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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-08) exists of draft-ietf-avtcore-ecn-for-rtp-06 == Outdated reference: A later version (-10) exists of draft-ietf-xrblock-rtcp-xr-meas-identity-02 == Outdated reference: A later version (-08) exists of draft-ietf-xrblock-rtcp-xr-pdv-02 == Outdated reference: A later version (-17) exists of draft-ietf-xrblock-rtcp-xr-qoe-00 -- Obsolete informational reference (is this intentional?): RFC 5117 (Obsoleted by RFC 7667) Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group Q. Wu, Ed. 3 Internet-Draft Huawei 4 Intended status: Informational G. Hunt 5 Expires: August 27, 2012 Unaffiliated 6 P. Arden 7 BT 8 February 24, 2012 10 Monitoring Architecture for RTP 11 draft-ietf-avtcore-monarch-10.txt 13 Abstract 15 This memo proposes an architecture for extending RTP Control Protocol 16 (RTCP) with a new RTCP Extended Reports (XR) (RFC3611) block type to 17 report new metrics regarding media transmission or reception quality, 18 following RTCP guideline established in RFC5968. This memo suggests 19 that a new block should contain a single metric or a small number of 20 metrics relevant to a single parameter of interest or concern, rather 21 than containing a number of metrics which attempt to provide full 22 coverage of all those parameters of concern to a specific 23 application. Applications may then "mix and match" to create a set 24 of blocks which covers their set of concerns. Where possible, a 25 specific block should be designed to be re-usable across more than 26 one application, for example, for all of voice, streaming audio and 27 video. 29 Status of this Memo 31 This Internet-Draft is submitted 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). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on August 27, 2012. 46 Copyright Notice 48 Copyright (c) 2012 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3. RTP monitoring architecture . . . . . . . . . . . . . . . . . 6 66 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 3.2. RTCP Metric Block Report and associated parameters . . . . 9 68 3.3. RTP Sender/Receiver entities located in network nodes . . 10 69 4. Issues with reporting metric block using RTCP XR extension . . 11 70 5. Guideline for reporting metric block using RTCP XR . . . . . . 13 71 5.1. Using single metrics blocks . . . . . . . . . . . . . . . 13 72 5.2. Correlating RTCP XR with the non-RTP data . . . . . . . . 13 73 5.3. Reducing Measurement information repetition . . . . . . . 14 74 5.4. Expanding the RTCP XR block namespace . . . . . . . . . . 14 75 6. An example of a metric block . . . . . . . . . . . . . . . . . 16 76 7. Application to RFC 5117 topologies . . . . . . . . . . . . . . 17 77 7.1. Applicability to MCU . . . . . . . . . . . . . . . . . . . 17 78 7.2. Applicability to Translators . . . . . . . . . . . . . . . 18 79 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 80 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 81 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 21 82 11. Informative References . . . . . . . . . . . . . . . . . . . . 22 83 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 24 84 A.1. draft-ietf-avtcore-monarch-00 . . . . . . . . . . . . . . 24 85 A.2. draft-ietf-avtcore-monarch-01 . . . . . . . . . . . . . . 24 86 A.3. draft-ietf-avtcore-monarch-02 . . . . . . . . . . . . . . 24 87 A.4. draft-ietf-avtcore-monarch-03 . . . . . . . . . . . . . . 25 88 A.5. draft-ietf-avtcore-monarch-04 . . . . . . . . . . . . . . 25 89 A.6. draft-ietf-avtcore-monarch-05 . . . . . . . . . . . . . . 25 90 A.7. draft-ietf-avtcore-monarch-06 . . . . . . . . . . . . . . 26 91 A.8. draft-ietf-avtcore-monarch-07 . . . . . . . . . . . . . . 26 92 A.9. draft-ietf-avtcore-monarch-08 . . . . . . . . . . . . . . 26 93 A.10. draft-ietf-avtcore-monarch-09 . . . . . . . . . . . . . . 26 94 A.11. draft-ietf-avtcore-monarch-10 . . . . . . . . . . . . . . 26 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 97 1. Introduction 99 As the delivery of multimedia services using the Real-Time Transport 100 Protocol (RTP) over IP network is gaining an increasing popularity, 101 uncertainties in the performance and availability of these services 102 are driving the need to support new standard methods for gathering 103 performance metrics from RTP applications. These rapidly emerging 104 standards, such as RTP Control Protocol Extended Reports (RTCP 105 XR)[RFC3611] and other RTCP extension to Sender Reports (SR), 106 Receiver Reports (RR) [RFC3550] are being developed for the purpose 107 of collecting and reporting performance metrics from endpoint devices 108 that can be used to correlate the metrics, provide end to end service 109 visibility and measure and monitor Quality of Experience (QoE) 110 [RFC6390]. 112 However the proliferation of RTP/RTCP specific metrics for transport 113 and application quality monitoring has been identified as a potential 114 problem for RTP/RTCP interoperability, which attempt to provide full 115 coverage of all those parameters of concern to a specific 116 application. Given that different applications layered on RTP may 117 have some monitoring requirements in common, these metrics should be 118 satisfied by a common design. 