------| 612 | | 613 |(4) FloorStatus | 614 |Transaction ID: 0 | 615 |User ID: 234 | 616 |FLOOR-ID:543 | 617 |FLOOR-REQUEST-INFORMATION | 618 | Floor Request ID: 635 | 619 | OVERALL-REQUEST-STATUS | 620 | Request Status: Granted | 621 | FLOOR-REQUEST-STATUS | 622 | Floor ID: 543 | 623 | BENEFICIARY-INFORMATION | 624 | Beneficiary ID: 154 | 625 |<----------------------------------------------| 627 Figure 3: Obtaining status information about a floor 629 FloorStatus messages contain information about the floor requests 630 they carry. For example, FloorStatus message (4) indicates that the 631 floor request with Floor Request ID 635 has as the beneficiary (i.e., 632 the participant that holds the floor when a particular floor request 633 is granted) the participant whose User ID is 154. The floor request 634 applies only to the floor whose Floor ID is 543. That is, this is 635 not a multi-floor floor request. 637 A multi-floor floor request applies to more than one floor (e.g., 638 a participant wants to be able to speak and write on the 639 whiteboard at the same time). The floor control server treats a 640 multi-floor floor request as an atomic package. That is, the 641 floor control server either grants the request for all floors or 642 denies the request for all floors. 644 4.2. Floor Chair to Floor Control Server Interface 646 Figure 4 shows a floor chair instructing a floor control server to 647 grant a floor. 649 Note, however, that although the floor control server needs to 650 take into consideration the instructions received in ChairAction 651 messages (e.g., granting a floor), it does not necessarily need to 652 perform them exactly as requested by the floor chair. The 653 operation that the floor control server performs depends on the 654 ChairAction message and on the internal state of the floor control 655 server. 657 For example, a floor chair may send a ChairAction message granting a 658 floor that was requested as part of an atomic floor request operation 659 that involved several floors. Even if the chair responsible for one 660 of the floors instructs the floor control server to grant the floor, 661 the floor control server will not grant it until the chairs 662 responsible for the other floors agree to grant them as well. In 663 another example, a floor chair may instruct the floor control server 664 to grant a floor to a participant. The floor control server needs to 665 revoke the floor from its current holder before granting it to the 666 new participant. 668 So, the floor control server is ultimately responsible for keeping a 669 coherent floor state using instructions from floor chairs as input to 670 this state. 672 Floor Chair Floor Control 673 Server 674 |(1) ChairAction | 675 |Transaction ID: 769 | 676 |User ID: 357 | 677 |FLOOR-REQUEST-INFORMATION | 678 | Floor Request ID: 635 | 679 | FLOOR-REQUEST-STATUS | 680 | Floor ID: 543 | 681 | Request Status: Granted | 682 |---------------------------------------------->| 683 | | 684 |(2) ChairActionAck | 685 |Transaction ID: 769 | 686 |User ID: 357 | 687 |<----------------------------------------------| 689 Figure 4: Chair instructing the floor control server 691 5. Packet Format 693 BFCP packets consist of a 12-octet common header followed by 694 attributes. All the protocol values MUST be sent in network byte 695 order. 697 5.1. COMMON-HEADER Format 699 The following is the format of the common header. 701 0 1 2 3 702 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 1 703 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 704 | Ver |R|F| Res | Primitive | Payload Length | 705 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 706 | Conference ID | 707 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 708 | Transaction ID | User ID | 709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 | Fragment Offset (if F is set) | Fragment Length (if F is set) | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 Figure 5: COMMON-HEADER format 715 Ver: This 3-bit field defines the version of BFCP that this message 716 adheres to. This specification defines two versions: 1 and 2. The 717 version field MUST be set to 1 when using BFCP over a reliable 718 transport, i.e. as in [15]. The version field MUST be set to 2 when 719 using BFCP over an unreliable transport with the extensions specified 720 in this document. If an endpoint receives a message with an 721 unsupported version field value, the receiving server SHOULD send an 722 Error message with parameter value 12 (Unsupported Version) to 723 indicate this. 725 R: The Transaction Responder (R) flag-bit has relevance only for use 726 of BFCP over an unreliable transport. When cleared, it indicates 727 that this message is a request initiating a new transaction, and the 728 Transaction ID that follows has been generated for this transaction. 729 When set, it indicates that this message is a response to a previous 730 request, and the Transaction ID that follows is the one associated 731 with that request. When BFCP is used over a reliable transport, the 732 flag has no significance and SHOULD be cleared by the sender and MUST 733 be ignored by the receiver. 735 F: The Fragmentation (F) flag-bit has relevance only for use of BFCP 736 over an unreliable transport. When cleared, the message is not 737 fragmented. When set, it indicates that the message is a fragment of 738 a large fragmented BFCP message. (The optional fields Fragment 739 Offset and Fragment Length described below are present only if the F 740 flag is set). When BFCP is used over a reliable transport, the flag 741 has no significance and SHOULD be cleared by the sender and MUST be 742 ignored by the receiver. 744 Res: At this point, the 3 bits in the reserved field SHOULD be set to 745 zero by the sender of the message and MUST be ignored by the 746 receiver. 748 Primitive: This 8-bit field identifies the main purpose of the 749 message. The following primitive values are defined: 751 +-------+-----------------------+--------------------+ 752 | Value | Primitive | Direction | 753 +-------+-----------------------+--------------------+ 754 | 1 | FloorRequest | P -> S | 755 | 2 | FloorRelease | P -> S | 756 | 3 | FloorRequestQuery | P -> S ; Ch -> S | 757 | 4 | FloorRequestStatus | P <- S ; Ch <- S | 758 | 5 | UserQuery | P -> S ; Ch -> S | 759 | 6 | UserStatus | P <- S ; Ch <- S | 760 | 7 | FloorQuery | P -> S ; Ch -> S | 761 | 8 | FloorStatus | P <- S ; Ch <- S | 762 | 9 | ChairAction | Ch -> S | 763 | 10 | ChairActionAck | Ch <- S | 764 | 11 | Hello | P -> S ; Ch -> S | 765 | 12 | HelloAck | P <- S ; Ch <- S | 766 | 13 | Error | P <- S ; Ch <- S | 767 | 14 | FloorRequestStatusAck | P -> S ; Ch -> S | 768 | 15 | FloorStatusAck | P -> S ; Ch -> S | 769 | 16 | Goodbye | P -> S ; Ch -> S ; | 770 | | | P <- S ; Ch <- S | 771 | 17 | GoodbyeAck | P -> S ; Ch -> S ; | 772 | | | P <- S ; Ch <- S | 773 +-------+-----------------------+--------------------+ 775 S: Floor Control Server / P: Floor Participant / Ch: Floor Chair 777 Table 1: BFCP primitives 779 Payload Length: This 16-bit field contains the length of the message 780 in 4-octet units, excluding the common header. If a Floor Control 781 Server receives a message with an incorrect Payload Length field 782 value, the receiving server SHOULD send an Error message with 783 parameter value 13 (Incorrect Message Length) to indicate this. 785 Note: BFCP is designed to achieve small message size, as explained 786 in Section 1, and BFCP entities are REQUIRED to keep the BFCP 787 message size smaller than the size limited by the 16-bit Payload 788 Length field. To convey information not strictly related to floor 789 control, other protocols should be used such as the XCON framework 790 (cf. Section 3). 792 Conference ID: This 32-bit unsigned integer field identifies the 793 conference the message belongs to. 795 Transaction ID: This field contains a 16-bit value that allows users 796 to match a given message with its response (see Section 8). 798 User ID: This field contains a 16-bit unsigned integer that uniquely 799 identifies a participant within a conference. 801 The identity used by a participant in BFCP, which is carried in 802 the User ID field, is generally mapped to the identity used by the 803 same participant in the session establishment protocol (e.g., in 804 SIP). The way this mapping is performed is outside the scope of 805 this specification. 807 Fragment Offset: This optional field is present only if the F flag is 808 set and contains a 16-bit value that specifies the number of 4-octet 809 units contained in previous fragments, excluding the common header. 811 Fragment Length: This optional field is present only if the F flag is 812 set and contains a 16-bit value that specifies the number of 4-octet 813 units contained in this fragment, excluding the common header. 815 5.2. Attribute Format 817 BFCP attributes are encoded in TLV (Type-Length-Value) format. 818 Attributes are 32-bit aligned. 820 0 1 2 3 821 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 1 822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 823 | Type |M| Length | | 824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 825 | | 826 / Attribute Contents / 827 / / 828 | | 829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 831 Figure 6: Attribute format 833 Type: This 7-bit field contains the type of the attribute. Each 834 attribute, identified by its type, has a particular format. The 835 attribute formats defined are: 837 Unsigned16: The contents of the attribute consist of a 16-bit 838 unsigned integer. 840 OctetString16: The contents of the attribute consist of 16 bits of 841 arbitrary data. 843 OctetString: The contents of the attribute consist of arbitrary 844 data of variable length. 846 Grouped: The contents of the attribute consist of a sequence of 847 attributes. 849 Note that extension attributes defined in the future may define 850 new attribute formats. 852 The following attribute types are defined: 854 +------+---------------------------+---------------+ 855 | Type | Attribute | Format | 856 +------+---------------------------+---------------+ 857 | 1 | BENEFICIARY-ID | Unsigned16 | 858 | 2 | FLOOR-ID | Unsigned16 | 859 | 3 | FLOOR-REQUEST-ID | Unsigned16 | 860 | 4 | PRIORITY | OctetString16 | 861 | 5 | REQUEST-STATUS | OctetString16 | 862 | 6 | ERROR-CODE | OctetString | 863 | 7 | ERROR-INFO | OctetString | 864 | 8 | PARTICIPANT-PROVIDED-INFO | OctetString | 865 | 9 | STATUS-INFO | OctetString | 866 | 10 | SUPPORTED-ATTRIBUTES | OctetString | 867 | 11 | SUPPORTED-PRIMITIVES | OctetString | 868 | 12 | USER-DISPLAY-NAME | OctetString | 869 | 13 | USER-URI | OctetString | 870 | 14 | BENEFICIARY-INFORMATION | Grouped | 871 | 15 | FLOOR-REQUEST-INFORMATION | Grouped | 872 | 16 | REQUESTED-BY-INFORMATION | Grouped | 873 | 17 | FLOOR-REQUEST-STATUS | Grouped | 874 | 18 | OVERALL-REQUEST-STATUS | Grouped | 875 +------+---------------------------+---------------+ 877 Table 2: BFCP attributes 879 M: The 'M' bit, known as the Mandatory bit, indicates whether support 880 of the attribute is required. If a Floor Control Server receives an 881 unrecognized attribute with the 'M' bit set the server SHOULD send an 882 Error message with parameter value 4 (Unknown Mandatory Attribute) to 883 indicate this. The 'M' bit is significant for extension attributes 884 defined in other documents only. All attributes specified in this 885 document MUST be understood by the receiver so that the setting of 886 the 'M' bit is irrelevant for these. In all other cases, the 887 unrecognized attribute is ignored but the message is processed. 889 Length: This 8-bit field contains the length of the attribute in 890 octets, excluding any padding defined for specific attributes. The 891 length of attributes that are not grouped includes the Type, 'M' bit, 892 and Length fields. The Length in grouped attributes is the length of 893 the grouped attribute itself (including Type, 'M' bit, and Length 894 fields) plus the total length (including padding) of all the included 895 attributes. 897 Attribute Contents: The contents of the different attributes are 898 defined in the following sections. 900 5.2.1. BENEFICIARY-ID 902 The following is the format of the BENEFICIARY-ID attribute. 904 0 1 2 3 905 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 1 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 907 |0 0 0 0 0 0 1|M|0 0 0 0 0 1 0 0| Beneficiary ID | 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 910 Figure 7: BENEFICIARY-ID format 912 Beneficiary ID: This field contains a 16-bit value that uniquely 913 identifies a user within a conference. 915 Note that although the formats of the Beneficiary ID and of the 916 User ID field in the common header are similar, their semantics 917 are different. The Beneficiary ID is used in third-party floor 918 requests and to request information about a particular 919 participant. 921 5.2.2. FLOOR-ID 923 The following is the format of the FLOOR-ID attribute. 925 0 1 2 3 926 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 1 927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 928 |0 0 0 0 0 1 0|M|0 0 0 0 0 1 0 0| Floor ID | 929 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 931 Figure 8: FLOOR-ID format 933 Floor ID: This field contains a 16-bit value that uniquely identifies 934 a floor within a conference. 936 5.2.3. FLOOR-REQUEST-ID 938 The following is the format of the FLOOR-REQUEST-ID attribute. 940 0 1 2 3 941 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 1 942 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 943 |0 0 0 0 0 1 1|M|0 0 0 0 0 1 0 0| Floor Request ID | 944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 946 Figure 9: FLOOR-REQUEST-ID format 948 Floor Request ID: This field contains a 16-bit value that identifies 949 a floor request at the floor control server. 951 5.2.4. PRIORITY 953 The following is the format of the PRIORITY attribute. 955 0 1 2 3 956 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 1 957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 958 |0 0 0 0 1 0 0|M|0 0 0 0 0 1 0 0|Prio | Reserved | 959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 961 Figure 10: PRIORITY format 963 Prio: This field contains a 3-bit priority value, as shown in 964 Table 3. Senders SHOULD NOT use values higher than 4 in this field. 965 Receivers MUST treat values higher than 4 as if the value received 966 were 4 (Highest). The default priority value when the PRIORITY 967 attribute is missing is 2 (Normal). 969 +-------+----------+ 970 | Value | Priority | 971 +-------+----------+ 972 | 0 | Lowest | 973 | 1 | Low | 974 | 2 | Normal | 975 | 3 | High | 976 | 4 | Highest | 977 +-------+----------+ 979 Table 3: Priority values 981 Reserved: At this point, the 13 bits in the reserved field SHOULD be 982 set to zero by the sender of the message and MUST be ignored by the 983 receiver. 985 5.2.5. REQUEST-STATUS 987 The following is the format of the REQUEST-STATUS attribute. 989 0 1 2 3 990 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 1 991 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 992 |0 0 0 0 1 0 1|M|0 0 0 0 0 1 0 0|Request Status |Queue Position | 993 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 995 Figure 11: REQUEST-STATUS format 997 Request Status: This 8-bit field contains the status of the request, 998 as described in the following table. 1000 +-------+-----------+ 1001 | Value | Status | 1002 +-------+-----------+ 1003 | 1 | Pending | 1004 | 2 | Accepted | 1005 | 3 | Granted | 1006 | 4 | Denied | 1007 | 5 | Cancelled | 1008 | 6 | Released | 1009 | 7 | Revoked | 1010 +-------+-----------+ 1012 Table 4: Request Status values 1014 Queue Position: This 8-bit field contains, when applicable, the 1015 position of the floor request in the floor request queue at the 1016 server. If the Request Status value is different from Accepted, if 1017 the floor control server does not implement a floor request queue, or 1018 if the floor control server does not want to provide the client with 1019 this information, all the bits of this field SHOULD be set to zero. 1021 A floor request is in Pending state if the floor control server needs 1022 to contact a floor chair in order to accept the floor request, but 1023 has not done it yet. Once the floor control chair accepts the floor 1024 request, the floor request is moved to the Accepted state. 1026 5.2.6. ERROR-CODE 1028 The following is the format of the ERROR-CODE attribute. 1030 0 1 2 3 1031 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 1032 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1033 |0 0 0 0 1 1 0|M| Length | Error Code | | 1034 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1035 | | 1036 | Error Specific Details | 1037 / / 1038 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1039 | | Padding | 1040 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1042 Figure 12: ERROR-CODE format 1044 Error Code: This 8-bit field contains an error code from the 1045 following table. If an error code is not recognized by the receiver, 1046 then the receiver MUST assume that an error exists, and therefore 1047 that the original message that triggered the Error message to be sent 1048 is processed, but the nature of the error is unclear. 