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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 FECFRAME Working Group Rajiv Asati 2 Internet Draft Cisco Systems 3 Intended status: Informational 4 Expires: July 2012 6 February 21, 2012 8 Methods to convey FEC Framework Configuration Information 9 draft-ietf-fecframe-config-signaling-07.txt 11 Abstract 13 FEC Framework document [RFC6363] defines the FEC Framework 14 Configuration Information necessary for the FEC framework operation. 15 This document describes using existing signaling protocols such as 16 Session Announcement Protocol (SAP), Session Initiation Protocol 17 (SIP), Real Time Stream Protocol (RTSP) etc. to determine and 18 dynamically communicate the Configuration information between 19 sender(s) and receiver(s). 21 Status of this Memo 23 This Internet-Draft is submitted to IETF in full conformance with 24 the provisions of BCP 78 and BCP 79. This document may contain 25 material from IETF Documents or IETF Contributions published or made 26 publicly available before November 10, 2008. The person(s) 27 controlling the copyright in some of this material may not have 28 granted the IETF Trust the right to allow modifications of such 29 material outside the IETF Standards Process. Without obtaining an 30 adequate license from the person(s) controlling the copyright in 31 such materials, this document may not be modified outside the IETF 32 Standards Process, and derivative works of it may not be created 33 outside the IETF Standards Process, except to format it for 34 publication as an RFC or to translate it into languages other than 35 English. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF), its areas, and its working groups. Note that 39 other groups may also distribute working documents as Internet- 40 Drafts. 42 Internet-Drafts are draft documents valid for a maximum of six 43 months and may be updated, replaced, or obsoleted by other documents 44 at any time. It is inappropriate to use Internet-Drafts as 45 reference material or to cite them other than as "work in progress." 47 The list of current Internet-Drafts can be accessed at 48 http://www.ietf.org/ietf/1id-abstracts.txt 50 The list of Internet-Draft Shadow Directories can be accessed at 51 http://www.ietf.org/shadow.html 53 This Internet-Draft will expire on July 21, 2012. 55 Copyright Notice 57 Copyright (c) 2011 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with 65 respect to this document. Code Components extracted from this 66 document must include Simplified BSD License text as described in 67 Section 4.e of the Trust Legal Provisions and are provided without 68 warranty as described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction...................................................3 73 2. Specification Language.........................................3 74 3. Terminology/Abbreviations......................................4 75 4. FEC Framework Configuration Information........................4 76 4.1. Encoding Format...........................................6 77 5. Signaling Protocol Usage.......................................6 78 5.1. Signaling Protocol for Multicasting.......................7 79 5.1.1. Sender Procedure.....................................9 80 5.1.2. Receiver Procedure..................................12 81 5.2. Signaling Protocol for Unicasting........................13 82 5.2.1. SIP.................................................13 83 5.2.2. RTSP................................................14 84 6. Security Considerations.......................................15 85 7. IANA Considerations...........................................15 86 8. Acknowledgments...............................................15 87 9. References....................................................16 88 9.1. Normative References.....................................16 89 9.2. Informative References...................................16 90 Author's Addresses...............................................17 92 1. Introduction 94 FEC Framework document [RFC6363] defines the FEC Framework 95 Configuration Information that governs the overall FEC framework 96 operation common to any FEC scheme. This information must be 97 available at both sender and reciever(s). 