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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Niemi 3 Internet-Draft Nokia 4 Intended status: Standards Track M. Garcia-Martin 5 Expires: June 6, 2012 Ericsson 6 G. Sandbakken, Ed. 7 Cisco Systems 8 December 4, 2011 10 Multi-party Chat Using the Message Session Relay Protocol (MSRP) 11 draft-ietf-simple-chat-11 13 Abstract 15 The Message Session Relay Protocol (MSRP) defines a mechanism for 16 sending instant messages within a peer-to-peer session, negotiated 17 using the Session Initiation Protocol (SIP) and the Session 18 Description Protocol (SDP). This document defines the necessary 19 tools for establishing multi-party chat sessions, or chat rooms, 20 using MSRP. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on June 6, 2012. 39 Copyright Notice 41 Copyright (c) 2011 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 This document may contain material from IETF Documents or IETF 55 Contributions published or made publicly available before November 56 10, 2008. The person(s) controlling the copyright in some of this 57 material may not have granted the IETF Trust the right to allow 58 modifications of such material outside the IETF Standards Process. 59 Without obtaining an adequate license from the person(s) controlling 60 the copyright in such materials, this document may not be modified 61 outside the IETF Standards Process, and derivative works of it may 62 not be created outside the IETF Standards Process, except to format 63 it for publication as an RFC or to translate it into languages other 64 than English. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 3. Motivations and Requirements . . . . . . . . . . . . . . . . . 6 71 4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 7 72 5. Creating, Joining, and Deleting a Chat Room . . . . . . . . . 10 73 5.1. Creating a Chat Room . . . . . . . . . . . . . . . . . . . 10 74 5.2. Joining a Chat Room . . . . . . . . . . . . . . . . . . . 10 75 5.3. Deleting a Chat Room . . . . . . . . . . . . . . . . . . . 11 76 6. Sending and Receiving Instant Messages . . . . . . . . . . . . 12 77 6.1. Regular Messages . . . . . . . . . . . . . . . . . . . . . 12 78 6.2. Private Messages . . . . . . . . . . . . . . . . . . . . . 13 79 6.3. MSRP reports and responses . . . . . . . . . . . . . . . . 15 80 7. Nicknames . . . . . . . . . . . . . . . . . . . . . . . . . . 16 81 7.1. Using Nicknames within a Conference . . . . . . . . . . . 16 82 7.2. Modifying a Nickname . . . . . . . . . . . . . . . . . . . 18 83 7.3. Removing a Nickname . . . . . . . . . . . . . . . . . . . 18 84 7.4. Nicknames in Conference Event Packages . . . . . . . . . . 18 85 8. The SDP 'chatroom' attribute . . . . . . . . . . . . . . . . . 19 86 9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 87 9.1. Joining a chat room . . . . . . . . . . . . . . . . . . . 21 88 9.2. Setting up a nickname . . . . . . . . . . . . . . . . . . 22 89 9.3. Sending a regular message to the chat room . . . . . . . . 24 90 9.4. Sending a private message to a participant . . . . . . . . 25 91 9.5. Chunked private message . . . . . . . . . . . . . . . . . 27 92 9.6. Nickname in a conference information document . . . . . . 28 93 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 94 10.1. New MSRP Method . . . . . . . . . . . . . . . . . . . . . 29 95 10.2. New MSRP Header . . . . . . . . . . . . . . . . . . . . . 30 96 10.3. New MSRP Status Codes . . . . . . . . . . . . . . . . . . 30 97 10.4. New SDP Attribute . . . . . . . . . . . . . . . . . . . . 30 98 11. Security Considerations . . . . . . . . . . . . . . . . . . . 31 99 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 32 100 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32 101 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32 102 14.1. Normative References . . . . . . . . . . . . . . . . . . . 32 103 14.2. Informative References . . . . . . . . . . . . . . . . . . 34 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34 106 1. Introduction 108 The Message Session Relay Protocol (MSRP) [RFC4975] defines a 109 mechanism for sending a series of instant messages within a session. 110 The Session Initiation Protocol (SIP) [RFC3261] in combination with 111 the Session Description Protocol (SDP) [RFC4566] allows for two peers 112 to establish and manage such sessions. 114 In another application of SIP, a user agent can join in a multi-party 115 conversation called a conference that is hosted by a specialized user 116 agent called a focus [RFC4353]. Such a conference can naturally 117 involve MSRP sessions. It is the responsibility of an entity 118 handling the media to relay instant messages received from one 119 participant to the rest of the participants in the conference. 121 Several such systems already exist in the Internet. Participants in 122 a chat room can be identified with a pseudonym or nickname, and 123 decide whether their real identity is disclosed to other 124 participants. Participants can also use a rich set of features such 125 as the ability to send private instant messages to other 126 participants. 128 Similar conferences supporting chat rooms are already available 129 today. For example, Internet Relay Chat (IRC) [RFC2810], Extensible 130 Messaging and Presence Protocol (XMPP): Core [RFC6120] based chat 131 rooms, and many other proprietary systems provide chat room 132 functionality. Specifying equivalent functionality for MSRP-based 133 systems provides competitive features and enables interworking 134 between the systems. 136 This document defines requirements, conventions, and extensions for 137 providing private messages and nickname management in centralized 138 conferences with MSRP. Participants in a chat room can be identified 139 by a pseudonym, and decide if their real identity is disclosed to 140 other participants. This memo uses the SIP Conferencing Framework 141 [RFC4353] as a design basis. It also aims to be compatible with the 142 A Framework for Centralized Conferencing [RFC5239]. It is expected 143 that future mechanisms will be developed for providing similar 144 functionality in generic conferences, i.e., where the media is not 145 only restricted to MSRP. The mechanisms described in this document 146 provide a future compatible short-term solution for MSRP centralized 147 conferences. 149 2. Terminology 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in RFC 2119, BCP 14 154 [RFC2119], and indicate requirement levels for compliant 155 implementations. 157 This memo deals with tightly coupled SIP conferences defined in SIP 158 Conferencing Framework [RFC4353] and adopts the terminology from that 159 document. In addition to that terminology, we introduce some new 160 terms: 162 Nickname: a pseudonym or descriptive name associated to a 163 participant. See Section 7 for details 165 Multi-party chat: an instance of a tightly coupled conference, in 166 which the media exchanged between the participants consist of MSRP 167 based instant messages. Also known as a chat room. 169 Chat Room: a synonym for a multi-party chat. 171 Chat Room URI: a URI that identifies a particular chat room, and is 172 a synonym of a Conference URI defined in RFC 4353 [RFC4353]. 174 Sender: the conference participant that originally created an 175 instant message and sent it to the chat room for delivery. 177 Recipient: the destination conference participant(s). This 178 defaults to the full conference participant list, minus the IM 179 Sender. 181 MSRP switch: a media level entity that is a MSRP endpoint. It is a 182 special MSRP endpoint that receives MSRP messages, and delivers 183 them to the other conference participants. The MSRP switch has a 184 similar role to a conference mixer with the exception that the 185 MSRP switch does not actually "mix" together different input media 186 streams; it merely relays the messages between participants. 