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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC4648' is defined on line 957, but no explicit reference was found in the text == Outdated reference: A later version (-12) exists of draft-ietf-ppsp-base-tracker-protocol-02 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PPSP Rui S. Cruz 3 INTERNET-DRAFT IST/INESC-ID/INOV 4 Intended Status: Standards Track Rachel Huang 5 Expires: July 28, 2014 Ning Zong 6 Huawei 7 Mario S. Nunes 8 INESC-ID/INOV 9 Joao P. Taveira 10 IST/INOV 11 January 24, 2014 13 PPSP Tracker Protocol-Extended Protocol 14 draft-huang-ppsp-extended-tracker-protocol-05 16 Abstract 18 This document specifies an extended Peer-to-Peer Streaming Protocol - 19 Tracker Protocol, which is a new extension protocol complementing the 20 basic core messages and usages specified in the base tracker protocol 21 for the exchange of meta information between trackers and peers, such 22 as initial offer/request of participation in multimedia content 23 streaming, content information, peer lists and reports of activity 24 and status. It extends the base tracker protocol to include new 25 optional messages providing new usages in the communications between 26 peer and tracker. The extension protocol is retro-compatible with the 27 base tracker protocol. 29 Status of this Memo 31 This Internet-Draft is submitted to IETF in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF), its areas, and its working groups. Note that 36 other groups may also distribute working documents as 37 Internet-Drafts. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 The list of current Internet-Drafts can be accessed at 45 http://www.ietf.org/1id-abstracts.html 46 The list of Internet-Draft Shadow Directories can be accessed at 47 http://www.ietf.org/shadow.html 49 Copyright and License Notice 51 Copyright (c) 2014 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 4. Extended Tracker Protocol Overview . . . . . . . . . . . . . . 5 70 4.1. Request-Response Extension . . . . . . . . . . . . . . . . 5 71 4.2. Protocol-level Extension . . . . . . . . . . . . . . . . . 6 72 4.3. Usage of Extended Request Messages . . . . . . . . . . . . 6 73 4.4. Extended Tracker Transaction State Machine . . . . . . . . 7 74 4.4.1. Normal Operation . . . . . . . . . . . . . . . . . . . 8 75 4.4.2. Error Conditions . . . . . . . . . . . . . . . . . . . 9 76 5 Extended Tracker Protocol Specification . . . . . . . . . . . . 9 77 5.1. Request/Response Syntax and Format . . . . . . . . . . . . 9 78 5.2. Extended Semantics of PPSPTrackerProtocol Elements . . . . 11 79 5.3. Extended Request/Response Element in Request Messages . . . 15 80 5.4. Compatibility with the Base Tracker Protocol . . . . . . . 15 81 5.5. Negotiation of Chunk Addressing Methods . . . . . . . . . . 15 82 6. Request/Response Processing . . . . . . . . . . . . . . . . . . 15 83 6.1. Enhanced CONNECT Request . . . . . . . . . . . . . . . . . 16 84 6.2. Enhanced FIND Request . . . . . . . . . . . . . . . . . . . 18 85 6.3. Enhanced STAT_REPORT Request . . . . . . . . . . . . . . . 20 86 6.4. DISCONNECT Request . . . . . . . . . . . . . . . . . . . . 22 87 7. Error and Recovery Conditions . . . . . . . . . . . . . . . . . 23 88 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 23 89 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 23 90 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 91 11 References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 92 11.1 Normative References . . . . . . . . . . . . . . . . . . . 24 93 11.2 Informative References . . . . . . . . . . . . . . . . . . 24 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 96 1. Introduction 98 The PPSP Tracker Protocol is one of the Peer-to-Peer Streaming 99 Protocol which specifies standard format/encoding of information and 100 messages between PPSP peers and PPSP trackers. Based on the 101 requirements defined in [RFC6972], the base tracker protocol 102 specified in [I-D.ietf-ppsp-base-tracker-protocol] has provided the 103 basic core messages to be exchanged between trackers and peers in 104 order to carry out some fundamental operations. They are mandatory 105 messages covering most basic and universal use cases and MUST be 106 implemented in all PPSP-based streaming systems. 108 This document specifies extensions to the base core messages of 109 [I-D.ietf-ppsp-base-tracker-protocol] and new optional request 110 messages providing new usages in some dedicated scenarios. The 111 extensions protocol is retro-compatible with the base tracker 112 protocol. Messages using this specification MUST be safely rejected 113 by trackers not supportting the extensions to avoid affecting 114 interoperability. 