99 This document describes how various signaling protocols such as 100 Session Announcement Protocol (SAP)[RFC2974], Session Initiation 101 Protocol (SIP)[RFC3261], Real Time Stream Protocol (RTSP)[RFC2326] 102 etc. could be used by the FEC scheme (and/or Content Delivery 103 Protocol (CDP))to communicate the Configuration information between 104 sender and receiver(s). The configuration information may be encoded 105 in any compatible format such as SDP [RFC4566], XML etc., though 106 this document references to SDP encoding usage quite extensively. 108 This document doesn't describe any FEC scheme specific information 109 (FSSI) (for example, how source blocks are constructed) or any 110 sender or receiver side operation for a particular FEC scheme (for 111 example, whether the receiver makes use of one or more repair flows 112 that are received). Such FEC scheme specifics should be covered in 113 separate document(s). This document doesn't mandate a particular 114 encoding format for the configuration information either. 116 This document is structured such that Section 2 describes the terms 117 used in this document, section 4 describes the FEC Framework 118 Configuration Information, section 5 describes how to use signaling 119 protocol for the multicast and unicast applications, and section 6 120 describes security consideration. 122 2. Specification Language 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 126 document are to be interpreted as described in [RFC2119]. 128 3. Terminology/Abbreviations 130 This document makes use of the terms/abbreviations defined in the 131 FEC Framework document [RFC6363] and defines the following 132 additional terms: 134 o Media Sender - Node providing original media flow(s) to the 135 'FEC Sender' 137 o Media Receiver - Node performing the Media decoding; 139 o FEC Sender - Node performing the FEC encoding on the 140 original media flow(s) to produce the FEC repair flow(s) 142 o FEC Receiver - Node performing the FEC decoding, as needed, 143 and providing the original media flow(s) to the Media receiver. 145 o Sender - Same as FEC Sender 147 o Receiver - Same as FEC Receiver 149 o (Media) Flow - A single media instance i.e., an audio stream 150 or a video stream. 152 This document deliberately refers to the 'FEC Sender' and 'FEC 153 Receiver' as the 'Sender' and 'Receiver' respectively. 155 4. FEC Framework Configuration Information 157 The FEC Framework [RFC6363] defines a minimum set of information 158 that is communicated between the sender and receiver(s) for a proper 159 operation of an FEC scheme. This information is referred to as "FEC 160 Framework Configuration Information". This is the information that 161 the FEC Framework needs in order to apply FEC protection to the 162 transport flows. 164 A single instance of the FEC Framework provides FEC protection for 165 all packets of a specified set of source packet flows, by means of 166 one or more packet flows consisting of repair packets. As per the 167 FEC Framework document [RFC6363] section 6.5, the FEC Framework 168 Configuration Information includes the following for each FEC 169 Framework instance: 171 1. Identification of the repair flow(s) 173 2. Identification of Source Flow(s) 175 3. Identification of FEC Scheme 177 4. Length of Explicit Source FEC payload ID 179 5. FEC Scheme Specific Information (FSSI) 181 FSSI basically provides an opaque container to encode FEC scheme 182 specific configuration information such as buffer size, decoding 183 wait-time etc. Please refer to the FEC Framework document [RFC6363] 184 for more details. 186 The usage of signaling protocols described in this document requires 187 that the application layer responsible for the FEC Framework 188 instance provide the value for each of the configuration information 189 parameter (listed above) encoded as per the chosen encoding format. 190 In case of failure to receive the complete information, the 191 signaling protocol module must return an error for the Operation, 192 Administration and Maintenance (OAM) purposes and optionally convey 193 this error to the application layer. Please refer to the figure 1 of 194 the FEC Framework document [RFC6363] for further illustration. 196 This document does not make any assumption that the 'FEC sender' and 197 'Media Sender' functionalities are implemented on the same device, 198 though that may be the case. Similarly, this document does not make 199 any assumption that 'FEC receiver' and 'Media Receiver' 200 functionalities are implemented on the same device, though that may 201 be the case. There may also be more than one Media Sender. 