188 Private Instant Message: an instant message sent in a chat room 189 intended for a single participant. A private IM is usually 190 rendered distinctly from the rest of the IMs, indicating that the 191 message was a private communication. 193 Anonymous URI: a URI concealing the participant's SIP AOR from the 194 other participants in the conference. The allocation of such a 195 URI is out of scope of this specification. An anonymous URI must 196 be valid for the length of the conference, and will be utilized by 197 the MSRP switch to forward messages to and from anonymous 198 participants. 200 Conference Event Package: a notification mechanism that allows 201 conference participants to learn conference information including 202 roster and state changes in a conference. This would typically be 203 A Session Initiation Protocol (SIP) Event Package for Conference 204 State [RFC4575] or Conference Event Package Data Format Extension 205 for Centralized Conferencing [I-D.ietf-xcon-event-package]. 207 3. Motivations and Requirements 209 Although conference frameworks describing many types of conferencing 210 applications already exist, such as the Framework for Centralized 211 Conferencing [RFC5239] and the SIP Conferencing Framework [RFC4353], 212 the exact details of session-based instant messaging conferences are 213 not well-defined at the moment. 215 To allow interoperable chat implementations, for both conference- 216 aware, and conference-unaware user agents, certain conventions for 217 MSRP conferences need to be defined. It also seems beneficial to 218 provide a set of features that enhance the baseline multi-party MSRP 219 in order to be able to create systems that have functionality on par 220 with existing chat systems, as well as enable building interworking 221 gateways to these existing chat systems. 223 We define the following requirements: 225 REQ-1: A basic requirement is the existence of a multi-party 226 conference, where participants can join and leave the 227 conference and get instant messages exchanged to the rest of 228 the participants. 230 REQ-2: A conference participant must be able to determine the 231 identities of the sender and recipient of the received IMs. 233 REQ-3: A conference participant must be able to determine the 234 recipient of the received message. For instance, the 235 recipient of the message might be the entire conference or a 236 single participant of the conference (i.e., a private 237 message). 239 REQ-4: It must be possible to send a message to a single participant 240 within the conference (i.e., a private instant message). 242 REQ-5: A conference participant may have a nickname or pseudonym 243 associated with their real identity. 245 REQ-6: It must be possible for a participant to change their 246 nickname during the progress of the conference. 248 REQ-7: It must be possible that a participant is only known by an 249 anonymous identity and not their real identity to the rest of 250 the conference. 252 REQ-8: It must be possible for the conference participants to learn 253 the chat room capabilities described in this document. 255 4. Overview of Operation 257 In order to set up a conference, one must first be created. Users 258 wishing to host a conference themselves can of course do just that; 259 their User Agent (UA) simply morphs from an ordinary UA into a 260 special purpose one called a Focus UA. Another, commonly used setup 261 is one where a dedicated node in the network functions as a Focus UA. 263 Each chat room has an identity of its own: a SIP URI that 264 participants use to join the conference, e.g. by sending an INVITE 265 request. The conference focus processes the invitations, and as 266 such, maintains SIP dialogs with each participant. In a multi-party 267 chat, or chat room, MSRP is one of the established media streams. 268 Each conference participant establishes an MSRP session with the MSRP 269 switch, which is a special purpose MSRP application. The MSRP 270 sessions can be relayed by one or more MSRP relays, which are 271 specified in RFC 4976 [RFC4976]. This is illustrated in Figure 1 272 MSRP Sessions 273 +---------------------------+ 274 | +-----------+ | 275 +---+--+ +---+--+ | | 276 | SIP | | SIP | | | 277 | MSRP | | MSRP | +--+---+----+ 278 |Client| |Client| | MSRP | 279 +---+--+ ++-----+ | Relay | 280 | | +-----+-----+ 281 SIP Dialogs | / | 282 | | | MSRP Sessions 283 +----+------+--+ | 284 | Conference | +-------+-----+ 285 | Focus UA | | MSRP | 286 | |........| Switch | 287 | | | | 288 +---+--------+-+ +-------+-----+ 289 | \ | 290 SIP Dialogs | | | MSRP Sessions 291 | \ | 292 +--+---+ +-+----+ +-----+------+ 293 | SIP | | SIP | | MSRP | 294 | MSRP | | MSRP | | Relay | 295 |Client| |Client| +-+-------+--+ 296 +---+--+ +--+---+ | | 297 | +-----------+ | 298 +------------------------------+ 299 MSRP sessions 301 Figure 1: Multi-party chat overview shown with MSRP Relays and a 302 conference Focus UA 304 The MSRP switch is similar to a conference mixer in that it handles 305 media sessions with each of the participants and bridges these 306 streams together. However, unlike a conference mixer, the MSRP 307 switch merely forwards messages between participants but doesn't 308 actually mix the streams in any way. The system is illustrated in 309 Figure 2. 311 +------+ 312 | MSRP | 313 |Client| 314 +------+ +--.---+ +------+ 315 | MSRP | | | MSRP | 316 |Client| | _|Client| 317 +------._ | ,' +------+ 318 `._ | ,' 319 `.. +----------+ ,' 320 `| |' 321 | MSRP | 322 | Switch | 323 ,| |_ 324 _,-'' +----------+ ``-._ 325 +------.-' | `--+------+ 326 | MSRP | | | MSRP | 327 |Client| | |Client| 328 +------+ | +------+ 329 +---'--+ 330 | MSRP | 331 |Client| 332 +------+ 334 Figure 2: Multi-party chat in a Centralized Conference 336 Typically conference participants also subscribe to a conference 337 event package to gather information about the conference roster in 338 the form of conference state notifications. For example, 339 participants can learn about other participants' identities, 340 including their nicknames. 342 All messages in the chat room use the 'Message/CPIM' wrapper content 343 type [RFC3862], so that it is possible to distinguish between private 344 and regular messages. When a participant wants to send an instant 345 message to the conference, it constructs an MSRP SEND request and 346 submits it to the MSRP switch including a regular payload (e.g. a 347 Message/CPIM message that contains a text, HTML, an image, etc.). 348 The Message/CPIM To header is set to the chat room URI. The switch 349 then fans out the SEND request to all of the other participants using 350 their existing MSRP sessions. 352 A participant can also send a private instant message addressed to a 353 participant whose identity has been learned, e.g. via a conference 354 event package. In this case the sender creates an MSRP SEND request 355 with a Message/CPIM wrapper whose To header contains not the chat 356 room URI but the recipient's URI. The MSRP switch then forwards the 357 SEND request to that recipient. This specification supports the 358 sending of private messages to one and only one recipient. However, 359 if the recipient is logged from different endpoints, the MSRP switch 360 will distribute the private message to each endpoint the recipient is 361 logged. 363 We extend the current MSRP negotiation that takes place in SDP 364 [RFC4566] to allow participants to learn whether the chat room 365 supports and is willing to accept (e.g. due to local policy 366 restrictions) certain MSRP functions defined in this memo, such as 367 nicknames or private messaging. 