120 The objective of this document is to define an extensible RTP 121 monitoring framework to provide a small number of re-usable Quality 122 of Service (QoS)/QoE metrics which facilitate reduced implementation 123 costs and help maximize inter-operability. RTCP Guideline [RFC5968] 124 has stated that, where RTCP is to be extended with a new metric, the 125 preferred mechanism is by the addition of a new RTCP XR [RFC3611] 126 block. This memo assumes that any requirement for a new metric to be 127 transported in RTCP will use a new RTCP XR block. 129 2. Terminology 131 This memo is informative and as such contains no normative 132 requirements. 134 In addition, the following terms are defined: 136 Transport level metrics 138 A set of metrics which characterise the three transport 139 impairments of packet loss, packet delay, and packet delay 140 variation. These metrics should be usable by any application 141 which uses RTP transport. 143 Application level metrics 145 Metrics relating to application specific parameters or QoE related 146 parameters. Application specific parameters are measured at the 147 application level and focus on quality of content rather than 148 network performance. QoE related parameters reflect the end-to- 149 end performance at the services level and is ususally measured at 150 the user endpoint. One example of such metrics is the QoE Metric 151 specified in QoE metric reporting Block [QOE]. 153 End System metrics 155 Metrics relating to the way a terminal deals with transport 156 impairments affecting the incident RTP stream. These may include 157 de-jitter buffering, packet loss concealment, and the use of 158 redundant streams (if any) for correction of error or loss. 160 Direct metrics 162 Metrics that can be directly measured or calculated and are not 163 dependent on other metric. 165 Composed metrics 167 Metrics that are calculated based on Direct metric that have been 168 measured or combination of Direct metrics that are identical to 169 the metric being composed. 171 Interval metrics 173 It is referred to as the metrics of which the reported values 174 apply to the most recent measurement interval duration between 175 successive metrics reports. 177 Cumulative metrics 179 It is referred to as the metrics of which the reported values 180 apply to the accumulation period characteristic of cumulative 181 measurements. 183 Sampled metrics 185 It is referred to as the metrics of which the reported values only 186 apply to the value of a continuously measured or calculated that 187 has been sampled at end of the interval. 189 3. RTP monitoring architecture 191 There are many ways in which the performance of an RTP session can be 192 monitored. These include RTP-based mechanisms such as the RTP SNMP 193 MIB [RFC2959], or the SIP event package for RTCP summary reports 194 [RFC6035], or non-RTP mechanisms such as generic MIBs, NetFlow, 195 IPFix, and so on. Together, these provide useful mechanisms for 196 exporting data on the performance of an RTP session to non-RTP 197 network management systems. It is desirable to also perform in- 198 session monitoring of RTP performance. RTCP provides the means to do 199 this. In the following, we specify an architecture for using and 200 extending RTCP for monitoring RTP sessions. One major benefit of 201 such architecture is ease of integration with other RTP/RTCP 202 mechanism. 204 3.1. Overview 206 The RTP monitoring architecture comprises the following two key 207 functional components shown below: 209 o RTP Monitor 211 o RTP Metric Block Structure 213 RTP Monitor is the functional component defined in the Real-time 214 Transport Protocol [RFC3550] that acts as a source of information 215 gathered for monitoring purposes. It may gather such information 216 reported by RTCP XR or other RTCP extension and calculate statistics 217 from multiple source. According to the definition of monitor in the 218 RTP Protocol [RFC3550], the end system that runs an application 219 program that sends or receives RTP data packets, an intermediate- 220 system that forwards RTP packets to End-devices or a third party that 221 observes the RTP and RTCP traffic but does not make itself visible to 222 the RTP Session participants (i.e., the third party monitor depicted 223 in figure 1) can be envisioned to act as the monitor within the RTP 224 monitoring architecture. Note that the third party monitor should be 225 placed on the RTP/RTCP paths between the sender, intermediate and the 226 receiver. 228 The RTP Metric Block exposes real time Application QoS/QoE metric 229 information in the appropriate report block format to the management 230 system (i.e., report collector) within the RTP monitoring 231 architecture. Such information can be formulated as: 233 o The direct metrics 235 o or the composed metrics 236 or formulated as 238 o The Interval metrics 240 o or cumulative metrics 242 o or sampled metrics 244 Both the RTCP or RTCP XR can be extended to convey these metrics. 