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Hunt 3 Group BT 4 Internet-Draft A. Clark 5 Intended status: Standards Track Telchemy 6 Expires: August 29, 2009 February 25, 2009 8 RTCP XR Report Block for Measurement Identity 9 draft-ietf-avt-rtcp-xr-meas-identity-01.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 August 29, 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 carrying parameters 48 which identify a measurement, to which one or more other RTCP XR 49 Report Blocks may refer. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 1.1. Measurement Identity Report Block . . . . . . . . . . . . 3 55 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 4 56 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4 57 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 58 2. Measurement Identity Block . . . . . . . . . . . . . . . . . . 5 59 2.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 60 2.2. Definition of Fields in Measurement Identity Report 61 Block . . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 3. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8 63 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 64 4.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 9 65 4.2. Contact information for registration . . . . . . . . . . . 9 66 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 67 6. Changes since last version . . . . . . . . . . . . . . . . . . 11 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 69 7.1. Normative References . . . . . . . . . . . . . . . . . . . 12 70 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 73 1. Introduction 75 1.1. Measurement Identity Report Block 77 This draft defines a new block type to augment those defined in 78 [RFC3611] for use in a range of RTP applications. This block type 79 does not itself contain any measurement results (metrics). However, 80 this new block type provides information relevant to a measurement 81 reported in one or more other block types, including 83 o a tag or key by which other blocks (containing metrics 84 information) may refer to this block 86 o the SSRC of the measured stream, 88 o a field for incorporation of an application-specific auxiliary 89 identifier, 91 o the sequence number of the first packet of the RTP session, 93 o the extended sequence numbers of the first packet of the current 94 measurement interval, and the last packet included in the 95 measurement, 97 o the duration of the most recent measurement interval and 99 o the duration of the interval applicable to cumulative measurements 100 (which may be the duration of the RTP session to date). 102 The method for calculation of the extended RTP sequence number is 103 provide in [RFC3550]. 105 This block is intended to provide a single copy of the information 106 necessary to relate measurement data in other blocks to the stream, 107 and measurement period, to which they refer. Commonly, multiple 108 other small blocks contain measurement data for the same stream and 109 period, and it would be a large overhead if all of these blocks 110 carried duplicated data for measurement identification. Other blocks 111 make a reference to this block (by tag). 113 A Measurement Identity block is associated with the set of RTCP XR 114 metrics blocks which share its tag value. There MAY be several such 115 sets in an RTCP packet, up to a limit of 8 arising from the use of 116 3-bit tags. There MAY also be RTCP XR blocks in the packet which are 117 not associated with a Measurement Identity block, for example blocks 118 which were defined before the Measurement Identity mechanism was 119 introduced by this document. 121 1.2. RTCP and RTCP XR Reports 123 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 124 defined an extensible structure for reporting using an RTCP Extended 125 Report (XR). This draft defines a new Extended Report block that 126 MUST be used as defined in [RFC3550] and [RFC3611]. 128 1.3. Performance Metrics Framework 130 The Performance Metrics Framework [PMOLFRAME] provides guidance on 131 the definition and specification of performance metrics. Metrics 132 described in this draft either reference external definitions or 133 define metrics generally in accordance with the guidelines in 134 [PMOLFRAME]. 136 1.4. Applicability 138 This block provides identification information for members of a 139 family of RTCP XR metrics blocks which are designed to use it. To 140 use the mechanism defined here, a metrics block must be in the same 141 RTCP packet as the Measurement Identity block and must refer to the 142 Measurement Identity block via the 3-bit tag field defined below. 144 2. Measurement Identity Block 146 2.1. Report Block Structure 148 0 1 2 3 149 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 7 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | BT=NMI |0| tag | resv | block length = 7 | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | SSRC of stream source | 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 | sub-identifier | 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 | reserved | first seq num | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 | extended first sequence number of interval | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | extended last sequence number | 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 | Measurement Duration (Cumulative) (ms) | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | Measurement Duration (Interval) (ms) | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 Figure 1: Report Block Structure 170 2.2. Definition of Fields in Measurement Identity Report Block 172 Bits shown as '0' in the figure SHOULD be set to zero. 174 block type (BT): 8 bits 176 A Measurement Identity Report Block is identified by the constant 177 NMI. 179 [Note to RFC Editor: please replace NMI with the IANA provided RTCP 180 XR block type for this block.] 