369 Naturally, when a participant wishes to leave a chat room, it sends a 370 SIP BYE request to the Focus UA and terminates the SIP dialog with 371 the focus and MSRP sessions with the MSRP switch. 373 This document assumes that each chat room is allocated its own SIP 374 URI. A user joining a chat room sends an INVITE request to that SIP 375 URI, and as a result, a new MSRP session is established between the 376 user and the MSRP switch. It is assumed that an MSRP session is 377 mapped to a chat room. If a user wants to join a second chat room, 378 he creates a different INVITE request, through a different SIP 379 dialog, which leads to the creation of a second MSRP session between 380 the user and the MSRP switch. Notice that these two MSRP sessions 381 can still be multiplexed over the same TCP connection as per regular 382 MSRP procedures. However, each chat room is associated to a unique 383 MSRP session and a unique SIP dialog. 385 5. Creating, Joining, and Deleting a Chat Room 387 5.1. Creating a Chat Room 389 Since we consider a chat room a particular type of conference having 390 MSRP media, the methods defined by the SIP Conference Framework 391 [RFC4353] for creating conferences are directly applicable to a chat 392 room. 394 Once a chat room is created, it is identified by a SIP URI, like any 395 other conference. 397 5.2. Joining a Chat Room 399 Participants usually join the conference by sending an INVITE request 400 to the conference URI. As long as the conference policy allows, the 401 INVITE request is accepted by the focus and the user is brought into 402 the conference. 404 The MSRP switch needs to be aware of the URIs of the participant 405 (SIP, Tel, or IM URIs) in order to validate messages sent from this 406 participant prior to their forwarding. This information is known to 407 the focus of the conference. Therefore an interface between the 408 focus and the MSRP switch is assumed. However, the interface between 409 the focus and the MSRP switch is outside the scope of this document. 411 Conference aware participants will detect that the peer is a focus 412 due to the presence of the "isfocus" feature tag [RFC3840] in the 413 Contact header field of the 200-class response to the INVITE request. 414 Conference unaware participants will not notice it is a focus, and 415 can not apply the additional mechanisms defined in this document. 416 Participants are also aware that the mixer is an MSRP switch due to 417 the presence of a 'message' media type and either TCP/MSRP or TCP/ 418 TLS/MSRP as the protocol field in the media line of SDP [RFC4566]. 420 The conference focus of a chat room MUST include support for a 421 Message/CPIM [RFC3862] top-level wrapper for the MSRP messages by 422 setting the 'accept-types' MSRP media line attribute in the SDP offer 423 or answer to include 'Message/CPIM'. 425 Note that the 'Message/CPIM' wrapper is used to carry the sender 426 information that, otherwise, it will not be available to the 427 recipient. Additionally, 'Message/CPIM' wrapper carries the 428 recipient information (e.g. To and Cc: headers). 430 If a participant wants to remain anonymous to the rest of the 431 participants in the conference, the participant's UA must provide an 432 anonymous URI to the conference focus. The URI will be used in the 433 From and To headers in the 'Message/CPIM' wrapper, and can be learned 434 by the other participants of the conference. Notice that in order 435 for the anonymity mechanism to work, the anonymous URI must not 436 reveal the participant's SIP AOR. The mechanism for acquiring an 437 anonymous URI is outside the scope of this specification. 439 The conference focus of a chat room MUST learn the chat room 440 capabilities of each participant that joins the chat room. The 441 conference focus MUST inform the MSRP switch of such support in order 442 to prevent the MSRP switch from distributing private messages to 443 participants who do not support private messaging. The recipient 444 would not be able to render the message as private, and any potential 445 reply would be sent to the whole chat room. 447 5.3. Deleting a Chat Room 449 As with creating a conference, the methods defined by the SIP 450 Conference Framework [RFC4353] for deleting a conference are directly 451 applicable to a chat room. The MSRP switch will terminate the MSRP 452 sessions with all the participants. 454 Deleting a chat room is an action that heavily depends on the policy 455 of the chat room. The policy can determine that the chat room is 456 deleted when the creator leaves the conference, or with any out of 457 band mechanism. 459 6. Sending and Receiving Instant Messages 461 6.1. Regular Messages 463 This section describes the conventions used to send and receive 464 instant messages that are addressed to all the participants in the 465 chat room. These are sent over a regular MSRP SEND request that 466 contains a Message/CPIM wrapper [RFC3862] that in turn contains the 467 desired payload (e.g. text, image, video-clip, etc.). 469 When a chat room participant wishes to send an instant message to all 470 the other participants in the chat room, it constructs an MSRP SEND 471 request according to the procedures specified in RFC 4975 [RFC4975]. 472 The sender MAY choose the desired MSRP report model (e.g., populate 473 the Success-Report and Failure-Report MSRP header fields). 475 The SEND request MUST contain a top-level wrapper of type 'Message/ 476 CPIM' according to RFC 3862 [RFC3862]. The actual instant message 477 payload MUST be included as payload of the 'Message/CPIM' wrapper and 478 MAY be of any type negotiated in the SDP 'accept-types' attribute 479 according to the MSRP rules. 481 On sending a regular message the sender MUST populate the To header 482 of the Message/CPIM wrapper with the URI of the chat room. The 483 sender SHOULD populate the From header of the Message/CPIM wrapper 484 with a proper identity by which the user is recognized in the 485 conference. Identities that can be used (among others) are: 487 o A SIP URI [RFC3261] representing the participant's address-of- 488 record 490 o A tel URI [RFC3966] representing the participant's telephone 491 number 493 o An IM URI [RFC3860] representing the participant's instant 494 messaging address 496 o An Anonymous URI representing the participant's anonymous address 498 An MSRP switch that receives a SEND request from a participant SHOULD 499 first verify that the From header field of the Message/CPIM wrapper 500 is correctly populated with a valid URI of a participant. This 501 imposes a requirement for the focus of the conference to inform the 502 MSRP switch of the URIs by which the participant is known, in order 503 for the MSRP switch to validate messages. Section 6.3 provides 504 further information with the actions to be taken in case this 505 validation fails. 507 If the MSRP switch receives a message containing several To header 508 fields in the Message/CPIM wrapper the MSRP switch MUST reject the 509 MSRP SEND request with a 403 response, as per procedures in RFC 4975 510 [RFC4975]. 512 Then the MSRP switch should inspect the To header field of the 513 Message/CPIM wrapper. If the To header field of the Message/CPIM 514 wrapper contains the chat room URI and there are no other To header 515 fields, the MSRP switch can generate a copy of the SEND request to 516 each of the participants in the conference except the sender. The 517 MSRP switch MUST NOT modify the content received in the SEND request. 518 However, the MSRP switch MAY re-chunk any of the outbound MSRP SEND 519 requests. 