245 The details on transport protocols for metric blocks are described in 246 Section 3.2. 248 +-------------------+ 249 | RTP Sender | 6 +----------+ 250 | +-----------+ ||------------>|Management| 251 -------------->| Monitor |----| 6 | System | 252 | | | | | |----------->| | 253 | | +-----------+ | | -------->| | 254 | |+-----------------+| | | +-------/--+ 255 | ||Application || | | -----------| | 256 | ||-Streaming video || | | | 1 | |6 257 | |---------|-VOIP || | | | +--------V------+ 258 | | ||-Video conference|| | | --- Third Party | 259 | | ||-Telepresence || | | | Monitor | 260 | | ||-Ad insertion || | 6| +---------------+ 261 5 | |+-----------------+| | | 262 | | +-------------------+ | | 263 | 1 | | 264 | | +Intermediate------------+ | | |------------------------+ 265 | | | RTP System | | | | RTP Receiver >--4-| | 266 | | | +----------- | | | | +-----------+ | 267 | | | | -----------| -------| | | | 268 | | | | | | | | Monitor |<-- | 269 |----------- Monitor |<--------5------|----| |<------| 270 | | | | Report Block | +----/------+ || 271 | | +----------+Transport Over | || 272 | | RTCP XR or RTCP | |2 || 273 | | +-----------------+ extension | +-------/---------+ || 274 | | |Application | | | |Application | || 275 | | |-Streaming video | | | |-Streaming video | || 276 | | |-VOIP | | 1 | |-VOIP | 3| 277 ---->-Video conference|--------------->|-Video conference || 278 | |-Telepresence | | | |-Telepresence | || 279 | |-Ad insertion | | | |-Ad insertion | || 280 | +-----------------+ | | +-----------------+ || 281 | +-----------------+ | | +-----------------+ || 282 | |Transport | | | |Transport | || 283 | |-IP/UDP/RTP | | | |-IP/UDP/RTP >---|| 284 | |-IP/TCP/RTP | | | |-IP/TCP/RTP | | 285 | |-IP/TCP/RTSP/RTP | | | |-IP/TCP/RTSP/RTP | | 286 | +-----------------+ | | +-----------------+ | 287 +------------------------+ +------------------------+ 289 Figure 1: RTP Monitoring Architecture 291 1. RTP communication between real time applications. 293 2. Application level metrics collection. 295 3. Transport level metrics collection. 297 4. End System metrics collection. 299 5. Metrics Reporting over the RTP/RTCP paths 301 6. RTCP information Export to the network management system. 303 RTP is used to multicast groups, both ASM and SSM. These groups can 304 be monitored using RTCP. In the ASM case, the monitor is a member of 305 the multicast group and listens to RTCP XR reports from all members 306 of the ASM group. In the SSM case, there is a unicast feedback 307 target that receives RTCP feedback from receivers and distributes it 308 to other members of the SSM group (see figure 1 of RFC5760). The 309 monitor will need to be co-located with the feedback target to 310 receive all feedback from the receivers (this may also be an 311 intermediate system). In both ASM and SSM scenarios, receivers can 312 send RTCP XR reports to enhance the reception quality reporting. 314 3.2. RTCP Metric Block Report and associated parameters 316 The basic RTCP Reception Report (RR) [RFC3550] conveys reception 317 statistics (i.e., transport level statistics) in metric block report 318 format for multiple RTP media streams including 320 o the fraction of packet lost since the last report 322 o the cumulative number of packets lost 324 o the highest sequence number received 326 o an estimate of the inter-arrival jitter 328 o and information to allow senders to calculate the network round 329 trip time. 331 The RTCP XRs [RFC3611] supplement the existing RTCP packets and 332 provide more detailed feedback on reception quality in several 333 categories: 335 o Loss and duplicate Run Length Encoding (RLE) reports 337 o Packet-receipt times reports 339 o Round-trip time reports 341 o Statistics Summary Reports 342 There are also various other scenarios in which it is desirable to 343 send RTCP Metric reports more frequently. For example, the Audio/ 344 Video Profile with Feedback [RFC4585] extends the standard Audio/ 345 Video Profile [RFC3551] to allow RTCP reports to be sent early 346 provided RTCP bandwidth allocation is respected. The following are 347 four use cases but are not limited to: 349 o RTCP NACK is used to provide feedback on the RTP sequence number 350 on a subset of the lost packets or the total lost packets 351 [RFC4585]. 353 o RTCP is extended to convey requests for full intra-coded frames or 354 select the reference picture, and signal changes in the desired 355 temporal/spatial trade-off and maximum media bit rate [RFC5104]. 357 o RTCP or RTCP XR is extended to provide feedback on Explicit 358 Congestion Notification (ECN) statistics information [ECN]. 360 o RTCP XR is extended to provide feedback on multicast acquisition 361 statistics information and parameters [RFC6332]. 