203 4.1. Encoding Format 205 The FEC Framework Configuration Information (listed above in section 206 4) may be encoded in any format such as SDP, XML etc. as chosen or 207 prefered by a particular FEC Framework instance. The selection of 208 such encoding format or syntax is independent of the signaling 209 protocol and beyond the scope of this document. 211 Whatever encoding format is selected for a particular FEC framework 212 instance, it must be known to the signaling protocol. This is to 213 provide a means (e.g. a field such as Payload Type) in the signaling 214 protocol message(s) to convey the chosen encoding format for the 215 configuration information so that the Payload i.e., configuration 216 information can be correctly parsed as per the semantics of the 217 chosen encoding format at the receiver. Please note that the 218 encoding format is not a negotiated parameter, but rather a property 219 of a particular FEC Framework instance and/or its implementation. 221 Additionally, the encoding format for each FEC Framework 222 configuration parameter must be defined in terms of a sequence of 223 octets that can be embedded within the payload of the signaling 224 protocol message(s). The length of the encoding format must either 225 be fixed, or derived by examining the encoded octets themselves. 226 For example, the initial octets may include some kind of length 227 indication. 229 Independent of the encoding formats supported by an FEC scheme, each 230 instance of the FEC Framework must use a single encoding format to 231 describe all of the configuration information associated with that 232 instance. The signaling protocol specified in this document should 233 not validate the encoded information, though it may validate the 234 syntax or length of the encoded information. 236 The reader may refer to the SDP elements document [RFC6364], which 237 describes the usage of 'SDP' encoding format as an example encoding 238 format for FEC Framework Configuration Information. 240 5. Signaling Protocol Usage 242 FEC Framework [RFC6363] requires certain FEC Framework Configuration 243 Information to be available to both sender and receiver(s). This 244 configuration information is almost always formulated at the sender 245 (or on behalf of a sender), and somehow made available at the 246 receiver(s). While one may envision a static method to populate the 247 configuration information at both sender and receiver(s), it would 248 not be optimal since it would (a) require the knowledge of every 249 receiver in advance, (b) require the time and means to configure 250 each receiver and sender, and (c) increase the misconfiguration 251 possibility. Hence, there is a benefit in using a dynamic method 252 i.e., signaling protocol to convey the configuration information 253 between sender and one or more receivers. 255 Since the configuration information may be needed at a particular 256 receiver versus many receivers (depending on the multimedia stream 257 being unicast e.g. Video on Demand, or multicast e.g. Broadcast or 258 IPTV), we need two types of signaling protocols - one to deliver the 259 configuration information to many receivers via multicasting 260 (described in section 5.1), and the other to deliver the 261 configuration information to one and only one receiver via 262 unicasting (described in section 5.2). 264 Figure 1 below illustrates a sample topology showing the FEC sender 265 and FEC receiver (that may or may not be the Media Sender and Media 266 Receiver respectively) such that FEC_Sender1 is serving 267 FEC_Receiver11,12,13 via the multicast signaling protocol, whereas 268 the FEC_Sender2 is serving only FEC_Receiver2 via the unicast 269 signaling protocol. 271 FEC_Sender2---------| |--------FEC_Receiver2 272 | | 273 FEC_Sender1-------IP/MPLS network 274 |-----------FEC_Receiver11 275 |-----------FEC_Receiver12 276 |-----------FEC_Receiver13 278 Figure 1 Topology using Sender and Receiver 280 The rest of the document continues to use the terms 'Sender' and 281 'Receiver' to refer to the 'FEC Sender' and 'FEC Receiver' 282 respectively. 