116 2. Terminology 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 120 document are to be interpreted as described in RFC 2119 [RFC2119]. 122 This draft uses terms defined in [RFC6972] and [I-D.ietf-ppsp-base- 123 tracker-protocol]. 125 3. Motivation 127 There are a number of possible usages and issues which may be useful 128 for discussion and which the base tracker protocol may not be able to 129 deal with. 131 1. In the base tracker protocol, the disconnection between peer and 132 tracker is achieved by a timeout (of periodic STAT_REPORT messages) 133 which means that trackers lack the ability to timely free up 134 resources. In some cases when the number of connected peers is 135 reaching the maximum capacity of a tracker, resources of the tracker 136 cannot be released immediately, even if some peers leave the swarm. 137 Some P2P applications may require to overcome this shortage of the 138 base tracker protocol. 140 2. A peer may have the requirement to start streaming the content 141 from some specific point of the content timeline. For example, when 142 the end user watched only part of a content and decided to stop and 143 leave, or paused for a long time. When the end user decides to 144 resume the session he/she expects to continue watching the content 145 from the point where he/she interrupted. The peer may then request 146 the tracker to select a subset of peers capable to provide that 147 specific content scope. 149 The above use cases require the base tracker protocol to be extended. 151 4. Extended Tracker Protocol Overview 153 The extended Tracker Protocol consists of three Request-Response 154 Extensions (to the CONNECT, FIND and STAT_REPORT Request messages of 155 the Base Protocol) and one Protocol-level Extension (a new DISCONNECT 156 Request message). 158 4.1. Request-Response Extension 160 In this section, the CONNECT, FIND and STAT_REPORT messages specified 161 in the base tracker protocol are extended to meet the needs of use 162 cases listed in section 3. 164 CONNECT: This enhanced CONNECT Request message tends to solve the 165 issue 2 raised in section 3. The extension of the CONNECT 166 Request message includes information of specific content 167 scopes, either media content representations or specific 168 chunks/segments of a media representation in a swarm. The 169 format and detailed processing of enhanced CONNECT Request 170 message is presented in Section 5.1. 172 FIND: The enhanced FIND Request message allows a peer to request 173 the tracker for a subset of peers in a swarm but including 174 specific content scopes, either media content 175 representations or specific chunks/segments of a media 176 representation in a swarm, and may also include an updated 177 network address of the peer. On receiving a FIND message, 178 the tracker selects a subset of peers satisfying the 179 requesting scope. To create the peer list, the tracker may 180 also take peer status, capabilities and peers priority into 181 consideration. Peer priority may be determined by network 182 topology preference, operator policy preference, etc. The 183 format and detailed processing of enhanced CONNECT Request 184 message is presented in Section 5.2. 186 STAT_REPORT: The enhanced STAT_REPORT Request message allows the 187 exchanges of content data information, like chunkmaps, 188 between an active peer and a tracker. The information can 189 be used by a tracker as a qualification to select 190 appropriate subsets of peers in the swarm satisfying 191 specific scopes (in terms of content). The format and 192 detailed processing of enhanced CONNECT Request message is 193 presented in Section 5.3. 195 4.2. Protocol-level Extension 197 A new Request message is introduced in this section to extend those 198 specified in the base tracker protocol [I-D.ietf-ppsp-base-tracker- 199 protocol], to meet the need of issue 1 listed in section 3. 201 DISCONNECT: The DISCONNECT Request message is used when the peer 202 intends to no longer participate in all swarms. When 203 receiving the DISCONNECT Request message from a peer, the 204 tracker deletes the corresponding activity records related 205 to the peer (including its status and all content status 206 for the corresponding swarms). In such a case, the 207 DISCONNECT Request message will have the same effect of 208 timer expiring (STAT_REPORT), but providing a graceful 209 disconnect of that peer from the system. 