521 Note that the MSRP switch does not need to wait for the reception of 522 the complete MSRP chunk or MSRP message before it starts the 523 distribution to the rest of the participants. Instead, once the MSRP 524 switch has received the headers of the Message/CPIM wrapper it SHOULD 525 start the distribution process. Having the header of the Message/ 526 CPIM wrapper only in the first chunk, the MSRP switch MUST track the 527 Message-Id until the last chunk of the message has been distributed. 529 An MSRP endpoint that receives a SEND request from the MSRP switch 530 containing a Message/CPIM wrapper SHOULD first inspect the To header 531 field of the Message/CPIM wrapper. If the To header field is set to 532 the chat room URI, it should render it as a regular message that has 533 been distributed to all the participants in the conference. Then the 534 MSRP endpoint SHOULD inspect the From header field of the Message/ 535 CPIM wrapper to identify the sender. The From header field will 536 include a URI that identifies the sender. The endpoint might have 537 also received further identity information through a subscription to 538 a conference event package. 540 6.2. Private Messages 542 This section describes the conventions used to send and receive 543 private instant messages, i.e., instant messages that are addressed 544 to one participant of the chat room rather to all of them. A chat 545 room can signal support for private messages using the chatroom- 546 attribute (see Section 8 for details). 548 When a chat room participant wishes to send a private instant message 549 to a participant in the chat room, it follows the same procedures for 550 creating a SEND request as for regular messages (Section 6.1). The 551 only difference is that the MSRP endpoint MUST populate a single To 552 header of the Message/CPIM wrapper with the identity of the intended 553 recipient. The identity can be SIP, TEL, and IM URIs typically 554 learned from the information received in notifications of a 555 conference event package. 557 As for regular messages, an MSRP switch that receives a SEND request 558 from a participant SHOULD first verify that the From header field of 559 the Message/CPIM wrapper is correctly populated with a valid URI 560 (i.e., the URI is a participant of this chat room). Section 6.3 561 provides further information with the actions to be taken in case 562 this validation fails. 564 If the MSRP switch receives a message containing several To header 565 fields in the Message/CPIM wrapper the MSRP switch MUST reject the 566 MSRP SEND request with a 403 response, as per procedures in RFC 4975 567 [RFC4975]. 569 Then the MSRP switch MUST verify that the To header of the Message/ 570 CPIM wrapper is a participant of the chat room. If this To header 571 field does not contain the URI of a participant of the chat room or 572 if the To header field cannot be resolved (e.g., caused by a mistyped 573 URI), the MSRP switch MUST reject the request with a 404 response. 574 This new 404 status code indicates a failure to resolve the recipient 575 URI in the To header field of the Message/CPIM wrapper. 577 Notice the importance of the From and To headers in the Message/ 578 CPIM wrapper. If an intermediary modifies these values, the MSRP 579 switch might not be able to identify the source or intended 580 destination of the message, resulting in a rejection of the 581 message. 583 Finally, the MSRP switch MUST verify that the recipient supports 584 private messages. If the recipient does not support private 585 messages, the MSRP switch MUST reject the request with a 428 586 response. This new response 428 indicates that the recipient does 587 not support private messages. Any potential REPORT request that the 588 MSRP switch sends to the sender MUST include a Message/CPIM wrapper 589 containing the original From header field included in the SEND 590 request and the To header field of the original Message/CPIM wrapper. 591 The MSRP switch MUST NOT forward private messages to a recipient that 592 does not support private messaging. 594 If successful, the MSRP switch should search its mapping table to 595 find the MSRP sessions established towards the recipient. If a match 596 is found the MSRP switch MUST create a SEND request and MUST copy the 597 contents of the sender's message to it. 599 An MSRP endpoint that receives a SEND request from the MSRP switch 600 does the same validations as for regular messages (Section 6.1). If 601 the To header field is different from the chat room URI, the MSRP 602 endpoints knows that this is a private message. The endpoint should 603 render who it is from based on the value of the From header of the 604 Message/CPIM wrapper. The endpoint can also use the sender's 605 nickname, possibly learned via a conference event package, to render 606 such nickname rather than the sender's actual URI. 608 It is possible that a participant, identified by a SIP Address of 609 Record or other valid URI, joins a conference of instant messages 610 from two or more different SIP UAs. It is RECOMMENDED that the MSRP 611 switch can map a URI to two or more MSRP sessions. If the policy of 612 the server allows for this, the MSRP switch MUST copy all messages 613 intended to the recipient through each MSRP session mapped to the 614 recipient's URI. 616 6.3. MSRP reports and responses 618 This section discusses the common procedures for regular and private 619 messages with respect to MSRP reports and responses. Any particular 620 procedure affecting only regular messages or only private messages is 621 discussed in the previous Section 6.1 or Section 6.2, respectively. 623 MSRP switches MUST follow the success report and failure report 624 handling described in section 7 of RFC 4975 [RFC4975], complemented 625 with the procedures described in this section. The MSRP switch MUST 626 act as an MSRP endpoint receiver of the request according to section 627 5.3 of RFC 4975 [RFC4975]. 629 If the MSRP switch receives an MSRP SEND request that does not 630 contain a Message/CPIM wrapper, the MSRP switch MUST reject the 631 request with a 415 response (specified in RFC 4975 [RFC4975]). 633 If the MSRP switch receives an MSRP SEND request where the URI 634 included in the From header field of the Message/CPIM wrapper is not 635 valid, (e.g, because it does not "belong" to the sender of the 636 message or is not a valid participant of the chat room), the MSRP 637 switch MUST reject the request with a 403 response. In non-error 638 cases, the MSRP switch MUST construct responses according to section 639 7.2 of RFC 4975 [RFC4975]. 641 When the MSRP switch forwards a SEND request, it MAY use any report 642 model in the copies intended for the recipients. The receiver 643 reports from the recipients MUST NOT be forwarded to the originator 644 of the original SEND request. This could lead to having the sender 645 receiving multiple reports for a single MSRP request. 647 7. Nicknames 649 A common characteristic of existing chat room services is that 650 participants have the ability to present themselves with a nickname 651 to the rest of the participants of the conference. It is used for 652 easy reference of participants in the chat room, and can also provide 653 anonymous participants with a meaningful descriptive name. 655 A nickname is a useful construct in many use cases, of which MSRP 656 chat is but one example. It is associated with a URI of which the 657 participant is known to the focus. Therefore, if a user joins the 658 chat room under the same URI from multiple devices, he or she may 659 request the same nickname across all these devices. 