1050 +-------+-----------------------------------------------------------+ 1051 | Value | Meaning | 1052 +-------+-----------------------------------------------------------+ 1053 | 1 | Conference does not Exist | 1054 | 2 | User does not Exist | 1055 | 3 | Unknown Primitive | 1056 | 4 | Unknown Mandatory Attribute | 1057 | 5 | Unauthorized Operation | 1058 | 6 | Invalid Floor ID | 1059 | 7 | Floor Request ID Does Not Exist | 1060 | 8 | You have Already Reached the Maximum Number of Ongoing | 1061 | | Floor Requests for this Floor | 1062 | 9 | Use TLS | 1063 | 10 | Unable to Parse Message | 1064 | 11 | Use DTLS | 1065 | 12 | Unsupported Version | 1066 | 13 | Incorrect Message Length | 1067 | 14 | Generic Error | 1068 +-------+-----------------------------------------------------------+ 1070 Table 5: Error Code meaning 1072 Note: The Generic Error error code is intended to be used by a 1073 BFCP entity when an error occurs and the other specific error 1074 codes do not apply. 1076 Error Specific Details: Present only for certain Error Codes. In 1077 this document, only for Error Code 4 (Unknown Mandatory Attribute). 1078 See Section 5.2.6.1 for its definition. 1080 Padding: One, two, or three octets of padding added so that the 1081 contents of the ERROR-CODE attribute is 32-bit aligned. If the 1082 attribute is already 32-bit aligned, no padding is needed. 1084 The Padding bits SHOULD be set to zero by the sender and MUST be 1085 ignored by the receiver. 1087 5.2.6.1. Error-Specific Details for Error Code 4 1089 The following is the format of the Error-Specific Details field for 1090 Error Code 4. 1092 0 1 2 3 1093 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 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1095 | Unknown Type|R| Unknown Type|R| Unknown Type|R| Unknown Type|R| 1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1097 | | 1098 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1099 | | Unknown Type|R| Unknown Type|R| 1100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1101 | Unknown Type|R| Unknown Type|R| 1102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1104 Figure 13: Unknown attributes format 1106 Unknown Type: These 7-bit fields contain the Types of the attributes 1107 (which were present in the message that triggered the Error message) 1108 that were unknown to the receiver. 1110 R: At this point, this bit is reserved. It SHOULD be set to zero by 1111 the sender of the message and MUST be ignored by the receiver. 1113 5.2.7. ERROR-INFO 1115 The following is the format of the ERROR-INFO attribute. 1117 0 1 2 3 1118 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 1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 |0 0 0 0 1 1 1|M| Length | | 1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1122 | | 1123 / Text / 1124 / +-+-+-+-+-+-+-+-+ 1125 | | Padding | 1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1128 Figure 14: ERROR-INFO format 1130 Text: This field contains UTF-8 [6] encoded text. 1132 In some situations, the contents of the Text field may be generated 1133 by an automaton. If this automaton has information about the 1134 preferred language of the receiver of a particular ERROR-INFO 1135 attribute, it MAY use this language to generate the Text field. 1137 Padding: One, two, or three octets of padding added so that the 1138 contents of the ERROR-INFO attribute is 32-bit aligned. The Padding 1139 bits SHOULD be set to zero by the sender and MUST be ignored by the 1140 receiver. If the attribute is already 32-bit aligned, no padding is 1141 needed. 1143 5.2.8. PARTICIPANT-PROVIDED-INFO 1145 The following is the format of the PARTICIPANT-PROVIDED-INFO 1146 attribute. 1148 0 1 2 3 1149 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 1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1151 |0 0 0 1 0 0 0|M| Length | | 1152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1153 | | 1154 / Text / 1155 / +-+-+-+-+-+-+-+-+ 1156 | | Padding | 1157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1159 Figure 15: PARTICIPANT-PROVIDED-INFO format 1161 Text: This field contains UTF-8 [6] encoded text. 1163 Padding: One, two, or three octets of padding added so that the 1164 contents of the PARTICIPANT-PROVIDED-INFO attribute is 32-bit 1165 aligned. The Padding bits SHOULD be set to zero by the sender and 1166 MUST be ignored by the receiver. If the attribute is already 32-bit 1167 aligned, no padding is needed. 1169 5.2.9. STATUS-INFO 1171 The following is the format of the STATUS-INFO attribute. 1173 0 1 2 3 1174 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 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1176 |0 0 0 1 0 0 1|M| Length | | 1177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1178 | | 1179 / Text / 1180 / +-+-+-+-+-+-+-+-+ 1181 | | Padding | 1182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1184 Figure 16: STATUS-INFO format 1186 Text: This field contains UTF-8 [6] encoded text. 1188 In some situations, the contents of the Text field may be generated 1189 by an automaton. If this automaton has information about the 1190 preferred language of the receiver of a particular STATUS-INFO 1191 attribute, it MAY use this language to generate the Text field. 1193 Padding: One, two, or three octets of padding added so that the 1194 contents of the STATUS-INFO attribute is 32-bit aligned. The Padding 1195 bits SHOULD be set to zero by the sender and MUST be ignored by the 1196 receiver. If the attribute is already 32-bit aligned, no padding is 1197 needed. 1199 5.2.10. SUPPORTED-ATTRIBUTES 1201 The following is the format of the SUPPORTED-ATTRIBUTES attribute. 1203 0 1 2 3 1204 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 1205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1206 |0 0 0 1 0 1 0|M| Length | Supp. Attr. |R| Supp. Attr. |R| 1207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1208 | Supp. Attr. |R| Supp. Attr. |R| Supp. Attr. |R| Supp. Attr. |R| 1209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1210 | | 1211 / / 1212 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1213 | | Padding | 1214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1216 Figure 17: SUPPORTED-ATTRIBUTES format 1218 Supp. Attr.: These fields contain the Types of the attributes that 1219 are supported by the floor control server in the following format: 1221 R: Reserved: This bit MUST be set to zero upon transmission and MUST 1222 be ignored upon reception. 1224 Padding: One, two, or three octets of padding added so that the 1225 contents of the SUPPORTED-ATTRIBUTES attribute is 32-bit aligned. If 1226 the attribute is already 32-bit aligned, no padding is needed. 1228 The Padding bits SHOULD be set to zero by the sender and MUST be 1229 ignored by the receiver. 1231 5.2.11. SUPPORTED-PRIMITIVES 1233 The following is the format of the SUPPORTED-PRIMITIVES attribute. 1235 0 1 2 3 1236 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 1237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1238 |0 0 0 1 0 1 1|M| Length | Primitive | Primitive | 1239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1240 | Primitive | Primitive | Primitive | Primitive | 1241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1242 | | 1243 / / 1244 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1245 | | Padding | 1246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1248 Figure 18: SUPPORTED-PRIMITIVES format 1250 Primitive: These fields contain the types of the BFCP messages that 1251 are supported by the floor control server. See Table 1 for the list 1252 of BFCP primitives. 1254 Padding: One, two, or three octets of padding added so that the 1255 contents of the SUPPORTED-PRIMITIVES attribute is 32-bit aligned. If 1256 the attribute is already 32-bit aligned, no padding is needed. 1258 The Padding bits SHOULD be set to zero by the sender and MUST be 1259 ignored by the receiver. 1261 5.2.12. USER-DISPLAY-NAME 1263 The following is the format of the USER-DISPLAY-NAME attribute. 1265 0 1 2 3 1266 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 1267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1268 |0 0 0 1 1 0 0|M| Length | | 1269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1270 | | 1271 / Text / 1272 / +-+-+-+-+-+-+-+-+ 1273 | | Padding | 1274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1276 Figure 19: USER-DISPLAY-NAME format 1278 Text: This field contains the UTF-8 encoded name of the user. 1280 Padding: One, two, or three octets of padding added so that the 1281 contents of the USER-DISPLAY-NAME attribute is 32-bit aligned. The 1282 Padding bits SHOULD be set to zero by the sender and MUST be ignored 1283 by the receiver. If the attribute is already 32-bit aligned, no 1284 padding is needed. 1286 5.2.13. USER-URI 1288 The following is the format of the USER-URI attribute. 1290 0 1 2 3 1291 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 1292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 |0 0 0 1 1 0 1|M| Length | | 1294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1295 | | 1296 / Text / 1297 / +-+-+-+-+-+-+-+-+ 1298 | | Padding | 1299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1301 Figure 20: USER-URI format 1303 Text: This field contains the UTF-8 encoded user's contact URI, that 1304 is, the URI used by the user to set up the resources (e.g., media 1305 streams) that are controlled by BFCP. For example, in the context of 1306 a conference set up by SIP, the USER-URI attribute would carry the 1307 SIP URI of the user. 1309 Messages containing a user's URI in a USER-URI attribute also 1310 contain the user's User ID. This way, a client receiving such a 1311 message can correlate the user's URI (e.g., the SIP URI the user 1312 used to join a conference) with the user's User ID. 1314 Padding: One, two, or three octets of padding added so that the 1315 contents of the USER-URI attribute is 32-bit aligned. The Padding 1316 bits SHOULD be set to zero by the sender and MUST be ignored by the 1317 receiver. If the attribute is already 32-bit aligned, no padding is 1318 needed. 1320 5.2.14. BENEFICIARY-INFORMATION 1322 The BENEFICIARY-INFORMATION attribute is a grouped attribute that 1323 consists of a header, which is referred to as BENEFICIARY- 1324 INFORMATION-HEADER, followed by a sequence of attributes. The 1325 following is the format of the BENEFICIARY-INFORMATION-HEADER: 1327 0 1 2 3 1328 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 1329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1330 |0 0 0 1 1 1 0|M| Length | Beneficiary ID | 1331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1333 Figure 21: BENEFICIARY-INFORMATION-HEADER format 1335 Beneficiary ID: This field contains a 16-bit value that uniquely 1336 identifies a user within a conference. 1338 The following is the ABNF (Augmented Backus-Naur Form) [2] of the 1339 BENEFICIARY-INFORMATION grouped attribute. (EXTENSION-ATTRIBUTE 1340 refers to extension attributes that may be defined in the future.) 1342 BENEFICIARY-INFORMATION = (BENEFICIARY-INFORMATION-HEADER) 1343 [USER-DISPLAY-NAME] 1344 [USER-URI] 1345 *(EXTENSION-ATTRIBUTE) 1347 Figure 22: BENEFICIARY-INFORMATION format 1349 5.2.15. FLOOR-REQUEST-INFORMATION 1351 The FLOOR-REQUEST-INFORMATION attribute is a grouped attribute that 1352 consists of a header, which is referred to as FLOOR-REQUEST- 1353 INFORMATION-HEADER, followed by a sequence of attributes. The 1354 following is the format of the FLOOR-REQUEST-INFORMATION-HEADER: 1356 0 1 2 3 1357 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 1358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1359 |0 0 0 1 1 1 1|M| Length | Floor Request ID | 1360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1362 Figure 23: FLOOR-REQUEST-INFORMATION-HEADER format 1364 Floor Request ID: This field contains a 16-bit value that identifies 1365 a floor request at the floor control server. 1367 The following is the ABNF of the FLOOR-REQUEST-INFORMATION grouped 1368 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1369 may be defined in the future.) 1371 FLOOR-REQUEST-INFORMATION = (FLOOR-REQUEST-INFORMATION-HEADER) 1372 [OVERALL-REQUEST-STATUS] 1373 1*(FLOOR-REQUEST-STATUS) 1374 [BENEFICIARY-INFORMATION] 1375 [REQUESTED-BY-INFORMATION] 1376 [PRIORITY] 1377 [PARTICIPANT-PROVIDED-INFO] 1378 *(EXTENSION-ATTRIBUTE) 1380 Figure 24: FLOOR-REQUEST-INFORMATION format 1382 5.2.16. REQUESTED-BY-INFORMATION 1384 The REQUESTED-BY-INFORMATION attribute is a grouped attribute that 1385 consists of a header, which is referred to as REQUESTED-BY- 1386 INFORMATION-HEADER, followed by a sequence of attributes. The 1387 following is the format of the REQUESTED-BY-INFORMATION-HEADER: 1389 0 1 2 3 1390 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 1391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1392 |0 0 1 0 0 0 0|M| Length | Requested-by ID | 1393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1395 Figure 25: REQUESTED-BY-INFORMATION-HEADER format 1397 Requested-by ID: This field contains a 16-bit value that uniquely 1398 identifies a user within a conference. 1400 The following is the ABNF of the REQUESTED-BY-INFORMATION grouped 1401 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1402 may be defined in the future.) 1404 REQUESTED-BY-INFORMATION = (REQUESTED-BY-INFORMATION-HEADER) 1405 [USER-DISPLAY-NAME] 1406 [USER-URI] 1407 *(EXTENSION-ATTRIBUTE) 1409 Figure 26: REQUESTED-BY-INFORMATION format 1411 5.2.17. FLOOR-REQUEST-STATUS 1413 The FLOOR-REQUEST-STATUS attribute is a grouped attribute that 1414 consists of a header, which is referred to as FLOOR-REQUEST-STATUS- 1415 HEADER, followed by a sequence of attributes. The following is the 1416 format of the FLOOR-REQUEST-STATUS-HEADER: 1418 0 1 2 3 1419 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 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1421 |0 0 1 0 0 0 1|M| Length | Floor ID | 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1424 Figure 27: FLOOR-REQUEST-STATUS-HEADER format 1426 Floor ID: this field contains a 16-bit value that uniquely identifies 1427 a floor within a conference. 1429 The following is the ABNF of the FLOOR-REQUEST-STATUS grouped 1430 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1431 may be defined in the future.) 1433 FLOOR-REQUEST-STATUS = (FLOOR-REQUEST-STATUS-HEADER) 1434 [REQUEST-STATUS] 1435 [STATUS-INFO] 1436 *(EXTENSION-ATTRIBUTE) 1438 Figure 28: FLOOR-REQUEST-STATUS format 1440 5.2.18. OVERALL-REQUEST-STATUS 1442 The OVERALL-REQUEST-STATUS attribute is a grouped attribute that 1443 consists of a header, which is referred to as OVERALL-REQUEST-STATUS- 1444 HEADER, followed by a sequence of attributes. The following is the 1445 format of the OVERALL-REQUEST-STATUS-HEADER: 1447 0 1 2 3 1448 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 1449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1450 |0 0 1 0 0 1 0|M| Length | Floor Request ID | 1451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1453 Figure 29: OVERALL-REQUEST-STATUS-HEADER format 1455 Floor Request ID: this field contains a 16-bit value that identifies 1456 a floor request at the floor control server. 1458 The following is the ABNF of the OVERALL-REQUEST-STATUS grouped 1459 attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that 1460 may be defined in the future.) 