211 4.3. Usage of Extended Request Messages 213 An example of usage of the extended request messages is the 214 illustrated in Figure 1. In that figure a peers starts by connecting 215 to the system and joining a specific swarm (swarm_a) in SEED mode. 217 While active, the peer periodically updates the tracker using 218 STAT_REPORT messages. Later, the peer CONNECTs to another swarm 219 (swarm_b) but in LEECH mode, i.e., the end-user intends to watch that 220 new content while still sharing the first one. During the streaming 221 the peer requests an updated list of peers in that new swarm to the 222 tracker. 224 When the end user wants to leave the second content, not having even 225 finished watching, the peer sends CONNECT message with a leave action 226 for the corresponding swarm (swarm_b) but remains sharing the first 227 content (swarm_a). Later the peer DISCONNECTs from the system. 229 When in a next time, the end user wants to continue watching the 230 content he/she previously left unfinished, the peer CONNECTs to the 231 corresponding swarm in LEECH mode but sending the specific content 232 information scope. 234 +--------+ +---------+ 235 | Peer | | Tracker | 236 +--------+ +---------+ 237 | | 238 |--CONNECT(swarm_a;SEED)---------->| 239 |<--------------------------OK-----| 240 : : 241 |--STAT_REPORT(activity)---------->| 242 |<--------------------------Ok-----| 243 : : 244 |--CONNECT(swarm_b;LEECH)--------->| 245 |<-----------------OK+PeerList-----| 246 : : 247 |--STAT_REPORT(ChunkMap_b)-------->| 248 |<--------------------------Ok-----| 249 : : 250 |--FIND(swarm_b)------------------>| 251 |<-----------------OK+PeerList-----| 252 : : 253 |--CONNECT(leave swarm_b)--------->| 254 |<--------------------------Ok-----| 255 : : 256 |--STAT_REPORT(activity)---------->| 257 |<--------------------------Ok-----| 258 : : 259 |--DISCONNECT(nil)---------------->| 260 |<---------------------Ok(BYE)-----| 261 : : 262 |-CONNECT(swarm_b;LEECH;ChunkMap)->| 263 |<-----------------OK+PeerList-----| 264 : : 266 Figure 1: Example of a session for a extended PPSP-TP. 268 4.4. Extended Tracker Transaction State Machine 270 The tracker state machine introduced in the base tracker protocol 271 [I-D.ietf-ppsp-base-tracker-protocol] is now updated in this 272 specification to reflect the extensions introduced. An updated "per- 273 Peer-ID" transaction state machine (Figure 2) is described, 274 corresponding to the enhanced functionalities and control steps of 275 the extended tracker protocol. This extended "per-Peer-ID" 276 transaction state machine is compatible with the one specified in the 277 base tracker protocol. 279 +-----------+ +-------+ rcv CONNECT 280 (Transient) | TERMINATE | | START | --------------- (1) 281 +-----------+ +-------+ strt init timer 282 rcv STAT_REPORT ^ | 283 rcv FIND | | 284 rcv DISCONNECT | | 285 on registration error | v 286 on action error | +------------+ 287 ---------------- (A) +<-----| PEER | (Transient) 288 stop init timer | | REGISTERED | 289 snd error | +------------+ 290 | | 291 | | process swarm actions 292 | | --------------------- (2) 293 on CONNECT Error (B) | | snd OK (PeerList) 294 on timeout (C) | / stop init timer 295 ---------------- | / strt track timer 296 stop track timer | / 297 clean peer info | | 298 del registration | | 299 snd error (B) | | 300 | | 301 rcv CONNECT(@leave) | | rcv FIND 302 rcv DISCONNECT (nil) | | ----------------- (3) 303 --------------- (5) \ | ---- snd OK (PeerList) 304 snd OK response ---- \ | / \ rst tracker timer 305 / \ \ | | | 306 rcv CONNECT | (4) | | | | | 307 ----------- | v | v v | rcv STAT_REPORT 308 snd OK \ +-------------+ / --------------- (3) 309 rst track timer ----| TRACKING |---- snd OK response 310 +--------------+ rst track timer 312 Figure 2: Extended Per-Peer-ID Transaction State Machine 314 The state diagram in Figure 2 illustrates the complete state changes 315 together with the causing events and resulting actions when 316 implementing the extensions to the base tracker protocol. Note that 317 Specific error conditions are not shown in the state diagram. 319 4.4.1. Normal Operation 321 On normal operation the extended process consists of the following 322 steps: 324 1) This step is same step 1) in section 2.4.1 of the base tracker 325 protocol [I-D.ietf-ppsp-base-tracker-protocol]. 327 2) This step is same step 2) in section 2.4.1 of the base tracker 328 protocol [I-D.ietf-ppsp-base-tracker-protocol]. 330 3) This step is same step 3) in section 2.4.1 of the base tracker 331 protocol [I-D.ietf-ppsp-base-tracker-protocol], but with extended 332 scope in the FIND Request message and in the STAT_REPORT Request 333 message. 