284 5.1. Signaling Protocol for Multicasting 286 This specification describes using Session Announcement Protocol 287 (SAP) version 2 [RFC2974] as the signaling protocol to multicast the 288 configuration information from one sender to many receivers. The 289 apparent advantage is that the server doesn't need to maintain any 290 state for any receiver using SAP. 292 SAP messages are carried over UDP over IP with destination UDP 293 port being 9875 and source UDP port being any available number, 294 as described in RFC2974. The SAP message(s) should contain an 295 authentication header using PGP authentication. 297 At the high level, a sender, acting as the SAP announcer, signals 298 the FEC Framework Configuration Information for each FEC Framework 299 instance available at the sender, using the SAP message(s). The 300 configuration information, encoded in a suitable format as per the 301 section 4.1, is carried in the Payload of the SAP message(s). A 302 receiver, acting as the SAP listener, listens on a well-known UDP 303 port and at least one well known multicast group IP address (as 304 explained in the section 5.1.1). This enables the receiver to 305 receive the SAP message(s) and obtains the FEC Framework 306 Configuration Information for each FEC Framework Instance. 308 Using the configuration information, the receiver becomes aware of 309 available FEC protection options, corresponding multicast trees (S,G 310 or *,G addresses) etc. The receiver may subsequently subscribe to 311 one or more multicast trees to receive the FEC streams using out-of- 312 band multicasting techniques such as PIM [RFC4601]. This, however, 313 is outside the scope of this document. 315 Figure 2 below illustrates the SAP packet format (it is reprinted 316 from the RFC2974) - 317 0 1 2 3 318 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 1 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | V=1 |A|R|T|E|C| auth len | msg id hash | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | | 323 : originating source (32 or 128 bits) : 324 : : 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | optional authentication data | 327 : .... : 328 *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* 329 | optional payload type | 330 + +-+- - - - - - - - - -+ 331 | |0| | 332 + - - - - - - - - - - - - - - - - - - - - +-+ | 333 | | 334 : payload : 335 | | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 338 Figure 2 SAP Message format 340 While the RFC2974 includes explanation for each field, it is worth 341 discussing the 'Payload' and 'Payload Type' fields. The 'Payload' 342 field is used to carry the FEC Framework Configuration Information. 343 Subsequently, the optional 'Payload Type' field, which is a MIME 344 content type specifier, is used to describe the encoding format used 345 to encode the Payload. 347 For example, the 'Payload Type' field may be application/sdp if 348 the FEC Framework Configuration Information is encoded in SDP 349 format and carried in the SAP payload. Similarly, it would be 350 application/xml if the FEC Framework Configuration Information was 351 encoded in XML format. 353 Section 5.1.1 describes the sender procedure, whereas the section 354 5.1.2 describes the receiver procedure in the context of config 355 signaling using RFC2974. 357 5.1.1. Sender Procedure 359 The sender signals the FEC framework configuration for each FEC 360 framework instance in a periodic SAP announcement message [RFC2974]. 361 The SAP announcement message is sent to a well known multicast IP 362 address and UDP port, as specified in [RFC2974]. The announcement is 363 multicast with the same scope as the session being announced. 365 The SAP module at the sender obtains the FEC Framework Configuration 366 Information per Instance from the 'FEC Framework' module and places 367 that in the SAP payload accordingly. A single SAP (announcement) 368 message must carry the FEC Framework Configuration Information for a 369 single FEC Framework Instance. The SAP message is then sent over UDP 370 over IP. 372 While it is possible to aggregate multiple SAP (announcement) 373 messages in a single UDP datagram as long as the resulting UDP 374 datagram length is less than the IP MTU of the outgoing interface, 375 this specification does not recommend it since there is no length 376 field in the SAP header to identify SAP message boundary. Hence, 377 this specification recommends single SAP announcement message to 378 be sent in a UDP datagram. 