363 3.3. RTP Sender/Receiver entities located in network nodes 365 The location of the RTP Sender/Receiver entities may impact a set of 366 meaningful metrics. For instance, application level metrics for QoE 367 related performance parameters are under most conditions measured at 368 the user device that receives RTP data packets. However in some 369 cases, given the factors ( "measurement point location", "measurement 370 model location", "awareness of content information", etc [P.NAMS]) 371 taken into account, such metrics may be measured in a network node 372 instead of a user device. 374 4. Issues with reporting metric block using RTCP XR extension 376 Issues that have come up in the past with reporting metric block 377 using RTCP XR extensions include (but are probably not limited to) 378 the following: 380 o Using compound metrics block. A single report block 381 (i.e.,compound metrics block) is designed to contain a large 382 number of parameters in different classes for a specific 383 application. For example, the RTCP Extended Reports (XRs) 384 [RFC3611] defines seven report block formats for network 385 management and quality monitoring. Some of these block types 386 defined in the RTCP XRs [RFC3611] are only specifically designed 387 for conveying multicast inference of network characteristics 388 (MINC) or voice over IP (VoIP) monitoring. However different 389 applications layered on RTP may have different monitoring 390 requirements. Design compound metrics block only for specific 391 applications may increase implementation cost and minimize 392 interoperability. 394 o Correlating RTCP XR with the non-RTP data. Canonical End-Point 395 Identifier SDES Item (CNAME) defined in the RTP Protocol [RFC3550] 396 is an example of existing tool that allows to bind an 397 Synchronization source (SSRC) that may change to a fixed source 398 name in one RTP session. It may be also fixed across multiple RTP 399 sessions from the same source. However there may be situations 400 where RTCP reports are sent to other participating endpoints using 401 non-RTP protocol in a session. For example, as described in the 402 SIP RTCP Summary Report Protocol [RFC6035], the data contained in 403 RTCP XR VoIP metrics reports [RFC3611] are forwarded to a central 404 collection server systems using SIP. In such case, there is a 405 large portfolio of quality parameters that can be associated with 406 real time application, e.g., VOIP application, but only a minimal 407 number of parameters are included on the RTCP-XR reports. 408 Therefore correlation between RTCP XR and non-RTP data should be 409 concerned if administration or management systems need to rely on 410 the mapping RTCP statistics to non-RTCP measurements to conducts 411 data analysis and creates alerts to the users. Without such 412 correlation, it is hard to provide accurate measures of real time 413 application quality with a minimal number of parameters included 414 on the RTCP-XR reports in such case. 416 o Measurement Information duplication. Measurement information 417 provides information relevant to a measurement reported in one or 418 more other block types. For example we may set a metric interval 419 for the session and monitor RTP packets within one or several 420 consecutive metric interval. In such case, the extra measurement 421 information (e.g., extended sequence number of 1st packet, 422 measurement period) may be expected. However if we put such extra 423 measurement information into each metric block, there may be 424 situations where an RTCP XR packet containing multiple metric 425 blocks, reports on the same streams from the same source. In 426 other words, duplicated data for the measurement is provided 427 multiple times, once in every metric block. Though this design 428 ensures immunity to packet loss, it may bring more packetization 429 complexity and the processing overhead is not completely trivial 430 in some cases. Therefore compromise between processing overhead 431 and reliability should be taken into account. 433 o Consumption of XR block code points. The RTCP XR block namespace 434 is limited by the 8-bit block type field in the RTCP XR header. 435 Space exhaustion may be a concern in the future. We therefore may 436 need a way to extend the block type space, so that new 437 specifications may continue to be developed. 439 5. Guideline for reporting metric block using RTCP XR 441 5.1. Using single metrics blocks 443 Different applications using RTP for media transport certainly have 444 differing requirements for metrics transported in RTCP to support 445 their operation. For many applications, the basic metrics for 446 transport impairments provided in RTCP SR and RR packets [RFC3550] 447 (together with source identification provided in RTCP SDES packets) 448 are sufficient. For other applications additional metrics may be 449 required or at least sufficiently useful to justify the overheads, 450 both of processing in endpoints and of increased session bandwidth. 