335 4) This step is same step 4) in section 2.4.1 of the base tracker 336 protocol [I-D.ietf-ppsp-base-tracker-protocol] 338 5) While TRACKING, a DISCONNECT message received from the peer, or a 339 CONNECT message with the action to leave the last swarm, the 340 tracker stops the "track timer", cleans the information associated 341 with the participation of the Peer-ID in the the swarm(s) joined, 342 responds with a successful condition, deletes the registration of 343 the Peer-ID and transitions to TERMINATED state for that Peer-ID. 345 4.4.2. Error Conditions 347 Peers MUST NOT generate protocol elements that are invalid. 348 However, several situations of a peer may lead to abnormal 349 conditions in the interaction with the tracker. The situations 350 may be related with peer malfunction or communications errors. 351 The tracker reacts to the abnormal situations depending on its 352 current state related to a Peer ID, as follows: 354 A) At PEER REGISTERED state, if the Peer ID is considered invalid (in 355 the case of a DISCONNECT requests received from an unregistered 356 Peer ID), the tracker responds with either error codes 401 357 Unauthorized or 403 Forbidden, transitions to TERMINATE state for 358 that Peer ID and the state machine is destroyed. 360 B) This step is the same step B) in section 2.4.2 of the base tracker 361 protocol [I-D.ietf-ppsp-base-tracker-protocol. 363 C) This step is the same step c) in section 2.4.2 of the base 364 tracker protocol [I-D.ietf-ppsp-base-tracker-protocol. 366 NOTE: These situations may correspond to a malfunction at the peer 367 or to malicious conditions. Therefore, as preventive measure, the 368 tracker proceeds to TERMINATE state for the Peer ID by de- 369 registering the peer and cleaning all peer information. 371 5 Extended Tracker Protocol Specification 373 5.1. Request/Response Syntax and Format 374 The architecture specified in the base tracker protocol [I-D.ietf- 375 ppsp-base-tracker-protocol] does not suffer any modification in the 376 extended protocol. The syntax is identical with some elements 377 extended to contain new optional attributes: 379 The SwarmID element MAY be present in DISCONNECT requests. 381 The element "ContentGroup" is added to the format of Request. It MAY 382 be present in requests referencing content, i.e., CONNECT and FIND, 383 if the request includes a content scope. 385 The extended semantics of the attributes and elements within a 386 PPSPTrackerProtocol root element is described in section 5.2. 388 5.2. Extended Semantics of PPSPTrackerProtocol Elements 390 The extension semantics of PPSPTrackerProtocol is a follows. 392 +----------------------+---------+----------------------------------+ 393 | Element Name or | Use | Description | 394 | Attribute Name | | | 395 +----------------------+---------+----------------------------------+ 396 | PPSPTrackerProtocol | 1 | The root element. | 397 | @version | M | Provides the version of PPSP-TP. | 398 | Request | 0...1 | Provides the request method | 399 | | | and MUST be present in Request. | 400 | Response | 0...1 | Provides the response method | 401 | | | and MUST be present in Response. | 402 | TransactionID | M | Root transaction Identification. | 403 | Result | 0...N | Result of @action MUST be present| 404 | | | in Responses. | 405 | @transactionID | CM | Identifier of the @action. | 406 | PeerID | 0...1 | Peer Identification. | 407 | | | MUST be present in Request. | 408 | SwarmID | 0...N | Swarm Identification. | 409 | | | MUST be present in Requests. | 410 | @action | CM | Must be set to JOIN or LEAVE. | 411 | @peerMode | CM | Mode of Peer participation in | 412 | | | the swarm, "LEECH" or "SEED". | 413 | @transactionID | CM | Identifier for the @action. | 414 | PeerNUM | 0...1 | Maximum peers to be received | 415 | | | with capabilities indicated. | 416 | @abilityNAT | CM | Type of NAT traversal peers, as | 417 | | | "No-NAT","STUN","TURN" or "PROXY"| 418 | @concurrentLinks| CM | Concurrent connectivity level of | 419 | | | peers, "HIGH", "LOW" or "NORMAL" | 420 | @onlineTime | CM | Availability or online duration | 421 | | | of peers, "HIGH" or "NORMAL" | 422 | @uploadBWlevel | CM | Upload bandwidth capability of | 423 | | | peers, "HIGH" or "NORMAL" | 424 | ContentGroup | 0...1 | Information on content (Table 4) | 425 | PeerGroup | 0...1 | Information on peers (Table 3) | 426 | StatisticsGroup | 0...1 | Statistic data (Table 5) | 427 +----------------------+---------+----------------------------------+ 428 | Legend: | 429 | Use for attributes: M=Mandatory, OP=Optional, | 430 | CM=Conditionally Mandatory | 431 | Use for elements: minOccurs...maxOccurs (N=unbounded) | 432 | Elements are represented by their name (case-sensitive) | 433 | Attribute names (case-sensitive) are preceded with an @ | 434 +-------------------------------------------------------------------+ 435 Table 1: Semantics of the Extended PPSPTrackerProtocol. 