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Lague 5 Expires: January 8, 2009 Cisco Systems 6 July 7, 2008 8 Post-Repair Loss RLE Report Block Type for RTCP XR 9 draft-ietf-avt-post-repair-rtcp-xr-00 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on January 8, 2009. 36 Copyright Notice 38 Copyright (C) The IETF Trust (2008). 40 Abstract 42 This document defines a new report block type within the framework of 43 RTP Control Protocol (RTCP) Extended Reports (XR). One of the 44 initial XR report block types is the Loss Run Length Encoding (RLE) 45 Report Block. This report conveys the information regarding the 46 individual Real-time Transport Protocol (RTP) packet receipt and loss 47 events experienced during the RTCP interval preceding the 48 transmission of the report. The new report, which is referred to as 49 the Post-repair Loss RLE Report, carries the information regarding 50 the remaining lost packets after all error-repair techniques are 51 applied. By comparing the RTP packet receipts/losses before and 52 after the error repair is completed, one can determine the 53 effectiveness of the error-repair techniques in an aggregated 54 fashion. This document also defines the signaling of the Post-repair 55 Loss RLE Report in the Session Description Protocol (SDP). 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 4 61 3. Post-Repair Loss RLE Report Block . . . . . . . . . . . . . . . 4 62 4. Session Description Protocol Signaling . . . . . . . . . . . . 5 63 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 64 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 65 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 68 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 70 Intellectual Property and Copyright Statements . . . . . . . . . . 8 72 1. Introduction 74 RTP Control Protocol (RTCP) is the out-of-band control protocol for 75 the applications that are using the Real-time Transport Protocol 76 (RTP) for media delivery and communications [RFC3550]. RTCP allows 77 the RTP entities to monitor the data delivery and provides them 78 minimal control functionality via sender and receiver reports as well 79 as other control packets. [RFC3611] expands the RTCP functionality 80 further by introducing the RTCP Extended Reports (XR). 82 One of the initial XR report block types defined in [RFC3611] is the 83 Loss Run Length Encoding (RLE) Report Block. This report conveys the 84 information regarding the individual RTP packet receipt and loss 85 events experienced during the RTCP interval preceding the 86 transmission of the report. However, the Loss RLE in an RTCP XR 87 report is usually collected only on the primary source stream before 88 any error-repair technique is applied. Once one or more error-repair 89 techniques, e.g., Forward Error Correction (FEC) 90 [I-D.begen-fecframe-1d2d-parity-scheme] and/or retransmission 91 [RFC4588], are applied, some or all of the lost packets on the 92 primary source stream may be recovered. However, the pre-repair Loss 93 RLE cannot indicate which source packets were recovered and which are 94 still missing. Thus, the pre-repair Loss RLE cannot specify how well 95 the error repair performed. 97 This issue can be addressed by generating an additional report block 98 (within the same RTCP XR report), which reflects the packet receipt/ 99 loss events after all error-repair techniques are applied. This 100 report block, which we refer to as the Post-repair Loss RLE, 101 indicates the remaining missing, i.e., unrepairable, source packets. 102 When the pre- and post-repair Loss RLEs are compared, the RTP sender 103 or another 3rd party entity can evaluate the effectiveness of the 104 error-repair techniques in an aggregated fashion. 106 Note that the idea of using pre- and post-repair Loss RLEs can be 107 further extended when multiple sequential error-repair techniques are 108 applied to the primary source stream. Reporting the Loss RLEs before 109 and after each error-repair technique can provide specific 110 information about the individual performances of these techniques. 111 However, it can be a difficult task to quantify the specific 112 contribution made by each error-repair technique in hybrid systems, 113 where different techniques collectively work together to repair the 114 lost source packets. Thus, in this specification we only consider 115 reporting the Loss RLE after all error-repair techniques are applied. 116 This document registers a new report block type to cover the Post- 117 repair Loss RLE within the framework of RTCP XR. 119 2. Requirements Notation 121 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 122 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 123 document are to be interpreted as described in [RFC2119]. 125 3. Post-Repair Loss RLE Report Block 127 The Post-repair Loss RLE Report Block is similar to the existing Loss 128 RLE Report Block defined in [RFC3611]. The report is formatted as 129 sketched in Figure 1. 131 0 1 2 3 132 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | BT=TBD | rsvd. | T | block length | 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | SSRC of source | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | begin_seq | end_seq | 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 | chunk 1 | chunk 2 | 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 : ... : 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 | chunk n-1 | chunk n | 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 147 Figure 1: Format for the post-repair loss RLE report block 149 o block type (BT): 8 bits 150 A Post-repair Loss RLE Report Block is identified by the constant 151 TBD. 153 o rsvd.: 4 bits 154 This field is reserved for future definition. In the absence of 155 such definition, the bits in this field MUST be set to zero and 156 MUST be ignored by the receiver. 