380 The IP packet carrying the SAP message must be sent to destination 381 IP address of one of the following depending on the selected scope: 383 - 224.2.127.254 (if IPv4 global scope 224.0.1.0-238.255.255.255 384 is selected for the FEC stream), or 386 - FF0X:0:0:0:0:0:2:7FFE (if IPv6 multicasting is selected for the 387 FEC stream, where X is the 4-bit scope value), or 389 - the highest multicast address (239.255.255.255, for example) in 390 the relevant administrative scope zone (if IPv4 administrative 391 scope 239.0.0.0-239.255.255.255 is selected for the FEC stream) 393 As defined in RFC2974, the IP packet carrying SAP message must use 394 destination UDP port being 9875 and source UDP port bein any 395 available number. The default IP TTL value (or Hop Limit value) 396 should be 255 at the sender, though the sender implementation may 397 allow it to be any other value to implicitly create the multicast 398 boundary for SAP announcements. The IP DSCP field may be set to any 399 value that indicates a desired QoS treatment in the IP network. 401 The IP packet carrying the SAP message must be sent with source IP 402 address that is reachable by the receiver. The sender may assign the 403 same IP address in the "originating source" field of the SAP 404 message, as the one used in the source IP address of the IP packet. 406 Furthermore, the FEC Framework Configuration Information must not 407 include any of the reserved multicast group IP addresses for the FEC 408 streams (i.e., source or repair flows), though it may use the same 409 IP address as the 'originating source' address to identify the FEC 410 streams (i.e., source or repair flows). Please refer to IANA 411 assignments for multicast addresses. 413 The sender must periodically send the 'SAP announcement' message to 414 ensure that the receiver doesn't purge the cached entry(s) from the 415 database and doesn't trigger the deletion of FEC Framework 416 Configuration Information. 418 While the time interval between repetitions of an announcement can 419 be calculated as per the very sophisticated but complex method 420 explained in [RFC2974], this document recommends a simpler method in 421 which the user specifies the time interval in the range of 1-200 422 seconds with suggested default value being 60 seconds. In this 423 method, the 'time interval' may be signaled in the SAP message 424 payload e.g. within the FEC Framework Configuration Information. 426 Note that SAP doesn't allow the time-interval to be signaled in 427 the SAP header. Hence, the usage of simpler method requires the 428 time-interval to be included in the FEC Framework Configuration 429 Information, if the default time interval (=60 seconds) for SAP 430 message repeations is not used. For example, the usage of "r=" 431 (repeat time) field in SDP may convey the time-interval value, if 432 SDP encoding format is used. 434 The time interval must be chosen to ensure that SAP announcement 435 messages are sent out before the corresponding multicast routing 436 entry e.g. (S,G) or (*,G) (corresponding to the SAP multicast 437 tree(s)) on the router(s) times out. (It is worth noting that the 438 default time-out period for the multicast routing entry is 210 439 seconds, per the PIM specification [RFC4601], though the time-out 440 period may be set to another value as allowed by the router 441 implementation.) 443 A SAP implementation may also support the complex method for 444 determining the SAP announcement time interval, and provide the 445 option to select it. 447 The sender may choose to delete the announced FEC Framework 448 Configuration Information, as defined in section 4 of RFC2974. The 449 explicit deletion is useful if the sender no longer desires to send 450 anymore FEC streams. 452 If the sender needs to modify the announced FEC Framework 453 Configuration Information for one or more FEC instances, then the 454 sender must send a new announcement message with a different 455 'Message Identifier Hash' value as per the rules described in 456 section 5 of RFC2974 [RFC2974]. Such announcement message should be 457 sent immediately (without having to wait for the time-interval) to 458 ensure that the modifications are received by the receiver as soon 459 as possible. The sender must also send the SAP deletion message to 460 delete the previous SAP announcement message (i.e., with the 461 previous 'Message Identifier Hash' value). 