437 The semantics of PeerGroup element is almost identical with that of the 438 base tracker protocol. 440 +----------------------+---------+----------------------------------+ 441 | Element Name or | Use | Description | 442 | Attribute Name | | | 443 +----------------------+---------+----------------------------------+ 444 | PeerGroup | 0...1 | Contains description of peers. | 445 | PeerInfo | 1...N | Provides information on a peer. | 446 | @swarmID | 0...1 | Swarm Identification. | 447 | PeerID | 0...1 | Peer Identification. | 448 | | | MAY be present in responses. | 449 | PeerAddress | 0...N | IP Address information. | 450 | @addrType | M | Type of IP address, which can be | 451 | | | "ipv4" or "ipv6" | 452 | @priority | CM | The priority of this interface. | 453 | | | Used for NAT traversal. | 454 | @type | CM | Describes the address for NAT | 455 | | | traversal, which can be "HOST" | 456 | | | "REFLEXIVE" or "PROXY". | 457 | @connection | OP | Access type ("3G", "ADSL", etc.) | 458 | @asn | OP | Autonomous System number. | 459 | @ip | M | IP address value. | 460 | @port | M | IP service port value. | 461 | @peerProtocol | OP | PPSP Peer Protocol supported. | 462 +----------------------+---------+----------------------------------+ 463 | Legend: | 464 | Use for attributes: M=Mandatory, OP=Optional, | 465 | CM=Conditionally Mandatory | 466 | Use for elements: minOccurs...maxOccurs (N=unbounded) | 467 | Elements are represented by their name (case-sensitive) | 468 | Attribute names (case-sensitive) are preceded with an @ | 469 +-------------------------------------------------------------------+ 470 Table 2: Semantics of PeerGroup. 472 Table 3 describes the semantics of StatisticsGroup element, extended 473 with content information attributes. 474 +----------------------+---------+----------------------------------+ 475 | Element Name or | Use | Description | 476 | Attribute Name | | | 477 +----------------------+---------+----------------------------------+ 478 | StatisticsGroup | 0...1 | Provides statistic data on peer | 479 | | | and content. | 480 | Stat | 1...N | Groups statistics property data. | 481 | @property | M | The property to be reported | 482 | | | property values and elements | 483 | | | in Table 5 of [I-D.ietf-ppsp-base| 484 | | | -tracker-protocol] | 485 | ContentGroup | 0...1 | Information on content (Table 4) | 486 +----------------------+---------+----------------------------------+ 487 | Legend: | 488 | Use for attributes: M=Mandatory, OP=Optional, | 489 | CM=Conditionally Mandatory | 490 | Use for elements: minOccurs...maxOccurs (N=unbounded) | 491 | Elements are represented by their name (case-sensitive) | 492 | Attribute names (case-sensitive) are preceded with an @ | 493 +-------------------------------------------------------------------+ 494 Table 3: Semantics of StatisticsGroup. 496 ContentGroup is a new element. The semantics of this element is 497 described in Table 4. 499 +----------------------+---------+----------------------------------+ 500 | Element Name or | Use | Description | 501 | Attribute Name | | | 502 +----------------------+---------+----------------------------------+ 503 | ContentGroup | 0...1 | Provides information on content. | 504 | CAM | 1 | Describes the chunk addressing | 505 | | | method of this content. The value| 506 | | | is identical with the value of | 507 | | | Table 6 of [I-D.ietf-ppsp-peer | 508 | | | -protocol] | 509 | Representation | 1...N | Describes a component of content.| 510 | @id | M | Unique identifier for this | 511 | | | Representation. | 512 | SegmentInfo | 1 | Provides segment information. | 513 | @startIndex | M | The index of the first media | 514 | | | segment in the request scope for | 515 | | | this Representation. | 516 | @endIndex | OP | The index of the last media | 517 | | | segment in the request scope for | 518 | | | this Representation. | 519 +----------------------+---------+----------------------------------+ 520 | Legend: | 521 | Use for attributes: M=Mandatory, OP=Optional, | 522 | CM=Conditionally Mandatory | 523 | Use for elements: minOccurs...maxOccurs (N=unbounded) | 524 | Elements are represented by their name (case-sensitive) | 525 | Attribute names (case-sensitive) are preceded with an @ | 526 +-------------------------------------------------------------------+ 528 Table 4: Semantics of ContentGroup 530 The Representation element describes a component of a content 531 identified by its attribute @id in the Media Presentation Description 532 (MPD). This element MAY be present for each component desired in the 533 scope of the FIND or CONNECT requests. The scope of each 534 Representation is indicated by the SegmentInfo element and the 535 attributes @startIndex and, optionally, @endIndex. 