158 o thinning (T): 4 bits 159 The amount of thinning performed on the sequence number space. 160 Only those packets with sequence numbers 0 mod 2^T are reported on 161 by this block. A value of 0 indicates that there is no thinning, 162 and all packets are reported on. The maximum thinning is one 163 packet in every 32,768 (amounting to two packets within each 16- 164 bit sequence space). 166 o block length: 16 bits 167 The length of this report block, including the header, in 32-bit 168 words minus one. 170 o SSRC of source: 32 bits 172 The SSRC of the RTP data packet source being reported upon by this 173 report block. 175 o begin_seq: 16 bits 177 The first sequence number that this block reports on. 179 o end_seq: 16 bits 181 The last sequence number that this block reports on plus one. 183 o chunk i: 16 bits 184 There are three chunk types: run length, bit vector, and 185 terminating null, defined in [RFC3611] (Section 4). If the chunk 186 is all zeroes, then it is a terminating null chunk. Otherwise, 187 the left most bit of the chunk determines its type: 0 for run 188 length and 1 for bit vector. 190 4. Session Description Protocol Signaling 192 A new parameter is defined for the Post-repair Loss RLE Report Block 193 to be used with Session Description Protocol (SDP) [RFC4566]. It has 194 the following syntax within the "rtcp-xr" attribute: 196 rtcp-xr-attrib = "a=rtcp-xr:" [xr-format *(SP xr-format)] CRLF 198 xr-format = "post-repair-loss-rle" ["=" max-size] 200 max-size = 1*DIGIT ; maximum block size in octets 201 DIGIT = %x30-39 202 CRLF = %d13.10 204 Figure 2 206 Refer to Section 5.1 of [RFC3611] for a detailed description of the 207 full syntax of the "rtcp-xr" attribute. 209 5. Security Considerations 211 The security considerations of [RFC3611] apply. 213 6. IANA Considerations 215 New block types for RTCP XR are subject to IANA registration. For 216 general guidelines on IANA considerations for RTCP XR, refer to 217 [RFC3611]. 219 This document assigns the block type value TBD in the RTCP XR Block 220 Type Registry to "Post-repair Loss RLE Report Block." This document 221 also registers the SDP [RFC4566] parameter "post-repair-loss-rle" for 222 the "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry. 224 The contact information for the registrations is: 226 Ali Begen 227 abegen@cisco.com 229 170 West Tasman Drive 230 San Jose, CA 95134 USA 232 7. Acknowledgments 234 The authors would like to thank the members of the VQE Team at Cisco 235 and Colin Perkins for their inputs and suggestions. 237 8. References 239 8.1. Normative References 241 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 242 Requirement Levels", BCP 14, RFC 2119, March 1997. 244 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 245 Jacobson, "RTP: A Transport Protocol for Real-Time 246 Applications", STD 64, RFC 3550, July 2003. 248 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 249 Protocol Extended Reports (RTCP XR)", RFC 3611, 250 November 2003. 252 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 253 Description Protocol", RFC 4566, July 2006. 255 8.2. Informative References 257 [I-D.begen-fecframe-1d2d-parity-scheme] 258 Begen, A. and R. Asati, "1-D and 2-D Parity FEC Scheme for 259 FEC Framework", draft-begen-fecframe-1d2d-parity-scheme-00 260 (work in progress), February 2008. 262 [RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. 263 Hakenberg, "RTP Retransmission Payload Format", RFC 4588, 264 July 2006. 266 Authors' Addresses 268 Ali Begen 269 Cisco Systems 270 170 West Tasman Drive 271 San Jose, CA 95134 272 USA 274 Email: abegen@cisco.com 276 Dong Hsu 277 Cisco Systems 278 1414 Massachusetts Ave. 279 Boxborough, MA 01719 280 USA 282 Email: dohsu@cisco.com 284 Michael Lague 285 Cisco Systems 286 1414 Massachusetts Ave. 287 Boxborough, MA 01719 288 USA 290 Email: mlague@cisco.com 292 Full Copyright Statement 294 Copyright (C) The IETF Trust (2008). 296 This document is subject to the rights, licenses and restrictions 297 contained in BCP 78, and except as set forth therein, the authors 298 retain all their rights. 300 This document and the information contained herein are provided on an 301 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 302 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 303 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 304 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 305 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 306 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 308 Intellectual Property 310 The IETF takes no position regarding the validity or scope of any 311 Intellectual Property Rights or other rights that might be claimed to 312 pertain to the implementation or use of the technology described in 313 this document or the extent to which any license under such rights 314 might or might not be available; nor does it represent that it has 315 made any independent effort to identify any such rights. 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