661 A nickname is a user selectable appearance of which the participant 662 wants to be known to the other participants. It is not a 'display- 663 name', but it is used somewhat like a display name. A main 664 difference is that a nickname is unique inside a chat room to allow 665 an unambiguous reference to a participant in the chat. Nicknames may 666 be long lived, or may be temporary. Users also need to reserve a 667 nickname prior to its utilization. 669 This memo specifies the nickname as a string. The nickname string 670 MUST be unambiguous within the scope of the chat room (conference 671 instance). This scope is similar to having a nickname unique inside 672 a chat room from Extensible Messaging and Presence Protocol 673 [RFC6120]. The chat room may have policies associated with 674 nicknames. It may not accept nickname strings at all, or a it may 675 provide a wider unambiguous scope like a domain or server, similar to 676 Internet Relay Chat (IRC) [RFC2810]. 678 7.1. Using Nicknames within a Conference 680 This memo provides a mechanism to reserve a nickname for a 681 participant for as long as the participant is logged into the chat 682 room. The mechanism is based on a NICKNAME MSRP method (see below) 683 and a new "Use-Nickname" header. Note that other mechanisms may 684 exist (for example, a web page reservation system), although they are 685 outside the scope of this document. 687 A conference participant who has established an MSRP session with the 688 MSRP switch, where the MSRP switch has indicated the support and 689 availability of nicknames with the 'nicknames' token in the 690 'chatroom' SDP attribute, MAY send a NICKNAME request to the MSRP 691 switch. The NICKNAME request MUST include a new Use-Nickname header 692 that contains the nickname string that the participant wants to 693 reserve. MSRP NICKNAME requests MUST NOT include Success-Report or 694 Failure-Report header fields. 696 An MSRP switch that receives a NICKNAME request containing a nickname 697 in the Use-Nickname header field SHOULD first verify whether the 698 policy of the chat room allows the nickname functionality. If not 699 allowed, the MSRP switch MUST reject the request with a 501 response, 700 as per RFC 4975 [RFC4975]. 702 If the policy of the chat room allows the usage of nicknames, the 703 MSRP switch SHOULD validate that the SIP AOR is entitled to reserve 704 the nickname. This may include, e.g., allowing that the 705 participant's URI may use the same nickname when the participant has 706 joined the chat room from different devices under the same URI. The 707 participant's authenticated identity can be derived after a 708 successful SIP Digest Authentication [RFC3261], be included in a 709 trusted SIP P-Asserted-Identity header field [RFC3325], be included 710 in a valid SIP Identity header field [RFC4474], or be derived from 711 any other present or future SIP authentication mechanism. Once the 712 MSRP switch has validated that the participant is entitled to reserve 713 the requested nickname, the MSRP switch MUST answer the NICKNAME 714 request with a 200 response as per regular MSRP procedures. 716 The reservation of a nickname can fail, e.g. if the NICKNAME request 717 contains a malformed or non-existent Use-Nickname header field, or if 718 the same nickname has already been reserved by another participant 719 (i.e., by another URI) in the chat room. The validation can also 720 fail where the sender of the message is not entitled to reserve the 721 nickname. In any of these cases the MSRP switch MUST answer the 722 NICKNAME request with a 423 response. The semantics of the 423 723 response are: "Nickname usage failed; the nickname is not allocated 724 to this user". 726 As indicated earlier, this specification defines a new MSRP header 727 field: "Use-Nickname". The Use-Nickname header field carries a 728 nickname string, and SHOULD be included in the NICKNAME requests. 730 The syntax of the NICKNAME method and the "Use-Nickname" header field 731 is built upon the MSRP formal syntax [RFC4975] 733 ext-method =/ NICKNAMEm 734 NICKNAMEm = %x4E.49.43.4B.4E.41.4D.45 ; NICKNAME in caps 735 ext-header =/ Use-Nickname 736 ; ext-header is specified in RFC 4975 737 Use-Nickname = "Use-Nickname" ":" nickname 738 nickname = quoted-string 740 Once the MSRP switch has reserved a nickname and has bound it to a 741 URI (e.g., a SIP Address-of-Record), the MSRP server MAY allow the 742 usage of the same nickname by the same user (identified by the same 743 URI, such as a SIP AoR) over a second MSRP session. This might be 744 the case if the user joins the same chat room from a different SIP 745 User Agent. In this case, the user MAY request the same or a 746 different nickname than that used in conjunction with the first MSRP 747 session; the MSRP server MAY accept the usage of the same nickname by 748 the same user. The MSRP switch MUST NOT automatically assign the 749 same nickname to more than one MSRP session established from the same 750 URI, because this can create confusion to the user as whether the 751 same nickname is bound to the second MSRP session. 753 7.2. Modifying a Nickname 755 Typically a participant will reserve a nickname as soon as the 756 participant joins the chat room. But it is also possible for a 757 participant to modify his/her own nickname and replace it with a new 758 one at any time during the duration of the MSRP session. 759 Modification of the nickname is not different from the initial 760 reservation and usage of a nickname, thus the NICKNAME method is used 761 as described in Section 7.1. 763 If a NICKNAME request that attempts to modify the current nickname of 764 the user for some reason fails, the current nickname stays in effect. 765 A new nickname comes into effect and the old one is released only 766 after a NICKNAME request is accepted with a 200 response. 768 7.3. Removing a Nickname 770 If the participant no longer wants to be known by a nickname in the 771 conference, the participant can follow the method described in 772 Section 7.2. The nickname element of the Use-Nickname header MUST be 773 set to an empty quoted string. 775 7.4. Nicknames in Conference Event Packages 777 Typically the conference focus acts as a notifier of the conference 778 event package. To notify subscribers of the nickname reserved for a 779 given participant, it is RECOMMENDED that conference focus and 780 endpoints support Conference Event Package Data Format Extension for 781 Centralized Conferencing [I-D.ietf-xcon-event-package]. The 782 Conference Information Data Model for Centralized Conferencing 783 [I-D.ietf-xcon-common-data-model] extends the user element from RFC 784 4575 [RFC4575] with a nickname attribute. 786 8. The SDP 'chatroom' attribute 788 There are a handful of use cases where a participant would like to 789 learn the chat room capabilities supported by the MSRP switch and the 790 chat room. For example, a participant would like to learn if the 791 MSRP switch supports private messaging, otherwise, the participant 792 may send what he believes is a private instant message addressed to a 793 participant, but since the MSRP switch does not support the functions 794 specified in this memo, the message gets eventually distributed to 795 all the participants of the chat room. 797 The reverse case also exists. A participant, say Alice, whose user 798 agent does not support the extensions defined by this document joins 799 the chat room. The MSRP switch learns that Alice's application does 800 not support private messaging nor nicknames. If another participant, 801 say Bob, sends a private message to Alice, the MSRP switch does not 802 distribute it to Alice, because Alice is not able to differentiate it 803 from a regular message sent to the whole roster. Furthermore, if 804 Alice replied to this message, she would do it to the whole roster. 