1462 OVERALL-REQUEST-STATUS = (OVERALL-REQUEST-STATUS-HEADER) 1463 [REQUEST-STATUS] 1464 [STATUS-INFO] 1465 *(EXTENSION-ATTRIBUTE) 1467 Figure 30: OVERALL-REQUEST-STATUS format 1469 5.3. Message Format 1471 This section contains the normative ABNF (Augmented Backus-Naur Form) 1472 [2] of the BFCP messages. Extension attributes that may be defined 1473 in the future are referred to as EXTENSION-ATTRIBUTE in the ABNF. 1475 5.3.1. FloorRequest 1477 Floor participants request a floor by sending a FloorRequest message 1478 to the floor control server. The following is the format of the 1479 FloorRequest message: 1481 FloorRequest = (COMMON-HEADER) 1482 1*(FLOOR-ID) 1483 [BENEFICIARY-ID] 1484 [PARTICIPANT-PROVIDED-INFO] 1485 [PRIORITY] 1486 *(EXTENSION-ATTRIBUTE) 1488 Figure 31: FloorRequest format 1490 5.3.2. FloorRelease 1492 Floor participants release a floor by sending a FloorRelease message 1493 to the floor control server. Floor participants also use the 1494 FloorRelease message to cancel pending floor requests. The following 1495 is the format of the FloorRelease message: 1497 FloorRelease = (COMMON-HEADER) 1498 (FLOOR-REQUEST-ID) 1499 *(EXTENSION-ATTRIBUTE) 1501 Figure 32: FloorRelease format 1503 5.3.3. FloorRequestQuery 1505 Floor participants and floor chairs request information about a floor 1506 request by sending a FloorRequestQuery message to the floor control 1507 server. The following is the format of the FloorRequestQuery 1508 message: 1510 FloorRequestQuery = (COMMON-HEADER) 1511 (FLOOR-REQUEST-ID) 1512 *(EXTENSION-ATTRIBUTE) 1514 Figure 33: FloorRequestQuery format 1516 5.3.4. FloorRequestStatus 1518 The floor control server informs floor participants and floor chairs 1519 about the status of their floor requests by sending them 1520 FloorRequestStatus messages. The following is the format of the 1521 FloorRequestStatus message: 1523 FloorRequestStatus = (COMMON-HEADER) 1524 (FLOOR-REQUEST-INFORMATION) 1525 *(EXTENSION-ATTRIBUTE) 1527 Figure 34: FloorRequestStatus format 1529 5.3.5. UserQuery 1531 Floor participants and floor chairs request information about a 1532 participant and the floor requests related to this participant by 1533 sending a UserQuery message to the floor control server. The 1534 following is the format of the UserQuery message: 1536 UserQuery = (COMMON-HEADER) 1537 [BENEFICIARY-ID] 1538 *(EXTENSION-ATTRIBUTE) 1540 Figure 35: UserQuery format 1542 5.3.6. UserStatus 1544 The floor control server provides information about participants and 1545 their related floor requests to floor participants and floor chairs 1546 by sending them UserStatus messages. The following is the format of 1547 the UserStatus message: 1549 UserStatus = (COMMON-HEADER) 1550 [BENEFICIARY-INFORMATION] 1551 *(FLOOR-REQUEST-INFORMATION) 1552 *(EXTENSION-ATTRIBUTE) 1554 Figure 36: UserStatus format 1556 5.3.7. FloorQuery 1558 Floor participants and floor chairs request information about a floor 1559 or floors by sending a FloorQuery message to the floor control 1560 server. The following is the format of the FloorRequest message: 1562 FloorQuery = (COMMON-HEADER) 1563 *(FLOOR-ID) 1564 *(EXTENSION-ATTRIBUTE) 1566 Figure 37: FloorQuery format 1568 5.3.8. FloorStatus 1570 The floor control server informs floor participants and floor chairs 1571 about the status (e.g., the current holder) of a floor by sending 1572 them FloorStatus messages. The following is the format of the 1573 FloorStatus message: 1575 FloorStatus = (COMMON-HEADER) 1576 [FLOOR-ID] 1577 *(FLOOR-REQUEST-INFORMATION) 1578 *(EXTENSION-ATTRIBUTE) 1580 Figure 38: FloorStatus format 1582 5.3.9. ChairAction 1584 Floor chairs send instructions to floor control servers by sending 1585 them ChairAction messages. The following is the format of the 1586 ChairAction message: 1588 ChairAction = (COMMON-HEADER) 1589 (FLOOR-REQUEST-INFORMATION) 1590 *(EXTENSION-ATTRIBUTE) 1592 Figure 39: ChairAction format 1594 5.3.10. ChairActionAck 1596 Floor control servers confirm that they have accepted a ChairAction 1597 message by sending a ChairActionAck message. The following is the 1598 format of the ChairActionAck message: 1600 ChairActionAck = (COMMON-HEADER) 1601 *(EXTENSION-ATTRIBUTE) 1603 Figure 40: ChairActionAck format 1605 5.3.11. Hello 1607 Floor participants and floor chairs check the liveliness of floor 1608 control servers by sending a Hello message. The following is the 1609 format of the Hello message: 1611 Hello = (COMMON-HEADER) 1612 *(EXTENSION-ATTRIBUTE) 1614 Figure 41: Hello format 1616 5.3.12. HelloAck 1618 Floor control servers confirm that they are alive on reception of a 1619 Hello message by sending a HelloAck message. The following is the 1620 format of the HelloAck message: 1622 HelloAck = (COMMON-HEADER) 1623 (SUPPORTED-PRIMITIVES) 1624 (SUPPORTED-ATTRIBUTES) 1625 *(EXTENSION-ATTRIBUTE) 1627 Figure 42: HelloAck format 1629 5.3.13. Error 1631 Floor control servers inform floor participants and floor chairs 1632 about errors processing requests by sending them Error messages. The 1633 following is the format of the Error message: 1635 Error = (COMMON-HEADER) 1636 (ERROR-CODE) 1637 [ERROR-INFO] 1638 *(EXTENSION-ATTRIBUTE) 1640 Figure 43: Error format 1642 5.3.14. FloorRequestStatusAck 1644 When communicating over an unreliable transport, floor participants 1645 and chairs acknowledge the receipt of a subsequent FloorRequestStatus 1646 message from the floor control server (cf. Section 13.1.2) by sending 1647 a FloorRequestStatusAck message. The following is the format of the 1648 FloorRequestStatusAck message: 1650 FloorRequestStatusAck = (COMMON-HEADER) 1651 *(EXTENSION-ATTRIBUTE) 1653 Figure 44: FloorRequestStatusAck format 1655 5.3.15. FloorStatusAck 1657 When communicating over an unreliable transport, floor participants 1658 and chairs acknowledge the receipt of a subsequent FloorStatus 1659 message from the floor control server (cf. Section 13.5.2) by sending 1660 a FloorStatusAck message. The following is the format of the 1661 FloorStatusAck message: 1663 FloorStatusAck = (COMMON-HEADER) 1664 *(EXTENSION-ATTRIBUTE) 1666 Figure 45: FloorStatusAck format 1668 5.3.16. Goodbye 1670 BFCP entities communicating over an unreliable transport that wish to 1671 dissociate themselves from their remote participant do so through the 1672 transmission of a Goodbye. The following is the format of the 1673 Goodbye message: 1675 Goodbye = (COMMON-HEADER) 1676 *(EXTENSION-ATTRIBUTE) 1678 Figure 46: Goodbye format 1680 5.3.17. GoodbyeAck 1682 BFCP entities communicating over an unreliable transport should 1683 acknowledge the receipt of a Goodbye message from a peer. The 1684 following is the format of the GoodbyeAck message: 1686 GoodbyeAck = (COMMON-HEADER) 1687 *(EXTENSION-ATTRIBUTE) 1689 Figure 47: GoodbyeAck format 1691 6. Transport 1693 The transport over which BFCP entities exchange messages depends on 1694 how clients obtain information to contact the floor control server 1695 (e.g., using an SDP offer/answer exchange [7] or the procedure 1696 specified in [16]). Two transports are supported: TCP, appropriate 1697 where connectivity is not impeded by network elements such as NAT 1698 devices or media relays; and UDP for those deployments where TCP may 1699 not be applicable or appropriate. 1701 6.1. Reliable Transport 1703 BFCP entities may elect to exchange BFCP messages using TCP 1704 connections. TCP provides an in-order reliable delivery of a stream 1705 of bytes. Consequently, message framing needs to be implemented in 1706 the application layer. BFCP implements application-layer framing 1707 using TLV-encoded attributes. 1709 A client MUST NOT use more than one TCP connection to communicate 1710 with a given floor control server within a conference. Nevertheless, 1711 if the same physical box handles different clients (e.g., a floor 1712 chair and a floor participant), which are identified by different 1713 User IDs, a separate connection per client is allowed. 1715 If a BFCP entity (a client or a floor control server) receives data 1716 that cannot be parsed, the entity MUST close the TCP connection, and 1717 the connection SHOULD be reestablished. Similarly, if a TCP 1718 connection cannot deliver a BFCP message and times out or receives an 1719 ICMP port unreachable message mid-connection, the TCP connection 1720 SHOULD be reestablished. 1722 The way connection reestablishment is handled depends on how the 1723 client obtains information to contact the floor control server. Once 1724 the TCP connection is reestablished, the client MAY resend those 1725 messages for which it did not get a response from the floor control 1726 server. 1728 If a floor control server detects that the TCP connection towards one 1729 of the floor participants is lost, it is up to the local policy of 1730 the floor control server what to do with the pending floor requests 1731 of the floor participant. In any case, it is RECOMMENDED that the 1732 floor control server keep the floor requests (i.e., that it does not 1733 cancel them) while the TCP connection is reestablished. 1735 If a client wishes to end its BFCP connection with a floor control 1736 server, the client closes (i.e., a graceful close) the TCP connection 1737 towards the floor control server. If a floor control server wishes 1738 to end its BFCP connection with a client (e.g., the Focus of the 1739 conference informs the floor control server that the client has been 1740 kicked out from the conference), the floor control server closes 1741 (i.e., a graceful close) the TCP connection towards the client. 1743 6.2. Unreliable Transport 1745 BFCP entities may elect to exchange BFCP messages using UDP 1746 datagrams. UDP is an unreliable transport where neither delivery nor 1747 ordering is assured. Each BFCP UDP datagram MUST contain exactly one 1748 BFCP message or message fragment. To keep large BFCP messages from 1749 being fragmented at the IP layer, the fragmentation of BFCP messages 1750 that exceed the path MTU size is performed at the BFCP level. 1751 Considerations related to fragmentation are covered in Section 6.2.3. 1752 The message format for BFCP messages is the same regardless of 1753 whether the messages are sent in UDP datagrams or over a TCP stream. 1755 Clients MUST announce their presence to the floor control server by 1756 sending a Hello message. The floor control server responds to the 1757 Hello message with a HelloAck message. The client considers the 1758 floor control service as present and available only upon receiving 1759 the HelloAck message. 1761 As described in Section 8, each request sent by a floor participant 1762 or chair shall form a client transaction that expects an 1763 acknowledgement message back from the floor control server within a 1764 retransmission window. Concordantly, messages sent by the floor 1765 control server that are not transaction-completing (e.g., FloorStatus 1766 announcements as part of a FloorQuery subscription) are server- 1767 initiated transactions that require acknowledgement messages from the 1768 floor participant and chair entities to which they were sent. 1770 If a Floor Control Server receives data that cannot be parsed, the 1771 receiving server SHOULD send an Error message with parameter value 10 1772 (Unable to parse message) indicating receipt of a malformed message. 1774 Entities MUST have at most one outstanding request transaction at any 1775 one time. Implicit subscriptions occur for a client-initiated 1776 request transaction whose acknowledgement is implied by the first 1777 server-initiated response for that transaction, followed by zero of 1778 more subsequent server-initiated messages corresponding to the same 1779 transaction. An example is a FloorRequest message for which there 1780 are potentially multiple responses from the floor control server as 1781 it processes intermediate states until a terminal state (e.g., 1782 Granted or Denied) is attained. The subsequent changes in state for 1783 the request are new transactions whose Transaction ID is determined 1784 by the floor control server and whose receipt by the client 1785 participant shall be acknowledged with a FloorRequestStatusAck 1786 message. 1788 By restricting entities to having at most one pending transaction 1789 open in a BFCP connection, both the out-of-order receipt of messages 1790 as well as the possibility for congestion are mitigated. Additional 1791 details regarding congestion control are provided in Section 6.2.1. 1792 A server-initiated request (e.g., a FloorStatus with an update from 1793 the floor control server) received by a participant before the 1794 initial FloorRequestStatus message that closes the client-initiated 1795 transaction that was instigated by the FloorRequest MUST be treated 1796 as superseding the information conveyed in any such late arriving 1797 response. As the floor control server cannot send a second update to 1798 the implicit floor status subscription until the first is 1799 acknowledged, ordinality is maintained. 1801 If a client wishes to end its BFCP connection with a floor control 1802 server, it is RECOMMENDED that the client send a Goodbye message to 1803 dissociate itself from any allocated resources. If a floor control 1804 server wishes to end its BFCP connection with a client (e.g., the 1805 Focus of the conference informs the floor control server that the 1806 client has been kicked out from the conference), it is RECOMMENDED 1807 that the floor control server send a Goodbye message towards the 1808 client. 1810 RFC 5018 [16] specifies how to establish a TCP connection to a floor 1811 control server outside the context of an offer/answer exchange. When 1812 using UDP the same set of data is needed for a BFCP connection as 1813 listed in [16], Section 3, i.e. transport address of the server, the 1814 conference identifier, and the user identifier. The procedures and 1815 considerations for resolving a host name into an IP address also 1816 applies to BFCP over an unreliable transport. In [16], Section 4 1817 applies, but when using BFCP over an unreliable transport the floor 1818 control server that receives a BFCP message over UDP (no DTLS) SHOULD 1819 request the use of DTLS by generating an Error message with an Error 1820 code with a value of 11 (Use DTLS). The recommendations for 1821 authentication in [16], Section 5 and the security considerations in 1822 Section 6 also apply when an unreliable transport is used, both for 1823 certificate-based server authentication and for client authentication 1824 based on a pre-shared secret. 1826 6.2.1. Congestion Control 1828 BFCP may be characterized to generate "low data-volume" traffic, per 1829 the classification in [24]. Nevertheless is it necessary to ensure 1830 suitable and necessary congestion control mechanisms are used for 1831 BFCP over UDP. As described in previous paragraph, within the same 1832 BFCP connection, every entity - client or server - is only allowed to 1833 send one request at a time, and await the acknowledging response. 1834 This way at most one datagram is sent per RTT given the message is 1835 not lost during transmission. In case the message is lost, the 1836 request retransmission timer T1 specified in Section 8.3.1 will fire 1837 and the message is retransmitted up to three times, in addition to 1838 the original transmission of the message. The default initial 1839 interval is set to 500ms and the interval is doubled after each 1840 retransmission attempt. This is identical to the specification of 1841 the timer A and its initial value T1 in SIP as described in Section 1842 17.1.1.2 of [14]. 1844 6.2.2. ICMP Error Handling 1846 If a BFCP entity receives an ICMP port unreachable message mid- 1847 connection, the entity SHOULD treat the BFCP connection as closed 1848 (e.g., an implicit Goodbye message from the peer). The entity MAY 1849 attempt to re-establish the BFCP connection afresh. The new BFCP 1850 connection will appear as originating from a wholly new floor 1851 participant, chair or floor control server with all state previously 1852 held about that participant lost. 1854 Informational note: The recommendation to treat the connection as 1855 closed in this case, stems from the fact that the peer entities 1856 cannot rely on IP and port tuple to uniquely identify the 1857 participant, nor would extending Hello to include an attribute 1858 that advertised what identity the entity previously was assigned 1859 (i.e., a User ID) be acceptable due to session hijacking. 1861 In deployments where NAT appliances or other such devices are present 1862 and affecting port reachability for each entity, one possibility is 1863 to utilize the peer connectivity checks, relay use and NAT pinhole 1864 maintenance mechanisms defined in ICE [13]. 1866 6.2.3. Fragmentation Handling 1868 When using UDP, a single BFCP message could be fragmented at the IP 1869 layer if its overall size exceeds the path MTU of the network. To 1870 avoid this happening at the IP layer, a fragmentation scheme for BFCP 1871 is defined below. 1873 BFCP is designed for achieving small message size, due to the binary 1874 encoding as described in Section 1. The fragmentation scheme is 1875 therefore deliberately kept simple and straightforward, since the 1876 probability of fragmentation of BFCP messages being required is 1877 small. By design, the fragmentation scheme does not acknowledge 1878 individual BFCP message fragments. The whole BFCP message is 1879 acknowledged if received completely. 1881 BFCP entities should consider the MTU size available between the 1882 sender and the receiver and MAY run MTU discovery, such as 1883 [19][20][21], for this purpose. 1885 When transmitting a BFCP message with size greater than the path MTU, 1886 the sender MUST fragment the message into a series of N contiguous 1887 data ranges. The sender then creates N BFCP fragment messages (one 1888 for each data range) with the same Transaction ID. The size of each 1889 of these N messages MUST be smaller than the path MTU. The F flag in 1890 the COMMON-HEADER is set to indicate fragmentation of the BFCP 1891 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 it has received the entire BFCP message. 1902 The state machine should handle the BFCP message only after all the 1903 fragments for the message have been received. 1905 If a fragment of a BFCP message is lost, the sender will not receive 1906 an acknowledgement for the message. Therefore the sender will 1907 retransmit the message with same transaction ID as specified in 1908 Section 8.3. If the acknowledgement message sent by the receiver is 1909 lost, then the entire message will be resent by the sender. The 1910 receiver must then retransmit the acknowledgement. The receiver MAY 1911 discard an incomplete buffer utilizing the Response Retransmission 1912 Timer, starting the timer after the receipt of the first fragment. 1914 A Denial of Service (DoS) attack utilizing the fragmentation 1915 scheme described above is mitigated by the fact that the Response 1916 Retransmission Timer is started after receipt of the first BFCP 1917 message fragment. In addition, the Payload Length field may be 1918 compared with the Fragment Offset and Fragment Length fields to 1919 verify the message fragments as they arrive. To make DoS attacks 1920 with spoofed IP addresses difficult, BFCP entities should use the 1921 cookie exchange mechanism in DTLS [5]. 1923 When deciding message fragment size based on path MTU, the BFCP 1924 fragmentation handling should take into account how the DTLS record 1925 framing expands the datagram size as described in Section 4.1.1.1 of 1926 [5]. 