451 For example an IPTV application using Forward Error Correction (FEC) 452 might use either a metric of post-repair loss or a metric giving 453 detailed information about pre-repair loss bursts to optimise payload 454 bandwidth and the strength of FEC required for changing network 455 conditions. However there are many metrics available. It is likely 456 that different applications or classes of applications will wish to 457 use different metrics. Any one application is likely to require 458 metrics for more than one parameter but if this is the case, 459 different applications will almost certainly require different 460 combinations of metrics. If larger blocks are defined containing 461 multiple metrics to address the needs of each application, it becomes 462 likely that many different such larger blocks are defined, which 463 becomes a danger to interoperability. 465 To avoid this pitfall, this memo proposes the use of single metrics 466 blocks each containing a very small number of individual metrics 467 characterizing only one parameter of interest to an application 468 running over RTP. For example, at the RTP transport layer, the 469 parameter of interest might be packet delay variation, and 470 specifically the metric "IP Packet Delay Variation (IPDV)" defined by 471 [Y1540]. See Section 6 for architectural considerations for a 472 metrics block, using as an example a metrics block to report packet 473 delay variation. 475 5.2. Correlating RTCP XR with the non-RTP data 477 There may be situation where more than one media transport protocols 478 are used by one application to interconnect to the same session in 479 the gateway. For example, one RTCP XR Packet is sent to the 480 participating endpoints using non-RTP-based media transport (e.g., 481 using SIP) in a VOIP session, one crucial factor lies in how to 482 handle their different identities that are corresponding to different 483 media transport. 485 This memo proposes an approach to facilitate the correlation of the 486 RTCP Session with other session-related non-RTP data. That is to say 487 if there is a need to correlate RTP sessions with non-RTP sessions, 488 then the correlation information needed should be conveyed in a new 489 RTCP Source Description (SDES) item, since such correlation 490 information describes the source, rather than providing a quality 491 report. An example use case is for a participant endpoint may convey 492 a call identifier or a global call identifier associated with the 493 SSRC of measured RTP stream. In such case, the participant endpoint 494 uses the SSRC of source to bind the call identifier using SDES item 495 in the SDES RTCP packet and send such correlation to the network 496 management system. A flow measurement tool that is configured with 497 the 5-tuple and not call-aware then forward the RTCP XR reports along 498 with the SSRC of the measured RTP stream which is included in the XR 499 Block header and 5-tuple to the network management system. Network 500 management system can then correlate this report using SSRC with 501 other diagnostic information such as call detail records. 503 5.3. Reducing Measurement information repetition 505 When multiple metric blocks are carried in one RTCP XR packet, 506 reporting on the same stream from the same source for the same time 507 period, RTCP should use the SSRC to identify and correlate the 508 multiple metric blocks between metric blocks. This memo proposes to 509 define a new XR Block that will be used to convey the common time 510 period and the number of packets sent during this period. If the 511 measurement interval for a metric is different from the RTCP 512 reporting interval, then this measurement duration in the Measurement 513 information block [MI] should be used to specify the interval. When 514 there may be multiple measurements information blocks with the same 515 SSRC in one RTCP XR compound packet, the measurement information 516 block should be put in order and followed by all the metric blocks 517 associated with this measurement information block. New RTCP XR 518 metric blocks that rely on the Measurement information block [MI] 519 must specify the response in case the new RTCP XR metric block is 520 received without an associated measurement information block. In 521 most cases, it is expected that the correct response is to discard 522 the received metric. In order to reduce measurement information 523 repetition in one RTCP XR compound packet containing multiple metric 524 blocks, the measurement information shall be sent before the related 525 metric blocks that are from the same reporting interval. Note that 526 for packet loss robustness if the report blocks for the same interval 527 span over more than one RTCP packet then each must have the 528 measurement identity information even if though they will be the 529 same. 531 5.4. Expanding the RTCP XR block namespace 533 The consumption of XR block code points isn't a major issue. However 534 if XR block codes points is really close to run out of space, it 535 might be desirable to define new fields in the XR report block or 536 define one XR block type for vendor-specific extensions, with an 537 enterprise number included to identify the vendor making the 538 extension. 540 6. An example of a metric block 542 This section uses the example of an existing proposed metrics block 543 to illustrate the application of the principles set out in 544 Section 5.1. 