805 Because of this, the MSRP switch also keeps track of users who do not 806 support the extensions defined in this document. 808 In another scenario, the policy of a chat room may indicate that 809 certain functions are not allowed. For example, the policy may 810 indicate that nicknames or private messages are not allowed. 812 In order to provide the user with a good chat room experience, we 813 define a new 'chatroom' SDP attribute. The 'chatroom' attribute is a 814 media-level value attribute [RFC4566] that MAY be included in 815 conjunction with an MSRP media stream (i.e., when an m= line in SDP 816 indicates "TCP/MSRP" or "TCP/TLS/MSRP"). The 'chatroom' attribute 817 indicates the intersection of support and chat room local policy 818 allowance for a number of functions specified in this document. 819 Specifically, we provide the means for indicating support to use 820 nicknames and private messaging. 822 The 'chatroom' SDP attribute has the following Augmented BNF (ABNF) 823 [RFC5234] syntax: 825 attribute /= chatroom-attr 826 chatroom-attr = chatroom-label ":" chat-token *(SP chat-token) 827 chatroom-label = "chatroom" 828 chat-token = (nicknames-token | private-msg-token | 829 ext-token) 830 nicknames-token = "nickname" 831 private-msg-token = "private-messages" 832 ext-token = private-token | standard-token 833 private-token = toplabel "." *(domainlabel ".") token 834 ; toplabel defined in RFC 3261 835 ; domainlabel defined in RFC 3261 836 ; token defined in RFC 3261 837 standard-token = token 839 A given 'chat-token' value MUST NOT appear more than once in a 840 'chatroom' attribute. 842 A conference focus that includes the 'nicknames' token in the session 843 description is signaling that the MSRP switch supports and the chat 844 room allows to use the procedures specified in Section 7. A 845 conference focus that includes the 'private-messages' in the SDP 846 description is signaling that the MSRP switch supports and the chat 847 room allows to use the procedures specified in Section 6.2. 849 Example of the 'chatroom' attribute for an MSRP media stream that 850 indicates the acceptance of nicknames and private messages: 852 a=chatroom:nickname private-messages 854 The 'chatroom' attribute allows extensibility with the addition of 855 new tokens. No IANA registry is provided at this time, since no 856 extensions are expected at the time of this writing. Extensions to 857 the 'chatroom' attribute can be defined in IETF documents or as 858 private vendor extensions. 860 Extensions defined in IETF document MUST follow the 'standard-token' 861 ABNF previously defined. In this type of extensions, are must be 862 taken in the selection of the token to avoid a clash with any of the 863 tokens previously defined. 865 Private extensions MUST follow the 'private-token' ABNF previously 866 defined. The 'private-token' MUST include the DNS name of the vendor 867 in reverse order in the token, in order to avoid clashes of tokens. 868 The following is an example of a "chat.foo" extension by vendor 869 "example.com" 871 a=chatroom:nickname private-messages com.example.chat.foo 873 9. Examples 875 9.1. Joining a chat room 877 Figure 3 presents a flow diagram where Alice joins a chat room by 878 sending an INVITE request. This INVITE request contains a session 879 description that includes the chatroom extensions defined in this 880 document. 882 Alice Conference focus 883 | | 884 |F1: (SIP) INVITE | 885 |----------------------->| 886 |F2: (SIP) 200 OK | 887 |<-----------------------| 888 |F3: (SIP) ACK | 889 |----------------------->| 890 | | 892 Figure 3: Flow diagram of a user joining a chat room 894 F1: Alice constructs an SDP description that includes an MSRP media 895 stream. She also indicates her support for the chatroom extensions 896 defined in this document. She sends the INVITE request to the chat 897 room server. 899 INVITE sip:chatroom22@chat.example.com SIP/2.0 900 Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 901 Max-Forwards: 70 902 From: Alice ;tag=9fxced76sl 903 To: Chatroom 22 904 Call-ID: 3848276298220188511@atlanta.example.com 905 CSeq: 1 INVITE 906 Contact: 907 Content-Type: application/sdp 908 Content-Length: 290 910 v=0 911 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com 912 s=- 913 c=IN IP4 client.atlanta.example.com 914 m=message 7654 TCP/MSRP * 915 a=accept-types:message/cpim text/plain text/html 916 a=path:msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 917 a=chatroom:nickname private-messages 919 F2: The chat room server accepts the session establishment. It 920 includes the 'isfocus' and other relevant feature tags in the Contact 921 header field of the response. The chat room server also builds an 922 SDP answer that forces the reception of messages wrapped in Message/ 923 CPIM wrappers. It also includes the chatroom attribute with the 924 allowed extensions. 926 SIP/2.0 200 OK 927 Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 928 ;received=192.0.2.101 929 From: Alice ;tag=9fxced76sl 930 To: Chatroom 22 ;tag=8321234356 931 Call-ID: 3848276298220188511@atlanta.example.com 932 CSeq: 1 INVITE 933 Contact: \ 934 ;methods="INVITE,BYE,OPTIONS,ACK,CANCEL,SUBSCRIBE,NOTIFY" \ 935 ;automata;isfocus;message;event="conference" 936 Content-Type: application/sdp 937 Content-Length: 290 939 v=0 940 o=chat 2890844527 2890844527 IN IP4 chat.example.com 941 s=- 942 c=IN IP4 chat.example.com 943 m=message 12763 TCP/MSRP * 944 a=accept-types:message/cpim 945 a=accept-wrapped-types:text/plain text/html * 946 a=path:msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 947 a=chatroom:nickname private-messages 949 F3: The session established is acknowledged (details not shown). 951 9.2. Setting up a nickname 953 Figure 4 shows an example of Alice setting up a nickname using the 954 conference as provider. Her first proposal is not accepted because 955 that proposed nickname is already in use. Then, she makes a second 956 proposal with a new nickname. This second proposal is accepted. 958 Alice MSRP switch 959 | | 960 |F1: (MSRP) NICKNAME | 961 |----------------------->| 962 |F2: (MSRP) 423 | 963 |<-----------------------| 964 |F3: (MSRP) NICKNAME | 965 |----------------------->| 966 |F4: (MSRP) 200 | 967 |<-----------------------| 968 | | 970 Figure 4: Flow diagram of a user setting up her nickname 972 F1: Alice sends an MSRP NICKNAME request that contains her proposed 973 nicknames in the Use-Nickname header field. 975 MSRP d93kswow NICKNAME 976 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 977 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 978 Use-Nickname: "Alice the great" 979 -------d93kswow$ 981 F2: The MSRP switch analyzes the existing allocation of nicknames and 982 detects that the nickname "Alice the great" is already provided to 983 another participant in the chat room. The MSRP switch answers with a 984 423 response. 986 MSRP d93kswow 423 Nickname usage failed 987 To-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 988 From-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 989 -------d93kswow$ 991 F3: Alice receives the response. She proposes a new nickname in a 992 second NICKNAME request. 994 MSRP 09swk2d NICKNAME 995 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 996 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 997 Use-Nickname: "Alice in Wonderland" 998 -------09swk2d$ 1000 F4: The MSRP switch accepts the nickname proposal and answers with a 1001 200 response. 1003 MSRP 09swk2d 200 OK 1004 To-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1005 From-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1006 -------09swk2d$ 1008 9.3. Sending a regular message to the chat room 1010 Figure 5 depicts a flow diagram where Alice is sending a regular 1011 message addressed to the chat room. The MSRP switch distributes the 1012 message to the rest of the participants. 