537 5.3. Extended Request/Response Element in Request Messages 539 Table 5 specifies the valid string representations for the requests 540 extended in this specification to complement those define in the base 541 tracker protocol. These values MUST be treated as case-sensitive. 543 +----------------------+ 544 | Extended XML Request | 545 | Methods String Values| 546 +----------------------+ 547 | DISCONNECT | 548 +----------------------+ 550 Table 5: Extended Valid Strings for Request Element of Requests. 552 The response elements in the extension are identical to those of the 553 base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol]. 555 5.4. Compatibility with the Base Tracker Protocol 557 Trackers are RECOMMENDED to implement extended tracker protocol to be 558 compatible with peers using base tracker protocol or peers using 559 extended tracker protocol. But it is not mandatory. When peers using 560 extended tracker protocol changes content information with a tracker 561 only supporting base tracker protocol, the tracker could directly 562 ignore the content related information, e.g. ContentGroup element and 563 Representation attribute. Peers implementing the extended tracker 564 protocol sending DISCONNECT message to legacy trackers will get 565 respond with 400 (Bad request, with reason-phrase "Unknown 566 Messages"), which indicate the messages could not be recognized by 567 the tracker. In this case, the peers MUST stop interacting with the 568 tracker in extended request messages and use the base tracker 569 protocol instead. 571 5.5. Negotiation of Chunk Addressing Methods 573 Multiple chunk addressing methods could be used in this document to 574 present content information. But only one of them MUST be used for 575 one swarm when a peer communicating with a tracker. Before peers 576 connect to a tracker, it MUST get the knowledge of the chunk 577 addressing methods supported by the tracker. How to get the 578 information is out of scope of the tracker protocol. It could be some 579 out-of-band methods. For example, the chunk addressing methods 580 supported by the tracker could be obtained from the web portal 581 together with other information of the tracker, e.g. IP address. 583 6. Request/Response Processing 584 6.1. Enhanced CONNECT Request 586 This method is used when a peer wants to join one or multiple swarms. 587 The tracker records the Peer-ID, connect-time, IP addresses and link 588 status. 590 The peer MUST properly form the XML message-body, set the Request 591 method to CONNECT, generate and set the TransactionID, and set the 592 PeerID with the identifier of the peer. The peer SHOULD also include 593 the IP addresses of its network interfaces in the CONNECT message. 595 Extended CONNECT request is retro-compatible with the CONNECT request 596 message defined in the base tracker protocol specification. 598 An example of the message-body of the extended CONNECT Request is the 599 following. 601 602 603 CONNECT 604 656164657220 605 12345.0 606 1111 608 5 612 613 614 615 616 617 618 619 620 621 622 624 628 629 630 631 In this example, the peer wants to participate in swarm 1111 to watch 632 the program as LEECH, and it also wishes to start from a specific 633 point of the content timeline. As such, the CONNECT request message 634 contains a ContentGroup element including the information to restrict 635 the search for peers in the swarm. The extended CONNECT request MAY 636 include a PeerNum element to indicate to the tracker the number of 637 peers to be returned in a list corresponding to the indicated 638 properties, being @abilityNAT for NAT traversal (considering that 639 PPSP-ICE NAT traversal techniques may be used), and optionally 640 @concurrentLinks, @onlineTime and @uploadBWlevel for the preferred 641 capabilities. In case PeerMode is LEECH, the tracker will search and 642 select a proper list of peers satisfying the conditions requested. 643 The peer list MUST contain the Peer-IDs and the corresponding IP 644 addresses. To create the peer list, the tracker may take peer status 645 and network location information into consideration, to express 646 network topology preference or operators' policy preferences, with 647 regard to the possibility of connecting with other IETF efforts such 648 as ALTO [I.D.ietf-alto-protocol]. Thus a PeerGroup MAY also be 649 needed in an extended CONNECT request messages. 