463 5.1.2. Receiver Procedure 465 The receiver must listen on UDP port 9875 for packets arriving with 466 IP destination address of either 224.2.127.254 (if IPv4 global scope 467 session is used for the FEC stream), or FF0X:0:0:0:0:0:2:7FFE (if 468 IPv6 is selected, where X is the 4-bit scope value), or the highest 469 IP address (239.255.255.255, for example) in the relevant 470 administrative scope zone (if IPv4 administrative scope 239.0.0.0- 471 239.255.255.255 is selected for the FEC stream). These IP addresses 472 are mandated for SAP usage by RFC2974 [RFC2974]. 474 The receiver, upon receiving a SAP announcement message, creates an 475 entry, if it doesn't already exist, in a local database and passes 476 the FEC Framework Configuration Information from the SAP Payload 477 field to the 'FEC Framework' module. Each entry also maintains a 478 time-out value, which is (re)set to five times the time-interval 479 value, which is either the default = 60 seconds, or the value 480 signaled by the sender. 482 Note that SAP doesn't allow the time-interval to be signaled in 483 the SAP header. Hence, the time-interval should be included in the 484 FEC Framework Configuration Information. For example, the usage of 485 "r=" (repeat time) field in SDP to convey the time-interval value, 486 if SDP encoding format is used. 488 The time-out value associated with each entry is reset when the 489 corresponding announcement (please see section 5 of [RFC2974]) is 490 received. If the time-out value for any entry reaches zero, then 491 that entry must be deleted from the database, as described in 492 section 4 of [RFC2974]. The receiver, upon receiving a SAP delete 493 message, must delete the matching SAP entry in its database, as 494 described in section 4 of [RFC2974]. 496 The deletion of SAP entry must result in the receiver no longer 497 using the relevant FEC Framework Configuration Information for the 498 corresponding instance, and must no longer subscribe to any related 499 FEC streams. 501 5.2. Signaling Protocol for Unicasting 503 This document describes leveraging any signaling protocol that is 504 already used by the unicast application, for exchanging the FEC 505 Framework Configuration Information between two nodes. 507 For example, a multimedia (VoD) client may send a request via 508 unicasting for a particular content to the multimedia (VoD) server, 509 which may offer various options such as encodings, bitrates, 510 transport etc. for the content. The client selects the suitable 511 options and answers to the server, paving the way for the content to 512 be unicast on the chosen transport from server to the client. This 513 offer/answer signaling, described in [RFC3264], is commonly utilized 514 by many application protocols such as SIP, RTSP etc. 516 The fact that two nodes desiring unicast communication almost always 517 rely on an application to first exchange the application related 518 parameters via the signaling protocol makes it logical to enhance 519 such signaling protocol(s) to (a) convey the desire for the FEC 520 protection and (b) subsequently also exchange FEC parameters i.e., 521 FEC Framework Configuration Information. This enables the node 522 acting as the offerer to offer 'FEC Framework Configuration 523 Information' for each of available FEC instances, and the node 524 acting as the answerer conveying the chosen FEC Framework 525 instance(s) to the offerer. The usage of FEC framework instance is 526 explained the FEC Framework document [RFC6363]. 528 While enhancing an application's signaling protocol to exchange FEC 529 parameters is one method (briefly explained above), an alternative 530 method would be to have a unicast based generic protocol that could 531 be used by two nodes independent of the application's signaling 532 protocol. The latter is not covered by this document, of course. 534 The remainder of this section provides example signaling protocols 535 and explains how they can be used to exchange FEC Framework 536 Configuration Information. 538 5.2.1. SIP 540 SIP [RFC3261] is an application-level signaling protocol to create, 541 modify, and terminate multimedia sessions with one or more 542 participants. SIP also enables the participants to discover one 543 another and to agree on a characterization of a multimedia session 544 they would like to share. SIP runs on either TCP or UDP or SCTP 545 transport, and uses SDP as the encoding format to describe multmedia 546 session attributes. 