1014 Alice MSRP switch Bob Charlie 1015 | | | | 1016 | F1: (MSRP) SEND | | | 1017 |--------------------->| F3: (MSRP) SEND | | 1018 | F2: (MSRP) 200 |----------------------->| | 1019 |<---------------------| F4: (MSRP) SEND | | 1020 | |------------------------------->| 1021 | | F5: (MSRP) 200 OK | | 1022 | |<-----------------------| | 1023 | | F6: (MSRP) 200 OK | | 1024 | |<------------------------------ | 1025 | | | | 1026 | | | | 1028 Figure 5: Sending a regular message to the chat room 1030 F1: Alice builds a text message and wraps it in a Message/CPIM 1031 wrapper. She addresses the message to the chat room. She encloses 1032 the resulting Message/CPIM wrapper in an MSRP SEND request and sends 1033 it to the MSRP switch via the existing TCP connection. 1035 MSRP 3490visdm SEND 1036 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1037 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1038 Message-ID: 99s9s2 1039 Byte-Range: 1-*/* 1040 Content-Type: message/cpim 1042 To: 1043 From: 1044 DateTime: 2009-03-02T15:02:31-03:00 1045 Content-Type: text/plain 1047 Hello guys, how are you today? 1048 -------3490visdm$ 1050 F2: The MSRP switch acknowledges the reception of the SEND request 1051 with a 200 (OK) response. 1053 MSRP 3490visdm 200 OK 1054 To-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1055 From-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1056 Message-ID: 99s9s2 1057 -------3490visdm$ 1059 F3: The MSRP switch creates a new MSRP SEND request that contains the 1060 received Message/CPIM wrapper and sends it to Bob. 1062 MSRP 490ej23 SEND 1063 To-Path: msrp://client.biloxi.example.com:4923/49dufdje2;tcp 1064 From-Path: msrp://chat.example.com:5678/jofofo3;tcp 1065 Message-ID: 304sse2 1066 Byte-Range: 1-*/* 1067 Content-Type: message/cpim 1069 To: 1070 From: 1071 DateTime: 2009-03-02T15:02:31-03:00 1072 Content-Type: text/plain 1074 Hello guys, how are you today? 1075 -------490ej23$ 1077 Since the received message is addressed to the chat room URI in the 1078 From header of the Message/CPIM header, Bob knows that this is a 1079 regular message distributed all participants in the chat room, rather 1080 that a private message addressed to him. 1082 The rest of the message flows are analogous to the previous. They 1083 are not shown here. 1085 9.4. Sending a private message to a participant 1087 Figure 6 depicts a flow diagram where Alice is sending a private 1088 message addressed to Bob's SIP AOR. The MSRP switch distributes the 1089 message only to Bob. 1091 Alice MSRP switch Bob 1092 | | | 1093 | F1: (MSRP) SEND | | 1094 |--------------------->| F3: (MSRP) SEND | 1095 | F2: (MSRP) 200 |----------------------->| 1096 |<---------------------| F4: (MSRP) 200 | 1097 | |<-----------------------| 1098 | | | 1100 Figure 6: Sending a private message to Bob 1102 F1: Alice builds a text message and wraps it in a Message/CPIM 1103 wrapper. She addresses the message to Bob's URI, which she learned 1104 from a notification in the conference event package. She encloses 1105 the resulting Message/CPIM wrapper in an MSRP SEND request and sends 1106 it to the MSRP switch via the existing TCP connection. 1108 MSRP 6959ssdf SEND 1109 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1110 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1111 Message-ID: okj3kw 1112 Byte-Range: 1-*/* 1113 Content-Type: message/cpim 1115 To: 1116 From: 1117 DateTime: 2009-03-02T15:02:31-03:00 1118 Content-Type: text/plain 1120 Hello Bob. 1121 -------6959ssdf$ 1123 F2: The MSRP switch acknowledges the reception of the SEND request 1124 with a 200 (OK) response. 1126 MSRP 6959ssdfm 200 OK 1127 To-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1128 From-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1129 Message-ID: okj3kw 1130 -------6959ssdfm$ 1132 F3: The MSRP switch creates a new MSRP SEND request that contains the 1133 received Message/CPIM wrapper and sends it only to Bob. Bob can 1134 distinguish the sender in the From header of the Message/CPIM 1135 wrapper. He also identifies this as a private message due to the 1136 presence of his own SIP AOR in the To header field of the Message/ 1137 CPIM wrapper. 1139 MSRP 9v9s2 SEND 1140 To-Path: msrp://client.biloxi.example.com:4923/49dufdje2;tcp 1141 From-Path: msrp://chat.example.com:5678/jofofo3;tcp 1142 Message-ID: d9fghe982 1143 Byte-Range: 1-*/* 1144 Content-Type: message/cpim 1146 To: 1147 From: 1148 DateTime: 2009-03-02T15:02:31-03:00 1149 Content-Type: text/plain 1151 Hello Bob. 1152 -------9v9s2$ 1154 F4: Bob acknowledges the reception of the SEND request with a 200 1155 (OK) response. 1157 MSRP 9v9s2 200 OK 1158 To-Path: msrp://chat.example.com:5678/jofofo3;tcp 1159 From-Path: msrp://client.biloxi.example.com:4923/49dufdje2;tcp 1160 Message-ID: d9fghe982 1161 -------9v9s2$ 1163 9.5. Chunked private message 1165 The MSRP message below depicts the example of the same private 1166 message described in Section 9.4, but now the message is split in two 1167 chunks. The MSRP switch must wait for the complete set of Message/ 1168 CPIM headers before distributing the messages. 1170 MSRP 7443ruls SEND 1171 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1172 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1173 Message-ID: aft4to 1174 Byte-Range: 1-*/174 1175 Content-Type: message/cpim 1177 To: 1178 From: 1179 -------7443ruls$ 1181 MSRP 7443ruls SEND 1182 To-Path: msrp://chat.example.com:12763/kjhd37s2s20w2a;tcp 1183 From-Path: msrp://client.atlanta.example.com:7654/jshA7weztas;tcp 1184 Message-ID: aft4to 1185 Byte-Range: 68-174/174 1186 Content-Type: message/cpim 1188 DateTime: 2009-03-02T15:02:31-03:00 1189 Content-Type: text/plain 1191 Hello Bob 1192 -------7443ruls$ 1194 9.6. Nickname in a conference information document 1196 Figure 7 depicts two user elements in a conference information 1197 document both having the nickname element with a nickname string. 1199 1200 1204 1207 1208 MSRP nickname example 1209 1210 1213 1214 2 1215 1216 1219 1220 1221 Dopey Donkey 1222 1223 1226 1227 Alice the great 1228 1229 1230 1232 Figure 7: Nickname in a conference information document 1234 10. IANA Considerations 1236 10.1. New MSRP Method 1238 This specification defines a new MSRP method to be added to the 1239 Methods sub-registry of the Message Session Relay Protocol (MSRP) 1240 Parameters registry: 1242 NICKNAME 1244 See section Section 7 for details. 1246 10.2. New MSRP Header 1248 This specification defines a new MSRP header to be added to the 1249 Header Field sub-registry of the Message Session Relay Protocol 1250 (MSRP) Parameters registry: 1252 Use-Nickname 1254 See Section 7 for details. 1256 10.3. New MSRP Status Codes 1258 This specification defines three new MSRP status codes to be added to 1259 the Status-Code sub-registry of the Message Session Relay Protocol 1260 (MSRP) parameters registry. 1262 The 404 status code indicates the failure to resolve the recipient 1263 URI in the To header field of the Message/CPIM wrapper in the SEND 1264 request, e.g, due to an unknown recipient. See Section 6.2 for 1265 details. 1267 The 423 response indicates a failure in allocating the requested 1268 NICKNAME. This can be caused by a malformed NICKNAME request (e.g., 1269 no Use-Nickname header field), an already allocated nickname, or a 1270 policy that prevents the sender to use nicknames. See Section 7 for 1271 details. 1273 The 428 status code indicates that the recipient of a SEND request 1274 does not support private messages. See Section 6.2 for details. 