182 tag: 3 bits 184 This field is a tag or key which identifies this Measurement 185 Identity block within the scope of an RTCP packet. If an RTCP 186 packet contains more than one Measurement Identity block, each 187 Measurement Identity block MUST have a unique tag field to enable 188 metrics blocks in the same RTCP packet to refer unambiguously to 189 the correct Measurement Identity block. The 3-bit field allows up 190 to 8 Measurement Identity blocks in each RTCP packet. If 191 additional metrics must be sent at a given time, and they require 192 more than 8 blocks of Measurement Identity information, then the 193 metrics must be sent in multiple RTCP packets. 195 resv: 4 bits 197 These bits are reserved. They MUST be set to zero by senders. 198 They MUST be ignored by receivers. 200 block length: 16 bits 202 The length of this report block in 32-bit words minus one. For 203 the Measurement Identity block, the block length is equal to 7. 205 SSRC of source: 32 bits 207 The SSRC [RFC3550] of the source of the stream being reported. 208 Note that the SSRC of the reporting RTP system (the originator of 209 the report block) is present in the RTCP XR header defined in 210 Section 2 of [RFC3611]. 212 sub-identifier: 32 bits 214 An additional identifier which is useful in the context of a 215 specific application, e.g. an MPEG-2 transport identifier [MPEG2]. 216 Where the identifier is less than 32 bits, the identifier SHOULD 217 be mapped into the most significant bits of the field. If no 218 additional identifier is provided, all bits of the field MUST be 219 set to zero. This field MUST be ignored by applications which are 220 not configured to make use of it. 222 reserved: 16 bits 224 These bits are reserved. They MUST be ignored by receivers. They 225 MUST be set to zero by senders. 227 first seq num: 16 bits 229 The RTP sequence number of the first received RTP packet of the 230 session, used to determine the number of packets contributing to 231 cumulative measurements. 233 extended first sequence number of interval: 32 bits 235 The extended RTP sequence number of the first received RTP packet 236 of the current measurement interval. 238 extended last sequence number: 32 bits 239 The extended RTP sequence number of the last received RTP packet 240 which contributed to this measurement. 242 Measurement Duration (Cumulative) (ms): 32 bits 244 The duration in ms of the reporting interval applicable to 245 Cumulative reports which use this Measurement Identity block. 247 Measurement Duration (Interval) (ms): 32 bits 249 The duration in ms of the reporting interval applicable to 250 Interval reports which use this Measurement Identity block. 252 3. SDP Signaling 254 [RFC3611] defines the use of SDP (Session Description Protocol) 255 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 256 without prior signaling. 258 No additional SDP signaling is defined for this block. Instead, the 259 need for this block SHOULD be inferred from a request in SDP 260 signalling for a block type (such as [DISCARD]) which depends on it. 262 4. IANA Considerations 264 New block types for RTCP XR are subject to IANA registration. For 265 general guidelines on IANA considerations for RTCP XR, refer to 266 [RFC3611]. 268 4.1. New RTCP XR Block Type value 270 This document assigns the block type value NMI in the IANA "RTCP XR 271 Block Type Registry" to the "Measurement Identity Block". 273 [Note to RFC Editor: please replace NMI with the IANA provided RTCP 274 XR block type for this block.] 276 4.2. Contact information for registration 278 The contact information for the registration is: 280 Geoff Hunt (geoff.hunt@bt.com) 282 Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United 283 Kingdom 285 5. Security Considerations 287 RTCP reports can contain sensitive information since they can provide 288 information about the nature and duration of a session established 289 between two or more endpoints. 291 6. Changes since last version 293 Expanded and clarified IANA Considerations section 295 Changed to remove explicit SDP signalling for this block - need for 296 block is implicit if a metrics block is requested which depends on 297 this block. 299 Modified block structure to send first sequence number without 300 extension, rather than extend to 32-bit number with leading 16 bits 301 set to 0. These 16 bits are now reserved. Addresses Colin Perkins' 302 comment of 15-Nov-2008 304 Removed "forwarding count" field following Colin Perkins' request for 305 a use case. The field had been intended for use by translators to 306 establish the "distance" (as a count of forwarding systems) to the 307 point at which a measurement was made. However a recommendation to 308 increment the count could have forced forwarding translator devices 309 to parse the packet on a slow (CPU) path, possibly compromising RTCP 310 measurement of round-trip delay [RFC3550]. 312 7. References 314 7.1. Normative References 316 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 317 Requirement Levels", RFC 2119, BCP 14, March 1997. 319 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 320 Applications", RFC 3550, July 2003. 322 [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP 323 XR)", RFC 3611, November 2003. 325 [RFC4566] Handley, M., "SDP: Session Description Protocol", 326 RFC 4566, July 2006. 328 7.2. Informative References 330 [DISCARD] Hunt, G., "RTCP XR Report Block for Discard metric 331 Reporting", ID draft-ietf-avt-rtcp-xr-discard-01, 332 February 2009. 334 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 335 ID draft-hunt-avt-monarch-01, August 2008. 337 [MPEG2] ISO/IEC, "Standard 13818-1", December 2000. 339 [PMOLFRAME] 340 Clark, A., "Framework for Performance Metric Development", 341 ID draft-ietf-pmol-metrics-framework-00, July 2008. 343 Authors' Addresses 345 Geoff Hunt 346 BT 347 Orion 2 PP3 348 Adastral Park 349 Martlesham Heath 350 Ipswich, Suffolk IP5 3RE 351 United Kingdom 353 Phone: +44 1473 651704 354 Email: geoff.hunt@bt.com 356 Alan Clark 357 Telchemy Incorporated 358 2905 Premiere Parkway, Suite 280 359 Duluth, GA 30097 360 USA 362 Email: alan.d.clark@telchemy.com