1928 6.2.4. NAT Traversal 1930 One of the key benefits when using UDP for BFCP communication is the 1931 ability to leverage the existing NAT traversal infrastructure and 1932 strategies deployed to facilitate transport of the media associated 1933 with the video conferencing sessions. Depending on the given 1934 deployment, this infrastructure typically includes some subset of ICE 1935 [13]. 1937 In order to facilitate the initial establishment of NAT bindings, and 1938 to maintain those bindings once established, BFCP entities using an 1939 unreliable transport are RECOMMENDED to use STUN [9] Binding 1940 Indication for keep-alives, as described for ICE [13]. [22], Section 1941 6.7 provides useful recommendations for middlebox interaction when 1942 DTLS is used. 1944 Informational note: Since the version number is set to 2 when BFCP 1945 is used over an unreliable transport, cf. the Ver field in 1946 Section 5.1, it is straight forward to distinguish between STUN 1947 and BFCP packets even without checking the STUN magic cookie [9]. 1949 In order to facilitate traversal of BFCP packets through NATs, BFCP 1950 entities using an unreliable transport are RECOMMENDED to use 1951 symmetric ports for sending and receiving BFCP packets, as 1952 recommended for RTP/RTCP [8]. 1954 7. Lower-Layer Security 1956 BFCP relies on lower-layer security mechanisms to provide replay and 1957 integrity protection and confidentiality. BFCP floor control servers 1958 and clients (which include both floor participants and floor chairs) 1959 MUST support TLS for transport over TCP [4] and MUST support DTLS [5] 1960 for transport over UDP. Any BFCP entity MAY support other security 1961 mechanisms. 1963 BFCP entities MUST support, at a minimum, the 1964 TLS_RSA_WITH_AES_128_CBC_SHA ciphersuite [4]. 1966 Which party, the client or the floor control server, acts as the TLS/ 1967 DTLS server depends on how the underlying TLS/DTLS connection is 1968 established. For a TCP/TLS connection established using an SDP 1969 offer/answer exchange [7], the answerer (which may be the client or 1970 the floor control server) always acts as the TLS server. For a UDP/ 1971 DTLS connection established using the same exchange, either party can 1972 be the DTLS server depending on the setup attributes exchanged; 1973 examples can be found in [22]. 1975 8. Protocol Transactions 1977 In BFCP, there are two types of transactions: client-initiated 1978 transactions and server-initiated transactions. 1980 Client-initiated transactions consist of a request from a client to a 1981 floor control server and a response from the floor control server to 1982 the client. The request carries a Transaction ID in its common 1983 header, which the floor control server copies into the response. 1984 Clients use Transaction ID values to match responses with previously 1985 issued requests. 1987 Server-initiated transactions have different requirements and 1988 behavior depending on underlying transport: 1990 When using a reliable transport, server-initiated transactions 1991 consist of a single message from a floor control server to a 1992 client (notifications). Since they do not trigger any response, 1993 their Transaction ID is set to 0. 1995 When using an unreliable transport, server-initiated transactions 1996 consist of a request from a floor control server to a client and a 1997 response from the client to the floor control server. The 1998 Transaction ID must be non-zero and unique in the context of 1999 outstanding transactions over an unreliable transport. The 2000 request carries a Transaction ID in its common header, which the 2001 client copies into the response. Floor control servers use 2002 Transaction ID values to match responses with previously issued 2003 requests. 2005 When using BFCP over an unreliable transport, it is important that 2006 the initiator of a transaction choose a Transaction ID value that 2007 lets the receiver distinguish the reception of the next message in a 2008 sequence of BFCP messages from a retransmission of a previous 2009 message. Therefore, BFCP entities using an unreliable transport 2010 SHOULD use monotonically increasing Transaction ID values. 2012 When using BFCP over an unreliable transport, all requests will use 2013 retransmission timer T1 (see Section 8.3) until the transaction is 2014 completed. 2016 8.1. Client Behavior 2018 A client starting a client-initiated transaction MUST set the 2019 Conference ID in the common header of the message to the Conference 2020 ID for the conference that the client obtained previously. 2022 The client MUST set the Transaction ID value in the common header to 2023 a number that is different from 0 and that MUST NOT be reused in 2024 another message from the client until a response from the server is 2025 received for the transaction. The client uses the Transaction ID 2026 value to match this message with the response from the floor control 2027 server. 2029 8.2. Server Behavior 2031 A floor control server sending a response within a client-initiated 2032 transaction MUST copy the Conference ID, the Transaction ID, and the 2033 User ID from the request received from the client into the response. 2035 Server-initiated transactions MUST contain a Transaction ID equal to 2036 0 when BFCP is used over a reliable transport. Over an unreliable 2037 transport, the Transaction ID shall have the same properties as for 2038 client-initiated transactions: the server MUST set the Transaction ID 2039 value in the common header to a number that is different from 0 and 2040 that MUST NOT be reused in another message from the server until the 2041 appropriate response from the client is received for the transaction. 2042 The server uses the Transaction ID value to match this message with 2043 the response from the floor participant or floor chair. 2045 8.3. Timers 2047 When BFCP entities are communicating over an unreliable transport, 2048 two retransmission timers are employed to help mitigate against loss 2049 of datagrams. Retransmission and response caching are not required 2050 when BFCP entities communicate over a reliable transport. 2052 8.3.1. Request Retransmission Timer, T1 2054 T1 is a timer that schedules retransmission of a request until an 2055 appropriate response is received or until the maximum number of 2056 retransmissions have occurred. The timer doubles on each re- 2057 transmit, failing after three unacknowledged retransmission attempts. 2059 If a valid response is not received for a client- or server-initiated 2060 transaction, the implementation MUST consider the BFCP connection as 2061 failed. Implementations SHOULD follow the reestablishment procedure 2062 described in section 6 (e.g., initiate a new offer/answer [10] 2063 exchange). 2065 8.3.2. Response Retransmission Timer, T2 2067 T2 is a timer that, when fires, signals that the BFCP entity can 2068 release knowledge of the transaction against which it is running. It 2069 is started upon the first transmission of the response to a request 2070 and is the only mechanism by which that response is released by the 2071 BFCP entity. Any subsequent retransmissions of the same request can 2072 be responded to by replaying the cached response, whilst that value 2073 is retained until the timer has fired. 2075 8.3.3. Timer Values 2077 The table below defines the different timers required when BFCP 2078 entities communicate over an unreliable transport. 2080 +-------+--------------------------------------+---------+ 2081 | Timer | Description | Value/s | 2082 +-------+--------------------------------------+---------+ 2083 | T1 | Initial request retransmission timer | 0.5s | 2084 | T2 | Response retransmission timer | 10s | 2085 +-------+--------------------------------------+---------+ 2087 Table 6: Timers 2089 The default value for T1 is 500 ms, this is an estimate of the RTT 2090 for completing the transaction. T1 MAY be chosen larger, and this is 2091 RECOMMENDED if it is known in advance that the RTT is larger. 2092 Regardless of the value of T1, the exponential backoffs on 2093 retransmissions described in Section 8.3.1 MUST be used. 2095 T2 SHALL be set such that it encompasses all legal retransmissions 2096 per T1 plus a factor to accommodate network latency between BFCP 2097 entities. The default value is based on the sum of the three 2098 retransmissions related to T1 using its default value (7.5s) and an 2099 extra 2.5s is added to take into account potential messages in 2100 transit due to latency. 2102 9. Authentication and Authorization 2104 BFCP clients SHOULD authenticate the floor control server before 2105 sending any BFCP message to it or accepting any BFCP message from it. 2106 Similarly, floor control servers SHOULD authenticate a client before 2107 accepting any BFCP message from it or sending any BFCP message to it. 2109 BFCP supports TLS/DTLS mutual authentication between clients and 2110 floor control servers, as specified in Section 9.1. This is the 2111 RECOMMENDED authentication mechanism in BFCP. 2113 Note that future extensions may define additional authentication 2114 mechanisms. 2116 In addition to authenticating BFCP messages, floor control servers 2117 need to authorize them. On receiving an authenticated BFCP message, 2118 the floor control server checks whether the client sending the 2119 message is authorized. If the client is not authorized to perform 2120 the operation being requested, the floor control server generates an 2121 Error message, as described in Section 13.8, with an Error code with 2122 a value of 5 (Unauthorized Operation). Messages from a client that 2123 cannot be authorized MUST NOT be processed further. 2125 9.1. TLS/DTLS Based Mutual Authentication 2127 BFCP supports TLS/DTLS based mutual authentication between clients 2128 and floor control servers. BFCP assumes that there is an integrity- 2129 protected channel between the client and the floor control server 2130 that can be used to exchange their self-signed certificates or, more 2131 commonly, the fingerprints of these certificates. These certificates 2132 are used at TLS/DTLS establishment time. 2134 The implementation of such an integrity-protected channel using 2135 SIP and the SDP offer/answer model is described in [7]. 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) can 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 SHOULD simply ignore unauthenticated 2143 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 SHOULD 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 MAY 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 MAY 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 SHOULD be set to 2378 zero. The floor chair SHOULD use the Status Revoked to revoke a 2379 floor that was granted (i.e., Granted status) and SHOULD use the 2380 Status Denied to reject floor requests in any other status (e.g., 2381 Pending 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 MAY use the Queue Position field to provide a queue 2387 position for the floor request. 2389 Note that a particular floor control server may 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 may 2393 involve several floors and that a ChairAction message may 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 use STATUS-INFO attributes to state the reason 2406 why the floor or floors are being accepted, granted, or revoked. The 2407 Text in the STATUS-INFO attribute is intended for human consumption. 2409 11.2. Receiving a Response 2411 A message from the floor control server is considered a response to 2412 the ChairAction message if the message from the server has the same 2413 Conference ID, Transaction ID, and User ID as the ChairAction 2414 message, as described in Section 8.1. On receiving such a response, 2415 the floor chair follows the rules in Section 9 that relate to floor 2416 control server authentication. 2418 A ChairActionAck message from the floor control server confirms that 2419 the floor control server has accepted the ChairAction message. An 2420 Error message indicates that the floor control server could not 2421 process the ChairAction message for some reason, which is described 2422 in the Error message. 2424 12. General Client Operations 2426 This section specifies operations that can be performed by any 2427 client. That is, they are not specific to floor participants or 2428 floor chairs. They can be performed by both. 2430 12.1. Requesting Information about Floors 2432 A client can obtain information about the status of a floor or floors 2433 in different ways, which include using BFCP and using out-of-band 2434 mechanisms. Clients using BFCP to obtain such information use the 2435 procedures described in this section. 2437 Clients request information about the status of one or several floors 2438 by sending a FloorQuery message to the floor control server. 2440 12.1.1. Sending a FloorQuery Message 2442 The ABNF in Section 5.3.7 describes the attributes that a FloorQuery 2443 message can contain. In addition, the ABNF specifies normatively 2444 which of these attributes are mandatory, and which ones are optional. 2446 The client sets the Conference ID and the Transaction ID in the 2447 common header following the rules given in Section 8.1. The client 2448 sets the User ID in the common header to the client's identifier. 2449 This User ID will be used by the floor control server to authenticate 2450 and authorize the request. 2452 The client inserts in the message all the Floor IDs it wants to 2453 receive information about. The floor control server will send 2454 periodic information about all of these floors. If the client does 2455 not want to receive information about a particular floor any longer, 2456 it sends a new FloorQuery message removing the FLOOR-ID of this 2457 floor. If the client does not want to receive information about any 2458 floor any longer, it sends a FloorQuery message with no FLOOR-ID 2459 attribute. 2461 12.1.2. Receiving a Response 2463 A message from the floor control server is considered a response to 2464 the FloorQuery message if the message from the floor control server 2465 has the same Conference ID, Transaction ID, and User ID as the 2466 FloorRequest message, as described in Section 8.1. On receiving such 2467 a response, the client follows the rules in Section 9 that relate to 2468 floor control server authentication. 2470 On reception of the FloorQuery message, the floor control server will 2471 respond with a FloorStatus message or with an Error message. If the 2472 response is a FloorStatus message, it will contain information about 2473 one of the floors the client requested information about. If the 2474 client did not include any FLOOR-ID attribute in its FloorQuery 2475 message (i.e., the client does not want to receive information about 2476 any floor any longer), the FloorStatus message from the floor control 2477 server will not include any FLOOR-ID attribute either. 2479 FloorStatus messages that carry information about a floor contain a 2480 FLOOR-ID attribute that identifies the floor. After this attribute, 2481 FloorStatus messages contain information about existing (one or more) 2482 floor requests that relate to that floor. The information about each 2483 particular floor request is encoded in a FLOOR-REQUEST-INFORMATION 2484 attribute. This grouped attribute carries a Floor Request ID that 2485 identifies the floor request, followed by a set of attributes that 2486 provide information about the floor request. 2488 After the first FloorStatus, the floor control server will continue 2489 sending FloorStatus messages, periodically informing the client about 2490 changes on the floors the client requested information about. 2492 12.1.3. Reception of a Subsequent FloorStatus Message 2494 When communicating over an unreliable transport and upon receiving a 2495 FloorStatus message from a floor control server, the participant MUST 2496 respond with a FloorStatusAck message within the transaction failure 2497 window to complete the transaction. 2499 12.2. Requesting Information about Floor Requests 2501 A client can obtain information about the status of one or several 2502 floor requests in different ways, which include using BFCP and using 2503 out-of-band mechanisms. Clients using BFCP to obtain such 2504 information use the procedures described in this section. 2506 Clients request information about the current status of a floor 2507 request by sending a FloorRequestQuery message to the floor control 2508 server. 2510 Requesting information about a particular floor request is useful in 2511 a number of situations. For example, on reception of a FloorRequest 2512 message, a floor control server may choose to return 2513 FloorRequestStatus messages only when the floor request changes its 2514 state (e.g., from Accepted to Granted), but not when the floor 2515 request advances in its queue. In this situation, if the user 2516 requests it, the floor participant can use a FloorRequestQuery 2517 message to poll the floor control server for the status of the floor 2518 request. 2520 12.2.1. Sending a FloorRequestQuery Message 2522 The ABNF in Section 5.3.3 describes the attributes that a 2523 FloorRequestQuery message can contain. In addition, the ABNF 2524 specifies normatively which of these attributes are mandatory, and 2525 which ones are optional. 2527 The client sets the Conference ID and the Transaction ID in the 2528 common header following the rules given in Section 8.1. The client 2529 sets the User ID in the common header to the client's identifier. 