1276 Table 1 summarizes the IANA registration data with respect to new 1277 MSRP status codes: 1279 +-------+---------------------------------------+-----------+ 1280 | Value | Description | Reference | 1281 +-------+---------------------------------------+-----------+ 1282 | 404 | Failure to resolve recipient's URI | RFC XXXX | 1283 | 423 | Unable to allocate requested nickname | RFC XXXX | 1284 | 428 | Private messages not supported | RFC XXXX | 1285 +-------+---------------------------------------+-----------+ 1287 Table 1: New status codes 1289 10.4. New SDP Attribute 1291 This specification defines a new media-level attribute in the Session 1292 Description Protocol (SDP) Parameters registry. The registration 1293 data is as follows: 1295 Contact: Miguel Garcia 1297 Phone: +34 91 339 1000 1299 Attribute name: chatroom 1301 Long-form attribute name: Chat Room 1303 Type of attribute: media level only 1305 This attribute is not subject to the charset attribute 1307 Description: This attribute identifies support and local policy 1308 allowance for a number of chat room related functions 1310 Specification: RFC XXXX 1312 See section Section 8 for details. 1314 11. Security Considerations 1316 This document proposes extensions to the Message Session Relay 1317 Protocol [RFC4975]. Therefore, the security considerations of that 1318 document apply to this document as well. 1320 If the participant's SIP user agent doesn't understand the "isfocus" 1321 feature tag [RFC3840], it will not know that it is connected to a 1322 conference instance. The participant might not be notified that the 1323 participant's MSRP client will try to send messages to the MSRP 1324 switch having potentially multiple recipients. If the participant's 1325 MSRP client doesn't support the extensions of this specification, it 1326 is unlikely that it will try to send a message using 'Message/CPIM' 1327 wrapper content type [RFC3862], and the MSRP switch will reject the 1328 request with a 415 response [RFC4975]. Still if a participant's MSRP 1329 client does create a message with a valid 'Message/CPIM' wrapper 1330 content type [RFC3862] having the To header set to the URI of the 1331 chat room and the From header set to the URI of which the participant 1332 is known to the conference, the participant might be unaware that the 1333 message can be forwarded to multiple recipients. Equally if the To 1334 header is set to a valid URI of a recipient known to the conference, 1335 the message can be forwarded as a private message without the 1336 participant knowing. 1338 If a participant wants to avoid eavesdropping, the participant's MSRP 1339 client can send the messages over a TLS [RFC5246] transport 1340 connection, as allowed by MSRP. It's up to the policy of the MSRP 1341 switch if the messages are forwarded to the other participant's in 1342 the chat room using TLS [RFC5246] transport. 1344 Nicknames will be used to show the appearances of the participants of 1345 the conference. A successful take over of a nickname from a 1346 participant might lead to private messages to be sent to the wrong 1347 destination. The recipient's URI will be different from the URI 1348 associated to the original owner of the nickname, but the sender 1349 might not notice this. To avoid takeovers the MSRP switch MUST make 1350 sure that a nickname is unique inside a chat room. Also the security 1351 consideration for any authenticated identity mechanisms used to 1352 validate the SIP AOR will apply to this document as well. If a 1353 nickname can be reserved if it previously has been used by another 1354 participant in the chat room, is up to the policy of the chat room. 1356 12. Contributors 1358 This work would have never been possible without the fruitful 1359 discussions in the SIMPLE WG mailing list, specially with Brian Rosen 1360 (Neustar) and Paul Kyzivat (Cisco), who provided extensive review and 1361 improvements throughout the document. 1363 13. Acknowledgments 1365 The authors want to thank Eva Leppanen, Adamu Haruna, Adam Roach, 1366 Matt Lepinski, Mary Barnes, Ben Campbell, Paul Kyzivat, Adrian 1367 Georgescu, Nancy Greene, and Flemming Andreasen for providing 1368 comments. 1370 14. References 1372 14.1. Normative References 1374 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1375 Requirement Levels", BCP 14, RFC 2119, March 1997. 1377 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1378 A., Peterson, J., Sparks, R., Handley, M., and E. 1379 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1380 June 2002. 1382 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 1383 with Session Description Protocol (SDP)", RFC 3264, 1384 June 2002. 1386 [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, 1387 "Indicating User Agent Capabilities in the Session 1388 Initiation Protocol (SIP)", RFC 3840, August 2004. 1390 [RFC3860] Peterson, J., "Common Profile for Instant Messaging 1391 (CPIM)", RFC 3860, August 2004. 1393 [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant 1394 Messaging (CPIM): Message Format", RFC 3862, August 2004. 1396 [RFC4353] Rosenberg, J., "A Framework for Conferencing with the 1397 Session Initiation Protocol (SIP)", RFC 4353, 1398 February 2006. 1400 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 1401 Description Protocol", RFC 4566, July 2006. 1403 [RFC4575] Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session 1404 Initiation Protocol (SIP) Event Package for Conference 1405 State", RFC 4575, August 2006. 1407 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message 1408 Session Relay Protocol (MSRP)", RFC 4975, September 2007. 1410 [RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions 1411 for the Message Sessions Relay Protocol (MSRP)", RFC 4976, 1412 September 2007. 1414 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1415 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1417 [RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for 1418 Centralized Conferencing", RFC 5239, June 2008. 1420 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1421 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 1423 [I-D.ietf-xcon-common-data-model] 1424 Novo, O., Camarillo, G., Morgan, D., and J. Urpalainen, 1425 "Conference Information Data Model for Centralized 1426 Conferencing (XCON)", draft-ietf-xcon-common-data-model-32 1427 (work in progress), September 2011. 1429 [I-D.ietf-xcon-event-package] 1430 Camarillo, G., Srinivasan, S., Even, R., and J. 1431 Urpalainen, "Conference Event Package Data Format 1432 Extension for Centralized Conferencing (XCON)", 1433 draft-ietf-xcon-event-package-01 (work in progress), 1434 September 2008. 1436 14.2. Informative References 1438 [RFC2810] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810, 1439 April 2000. 1441 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 1442 Extensions to the Session Initiation Protocol (SIP) for 1443 Asserted Identity within Trusted Networks", RFC 3325, 1444 November 2002. 1446 [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", 1447 RFC 3966, December 2004. 1449 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 1450 Authenticated Identity Management in the Session 1451 Initiation Protocol (SIP)", RFC 4474, August 2006. 1453 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 1454 Protocol (XMPP): Core", RFC 6120, March 2011. 1456 Authors' Addresses 1458 Aki Niemi 1459 Nokia 1460 P.O. Box 407 1461 NOKIA GROUP, FIN 00045 1462 Finland 1464 Phone: +358 50 389 1644 1465 Email: aki.niemi@nokia.com 1467 Miguel A. Garcia-Martin 1468 Ericsson 1469 Calle Via de los Poblados 13 1470 Madrid, ES 28033 1471 Spain 1473 Email: miguel.a.garcia@ericsson.com 1474 Geir A. Sandbakken (editor) 1475 Cisco Systems 1476 Philip Pedersens vei 20 1477 N-1366 Lysaker 1478 Norway 1480 Phone: +47 67 125 125 1481 Email: geirsand@cisco.com 1482 URI: http://www.cisco.com