548 SIP already uses an offer/answer model with SDP, described in 549 [RFC3264], to exchange the information between two nodes to 550 establish unicast sessions between them. This document extends the 551 usage of this model for exchanging the FEC Framework Configuration 552 Information, explained in section 4. Any SDP specific enhancements 553 to accommodate the FEC Framework are covered in the SDP Elements 554 specification [RFC6364]. 556 5.2.2. RTSP 558 Real-Time Streaming Protocol (RTSP) [RFC2326] is an application- 559 level signaling protocol for control over the delivery of data with 560 real-time properties. RTSP provides an extensible framework to 561 enable controlled, on-demand delivery of real-time data, such as 562 audio and video. RTSP runs on either TCP or UDP transports. 564 RTSP already provides an ability to extend the existing method with 565 new parameters. This specification defines 'FEC Protection Needed' 566 option-tag (please see section 7 for IANA Considerations) and 567 prescribes including it in the Require (or Proxy-Require) header of 568 SETUP (method) request message, so as to request for FEC protection 569 for the data. 571 The node receiving such request either responds with "200 OK" 572 message that includes offers i.e., available FEC options (e.g. FEC 573 Framework Configuration Information for each Instance) or "551 574 Option not supported" message. A sample of related message exchange 575 is shown below - 577 Node1->Node2: SETUP < ... > RTSP/1.0 578 CSeq: 1 579 Transport: 580 Require: FEC-protection-needed 582 Node2->Node1: RTSP/1.0 200 OK 583 CSeq: 1 584 Transport: 586 The requesting node (Node1) may then send a new SETUP message to 587 convey the selected FEC protection to Node2, and proceed with 588 regular RTSP messaging. 590 Suffice to say, if the requesting node (Node1) received '551 Option 591 not supported' response from Node2, then the requesting node (Node1) 592 may send the SETUP message without using the Require header. 594 6. Security Considerations 596 This document recommends SAP message(s) be authenticated to ensure 597 sender authentication, as described in section 5.1. 599 There is no additional security consideration other than what's 600 already covered in [RFC2974] for SAP, [RFC2326] for RTSP, and 601 [RFC3261] for SIP. 603 7. IANA Considerations 605 This document requests IANA to register a new RTSP Option tag 606 (option-tag) listed below in the RTSP/1.0 Option Tags table of the 607 "Real Time Streaming Protocol (RTSP)/1.0 Parameters" registry 608 available from http://www.iana.org/, and provides the following 609 information in compliance with section 3.8.1 in [RFC2326]: 611 . Name of option-tag = FEC-protection-needed 613 . Description = See section 5.2.2 615 . Change of Control = IETF 617 8. Acknowledgments 619 Thanks to Colin Perkins for pointing out the issue with the time- 620 interval for the SAP messages. Additionally, thanks to Vincent Roca, 621 Ali Begen, Mark Watson, Ulas Kozat and David Harrington for greatly 622 improving this document. 624 This document was prepared using 2-Word-v2.0.template.dot. 626 9. References 628 9.1. Normative References 630 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 631 Requirement Levels", BCP 14, RFC 2119, March 1997. 633 [RFC6363] Watson, M., "Forward Error Correction (FEC) Framework", 634 RFC6363, March 2011. 636 [RFC6364] Begen, A., "Session Description Protocol Elements for 637 FEC Framework ", RFC6364, October 2011. 639 [RFC2974] Handley, M., Perkins, C. and E. Whelan, "Session 640 Announcement Protocol", RFC 2974, October 2000. 642 9.2. Informative References 644 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 645 Description Protocol", RFC 4566, July 2006. 647 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 648 with Session Description Protocol (SDP)", RFC 3264, June 649 2002. 651 [RFC2326] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time 652 Streaming Protocol (RTSP)", RFC 2326, April 1998. 654 [RFC3261] Handley, M., Schulzrinne, H., Schooler, E. and J. 655 Rosenberg, "SIP: Session Initiation Protocol", RFC 3261, 656 June 2002. 658 [RFC4601] Fenner, etc., "Protocol Independent Multicast - Sparse 659 Mode (PIM-SM): Protocol Specification", RFC 4601, August 660 2006. 662 [RFC3547] Baugher, etc., "The Group Domain of Interpretation", RFC 663 3547, July 2003. 665 Author's Addresses 667 Rajiv Asati 668 Cisco Systems, 669 7025-6 Kit Creek Rd, RTP, NC, 27709-4987 670 Email: rajiva@cisco.com