651 The response MUST have the same TransactionID value as the request. 652 An example of a Response message for the extended CONNECT Request 653 from a leecher is the following: 655 656 657 SUCCESSFUL 658 12345 659 660 661 656164657220 662 667 668 669 956264622298 670 672 673 674 3332001256741 675 677 678 680 682 6.2. Enhanced FIND Request 684 This method allows peers to request to the tracker, whenever needed, 685 a new peer list for the swarm for specific scope of chunks/segments 686 of a media content representation of that swarm. 688 The peer MUST properly form the XML message-body, set the request 689 method to FIND, set the PeerID with the identifier of the peer, set 690 the SwarmID with the identifier of the swarm the peer is interested 691 in. And optionally, in order to find peer having the specific 692 chunks/segments, the peer may include the ContentGroup element in the 693 JOIN request message to indicate a specific point in the content 694 timeline. 696 This message is mainly used for leechers to update the peer list. It 697 is unnecessary to set the PeerMode element in FIND request messages. 699 The peer MUST generate and set the TransactionID for the request. 701 An example of the message-body of a FIND Request is the following: 703 704 705 FIND 706 656164657221 707 1111 708 12345 709 5 713 714 715 716 717 718 720 The FIND request MAY include a PeerNum element to indicate to the 721 tracker the number of peers to be returned in a list corresponding to 722 the indicated properties, being @abilityNAT for NAT traversal 723 (considering that PPSP-ICE NAT traversal techniques may be used), and 724 optionally @concurrentLinks, @onlineTime and @uploadBWlevel for the 725 preferred capabilities. 727 In the case of a FIND with a specific scope of a stream content the 728 request SHOULD include a ContentGroup to specify the segment range of 729 content Representations. 731 When receiving a well-formed FIND Request the tracker processes the 732 information to check if it is valid. In case of success a response 733 message with a Response value of SUCCESSFUL will be generated and the 734 tracker will include the appropriate list of peers satisfying the 735 conditions requested. The peer list returned MUST contain the Peer- 736 IDs and the corresponding IP Addresses. 738 The tracker may take peer status and network location information 739 into consideration when selecting the peer list to return, to express 740 network topology preferences or Operators' policy preferences, with 741 regard to the possibility of connecting with other IETF efforts such 742 as ALTO [I.D.ietf-alto-protocol]. 744 An example of a Response message for the FIND Request is: 746 747 748 SUCCESSFUL 749 12345 750 751 752 956264622298 753 755 756 757 3332001256741 758 760 761 762 764 The Response MUST include a PeerGroup with PeerInfo data that 765 includes the public IP address of the selected active peers in the 766 swarm. 768 The tracker MAY also include the attribute @asn with network location 769 information of the transport addresses of the peers, corresponding to 770 the Autonomous System Numbers of the access network provider of each 771 peer in the list. 773 The response MAY also include a PeerGroup with PeerInfo data that 774 includes the requesting peer public IP address. If STUN-like 775 function is enabled in the tracker, the PeerAddress includes the 776 attribute @type with a value of REFLEXIVE, corresponding to the 777 transport address "candidate" of the peer. 779 An example of a Response message for the FIND Request including the 780 requesting peer public IP address is the following: 782 783 784 SUCCESSFUL 785 12345 786 787 788 656164657221 789 794 795 796 956264622298 797 799 800 801 3332001256741 802 804 805 806 808 6.3. Enhanced STAT_REPORT Request 810 This message still uses the specifications of the base tracker 811 protocol [I-D.ietf-ppsp-base-tracker-protocol]. The Stat element has 812 been extended with one property, "ContentMap", to allow peers 813 reporting map of chunks they have. The tracker would not have the 814 ability to treat the FIND requests for specific content chunks, 815 unless peers report this kind of information. 