2530 This User ID will be used by the floor control server to authenticate 2531 and authorize the request. 2533 The client must insert a FLOOR-REQUEST-ID attribute that identifies 2534 the floor request at the floor control server. 2536 12.2.2. Receiving a Response 2538 A message from the floor control server is considered a response to 2539 the FloorRequestQuery message if the message from the floor control 2540 server has the same Conference ID, Transaction ID, and User ID as the 2541 FloorRequestQuery message, as described in Section 8.1. On receiving 2542 such a response, the client follows the rules in Section 9 that 2543 relate to floor control server authentication. 2545 If the response is a FloorRequestStatus message, the client obtains 2546 information about the status of the FloorRequest the client requested 2547 information about in a FLOOR-REQUEST-INFORMATION attribute. 2549 If the response is an Error message, the floor control server could 2550 not process the FloorRequestQuery message for some reason, which is 2551 described in the Error message. 2553 12.3. Requesting Information about a User 2555 A client can obtain information about a participant and the floor 2556 requests related to this participant in different ways, which include 2557 using BFCP and using out-of-band mechanisms. Clients using BFCP to 2558 obtain such information use the procedures described in this section. 2560 Clients request information about a participant and the floor 2561 requests related to this participant by sending a UserQuery message 2562 to the floor control server. 2564 This functionality may be useful for floor chairs or floor 2565 participants interested in the display name and the URI of a 2566 particular floor participant. In addition, a floor participant may 2567 find it useful to request information about itself. For example, a 2568 floor participant, after experiencing connectivity problems (e.g., 2569 its TCP connection with the floor control server was down for a while 2570 and eventually was re-established), may need to request information 2571 about all the floor requests associated to itself that still exist. 2573 12.3.1. Sending a UserQuery Message 2575 The ABNF in Section 5.3.5 describes the attributes that a UserQuery 2576 message can contain. In addition, the ABNF specifies normatively 2577 which of these attributes are mandatory, and which ones are optional. 2579 The client sets the Conference ID and the Transaction ID in the 2580 common header following the rules given in Section 8.1. The client 2581 sets the User ID in the common header to the client's identifier. 2582 This User ID will be used by the floor control server to authenticate 2583 and authorize the request. 2585 If the floor participant the client is requesting information about 2586 is not the client issuing the UserQuery message (which is identified 2587 by the User ID in the common header of the message), the client MUST 2588 insert a BENEFICIARY-ID attribute. 2590 12.3.2. Receiving a Response 2592 A message from the floor control server is considered a response to 2593 the UserQuery message if the message from the floor control server 2594 has the same Conference ID, Transaction ID, and User ID as the 2595 UserQuery message, as described in Section 8.1. On receiving such a 2596 response, the client follows the rules in Section 9 that relate to 2597 floor control server authentication. 2599 If the response is a UserStatus message, the client obtains 2600 information about the floor participant in a BENEFICIARY-INFORMATION 2601 grouped attribute and about the status of the floor requests 2602 associated with the floor participant in FLOOR-REQUEST-INFORMATION 2603 attributes. 2605 If the response is an Error message, the floor control server could 2606 not process the UserQuery message for some reason, which is described 2607 in the Error message. 2609 12.4. Obtaining the Capabilities of a Floor Control Server 2611 A client that wishes to obtain the capabilities of a floor control 2612 server does so by sending a Hello message to the floor control 2613 server. 2615 12.4.1. Sending a Hello Message 2617 The ABNF in Section 5.3.11 describes the attributes that a Hello 2618 message can contain. In addition, the ABNF specifies normatively 2619 which of these attributes are mandatory, and which ones are optional. 2621 The client sets the Conference ID and the Transaction ID in the 2622 common header following the rules given in Section 8.1. The client 2623 sets the User ID in the common header to the client's identifier. 2624 This User ID will be used by the floor control server to authenticate 2625 and authorize the request. 2627 12.4.2. Receiving Responses 2629 A message from the floor control server is considered a response to 2630 the Hello message by the client if the message from the floor control 2631 server has the same Conference ID, Transaction ID, and User ID as the 2632 Hello message, as described in Section 8.1. On receiving such a 2633 response, the client follows the rules in Section 9 that relate to 2634 floor control server authentication. 2636 If the response is a HelloAck message, the floor control server could 2637 process the Hello message successfully. The SUPPORTED-PRIMITIVES and 2638 SUPPORTED-ATTRIBUTES attributes indicate which primitives and 2639 attributes, respectively, are supported by the server. 2641 If the response is an Error message, the floor control server could 2642 not process the Hello message for some reason, which is described in 2643 the Error message. 2645 13. Floor Control Server Operations 2647 This section specifies how floor control servers can perform 2648 different operations, such as granting a floor, using the protocol 2649 elements described in earlier sections. 2651 On reception of a message from a client, the floor control server 2652 MUST check whether the value of the Primitive is supported. If it is 2653 not, the floor control server SHOULD send an Error message, as 2654 described in Section 13.8, with Error code 3 (Unknown Primitive). 2656 On reception of a message from a client, the floor control server 2657 MUST check whether the value of the Conference ID matched an existing 2658 conference. If it does not, the floor control server SHOULD send an 2659 Error message, as described in Section 13.8, with Error code 1 2660 (Conference does not Exist). 2662 On reception of a message from a client, the floor control server 2663 follows the rules in Section 9 that relate to the authentication of 2664 the message. 2666 On reception of a message from a client, the floor control server 2667 MUST check whether it understands all the mandatory ('M' bit set) 2668 attributes in the message. If the floor control server does not 2669 understand all of them, the floor control server SHOULD send an Error 2670 message, as described in Section 13.8, with Error code 4 (Unknown 2671 Mandatory Attribute). The Error message SHOULD list the attributes 2672 that were not understood. 2674 13.1. Reception of a FloorRequest Message 2676 On reception of a FloorRequest message, the floor control server 2677 follows the rules in Section 9 that relate to client authentication 2678 and authorization. If while processing the FloorRequest message, the 2679 floor control server encounters an error, it SHOULD generate an Error 2680 response following the procedures described in Section 13.8. 2682 BFCP allows floor participants to have several ongoing floor 2683 requests for the same floor (e.g., the same floor participant can 2684 occupy more than one position in a queue at the same time). A 2685 floor control server that only supports a certain number of 2686 ongoing floor requests per floor participant (e.g., one) can use 2687 Error Code 8 (You have Already Reached the Maximum Number of 2688 Ongoing Floor Requests for this Floor) to inform the floor 2689 participant. 2691 When communicating over an unreliable transport and upon receiving a 2692 FloorRequest from a participant, the floor control server MUST 2693 respond with a FloorRequestStatus message within the transaction 2694 failure window to complete the transaction. 2696 13.1.1. Generating the First FloorRequestStatus Message 2698 The successful processing of a FloorRequest message by a floor 2699 control server involves generating one or several FloorRequestStatus 2700 messages, the first of which SHOULD be generated as soon as possible. 2701 If the floor control server cannot accept, grant, or deny the floor 2702 request right away (e.g., a decision from a chair is needed), it 2703 SHOULD use a Request Status value of Pending in the OVERALL-REQUEST- 2704 STATUS attribute (within the FLOOR-REQUEST-INFORMATION grouped 2705 attribute) of the first FloorRequestStatus message it generates. 2707 The policy that a floor control server follows to grant or deny 2708 floors is outside the scope of this document. A given floor 2709 control server may perform these decisions automatically while 2710 another may contact a human acting as a chair every time a 2711 decision needs to be made. 2713 The floor control server MUST copy the Conference ID, the Transaction 2714 ID, and the User ID from the FloorRequest into the 2715 FloorRequestStatus, as described in Section 8.2. Additionally, the 2716 floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped 2717 attribute to the FloorRequestStatus. The attributes contained in 2718 this grouped attribute carry information about the floor request. 2720 The floor control server MUST assign an identifier that is unique 2721 within the conference to this floor request, and MUST insert it in 2722 the Floor Request ID field of the FLOOR-REQUEST-INFORMATION 2723 attribute. This identifier will be used by the floor participant (or 2724 by a chair or chairs) to refer to this specific floor request in the 2725 future. 2727 The floor control server MUST copy the Floor IDs in the FLOOR-ID 2728 attributes of the FloorRequest into the FLOOR-REQUEST-STATUS 2729 attributes in the FLOOR-REQUEST-INFORMATION grouped attribute. These 2730 Floor IDs identify the floors being requested (i.e., the floors 2731 associated with this particular floor request). 2733 The floor control server SHOULD copy (if present) the contents of the 2734 BENEFICIARY-ID attribute from the FloorRequest into a BENEFICIARY- 2735 INFORMATION attribute inside the FLOOR-REQUEST-INFORMATION grouped 2736 attribute. Additionally, the floor control server MAY provide the 2737 display name and the URI of the beneficiary in this BENEFICIARY- 2738 INFORMATION attribute. 2740 The floor control server MAY provide information about the requester 2741 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2742 FLOOR-REQUEST-INFORMATION grouped attribute. 2744 The floor control server MAY copy (if present) the PRIORITY attribute 2745 from the FloorRequest into the FLOOR-REQUEST-INFORMATION grouped 2746 attribute. 2748 Note that this attribute carries the priority requested by the 2749 participant. The priority that the floor control server assigns 2750 to the floor request depends on the priority requested by the 2751 participant and the rights the participant has according to the 2752 policy of the conference. For example, a participant that is only 2753 allowed to use the Normal priority may request Highest priority 2754 for a floor request. In that case, the floor control server would 2755 ignore the priority requested by the participant. 2757 The floor control server MAY copy (if present) the PARTICIPANT- 2758 PROVIDED-INFO attribute from the FloorRequest into the FLOOR-REQUEST- 2759 INFORMATION grouped attribute. 2761 13.1.2. Generation of Subsequent FloorRequestStatus Messages 2763 A floor request is considered to be ongoing as long as it is not in 2764 the Cancelled, Released, or Revoked states. If the OVERALL-REQUEST- 2765 STATUS attribute (inside the FLOOR-REQUEST-INFORMATION grouped 2766 attribute) of the first FloorRequestStatus message generated by the 2767 floor control server did not indicate any of these states, the floor 2768 control server will need to send subsequent FloorRequestStatus 2769 messages. 2771 When the status of the floor request changes, the floor control 2772 server SHOULD send new FloorRequestStatus messages with the 2773 appropriate Request Status. The floor control server MUST add a 2774 FLOOR-REQUEST-INFORMATION attribute with a Floor Request ID equal to 2775 the one sent in the first FloorRequestStatus message to any new 2776 FloorRequestStatus related to the same floor request. (The Floor 2777 Request ID identifies the floor request to which the 2778 FloorRequestStatus applies.) 2780 When using BFCP over a reliable transport, the floor control server 2781 MUST set the Transaction ID of subsequent FloorRequestStatus messages 2782 to 0. When using BFCP over an unreliable transport, the Transaction 2783 ID MUST be non-zero and unique in the context of outstanding 2784 transactions over an unreliable transport as described in Section 8. 2786 The rate at which the floor control server sends 2787 FloorRequestStatus messages is a matter of local policy. A floor 2788 control server may choose to send a new FloorRequestStatus message 2789 every time the floor request moves in the floor request queue, 2790 while another may choose only to send a new FloorRequestStatus 2791 message when the floor request is Granted or Denied. 2793 The floor control server may add a STATUS-INFO attribute to any of 2794 the FloorRequestStatus messages it generates to provide extra 2795 information about its decisions regarding the floor request (e.g., 2796 why it was denied). 2798 Floor participants and floor chairs may request to be informed 2799 about the status of a floor following the procedures in 2800 Section 12.1. If the processing of a floor request changes the 2801 status of a floor (e.g., the floor request is granted and 2802 consequently the floor has a new holder), the floor control server 2803 needs to follow the procedures in Section 13.5 to inform the 2804 clients that have requested that information. 2806 The common header and the rest of the attributes are the same as in 2807 the first FloorRequestStatus message. 2809 The floor control server can discard the state information about a 2810 particular floor request when this reaches a status of Cancelled, 2811 Released, or Revoked. 2813 When communicating over an unreliable transport and a 2814 FloorRequestStatusAck message is not received within the transaction 2815 failure window, the floor control server MUST retransmit the 2816 FloorRequestStatus message according to Section 6.2. 2818 13.2. Reception of a FloorRequestQuery Message 2820 On reception of a FloorRequestQuery message, the floor control server 2821 follows the rules in Section 9 that relate to client authentication 2822 and authorization. If while processing the FloorRequestQuery 2823 message, the floor control server encounters an error, it SHOULD 2824 generate an Error response following the procedures described in 2825 Section 13.8. 2827 The successful processing of a FloorRequestQuery message by a floor 2828 control server involves generating a FloorRequestStatus message, 2829 which SHOULD be generated as soon as possible. 2831 When communicating over an unreliable transport and upon receiving a 2832 FloorRequestQuery from a participant, the floor control server MUST 2833 respond with a FloorRequestStatus message within the transaction 2834 failure window to complete the transaction. 2836 The floor control server MUST copy the Conference ID, the Transaction 2837 ID, and the User ID from the FloorRequestQuery message into the 2838 FloorRequestStatus message, as described in Section 8.2. 2839 Additionally, the floor control server MUST include information about 2840 the floor request in the FLOOR-REQUEST-INFORMATION grouped attribute 2841 to the FloorRequestStatus. 2843 The floor control server MUST copy the contents of the 2844 FLOOR-REQUEST-ID attribute from the FloorRequestQuery message into 2845 the Floor Request ID field of the FLOOR-REQUEST-INFORMATION 2846 attribute. 2848 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 2849 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2850 floors being requested (i.e., the floors associated with the floor 2851 request identified by the FLOOR-REQUEST-ID attribute). 2853 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 2854 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2855 beneficiary of the floor request. Additionally, the floor control 2856 server MAY provide the display name and the URI of the beneficiary in 2857 this BENEFICIARY-INFORMATION attribute. 2859 The floor control server MAY provide information about the requester 2860 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2861 FLOOR-REQUEST-INFORMATION grouped attribute. 2863 The floor control server MAY provide the reason why the floor 2864 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 2866 The floor control server MAY also add to the FLOOR-REQUEST- 2867 INFORMATION grouped attribute a PRIORITY attribute with the Priority 2868 value requested for the floor request and a STATUS-INFO attribute 2869 with extra information about the floor request. 2871 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 2872 to the FLOOR-REQUEST-INFORMATION grouped attribute with the current 2873 status of the floor request. The floor control server MAY provide 2874 information about the status of the floor request as it relates to 2875 each of the floors being requested in the FLOOR-REQUEST-STATUS 2876 attributes. 