546 The example [PDV] is a block to convey information about packet delay 547 variation (PDV) only, consistent with the principle that a metrics 548 block should address only one parameter of interest. One simple 549 metric of PDV is available in the RTCP RR packet as the "interarrival 550 jitter" field. There are other PDV metrics with a certain similarity 551 in metric structure which may be more useful to certain applications. 552 Two such metrics are the IPDV metric ([Y1540], [RFC3393]) and the 553 mean absolute packet delay variation 2 (MAPDV2) metric [G1020]. Use 554 of these metrics is consistent with the principle in Section 5 of 555 RTCP guideline [RFC5968] that metrics should usually be defined 556 elsewhere, so that RTCP standards define only the transport of the 557 metric rather than its nature. The purpose of this section is to 558 illustrate the architecture using the example of [PDV] rather than to 559 document the design of the PDV metrics block or to provide a tutorial 560 on PDV in general. 562 Given the availability of at least three metrics for PDV, there are 563 design options for the allocation of metrics to RTCP XR blocks: 565 o provide an RTCP XR block per metric 567 o provide a single RTCP XR block which contains all three metrics 569 o provide a single RTCP block to convey any one of the three 570 metrics, together with a identifier to inform the receiving RTP 571 system of the specific metric being conveyed 573 In choosing between these options, extensibility is important, 574 because additional metrics of PDV may well be standardized and 575 require inclusion in this framework. The first option is extensible 576 but only by use of additional RTCP XR blocks, which may consume the 577 limited namespace for RTCP XR blocks at an unacceptable rate. The 578 second option is not extensible, so could be rejected on that basis, 579 but in any case a single application is quite unlikely to require 580 transport of more than one metric for PDV. Hence the third option 581 was chosen. This implies the creation of a subsidiary namespace to 582 enumerate the PDV metrics which may be transported by this block, as 583 discussed further in [PDV]. 585 7. Application to RFC 5117 topologies 587 The topologies specified in [RFC5117] fall into two categories. The 588 first category relates to the RTP system model utilizing multicast 589 and/or unicast. The topologies in this category are specifically 590 Topo-Point-to-Point, Topo- Multicast, Topo-Translator (both variants, 591 Topo-Trn-Translator and Topo-Media-Translator, and combinations of 592 the two), and Topo-Mixer. These topologies use RTP end systems, RTP 593 mixers and RTP translators defined in the RTP protocol [RFC3550]. 594 For purposes of reporting connection quality to other RTP systems, 595 RTP mixers and RTP end systems are very similar. Mixers 596 resynchronize packets and do not relay RTCP reports received from one 597 cloud towards other cloud(s). Translators do not resynchronize 598 packets and should forward certain RTCP reports between clouds. In 599 this category, the RTP system (end system, mixer or translator) which 600 originates, terminates or forwards RTCP XR blocks is expected to 601 handle RTCP, including RTCP XR, according to the RTP protocol 602 [RFC3550]. Provided this expectation is met, an RTP system using 603 RTCP XR is architecturally no different from an RTP system of the 604 same class (end system, mixer, or translator) which does not use RTCP 605 XR. The second category relates to deployed system models used in 606 many H.323 [H323] video conferences. The topologies in this category 607 are Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU. Such 608 topologies based on systems do not behave according to the RTP 609 protocol [RFC3550]. 611 Considering the MCU and translator are two typical topologies in the 612 two categories mentioned above, this document will take them as two 613 typical examples to explain how RTCP XR report works in different 614 RFC5117 topologies. 616 7.1. Applicability to MCU 618 Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU, suffer from the 619 difficulties described in [RFC5117]. These difficulties apply to 620 systems sending, and expecting to receive, RTCP XR blocks as much as 621 to systems using other RTCP packet types. For example, a participant 622 RTP end system may send media to a video switch MCU. If the media 623 stream is not selected for forwarding by the switch, neither RTCP RR 624 packets nor RTCP XR blocks referring to the end system's generated 625 stream will be received at the RTP end system. Strictly the RTP end 626 system can only conclude that its RTP has been lost in the network, 627 though an RTP end system complying with the robustness principle of 628 [RFC1122] should survive with essential functions (i.e.,media 629 distribution) unimpaired. 