817 An example of the message-body of an enhanced STAT_REPORT request is 818 the following: 820 821 822 STAT_REPORT 823 656164657221 824 12345 825 826 827 1111 828 512 829 768 830 1024000 831 832 833 2222 834 1024 835 2048 836 512000 837 838 839 1111 840 841 842 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 843 844 845 846 847 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 848 849 850 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 851 852 853 854 855 2222 856 857 858 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 859 860 861 862 863 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 864 865 866 867 868 870 If the request is valid the tracker process the received information 871 for future use, and generates a response message with a Response 872 value of SUCCESSFUL. 874 The response MUST have the same TransactionID value as the request. 876 An example of a Response message for the START_REPORT Request is the 877 following: 879 880 881 SUCCESSFUL 882 12345 883 885 6.4. DISCONNECT Request 887 This method is used when the peer intends to leave the system and no 888 longer participate. 890 The tracker SHOULD delete the corresponding activity records related 891 with the peer in the corresponding swarms (including its status and 892 all content status). 894 The peer MUST properly form the XML message-body, set the Request 895 method to DISCONNECT, set the PeerID with the identifier of the peer, 896 randomly generate and set the TransactionID. 898 An example of the message-body of a DISCONNECT Request for the peer 899 leaving all joined swarms is the following: 901 902 903 DISCONNECT 904 656164657221 905 12345 906 908 An example of a Response message for the DISCONNECT Request is the 909 following: 911 912 913 SUCCESSFUL 914 12345 915 917 7. Error and Recovery Conditions 919 This document does not introduces any new error and recovery 920 conditions. The implementation of error treatment MUST refer to the 921 base tracker protocol specification [I-D.ietf-ppsp-base-tracker- 922 protocol]. 924 8. Security Considerations 926 The extended tracker protocol proposed in this document introduces no 927 new security considerations beyond those described in the base 928 tracker protocol specification [I-D.ietf-ppsp-base-tracker-protocol]. 930 9. IANA Considerations 932 There are presently no IANA considerations with this document. 934 10. Acknowledgments 936 The authors would like to thank many people for their help and 937 comments, particularly: Zhang Yunfei, Martin Stiemerling, Johan 938 Pouwelse and Arno Bakker. 940 The authors would also like to thank the people participating in the 941 EU FP7 project SARACEN (contract no. ICT-248474) 942 [refs.saracenwebpage] for contributions and feedback to this 943 document. 945 The views and conclusions contained herein are those of the authors 946 and should not be interpreted as necessarily representing the 947 official policies or endorsements, either expressed or implied, of 948 the SARACEN project or the European Commission. 950 11 References 952 11.1 Normative References 954 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 955 Requirement Levels", BCP 14, RFC 2119, March 1997. 957 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 958 Encodings", RFC 4648, October 2006. 960 [ISO.8601.2004] International Organization for Standardization, "Data 961 elements and interchange formats - Information interchange 962 - Representation of dates and times", ISO Standard 8601, 963 December 2004. 965 11.2 Informative References 967 [RFC6972] Zhang, Y. and N. Zong, "Problem Statement and Requirements 968 of the Peer-to-Peer Streaming Protocol (PPSP)", RFC 6972, 969 July 2013.. 971 [I-D.ietf-ppsp-base-tracker-protocol] Cruz, R., Nunes, M., Gu, Y., 972 Xia, J., and J. Taveira, "PPSP Tracker Protocol-Base 973 Protocol (PPSP-TP/1.0)", draft-ietf-ppsp-base-tracker- 974 protocol-02 (work in progress), October 2013. 976 [I.D.ietf-alto-protocol] Alimi, R., Penno, R. and Y. Yang, "ALTO 977 Protocol", draft-ietf-alto-protocol-20, (work in 978 progress), October 2013. 980 [ISO.IEC.23009-1] ISO/IEC, "Information technology -- Dynamic 981 adaptive streaming over HTTP (DASH) -- Part 1: Media 982 presentation description and segment formats", ISO/IEC DIS 983 23009-1, Aug. 2011. 985 [refs.saracenwebpage] "SARACEN Project Website", 986 http://www.saracen-p2p.eu/. 988 Authors' Addresses 990 Rui Santos Cruz 991 IST/INESC-ID/INOV 992 Phone: +351.939060939 993 Email: rui.cruz@ieee.org 995 Rachel Huang 996 Huawei 997 Phone: +86-25-56623633 998 EMail: rachel.huang@huawei.com 1000 Ning Zong 1001 Huawei 1002 Phone: +86-25-56624760 1003 EMail: zongning@huawei.com 1005 Mario Serafim Nunes 1006 INESC-ID/INOV 1007 Rua Alves Redol, n.9 1008 1000-029 LISBOA, Portugal 1009 Phone: +351.213100256 1010 Email: mario.nunes@inov.pt 1012 Joao P. Taveira 1013 IST/INOV 1014 Email: joao.silva@inov.pt