2878 13.3. Reception of a UserQuery Message 2880 On reception of a UserQuery message, the floor control server follows 2881 the rules in Section 9 that relate to client authentication and 2882 authorization. If while processing the UserQuery message, the floor 2883 control server encounters an error, it SHOULD generate an Error 2884 response following the procedures described in Section 13.8. 2886 The successful processing of a UserQuery message by a floor control 2887 server involves generating a UserStatus message, which SHOULD be 2888 generated as soon as possible. 2890 When communicating over an unreliable transport and upon receiving a 2891 UserQuery from a participant, the floor control server MUST respond 2892 with a UserStatus message within the transaction failure window to 2893 complete the transaction. 2895 The floor control server MUST copy the Conference ID, the Transaction 2896 ID, and the User ID from the UserQuery message into the USerStatus 2897 message, as described in Section 8.2. 2899 The sender of the UserQuery message is requesting information about 2900 all the floor requests associated with a given participant (i.e., the 2901 floor requests where the participant is either the beneficiary or the 2902 requester). This participant is identified by a BENEFICIARY-ID 2903 attribute or, in the absence of a BENEFICIARY-ID attribute, by a the 2904 User ID in the common header of the UserQuery message. 2906 The floor control server MUST copy, if present, the contents of the 2907 BENEFICIARY-ID attribute from the UserQuery message into a 2908 BENEFICIARY-INFORMATION attribute in the UserStatus message. 2909 Additionally, the floor control server MAY provide the display name 2910 and the URI of the participant about which the UserStatus message 2911 provides information in this BENEFICIARY-INFORMATION attribute. 2913 The floor control server SHOULD add to the UserStatus message a 2914 FLOOR-REQUEST-INFORMATION grouped attribute for each floor request 2915 related to the participant about which the message provides 2916 information (i.e., the floor requests where the participant is either 2917 the beneficiary or the requester). For each FLOOR-REQUEST- 2918 INFORMATION attribute, the floor control server follows the following 2919 steps. 2921 The floor control server MUST identify the floor request the FLOOR- 2922 REQUEST-INFORMATION attribute applies to by filling the Floor Request 2923 ID field of the FLOOR-REQUEST-INFORMATION attribute. 2925 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 2926 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2927 floors being requested (i.e., the floors associated with the floor 2928 request identified by the FLOOR-REQUEST-ID attribute). 2930 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 2931 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 2932 beneficiary of the floor request. Additionally, the floor control 2933 server MAY provide the display name and the URI of the beneficiary in 2934 this BENEFICIARY-INFORMATION attribute. 2936 The floor control server MAY provide information about the requester 2937 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 2938 FLOOR-REQUEST-INFORMATION grouped attribute. 2940 The floor control server MAY provide the reason why the floor 2941 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 2943 The floor control server MAY also add to the FLOOR-REQUEST- 2944 INFORMATION grouped attribute a PRIORITY attribute with the Priority 2945 value requested for the floor request. 2947 The floor control server MUST include the current status of the floor 2948 request in an OVERALL-REQUEST-STATUS attribute to the FLOOR-REQUEST- 2949 INFORMATION grouped attribute. The floor control server MAY add a 2950 STATUS-INFO attribute with extra information about the floor request. 2952 The floor control server MAY provide information about the status of 2953 the floor request as it relates to each of the floors being requested 2954 in the FLOOR-REQUEST-STATUS attributes. 2956 13.4. Reception of a FloorRelease Message 2958 On reception of a FloorRelease message, the floor control server 2959 follows the rules in Section 9 that relate to client authentication 2960 and authorization. If while processing the FloorRelease message, the 2961 floor control server encounters an error, it SHOULD generate an Error 2962 response following the procedures described in Section 13.8. 2964 The successful processing of a FloorRelease message by a floor 2965 control server involves generating a FloorRequestStatus message, 2966 which SHOULD be generated as soon as possible. 2968 When communicating over an unreliable transport and upon receiving a 2969 FloorRelease from a participant, the floor control server MUST 2970 respond with a FloorRequestStatus message within the transaction 2971 failure window to complete the transaction. 2973 The floor control server MUST copy the Conference ID, the Transaction 2974 ID, and the User ID from the FloorRelease message into the 2975 FloorRequestStatus message, as described in Section 8.2. 2977 The floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped 2978 attribute to the FloorRequestStatus. The attributes contained in 2979 this grouped attribute carry information about the floor request. 2981 The FloorRelease message identifies the floor request it applies to 2982 using a FLOOR-REQUEST-ID. The floor control server MUST copy the 2983 contents of the FLOOR-REQUEST-ID attribute from the FloorRelease 2984 message into the Floor Request ID field of the FLOOR-REQUEST- 2985 INFORMATION attribute. 2987 The floor control server MUST identify the floors being released 2988 (i.e., the floors associated with the floor request identified by the 2989 FLOOR-REQUEST-ID attribute) in FLOOR-REQUEST-STATUS attributes to the 2990 FLOOR-REQUEST-INFORMATION grouped attribute. 2992 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 2993 to the FLOOR-REQUEST-INFORMATION grouped attribute. The Request 2994 Status value SHOULD be Released, if the floor (or floors) had been 2995 previously granted, or Cancelled, if the floor (or floors) had not 2996 been previously granted. The floor control server MAY add a STATUS- 2997 INFO attribute with extra information about the floor request. 2999 13.5. Reception of a FloorQuery Message 3001 On reception of a FloorQuery message, the floor control server 3002 follows the rules in Section 9 that relate to client authentication. 3003 If while processing the FloorQuery message, the floor control server 3004 encounters an error, it SHOULD generate an Error response following 3005 the procedures described in Section 13.8. 3007 When communicating over an unreliable transport and upon receiving a 3008 FloorQuery from a participant, the floor control server MUST respond 3009 with a FloorStatus message within the transaction failure window to 3010 complete the transaction. 3012 A floor control server receiving a FloorQuery message from a client 3013 SHOULD keep this client informed about the status of the floors 3014 identified by FLOOR-ID attributes in the FloorQuery message. Floor 3015 Control Servers keep clients informed by using FloorStatus messages. 3017 An individual FloorStatus message carries information about a single 3018 floor. So, when a FloorQuery message requests information about more 3019 than one floor, the floor control server needs to send separate 3020 FloorStatus messages for different floors. 3022 The information FloorQuery messages carry may depend on the user 3023 requesting the information. For example, a chair may be able to 3024 receive information about pending requests, while a regular user may 3025 not be authorized to do so. 3027 13.5.1. Generation of the First FloorStatus Message 3029 The successful processing of a FloorQuery message by a floor control 3030 server involves generating one or several FloorStatus messages, the 3031 first of which SHOULD be generated as soon as possible. 3033 The floor control server MUST copy the Conference ID, the Transaction 3034 ID, and the User ID from the FloorQuery message into the FloorStatus 3035 message, as described in Section 8.2. 3037 If the FloorQuery message did not contain any FLOOR-ID attribute, the 3038 floor control server sends the FloorStatus message without adding any 3039 additional attribute and does not send any subsequent FloorStatus 3040 message to the floor participant. 3042 If the FloorQuery message contained one or more FLOOR-ID attributes, 3043 the floor control server chooses one from among them and adds this 3044 FLOOR-ID attribute to the FloorStatus message. The floor control 3045 server SHOULD add a FLOOR-REQUEST-INFORMATION grouped attribute for 3046 each floor request associated to the floor. Each FLOOR-REQUEST- 3047 INFORMATION grouped attribute contains a number of attributes that 3048 provide information about the floor request. For each FLOOR-REQUEST- 3049 INFORMATION attribute, the floor control server follows the following 3050 steps. 3052 The floor control server MUST identify the floor request the FLOOR- 3053 REQUEST-INFORMATION attribute applies to by filling the Floor Request 3054 ID field of the FLOOR-REQUEST-INFORMATION attribute. 3056 The floor control server MUST add FLOOR-REQUEST-STATUS attributes to 3057 the FLOOR-REQUEST-INFORMATION grouped attribute identifying the 3058 floors being requested (i.e., the floors associated with the floor 3059 request identified by the FLOOR-REQUEST-ID attribute). 3061 The floor control server SHOULD add a BENEFICIARY-ID attribute to the 3062 FLOOR-REQUEST-INFORMATION grouped attribute identifying the 3063 beneficiary of the floor request. Additionally, the floor control 3064 server MAY provide the display name and the URI of the beneficiary in 3065 this BENEFICIARY-INFORMATION attribute. 3067 The floor control server MAY provide information about the requester 3068 of the floor in a REQUESTED-BY-INFORMATION attribute inside the 3069 FLOOR-REQUEST-INFORMATION grouped attribute. 3071 The floor control server MAY provide the reason why the floor 3072 participant requested the floor in a PARTICIPANT-PROVIDED-INFO. 3074 The floor control server MAY also add to the FLOOR-REQUEST- 3075 INFORMATION grouped attribute a PRIORITY attribute with the Priority 3076 value requested for the floor request. 3078 The floor control server MUST add an OVERALL-REQUEST-STATUS attribute 3079 to the FLOOR-REQUEST-INFORMATION grouped attribute with the current 3080 status of the floor request. The floor control server MAY add a 3081 STATUS-INFO attribute with extra information about the floor request. 3083 The floor control server MAY provide information about the status of 3084 the floor request as it relates to each of the floors being requested 3085 in the FLOOR-REQUEST-STATUS attributes. 3087 13.5.2. Generation of Subsequent FloorStatus Messages 3089 If the FloorQuery message carried more than one FLOOR-ID attribute, 3090 the floor control server SHOULD generate a FloorStatus message for 3091 each of them (except for the FLOOR-ID attribute chosen for the first 3092 FloorStatus message) as soon as possible. These FloorStatus messages 3093 are generated following the same rules as those for the first 3094 FloorStatus message (see Section 13.5.1), but their Transaction ID is 3095 0 when using a reliable transport and non-zero and unique in the 3096 context of outstanding transactions when using an unreliable 3097 transport (cf. Section 8). 3099 After generating these messages, the floor control server sends 3100 FloorStatus messages, periodically keeping the client informed about 3101 all the floors for which the client requested information. The 3102 Transaction ID of these messages MUST be 0 when using a reliable 3103 transport and non-zero and unique in the context of outstanding 3104 transactions when using an unreliable transport (cf. Section 8). 3106 The rate at which the floor control server sends FloorStatus 3107 messages is a matter of local policy. A floor control server may 3108 choose to send a new FloorStatus message every time a new floor 3109 request arrives, while another may choose to only send a new 3110 FloorStatus message when a new floor request is Granted. 3112 When communicating over an unreliable transport and a FloorStatusAck 3113 message is not received within the transaction failure window, the 3114 floor control server MUST retransmit the FloorStatus message 3115 according to Section 6.2. 3117 13.6. Reception of a ChairAction Message 3119 On reception of a ChairAction message, the floor control server 3120 follows the rules in Section 9 that relate to client authentication 3121 and authorization. If while processing the ChairAction message, the 3122 floor control server encounters an error, it SHOULD generate an Error 3123 response following the procedures described in Section 13.8. 3125 The successful processing of a ChairAction message by a floor control 3126 server involves generating a ChairActionAck message, which SHOULD be 3127 generated as soon as possible. 3129 When communicating over an unreliable transport and upon receiving a 3130 ChairAction from a chair, the floor control server MUST respond with 3131 a ChairActionAck message within the transaction failure window to 3132 complete the transaction. 3134 The floor control server MUST copy the Conference ID, the Transaction 3135 ID, and the User ID from the ChairAction message into the 3136 ChairActionAck message, as described in Section 8.2. 3138 The floor control server needs to take into consideration the 3139 operation requested in the ChairAction message (e.g., granting a 3140 floor) but does not necessarily need to perform it as requested by 3141 the floor chair. The operation that the floor control server 3142 performs depends on the ChairAction message and on the internal state 3143 of the floor control server. 3145 For example, a floor chair may send a ChairAction message granting a 3146 floor that was requested as part of an atomic floor request operation 3147 that involved several floors. Even if the chair responsible for one 3148 of the floors instructs the floor control server to grant the floor, 3149 the floor control server will not grant it until the chairs 3150 responsible for the other floors agree to grant them as well. 3152 So, the floor control server is ultimately responsible for keeping a 3153 coherent floor state using instructions from floor chairs as input to 3154 this state. 3156 If the new Status in the ChairAction message is Accepted and all the 3157 bits of the Queue Position field are zero, the floor chair is 3158 requesting that the floor control server assign a queue position 3159 (e.g., the last in the queue) to the floor request based on the local 3160 policy of the floor control server. (Of course, such a request only 3161 applies if the floor control server implements a queue.) 3163 13.7. Reception of a Hello Message 3165 On reception of a Hello message, the floor control server follows the 3166 rules in Section 9 that relate to client authentication. If while 3167 processing the Hello message, the floor control server encounters an 3168 error, it SHOULD generate an Error response following the procedures 3169 described in Section 13.8. 3171 If the version of BFCP specified in the Version field of the COMMON- 3172 HEADER is supported by the floor control server, it MUST respond with 3173 the same version number in the HelloAck; this defines the version for 3174 all subsequent BFCP messages within this BFCP Connection. If the 3175 version given in the Hello message is not supported, the receiving 3176 server MUST instead send an Error message with parameter value 12 3177 (Unsupported Version). 3179 When communicating over an unreliable transport and upon receiving a 3180 Hello from a participant, the floor control server MUST respond with 3181 a HelloAck message within the transaction failure window to complete 3182 the transaction. 3184 The successful processing of a Hello message by a floor control 3185 server involves generating a HelloAck message, which SHOULD be 3186 generated as soon as possible. The floor control server MUST copy 3187 the Conference ID, the Transaction ID, and the User ID from the Hello 3188 into the HelloAck, as described in Section 8.2. 3190 The floor control server MUST add a SUPPORTED-PRIMITIVES attribute to 3191 the HelloAck message listing all the primitives (i.e., BFCP messages) 3192 supported by the floor control server. 3194 The floor control server MUST add a SUPPORTED-ATTRIBUTES attribute to 3195 the HelloAck message listing all the attributes supported by the 3196 floor control server. 3198 13.8. Error Message Generation 3200 Error messages are always sent in response to a previous message from 3201 the client as part of a client-initiated transaction. The ABNF in 3202 Section 5.3.13 describes the attributes that an Error message can 3203 contain. In addition, the ABNF specifies normatively which of these 3204 attributes are mandatory and which ones are optional. 3206 The floor control server MUST copy the Conference ID, the Transaction 3207 ID, and the User ID from the message from the client into the Error 3208 message, as described in Section 8.2. 