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Clark 5 Intended status: Standards Track Telchemy 6 Expires: November 16, 2009 May 15, 2009 8 RTCP XR Report Block for Delay metric Reporting 9 draft-ietf-avt-rtcp-xr-delay-02.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on November 16, 2009. 34 Copyright Notice 36 Copyright (c) 2009 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 This document defines an RTCP XR Report Block that allows the 48 reporting of Delay metrics for use in a range of RTP applications. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 1.1. Delay Report Block . . . . . . . . . . . . . . . . . . . . 3 54 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 55 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 56 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 3. Delay Block . . . . . . . . . . . . . . . . . . . . . . . . . 5 59 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 60 3.2. Definition of Fields in Delay Metrics Report Block . . . . 5 61 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 63 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 9 64 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 9 65 5.3. Contact information for registrations . . . . . . . . . . 9 66 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 67 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11 68 8. Changes from previous version . . . . . . . . . . . . . . . . 12 69 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 70 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 71 9.2. Informative References . . . . . . . . . . . . . . . . . . 13 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 74 1. Introduction 76 1.1. Delay Report Block 78 This draft defines a new block type to augment those defined in 79 [RFC3611] for use in a range of RTP applications. The new block type 80 supports the reporting of the mean, minimum and maximum values of the 81 network round-trip delay between RTP interfaces in peer RTP end 82 systems as measured, for example, using the RTCP method described in 83 [RFC3550]. It also supports reporting of the component of the round- 84 trip delay internal to the local RTP system. 86 The network metrics belong to the class of packet transport delay 87 metrics defined in [MONARCH] (work in progress). 89 Instances of this Metrics Block refer by tag to the separate 90 auxiliary Measurement Identity block [MEASIDENT] which contains 91 information such as the SSRC of the measured stream, and RTP sequence 92 numbers and time intervals indicating the span of the report. 94 1.2. RTCP and RTCP XR Reports 96 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 97 defined an extensible structure for reporting using an RTCP Extended 98 Report (XR). This draft defines a new Extended Report block that 99 MUST be used as defined in [RFC3550] and [RFC3611]. 101 1.3. Performance Metrics Framework 103 The Performance Metrics Framework [PMOLFRAME] provides guidance on 104 the definition and specification of performance metrics. Metrics 105 described in this draft either reference external definitions or 106 define metrics generally in accordance with the guidelines in 107 [PMOLFRAME]. 109 1.4. Applicability 111 This metric is believed to be applicable to all RTP applications. 113 2. Definitions 115 Numeric formats 117 This report block makes use of binary fractions. The terminology 118 used is 120 S X:Y 122 where S indicates a two's complement signed representation, X the 123 number of bits prior to the decimal place and Y the number of bits 124 after the decimal place. 126 Hence 8:8 represents an unsigned number in the range 0.0 to 127 255.996 with a granularity of 0.0039. S7:8 would represent the 128 range -128.000 to +127.996. 0:16 represents a proper binary 129 fraction with range 131 0.0 to 1 - 1/65536 = 0.9999847 133 though note that use of flag values at the top of the numeric 134 range slightly reduces this upper limit. For example, if the 16- 135 bit values 0xfffe and 0xffff are used as flags for "over-range" 136 and "unavailable" conditions, a 0:16 quantity has range 138 0.0 to 1 - 3/65536 = 0.9999542 140 3. Delay Block 142 3.1. Report Block Structure 144 Delay metrics block 145 0 1 2 3 146 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | BT=NDEL |I| tag | resv | block length = 2 | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | Mean Network Round Trip Delay | End System Delay | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Min Network Round Trip Delay | Max Network Round Trip Delay | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 Figure 1: Report Block Structure 157 3.2. Definition of Fields in Delay Metrics Report Block 159 block type (BT): 8 bits 161 A Delay Report Block is identified by the constant NDEL. 163 [Note to RFC Editor: please replace NDEL with the IANA provided RTCP 164 XR block type for this block.] 166 Interval Metric flag (I): 1 bit 168 This field is used to indicate whether the Delay metric block is 169 an Interval or a Cumulative metric block, that is, whether the 170 reported values apply to the most recent measurement interval 171 duration between successive metrics reports (I=1) (the Interval 172 Duration) or to the accumulation period characteristic of 173 cumulative measurements (I=0) (the Cumulative Duration). 174 Numerical values for both these intervals are provided in the 175 Measurement Identifier block referenced by the tag field below. 177 Measurement Identifier association (tag): 3 bits 179 This field is used to identify the Measurement Identifier block 180 [MEASIDENT] which describes this measurement. The relevant 181 Measurement Identifier block has the same tag value as the Delay 182 block. Note that there may be more than one Measurement 183 Identifier block per RTCP packet. 185 Reserved (resv): 4 bits 186 These bits are reserved. They SHOULD be set to zero by senders 187 and MUST be ignored by receivers. 