631 7.2. Applicability to Translators 633 Section 7.2 of the RTP protocol [RFC3550] describes processing of 634 RTCP by translators. RTCP XR is within the scope of the 635 recommendations of the RTP protocol [RFC3550]. Some RTCP XR metrics 636 blocks may usefully be measured at, and reported by, translators. As 637 described in the RTP protocol [RFC3550] this creates a requirement 638 for the translator to allocate an SSRC for the monitor collocated 639 with itself so that the monitor may populate the SSRC in the RTCP XR 640 packet header as packet sender SSRC and send it out(although the 641 translator is not a Synchronisation Source in the sense of 642 originating RTP media packets). It must also supply this SSRC and 643 the corresponding CNAME in RTCP SDES packets. 645 In RTP sessions where one or more translators generate any RTCP 646 traffic towards their next-neighbour RTP system, other translators in 647 the session have a choice as to whether they forward a translator's 648 RTCP packets. Forwarding may provide additional information to other 649 RTP systems in the connection but increases RTCP bandwidth and may in 650 some cases present a security risk. RTP translators may have 651 forwarding behaviour based on local policy, which might differ 652 between different interfaces of the same translator. 654 8. IANA Considerations 656 There is no IANA action in this document. 658 9. Security Considerations 660 This document focuses on the RTCP reporting extension using RTCP XR 661 and should not give rise to any new security vulnerabilities beyond 662 those described in RTCP XRs [RFC3611]. However it also describes the 663 architectural framework to be used for monitoring at RTP layer. The 664 security issues with monitoring needs to be considered. 666 In RTP sessions, a RTP system may use its own SSRC to send its 667 monitoring reports towards its next-neighbour RTP system. Other RTP 668 system in the session may have a choice as to whether they forward 669 this RTP system's RTCP packets. This present a security issue since 670 the information in the report may be exposed by the other RTP system 671 to any malicious node. Therefore if the information is considered as 672 sensitive, the monitoring report should be encrypted. 674 Also note that the third party monitors are not visible at the RTP 675 layer since they do not send any RTCP packets. In order to prevent 676 any sensitive information leakage, the monitoring from the third 677 party monitors should be prohibited unless the security is in place 678 to authenticate them. 680 10. Acknowledgement 682 The authors would also like to thank Colin Perkins, Graeme Gibbs, 683 Debbie Greenstreet, Keith Drage, Dan Romascanu, Ali C. Begen, Roni 684 Even, Magnus Westerlund for their valuable comments and suggestions 685 on the early version of this document. 687 11. Informative References 689 [ECN] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., 690 and K. Carlberg, "Explicit Congestion Notification (ECN) 691 for RTP over UDP", ID draft-ietf-avtcore-ecn-for-rtp-06, 692 February 2012. 694 [G1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter 695 definitions for quality of speech and other voiceband 696 applications utilizing IP networks", July 2006. 698 [H323] ITU-T, "ITU-T Rec. H.323, Packet-based multimedia 699 communications systems", June 2006. 701 [MI] Wu, Q., "Measurement Identity and information Reporting 702 using SDES item and XR Block", 703 ID draft-ietf-xrblock-rtcp-xr-meas-identity-02, 704 January 2012. 706 [P.NAMS] ITU-T, "Non-intrusive parametric model for the Assessment 707 of performance of Multimedia Streaming", ITU-T 708 Recommendation P.NAMS, November 2009. 710 [PDV] Hunt, G., Clark, A., and Q. Wu, "RTCP XR Report Block for 711 Packet Delay Variation Metric Reporting", 712 ID draft-ietf-xrblock-rtcp-xr-pdv-02, December 2011. 714 [QOE] Hunt, G., Clark, A., Wu, Q., Schott, R., and G. Zorn, 715 "RTCP XR Blocks for QoE Metric Reporting", 716 ID draft-ietf-xrblock-rtcp-xr-qoe-00, February 2012. 718 [RFC1122] Braden, R., "Requirements for Internet Hosts -- 719 Communication Layers", RFC 1122, October 1989. 721 [RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time 722 Transport Protocol Management Information Base", RFC 2959, 723 October 2000. 725 [RFC3393] Demichelis, C., "IP Packet Delay Variation Metric for IP 726 Performance Metrics (IPPM)", RFC 3393, November 2002. 728 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 729 Applications", RFC 3550, July 2003. 731 [RFC3551] Schulzrinne , H. and S. Casner, "Extended RTP Profile for 732 Real-time Transport Control Protocol (RTCP)-Based Feedback 733 (RTP/AVPF)", RFC 3551, July 2003. 735 [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP 736 XR)", RFC 3611, November 2003. 738 [RFC4585] Ott, J. and S. Wenger, "Extended RTP Profile for Real-time 739 Transport Control Protocol (RTCP)-Based Feedback (RTP/ 740 AVPF)", RFC 4585, July 2006. 742 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 743 "Session Initiation Protocol Event Package for Voice 744 Quality Reporting", RFC 5104, February 2008. 746 [RFC5117] Westerlund, M., "RTP Topologies", RFC 5117, January 2008. 748 [RFC5968] Ott, J. and C. Perkins, "Guidelines for Extending the RTP 749 Control Protocol (RTCP)", RFC 5968, September 2010. 