3210 The floor control server MUST add an ERROR-CODE attribute to the 3211 Error message. The ERROR-CODE attribute contains an Error Code from 3212 Table 5. Additionally, the floor control server may add an ERROR- 3213 INFO attribute with extra information about the error. 3215 14. Security Considerations 3217 BFCP uses TLS/DTLS to provide mutual authentication between clients 3218 and servers. TLS/DTLS also provides replay and integrity protection 3219 and confidentiality. It is RECOMMENDED that TLS/DTLS with non-null 3220 encryption always be used. BFCP entities MAY use other security 3221 mechanisms as long as they provide similar security properties. 3223 The remainder of this section analyzes some of the threats against 3224 BFCP and how they are addressed. 3226 An attacker may attempt to impersonate a client (a floor participant 3227 or a floor chair) in order to generate forged floor requests or to 3228 grant or deny existing floor requests. Client impersonation is 3229 avoided by having servers only accept BFCP messages over 3230 authenticated TLS/DTLS connections. The floor control server assumes 3231 that attackers cannot high-jack the TLS/DTLS connection and, 3232 therefore, that messages over the TLS/DTLS connection come from the 3233 client that was initially authenticated. 3235 An attacker may attempt to impersonate a floor control server. A 3236 successful attacker would be able to make clients think that they 3237 hold a particular floor so that they would try to access a resource 3238 (e.g., sending media) without having legitimate rights to access it. 3239 Floor control server impersonation is avoided by having servers only 3240 accept BFCP messages over authenticated TLS/DTLS connections, as well 3241 as ensuring clients only send and accept messages over authenticated 3242 TLS/DTLS connections. 3244 Attackers may attempt to modify messages exchanged by a client and a 3245 floor control server. The integrity protection provided by TLS/DTLS 3246 connections prevents this attack. 3248 An attacker may attempt to fetch a valid message sent by a client to 3249 a floor control server and replay it over a connection between the 3250 attacker and the floor control server. This attack is prevented by 3251 having floor control servers check that messages arriving over a 3252 given authenticated TLS/DTLS connection use an authorized user ID 3253 (i.e., a user ID that the user that established the authenticated 3254 TLS/DTLS connection is allowed to use). 3256 Attackers may attempt to pick messages from the network to get access 3257 to confidential information between the floor control server and a 3258 client (e.g., why a floor request was denied). TLS/DTLS 3259 confidentiality prevents this attack. Therefore, it is RECOMMENDED 3260 that TLS/DTLS be used with a non-null encryption algorithm. 3262 15. IANA Considerations 3264 [Editorial note: This section instructs the IANA to register new 3265 entries in the BFCP Primitive subregistry in Section 15.2 and for 3266 the BFCP Error Code subregistry in Section 15.4.] 3268 The IANA has created a registry for BFCP parameters called "Binary 3269 Floor Control Protocol (BFCP) Parameters". This registry has a 3270 number of subregistries, which are described in the following 3271 sections. 3273 15.1. Attribute Subregistry 3275 This section establishes the Attribute subregistry under the BFCP 3276 Parameters registry. As per the terminology in RFC 5226 [3], the 3277 registration policy for BFCP attributes shall be "Specification 3278 Required". For the purposes of this subregistry, the BFCP attributes 3279 for which IANA registration is requested MUST be defined by a 3280 standards-track RFC. Such an RFC MUST specify the attribute's type, 3281 name, format, and semantics. 3283 For each BFCP attribute, the IANA registers its type, its name, and 3284 the reference to the RFC where the attribute is defined. The 3285 following table contains the initial values of this subregistry. 3287 +------+---------------------------+------------+ 3288 | Type | Attribute | Reference | 3289 +------+---------------------------+------------+ 3290 | 1 | BENEFICIARY-ID | [RFC XXXX] | 3291 | 2 | FLOOR-ID | [RFC XXXX] | 3292 | 3 | FLOOR-REQUEST-ID | [RFC XXXX] | 3293 | 4 | PRIORITY | [RFC XXXX] | 3294 | 5 | REQUEST-STATUS | [RFC XXXX] | 3295 | 6 | ERROR-CODE | [RFC XXXX] | 3296 | 7 | ERROR-INFO | [RFC XXXX] | 3297 | 8 | PARTICIPANT-PROVIDED-INFO | [RFC XXXX] | 3298 | 9 | STATUS-INFO | [RFC XXXX] | 3299 | 10 | SUPPORTED-ATTRIBUTES | [RFC XXXX] | 3300 | 11 | SUPPORTED-PRIMITIVES | [RFC XXXX] | 3301 | 12 | USER-DISPLAY-NAME | [RFC XXXX] | 3302 | 13 | USER-URI | [RFC XXXX] | 3303 | 14 | BENEFICIARY-INFORMATION | [RFC XXXX] | 3304 | 15 | FLOOR-REQUEST-INFORMATION | [RFC XXXX] | 3305 | 16 | REQUESTED-BY-INFORMATION | [RFC XXXX] | 3306 | 17 | FLOOR-REQUEST-STATUS | [RFC XXXX] | 3307 | 18 | OVERALL-REQUEST-STATUS | [RFC XXXX] | 3308 +------+---------------------------+------------+ 3310 Table 7: Initial values of the BFCP Attribute subregistry 3312 15.2. Primitive Subregistry 3314 [Editorial note: This section instructs the IANA to register the 3315 following new values for the BFCP Primitive subregistry: 3316 FloorRequestStatusAck, FloorStatusAck, Goodbye, and GoodbyeAck.] 3318 This section establishes the Primitive subregistry under the BFCP 3319 Parameters registry. As per the terminology in RFC 5226 [3], the 3320 registration policy for BFCP primitives shall be "Specification 3321 Required". For the purposes of this subregistry, the BFCP primitives 3322 for which IANA registration is requested MUST be defined by a 3323 standards-track RFC. Such an RFC MUST specify the primitive's value, 3324 name, format, and semantics. 3326 For each BFCP primitive, the IANA registers its value, its name, and 3327 the reference to the RFC where the primitive is defined. The 3328 following table contains the initial values of this subregistry. 3330 +-------+-----------------------+------------+ 3331 | Value | Primitive | Reference | 3332 +-------+-----------------------+------------+ 3333 | 1 | FloorRequest | [RFC XXXX] | 3334 | 2 | FloorRelease | [RFC XXXX] | 3335 | 3 | FloorRequestQuery | [RFC XXXX] | 3336 | 4 | FloorRequestStatus | [RFC XXXX] | 3337 | 5 | UserQuery | [RFC XXXX] | 3338 | 6 | UserStatus | [RFC XXXX] | 3339 | 7 | FloorQuery | [RFC XXXX] | 3340 | 8 | FloorStatus | [RFC XXXX] | 3341 | 9 | ChairAction | [RFC XXXX] | 3342 | 10 | ChairActionAck | [RFC XXXX] | 3343 | 11 | Hello | [RFC XXXX] | 3344 | 12 | HelloAck | [RFC XXXX] | 3345 | 13 | Error | [RFC XXXX] | 3346 | 14 | FloorRequestStatusAck | [RFC XXXX] | 3347 | 15 | FloorStatusAck | [RFC XXXX] | 3348 | 16 | Goodbye | [RFC XXXX] | 3349 | 17 | GoodbyeAck | [RFC XXXX] | 3350 +-------+-----------------------+------------+ 3352 Table 8: Initial values of the BFCP primitive subregistry 3354 15.3. Request Status Subregistry 3356 This section establishes the Request Status subregistry under the 3357 BFCP Parameters registry. As per the terminology in RFC 5226 [3], 3358 the registration policy for BFCP request status shall be 3359 "Specification Required". For the purposes of this subregistry, the 3360 BFCP request status for which IANA registration is requested MUST be 3361 defined by a standards-track RFC. Such an RFC MUST specify the value 3362 and the semantics of the request status. 3364 For each BFCP request status, the IANA registers its value, its 3365 meaning, and the reference to the RFC where the request status is 3366 defined. The following table contains the initial values of this 3367 subregistry. 3369 +-------+-----------+------------+ 3370 | Value | Status | Reference | 3371 +-------+-----------+------------+ 3372 | 1 | Pending | [RFC XXXX] | 3373 | 2 | Accepted | [RFC XXXX] | 3374 | 3 | Granted | [RFC XXXX] | 3375 | 4 | Denied | [RFC XXXX] | 3376 | 5 | Cancelled | [RFC XXXX] | 3377 | 6 | Released | [RFC XXXX] | 3378 | 7 | Revoked | [RFC XXXX] | 3379 +-------+-----------+------------+ 3381 Table 9: Initial values of the Request Status subregistry 3383 15.4. Error Code Subregistry 3385 [Editorial note: This section instructs the IANA to register the 3386 following new values for the BFCP Error Code subregistry: 10, 11, 3387 12, 13 and 14.] 3389 This section establishes the Error Code subregistry under the BFCP 3390 Parameters registry. As per the terminology in RFC 5226 [3], the 3391 registration policy for BFCP error codes shall be "Specification 3392 Required". For the purposes of this subregistry, the BFCP error 3393 codes for which IANA registration is requested MUST be defined by a 3394 standards-track RFC. Such an RFC MUST specify the value and the 3395 semantics of the error code, and any Error Specific Details that 3396 apply to it. 3398 For each BFCP primitive, the IANA registers its value, its meaning, 3399 and the reference to the RFC where the primitive is defined. The 3400 following table contains the initial values of this subregistry. 3402 +-------+--------------------------------------+------------+ 3403 | Value | Meaning | Reference | 3404 +-------+--------------------------------------+------------+ 3405 | 1 | Conference does not Exist | [RFC XXXX] | 3406 | 2 | User does not Exist | [RFC XXXX] | 3407 | 3 | Unknown Primitive | [RFC XXXX] | 3408 | 4 | Unknown Mandatory Attribute | [RFC XXXX] | 3409 | 5 | Unauthorized Operation | [RFC XXXX] | 3410 | 6 | Invalid Floor ID | [RFC XXXX] | 3411 | 7 | Floor Request ID Does Not Exist | [RFC XXXX] | 3412 | 8 | You have Already Reached the Maximum | [RFC XXXX] | 3413 | | Number of Ongoing Floor Requests for | | 3414 | | this Floor | | 3415 | 9 | Use TLS | [RFC XXXX] | 3416 | 10 | Unable to parse message | [RFC XXXX] | 3417 | 11 | Use DTLS | [RFC XXXX] | 3418 | 12 | Unsupported Version | [RFC XXXX] | 3419 | 13 | Incorrect Message Length | [RFC XXXX] | 3420 | 14 | Generic Error | [RFC XXXX] | 3421 +-------+--------------------------------------+------------+ 3423 Table 10: Initial Values of the Error Code subregistry 3425 16. Changes from RFC 4582 3427 Following is the list of technical changes and other non-trivial 3428 fixes from [15]. 3430 16.1. Extensions for an unreliable transport 3432 Main purpose of this work was to revise the specification to support 3433 BFCP over an unreliable transport, resulting in the following 3434 changes: 3436 Overview of Operation (Section 4): 3437 Changed the description of client-initiated and server- 3438 initiated transactions, referring to Section 8. 3440 COMMON-HEADER Format (Section 5.1): 3441 Ver(sion) field, where the value 2 is used for the extensions 3442 for an unreliable transport. Added new R and F flag-bits for 3443 an unreliable transport. Res(erved) field is now 3 bit. New 3444 optional Fragment Offset and Fragment Length fields. 3446 New primitives (Section 5.1): 3447 Added four new primitives: FloorRequestStatusAck, 3448 FloorStatusAck, Goodbye, and GoodbyeAck. 3450 New error codes (Section 5.2.6): 3451 Added three new error codes: "Unable to Parse Message", "Use 3452 DTLS" and "Unsupported Version". Note that two additional 3453 error codes were added, see Section 16.2. 3455 ABNF for new primitives (Section 5.3): 3456 New subsections with normative ABNF for the new primitives. 3458 Transport split in two (Section 6): 3459 Section 6 specifying the transport was split in two 3460 subsections; Section 6.1 for a reliable transport and 3461 Section 6.2 for an unreliable transport. Where the 3462 specification for an unreliable transport amongst other issues 3463 deals with reliability, congestion control, fragmentation and 3464 ICMP. 3466 Mandate DTLS (Section 7 and Section 9): 3467 Mandate DTLS support when transport over UDP is used. 3469 Transaction changes (Section 8): 3470 Server-initiated transactions over an unreliable transport has 3471 non-zero and unique Transaction ID. Over an unreliable 3472 transport, the retransmit timers T1 and T2 described in 3473 Section 8.3 applies. 3475 Requiring timely response (Section 10.1.2, Section 10.2.2, 3476 Section 11.2, Section 12.1.2, Section 12.2.2, Section 12.3.2, 3477 Section 12.4.2, Section 10.1.3 and Section 12.1.3): 3478 Describing that a given response must be sent within the 3479 transaction failure window to complete the transaction. 3481 Updated IANA Considerations (Section 15): 3482 Added the new primitives and error codes to Section 15.2 and 3483 Section 15.4 respectively. 3485 Examples over an unreliable transport (Appendix A): 3486 Added sample interactions over an unreliable transport for the 3487 scenarios in Figure 2 and Figure 3 3489 Motivation for an unreliable transport (Appendix B): 3490 Introduction to and motivation for extending BFCP to support an 3491 unreliable transport. 3493 16.2. Other changes 3495 The clarification and bug fixes: 3497 ABNF fixes (Figure 22, Figure 24, ="fig:reqby-information"/>, 3498 Figure 28, Figure 30, and the ABNF figures in Section 5.3): 3499 Although formally correct in [15], the notation has changed in a 3500 number of Figures to an equivalent form for clarity, e.g., 3501 s/*1(FLOOR-ID)/[FLOOR-ID]/ in Figure 38 and s/*[XXX]/*(XXX)/ in 3502 the other figures. 3504 Typo (Section 12.4.2): 3505 Change from SUPPORTED-PRIMITVIES to SUPPORTED-PRIMITIVES in the 3506 second paragraph. 3508 Corrected attribute type (Section 13.1.1): 3509 Change from PARTICIPANT-PROVIDED-INFO to PRIORITY attributed in 3510 the eighth paragraph, since the note below describes priority and 3511 that the last paragraph deals with PARTICIPANT-PROVIDED-INFO. 3513 New error codes (Section 5.2.6): 3514 Added two additional error codes: "Incorrect Message Length" and 3515 "Generic Error". 3517 17. Acknowledgements 3519 The XCON WG chairs, Adam Roach and Alan Johnston, provided useful 3520 ideas for RFC 4582 [15]. Additionally, Xiaotao Wu, Paul Kyzivat, 3521 Jonathan Rosenberg, Miguel A. Garcia-Martin, Mary Barnes, Ben 3522 Campbell, Dave Morgan, and Oscar Novo provided useful comments during 3523 the work with RFC 4582. The authors also acknowledge contributions 3524 to the revision of BFCP for use over an unreliable transport from 3525 Geir Arne Sandbakken who had the initial idea, Alfred E. Heggestad, 3526 Trond G. Andersen, Gonzalo Camarillo, Roni Even, Lorenzo Miniero, 3527 Joerg Ott, Eoin McLeod, Mark K. Thompson, Hadriel Kaplan, Dan Wing, 3528 Cullen Jennings, David Benham, Nivedita Melinkeri, Woo Johnman, 3529 Vijaya Mandava and Alan Ford. In the final phase Ernst Horvath did a 3530 thorough review revealing issues that needed clarification and 3531 changes. 3533 18. References 3535 18.1. Normative References 3537 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 3538 Levels", BCP 14, RFC 2119, March 1997. 3540 [2] Crocker, D. and P. Overell, "Augmented BNF for Syntax 3541 Specifications: ABNF", STD 68, RFC 5234, January 2008. 3543 [3] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 3544 Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. 3546 [4] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) 3547 Protocol Version 1.2", RFC 5246, August 2008. 3549 [5] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 3550 Security Version 1.2", RFC 6347, January 2012. 3552 [6] Yergeau, F., "UTF-8, a transformation format of ISO 10646", 3553 STD 63, RFC 3629, November 2003. 3555 [7] Camarillo, G. and T. Kristensen, "Session Description Protocol 3556 (SDP) Format for Binary Floor Control Protocol (BFCP) Streams", 3557 draft-ietf-bfcpbis-rfc4583bis-08 (work in progress), 3558 November 2013. 3560 [8] Wing, D., "Symmetric RTP / RTP Control Protocol (RTCP)", 3561 BCP 131, RFC 4961, July 2007. 3563 [9] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session 3564 Traversal Utilities for NAT (STUN)", RFC 5389, October 2008. 3566 18.2. Informational References 3568 [10] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with 3569 Session Description Protocol (SDP)", RFC 3264, June 2002. 3571 [11] Koskelainen, P., Ott, J., Schulzrinne, H., and X. Wu, 3572 "Requirements for Floor Control Protocols", RFC 4376, 3573 February 2006. 3575 [12] Barnes, M., Boulton, C., and O. Levin, "A Framework for 3576 Centralized Conferencing", RFC 5239, June 2008. 3578 [13] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A 3579 Protocol for Network Address Translator (NAT) Traversal for 3580 Offer/Answer Protocols", RFC 5245, April 2010. 3582 [14] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 3583 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 3584 Session Initiation Protocol", RFC 3261, June 2002. 3586 [15] Camarillo, G., Ott, J., and K. Drage, "The Binary Floor Control 3587 Protocol (BFCP)", RFC 4582, November 2006. 3589 [16] Camarillo, G., "Connection Establishment in the Binary Floor 3590 Control Protocol (BFCP)", RFC 5018, September 2007. 3592 [17] Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne, 3593 "Centralized Conferencing Manipulation Protocol", RFC 6503, 3594 March 2012. 3596 [18] Barnes, M., Miniero, L., Presta, R., and SP. Romano, 3597 "Centralized Conferencing Manipulation Protocol (CCMP) Call 3598 Flow Examples", RFC 6504, March 2012. 3600 [19] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, 3601 November 1990. 3603 [20] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery for 3604 IP version 6", RFC 1981, August 1996. 3606 [21] Mathis, M. and J. Heffner, "Packetization Layer Path MTU 3607 Discovery", RFC 4821, March 2007. 3609 [22] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework for 3610 Establishing a Secure Real-time Transport Protocol (SRTP) 3611 Security Context Using Datagram Transport Layer Security 3612 (DTLS)", RFC 5763, May 2010. 