189 block length: 16 bits 191 The length of this report block in 32-bit words, minus one. For 192 the Delay block, the block length is equal to 2. 194 Mean Network Round Trip Delay (ms): 16 bits 196 The Mean Network Round Trip Delay is the mean value of the RTP-to- 197 RTP interface round trip delay in ms over the measurement period, 198 typically determined using RTCP SR/RR. 200 If only one measurement of Round Trip Delay is available for the 201 timespan of the report (whether Interval or Cumulative), this 202 single value should be reported as the mean value. 204 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 205 reported to indicate an over-range measurement. If the 206 measurement is unavailable, the value 0xFFFF SHOULD be reported. 208 End System Delay (ms): 16 bits 210 The End System Delay is the internal round trip delay within the 211 reporting endpoint, calculated using the nominal value of the 212 jitter buffer delay plus the accumulation/ encoding and decoding / 213 playout delay associated with the codec being used. 215 If the measured or estimated value exceeds 0xFFFD, the value 216 0xFFFE SHOULD be reported to indicate an over-range measurement. 217 If the measurement is unavailable, the value 0xFFFF SHOULD be 218 reported. 220 Min Network Round Trip Delay (ms): 16 bits 222 The Min Network Round Trip Delay is the minimum value of the RTP- 223 to-RTP interface round trip delay in ms over the measurement 224 period, typically determined using RTCP SR/RR. 226 If only one measurement of Round Trip Delay is available for the 227 timespan of the report (whether Interval or Cumulative), this 228 single value should be reported as the minimum value. 230 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 231 reported to indicate an over-range measurement. If the 232 measurement is unavailable, the value 0xFFFF SHOULD be reported. 234 Max Network Round Trip Delay (ms): 16 bits 236 The Max Network Round Trip Delay is the maximum value of the RTP- 237 to-RTP interface round trip delay in ms over the measurement 238 period, typically determined using RTCP SR/RR. 240 If only one measurement of Round Trip Delay is available for the 241 timespan of the report (whether Interval or Cumulative), this 242 single value should be reported as the maximum value. 244 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 245 reported to indicate an over-range measurement. If the 246 measurement is unavailable, the value 0xFFFF SHOULD be reported. 248 4. SDP Signaling 250 [RFC3611] defines the use of SDP (Session Description Protocol) 251 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 252 without prior signaling. 254 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 255 in [RFC3611] by providing an additional value of "xr-format" to 256 signal the use of the report block defined in this document. 258 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF 260 (defined in [RFC3611]) 262 xr-format =/ xr-delay-block 264 xr-delay-block = "delay" 266 5. IANA Considerations 268 New block types for RTCP XR are subject to IANA registration. For 269 general guidelines on IANA considerations for RTCP XR, refer to 270 [RFC3611]. 272 5.1. New RTCP XR Block Type value 274 This document assigns the block type value NDEL in the IANA "RTCP XR 275 Block Type Registry" to the "Delay Metrics Block". 277 [Note to RFC Editor: please replace NDEL with the IANA provided RTCP 278 XR block type for this block.] 280 5.2. New RTCP XR SDP Parameter 282 This document also registers a new parameter "delay" in the "RTCP XR 283 SDP Parameters Registry". 285 5.3. Contact information for registrations 287 The contact information for the registrations is: 289 Geoff Hunt (geoff.hunt@bt.com) 291 Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United 292 Kingdom 294 6. Security Considerations 296 It is believed that this proposed RTCP XR report block introduces no 297 new security considerations beyond those described in [RFC3611]. 298 This block does not provide per-packet statistics so the risk to 299 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 300 does not apply. 302 7. Contributors 304 The authors gratefully acknowledge the comments and contributions 305 made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin 306 Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert 307 Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith 308 Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, 309 Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. 311 8. Changes from previous version 313 Changed BNF for SDP following Christian Groves' and Tom Taylor's 314 comments (4th and 5th May 2009), now aligned with RFC 5234 section 315 3.3 "Incremental Alternatives". 317 Updated references 319 9. References 321 9.1. Normative References 323 [MEASIDENT] 324 Hunt, G., "RTCP XR Measurement Identifier Block", 325 ID draft-ietf-avt-rtcp-xr-meas-identity-02, May 2009. 327 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 328 Requirement Levels", RFC 2119, BCP 14, March 1997. 330 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 331 Applications", RFC 3550, July 2003. 333 [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP 334 XR)", RFC 3611, November 2003. 336 [RFC4566] Handley, M., "SDP: Session Description Protocol", 337 RFC 4566, July 2006. 339 9.2. Informative References 341 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 342 ID draft-hunt-avt-monarch-01, August 2008. 344 [PMOLFRAME] 345 Clark, A., "Framework for Performance Metric Development", 346 ID draft-ietf-pmol-metrics-framework-02, March 2009. 348 Authors' Addresses 350 Geoff Hunt 351 BT 352 Orion 2 PP3 353 Adastral Park 354 Martlesham Heath 355 Ipswich, Suffolk IP5 3RE 356 United Kingdom 358 Phone: +44 1473 651704 359 Email: geoff.hunt@bt.com 361 Alan Clark 362 Telchemy Incorporated 363 2905 Premiere Parkway, Suite 280 364 Duluth, GA 30097 365 USA 367 Email: alan.d.clark@telchemy.com