751 [RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich, 752 "Session Initiation Protocol Event Package for Voice 753 Quality Reporting", RFC 6035, November 2010. 755 [RFC6332] Begen, A. and E. Friedrich, "Multicast Acquisition Report 756 Block Type for RTP Control Protocol (RTCP) Extended 757 Reports (XRs)", RFC 6332, July 2011. 759 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 760 Performance Metric Development", RFC 6390, October 2011. 762 [Y1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and 763 availability performance parameters", November 2007. 765 Appendix A. Change Log 767 Note to the RFC-Editor: please remove this section prior to 768 publication as an RFC. 770 A.1. draft-ietf-avtcore-monarch-00 772 The following are the major changes compared to 773 draft-hunt-avtcore-monarch-02: 775 o Move Geoff Hunt and Philip Arden to acknowledgement section. 777 A.2. draft-ietf-avtcore-monarch-01 779 The following are the major changes compared to 00: 781 o Restructure the document by merging section 4 into section 3. 783 o Remove section 4.1,section 5 that is out of scope of this 784 document. 786 o Remove the last bullet in section 6 and section 7.3 based on 787 conclusion of last meeting. 789 o Update figure 1 and related text in section 3 according to the 790 monitor definition in RFC3550. 792 o Revise section 9 to address monitor declaration issue. 794 o Merge the first two bullet in section 6. 796 o Add one new bullet to discuss metric block association in section 797 6. 799 A.3. draft-ietf-avtcore-monarch-02 801 The following are the major changes compared to 01: 803 o Deleting first paragraph of Section 1. 805 o Deleting Section 3.1, since the interaction with the management 806 application is out of scope of this draft. 808 o Separate identity information correlation from section 5.2 as new 809 section 5.3. 811 o Remove figure 2 and related text from section 5.2. 813 o Editorial changes in the section 4 and the first paragraph of 814 section 7. 816 A.4. draft-ietf-avtcore-monarch-03 818 The following are the major changes compared to 02: 820 o Update bullet 2 in section 4 to explain the ill-effect of Identity 821 Information duplication. 823 o Update bullet 3 in section 4 to explain why Correlating RTCP XR 824 with the non-RTP data is needed. 826 o Update section 5.2 to focus on how to reduce the identity 827 information repetition 829 o Update section 5.3 to explain how to correlate identity 830 information with the non-RTP data 832 A.5. draft-ietf-avtcore-monarch-04 834 The following are the major changes compared to 03: 836 o Update section 5.2 to clarify using SDES packet to carry 837 correlation information. 839 o Remove section 5.3 since additional identity information goes to 840 SDES packet and using SSRC to identify each block is standard RTP 841 feature. 843 o Swap the last two paragraphs in the section 4 since identity 844 information duplication can not been 100% avoided. 846 o Other editorial changes. 848 A.6. draft-ietf-avtcore-monarch-05 850 The following are the major changes compared to 04: 852 o Replace "chunk" with "new SDES item". 854 o Add texts in security section to discussion potential security 855 issues. 857 o Add new sub-section 5.3 to discuss Reducing Measurement 858 information repetition. 860 o Other editorial changes. 862 A.7. draft-ietf-avtcore-monarch-06 864 The following are the major changes compared to 05: 866 o Some editorial changes. 868 A.8. draft-ietf-avtcore-monarch-07 870 The following are the major changes compared to 06: 872 o Clarify the XR block code points consumption issue in the section 873 4 and new section 5.4. 875 o Other editorial changes. 877 A.9. draft-ietf-avtcore-monarch-08 879 The following are the major changes compared to 07: 881 o Editorial change to the reference. 883 A.10. draft-ietf-avtcore-monarch-09 885 The following are the major changes compared to 07: 887 o Rephrase application level metric definition. 889 o Add one new section to clarify where to measure QoE related 890 parameters. 892 o Add text in section 5.3 to clarify the failure case when 893 measurement interval is not sent. 895 o Add text in section 5.3 to clarify how to deal with multiple 896 measurements information blocks carried in the same packet. 898 A.11. draft-ietf-avtcore-monarch-10 900 The following are the major changes compared to 09: 902 o Discuss what exist already for monitoring in section 3.1. 904 o Provide benefit using RTCP XR based monitoring in section 3.1. 906 o add one new paragraph in section 3.1 to describe how monitoring 907 architecture is applied to ASM/SSM. 909 o Other Editorial Changes. 911 Authors' Addresses 913 Qin Wu (editor) 914 Huawei 915 101 Software Avenue, Yuhua District 916 Nanjing, Jiangsu 210012 917 China 919 Email: sunseawq@huawei.com 921 Geoff Hunt 922 Unaffiliated 924 Email: r.geoff.hunt@gmail.com 926 Philip Arden 927 BT 928 Orion 3/7 PP4 929 Adastral Park 930 Martlesham Heath 931 Ipswich, Suffolk IP5 3RE 932 United Kingdom 934 Phone: +44 1473 644192 935 Email: philip.arden@bt.com