3614 [23] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network 3615 Address Translations (NATs)", RFC 4380, February 2006. 3617 [24] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines for 3618 Application Designers", BCP 145, RFC 5405, November 2008. 3620 [25] Thaler, D., "Teredo Extensions", RFC 6081, January 2011. 3622 [26] Stewart, R., "Stream Control Transmission Protocol", RFC 4960, 3623 September 2007. 3625 [27] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach, "TCP 3626 Candidates with Interactive Connectivity Establishment (ICE)", 3627 RFC 6544, March 2012. 3629 [28] Manner, J., Varis, N., and B. Briscoe, "Generic UDP Tunnelling 3630 (GUT)", draft-manner-tsvwg-gut-02 (work in progress), 3631 July 2010. 3633 [29] Stucker, B., Tschofenig, H., and G. Salgueiro, "Analysis of 3634 Middlebox Interactions for Signaling Protocol Communication 3635 along the Media Path", 3636 draft-ietf-mmusic-media-path-middleboxes-05 (work in progress), 3637 July 2012. 3639 [30] Guha, S. and P. Francis, "Characterization and Measurement of 3640 TCP Traversal through NATs and Firewalls", 2005, 3641 . 3643 [31] Ford, B., Srisuresh, P., and D. Kegel, "Peer-to-Peer 3644 Communication Across Network Address Translators", April 2005, 3645 . 3647 Appendix A. Example Call Flows for BFCP over an Unreliable Transport 3649 With reference to Section 4.1, the following figures show 3650 representative call-flows for requesting and releasing a floor, and 3651 obtaining status information about a floor when BFCP is deployed over 3652 an unreliable transport. The figures here show a loss-less 3653 interaction. 3655 Floor Participant Floor Control 3656 Server 3657 |(1) FloorRequest | 3658 |Transaction ID: 123 | 3659 |User ID: 234 | 3660 |FLOOR-ID: 543 | 3661 |---------------------------------------------->| 3662 | | 3663 |(2) FloorRequestStatus | 3664 |Transaction ID: 123 | 3665 |User ID: 234 | 3666 |FLOOR-REQUEST-INFORMATION | 3667 | Floor Request ID: 789 | 3668 | OVERALL-REQUEST-STATUS | 3669 | Request Status: Pending | 3670 | FLOOR-REQUEST-STATUS | 3671 | Floor ID: 543 | 3672 |<----------------------------------------------| 3673 | | 3674 |(3) FloorRequestStatus | 3675 |Transaction ID: 4098 | 3676 |User ID: 234 | 3677 |FLOOR-REQUEST-INFORMATION | 3678 | Floor Request ID: 789 | 3679 | OVERALL-REQUEST-STATUS | 3680 | Request Status: Accepted | 3681 | Queue Position: 1st | 3682 | FLOOR-REQUEST-STATUS | 3683 | Floor ID: 543 | 3684 |<----------------------------------------------| 3685 | | 3686 |(4) FloorRequestStatusAck | 3687 |Transaction ID: 4098 | 3688 |User ID: 234 | 3689 |---------------------------------------------->| 3690 | | 3691 |(5) FloorRequestStatus | 3692 |Transaction ID: 4130 | 3693 |User ID: 234 | 3694 |FLOOR-REQUEST-INFORMATION | 3695 | Floor Request ID: 789 | 3696 | OVERALL-REQUEST-STATUS | 3697 | Request Status: Granted | 3698 | FLOOR-REQUEST-STATUS | 3699 | Floor ID: 543 | 3700 |<----------------------------------------------| 3701 | | 3702 |(6) FloorRequestStatusAck | 3703 |Transaction ID: 4130 | 3704 |User ID: 234 | 3705 |---------------------------------------------->| 3706 | | 3707 |(7) FloorRelease | 3708 |Transaction ID: 154 | 3709 |User ID: 234 | 3710 |FLOOR-REQUEST-ID: 789 | 3711 |---------------------------------------------->| 3712 | | 3713 |(8) FloorRequestStatus | 3714 |Transaction ID: 154 | 3715 |User ID: 234 | 3716 |FLOOR-REQUEST-INFORMATION | 3717 | Floor Request ID: 789 | 3718 | OVERALL-REQUEST-STATUS | 3719 | Request Status: Released | 3720 | FLOOR-REQUEST-STATUS | 3721 | Floor ID: 543 | 3722 |<----------------------------------------------| 3724 Figure 48: Requesting and releasing a floor 3726 Note that in Figure 48, the FloorRequestStatus message from the floor 3727 control server to the floor participant is a transaction-closing 3728 message as a response to the client-initiated transaction with 3729 Transaction ID 154. It does not and SHOULD NOT be followed by a 3730 FloorRequestStatusAck message from the floor participant to the floor 3731 control server. 3733 Floor Participant Floor Control 3734 Server 3735 |(1) FloorQuery | 3736 |Transaction ID: 257 | 3737 |User ID: 234 | 3738 |FLOOR-ID: 543 | 3739 |---------------------------------------------->| 3740 | | 3741 |(2) FloorStatus | 3742 |Transaction ID: 257 | 3743 |User ID: 234 | 3744 |FLOOR-ID:543 | 3745 |FLOOR-REQUEST-INFORMATION | 3746 | Floor Request ID: 764 | 3747 | OVERALL-REQUEST-STATUS | 3748 | Request Status: Accepted | 3749 | Queue Position: 1st | 3750 | FLOOR-REQUEST-STATUS | 3751 | Floor ID: 543 | 3752 | BENEFICIARY-INFORMATION | 3753 | Beneficiary ID: 124 | 3754 |FLOOR-REQUEST-INFORMATION | 3755 | Floor Request ID: 635 | 3756 | OVERALL-REQUEST-STATUS | 3757 | Request Status: Accepted | 3758 | Queue Position: 2nd | 3759 | FLOOR-REQUEST-STATUS | 3760 | Floor ID: 543 | 3761 | BENEFICIARY-INFORMATION | 3762 | Beneficiary ID: 154 | 3763 |<----------------------------------------------| 3764 | | 3765 |(3) FloorStatus | 3766 |Transaction ID: 4319 | 3767 |User ID: 234 | 3768 |FLOOR-ID:543 | 3769 |FLOOR-REQUEST-INFORMATION | 3770 | Floor Request ID: 764 | 3771 | OVERALL-REQUEST-STATUS | 3772 | Request Status: Granted | 3773 | FLOOR-REQUEST-STATUS | 3774 | Floor ID: 543 | 3775 | BENEFICIARY-INFORMATION | 3776 | Beneficiary ID: 124 | 3777 |FLOOR-REQUEST-INFORMATION | 3778 | Floor Request ID: 635 | 3779 | OVERALL-REQUEST-STATUS | 3780 | Request Status: Accepted | 3781 | Queue Position: 1st | 3782 | FLOOR-REQUEST-STATUS | 3783 | Floor ID: 543 | 3784 | BENEFICIARY-INFORMATION | 3785 | Beneficiary ID: 154 | 3786 |<----------------------------------------------| 3787 | | 3788 |(4) FloorStatusAck | 3789 |Transaction ID: 4319 | 3790 |User ID: 234 | 3791 |---------------------------------------------->| 3792 | | 3793 |(5) FloorStatus | 3794 |Transaction ID: 4392 | 3795 |User ID: 234 | 3796 |FLOOR-ID:543 | 3797 |FLOOR-REQUEST-INFORMATION | 3798 | Floor Request ID: 635 | 3799 | OVERALL-REQUEST-STATUS | 3800 | Request Status: Granted | 3801 | FLOOR-REQUEST-STATUS | 3802 | Floor ID: 543 | 3803 | BENEFICIARY-INFORMATION | 3804 | Beneficiary ID: 154 | 3805 |<----------------------------------------------| 3806 | | 3807 |(6) FloorStatusAck | 3808 |Transaction ID: 4392 | 3809 |User ID: 234 | 3810 |---------------------------------------------->| 3812 Figure 49: Obtaining status information about a floor 3814 Appendix B. Motivation for Supporting an Unreliable Transport 3816 [Editorial note: This appendix is contained in this draft as an 3817 aid and rationale for new readers and reviewers. However, it is 3818 not yet decided whether this Appendix will be part of the final 3819 (RFC) version or not.] 3821 B.1. Motivation 3823 In existing video conferencing deployments, BFCP is used to manage 3824 the floor for the content sharing associated with the conference. 3825 For peer to peer scenarios, including business to business 3826 conferences and point to point conferences in general, it is 3827 frequently the case that one or both endpoints exists behind a NAT. 3828 BFCP roles are negotiated in the offer/answer exchange as specified 3829 in [7], resulting in one endpoint being responsible for opening the 3830 TCP connection used for the BFCP communication. 3832 +---------+ 3833 | Network | 3834 +---------+ 3835 +-----+ / \ +-----+ 3836 | NAT |/ \| NAT | 3837 +-----+ +-----+ 3838 +----+ / \ +----+ 3839 |BFCP|/ \|BFCP| 3840 | UA | | UA | 3841 +----+ +----+ 3843 Figure 50: Use Case 3845 The communication session between the video conferencing endpoints 3846 typically consists of a number of RTP over UDP media streams, for 3847 audio and video, and a BFCP connection for floor control. Existing 3848 deployments are most common in, but not limited to, enterprise 3849 networks. In existing deployments, NAT traversal for the RTP streams 3850 works using ICE and/or other methods, including those described in 3851 [29]. 3853 When enhancing an existing SIP based video conferencing deployment 3854 with support for content sharing, the BFCP connection often poses a 3855 problem. The reasons for this fall into two general classes. First, 3856 there may be a strong preference for UDP based signaling in general. 3857 On high capacity endpoints (e.g., PSTN gateways or SIP/H.323 inter- 3858 working gateways), TCP can suffer from head of line blocking, and it 3859 uses many kernel buffers. Network operators view UDP as a way to 3860 avoid both of these. Second, establishment and traversal of the TCP 3861 connection involving ephemeral ports, as is typically the case with 3862 BFCP over TCP, can be problematic, as described in Appendix A of 3863 [27]. A broad study of NAT behavior and peer-to-peer TCP 3864 establishment for a comprehensive set of TCP NAT traversal techniques 3865 over a wide range of commercial NAT products concluded it was not 3866 possible to establish a TCP connection in 11% of the cases [30]. The 3867 results are worse when focusing on enterprise NATs. A study of hole 3868 punching as a NAT traversal technique across a wide variety of 3869 deployed NATs reported consistently higher success rates when using 3870 UDP than when using TCP [31]. 3872 It is worth noticing that BFCP over UDP were already used in real 3873 deployments, underlining the necessity to specify a common way to 3874 exchange BFCP messages where TCP is not appropriate, to avoid a 3875 situation where multiple different and non-interoperable would co- 3876 exist in the market. The purpose of this draft is to formalize and 3877 publish the extension from the standard specification to facilitate 3878 complete interoperability between implementations. 3880 B.1.1. Alternatives Considered 3882 In selecting the approach of defining UDP as an alternate transport 3883 for BFCP, several alternatives were considered and explored to some 3884 degree. Each of these is discussed briefly in the following 3885 subsections. In summary, while the not chosen alternatives work in a 3886 number of scenarios, they are not sufficient, in and of themselves, 3887 to address the use case targeted by this draft. The last 3888 alternative, presented in Appendix B.1.1.7, is the selected one and 3889 is specified in this draft. 3891 It is also worth noting that the IETF Transport Area were asked for a 3892 way to tunnel TCP over UDP, but at that point there was no consensus 3893 on how to achieve that. 3895 B.1.1.1. ICE TCP 3897 ICE TCP [27] extends ICE to TCP based media, including the ability to 3898 offer a mix of TCP and UDP based candidates for a single stream. ICE 3899 TCP has, in general, a lower success probability for enabling TCP 3900 connectivity without a relay if both of the hosts are behind a NAT 3901 (see Appendix A of [27]) than enabling UDP connectivity in the same 3902 scenarios. The happens because many of the currently deployed NATs 3903 in video conferencing networks do not support the flow of TCP hand 3904 shake packets seen in case of TCP simultaneous-open, either because 3905 they do not allow incoming TCP SYN packets from an address to which a 3906 SYN packet has been sent to recently, or because they do not properly 3907 process the subsequent SYNACK. Implementing various techniques 3908 advocated for candidate collection in [27] should increase the 3909 success probability, but many of these techniques require support 3910 from some network elements (e.g., from the NATs). Such support is 3911 not common in enterprise NATs. 3913 B.1.1.2. Teredo 3915 Teredo [23] enables nodes located behind one or more IPv4 NATs to 3916 obtain IPv6 connectivity by tunneling packets over UDP. Teredo 3917 extensions [25] provide additional capabilities to Teredo, including 3918 support for more types of NATs and support for more efficient 3919 communication. 3921 As defined, Teredo could be used to make BFCP work for the video 3922 conferencing use cases addressed in this draft. However, running the 3923 service requires the help of "Teredo servers" and "Teredo relays" 3924 [23]. These servers and relays generally do not exist in the 3925 existing video conferencing deployments. It also requires IPv6 3926 awareness on the endpoints. It should also be noted that ICMP6, as 3927 used with Teredo to complete an initial protocol exchange and confirm 3928 that the appropriate NAT bindings have been set up, is not a 3929 conventional feature of IPv4 or even IPv6, and some currently 3930 deployed IPv6 firewalls discard ICMP messages. As these networks 3931 continue to evolve and tackle the transaction to IPv6, Teredo servers 3932 and relays may be deployed, making Teredo available as a suitable 3933 alternative to BFCP over UDP. 3935 B.1.1.3. GUT 3937 GUT [28] attempts to facilitate tunneling over UDP by encapsulating 3938 the native transport protocol and its payload (in general the whole 3939 IP payload) within a UDP packet destined to the well-known port 3940 GUT_P. Unfortunately, it requires user-space TCP, for which there is 3941 not a readily available implementation, and creating one is a large 3942 project in itself. This draft has expired and its future is still 3943 not clear as it has not yet been adopted by a working group. 3945 B.1.1.4. UPnP IGD 3947 Universal Plug and Play Internet Gateway Devices (UPnP IGD) sit on 3948 the edge of the network, providing connectivity to the Internet for 3949 computers internal to the LAN, but do not allow Internet devices to 3950 connect to computers on the internal LAN. IGDs enable a computer on 3951 an internal LAN to create port mappings on their NAT, through which 3952 hosts on the Internet can send data that will be forwarded to the 3953 computer on the internal LAN. IGDs may be self-contained hardware 3954 devices or may be software components provided within an operating 3955 system. 3957 In considering UPnP IGD, several issues exist. Not all NATs support 3958 UPnP, and many that do support it are configured with it turned off 3959 by default. NATs are often multilayered, and UPnP does not work well 3960 with such NATs. For example, a typical DSL modems acts as a NAT, and 3961 the user plugs in a wireless access point behind that, which adds 3962 another layer NAT. The client can discover the first layer of NAT 3963 using multicast but it is harder to figure out how to discover and 3964 control NATs in the next layer up. 3966 B.1.1.5. NAT PMP 3968 The NAT Port Mapping Protocol (NAT PMP) allows a computer in a 3969 private network (behind a NAT router) to automatically configure the 3970 router to allow parties outside the private network to contact it. 3971 NAT PMP runs over UDP. It essentially automates the process of port 3972 forwarding. Included in the protocol is a method for retrieving the 3973 public IP address of a NAT gateway, thus allowing a client to make 3974 this public IP address and port number known to peers that may wish 3975 to communicate with it. 3977 Many NATs do not support PMP. In those that do support it, it has 3978 similar issues with negotiation of multilayer NATs as UPnP. Video 3979 conferencing is used extensively in enterprise networks, and NAT PMP 3980 is not generally available in enterprise-class routers. 3982 B.1.1.6. SCTP 3984 It would be quite straight forward to specify a BFCP binding for SCTP 3985 [26], and then tunnel SCTP over UDP in the use case described in 3986 Appendix B.1. SCTP is gaining some momentum currently. There is 3987 ongoing discussion in the RTCWeb WG regarding this approach. 3988 However, this approach for tunneling over UDP was not mature enough 3989 when considered and not even fully specified. 3991 B.1.1.7. BFCP over UDP transport 3993 To overcome the problems with establishing TCP flows between BFCP 3994 entities, an alternative is to define UDP as an alternate transport 3995 for BFCP, leveraging the same mechanisms in place for the RTP over 3996 UDP media streams for the BFCP communication. When using UDP as the 3997 transport, it is recommended to follow the guidelines provided in 3998 [24]. 4000 Minor changes to the transaction model are introduced in that all 4001 requests now have an appropriate response to complete the 4002 transaction. The requests are sent with a retransmit timer 4003 associated with the response to achieve reliability. This 4004 alternative does not change the semantics of BFCP. It permits UDP as 4005 an alternate transport. 4007 Existing implementations, in the spirit of the approach detailed in 4008 earlier versions of this draft, have demonstrated this approach to be 4009 feasible. Initial compatibility among implementations has been 4010 achieved at previous interoperability events. The authors view this 4011 extension as a pragmatic solution to an existing deployment 4012 challenge. This is the chosen approach, and the extensions is 4013 specified in this document. 4015 Authors' Addresses 4017 Gonzalo Camarillo 4018 Ericsson 4019 Hirsalantie 11 4020 Jorvas 02420 4021 Finland 4023 Email: gonzalo.camarillo@ericsson.com 4025 Keith Drage 4026 Alcatel-Lucent 4027 Quadrant, StoneHill Green, Westlea 4028 Swindon, Wilts 4029 UK 4031 Email: drage@alcatel-lucent.com 4033 Tom Kristensen 4034 Cisco 4035 Philip Pedersens vei 22 4036 N-1366 Lysaker 4037 Norway 4039 Email: tomkrist@cisco.com, tomkri@ifi.uio.no 4041 Joerg Ott 4042 Aalto University 4043 Otakaari 5 A 4044 Espoo, FIN 02150 4045 Finland 4047 Email: jo@comnet.tkk.fi 4048 Charles Eckel 4049 Cisco 4050 707 Tasman Drive 4051 California, CA 95035 4052 United States 4054 Email: eckelcu@cisco.com