draft-ietf-avt-post-repair-rtcp-xr-01.txt   draft-ietf-avt-post-repair-rtcp-xr-02.txt 
AVT A. Begen AVT A. Begen
Internet-Draft D. Hsu Internet-Draft D. Hsu
Intended status: Standards Track M. Lague Intended status: Standards Track M. Lague
Expires: February 7, 2009 Cisco Systems Expires: April 20, 2009 Cisco Systems
August 6, 2008 October 17, 2008
Post-Repair Loss RLE Report Block Type for RTCP XR Post-Repair Loss RLE Report Block Type for RTCP XR
draft-ietf-avt-post-repair-rtcp-xr-01 draft-ietf-avt-post-repair-rtcp-xr-02
Status of this Memo Status of this Memo
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aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on February 7, 2009. This Internet-Draft will expire on April 20, 2009.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
Abstract Abstract
This document defines a new report block type within the framework of This document defines a new report block type within the framework of
RTP Control Protocol (RTCP) Extended Reports (XR). One of the RTP Control Protocol (RTCP) Extended Reports (XR). One of the
initial XR report block types is the Loss Run Length Encoding (RLE) initial XR report block types is the Loss Run Length Encoding (RLE)
Report Block. This report conveys the information regarding the Report Block. This report conveys the information regarding the
individual Real-time Transport Protocol (RTP) packet receipt and loss individual Real-time Transport Protocol (RTP) packet receipt and loss
events experienced during the RTCP interval preceding the events experienced during the RTCP interval preceding the
transmission of the report. The new report, which is referred to as transmission of the report. The new report, which is referred to as
the Post-repair Loss RLE Report, carries the information regarding the Post-repair Loss RLE Report, carries the information regarding
the remaining lost packets after all error-repair techniques are the remaining lost packets after all loss-repair methods are applied.
applied. By comparing the RTP packet receipts/losses before and By comparing the RTP packet receipts/losses before and after the loss
after the error repair is completed, one can determine the repair is completed, one can determine the effectiveness of the loss-
effectiveness of the error-repair techniques in an aggregated repair methods in an aggregated fashion. This document also defines
fashion. This document also defines the signaling of the Post-repair the signaling of the Post-repair Loss RLE Report in the Session
Loss RLE Report in the Session Description Protocol (SDP). Description Protocol (SDP).
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 4
3. Post-Repair Loss RLE Report Block . . . . . . . . . . . . . . . 4 3. Post-Repair Loss RLE Report Block . . . . . . . . . . . . . . . 4
4. Session Description Protocol Signaling . . . . . . . . . . . . 5 4. Session Description Protocol Signaling . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 9
1. Introduction 1. Introduction
RTP Control Protocol (RTCP) is the out-of-band control protocol for RTP Control Protocol (RTCP) is the out-of-band control protocol for
the applications that are using the Real-time Transport Protocol the applications that are using the Real-time Transport Protocol
(RTP) for media delivery and communications [RFC3550]. RTCP allows (RTP) for media delivery and communications [RFC3550]. RTCP allows
the RTP entities to monitor the data delivery and provides them the RTP entities to monitor the data delivery and provides them
minimal control functionality via sender and receiver reports as well minimal control functionality via sender and receiver reports as well
as other control packets. [RFC3611] expands the RTCP functionality as other control packets. [RFC3611] expands the RTCP functionality
further by introducing the RTCP Extended Reports (XR). further by introducing the RTCP Extended Reports (XR).
One of the initial XR report block types defined in [RFC3611] is the One of the initial XR report block types defined in [RFC3611] is the
Loss Run Length Encoding (RLE) Report Block. This report conveys the Loss Run Length Encoding (RLE) Report Block. This report conveys the
information regarding the individual RTP packet receipt and loss information regarding the individual RTP packet receipt and loss
events experienced during the RTCP interval preceding the events experienced during the RTCP interval preceding the
transmission of the report. However, the Loss RLE in an RTCP XR transmission of the report. However, the Loss RLE in an RTCP XR
report is usually collected only on the primary source stream before report is usually collected only on the primary source stream before
any error-repair technique is applied. Once one or more error-repair any loss-repair method is applied. Once one or more loss-repair
techniques, e.g., Forward Error Correction (FEC) [RFC5109] and/or methods, e.g., Forward Error Correction (FEC) [RFC5109] and/or
retransmission [RFC4588], are applied, some or all of the lost retransmission [RFC4588], are applied, some or all of the lost
packets on the primary source stream may be recovered. However, the packets on the primary source stream may be recovered. However, the
pre-repair Loss RLE cannot indicate which source packets were pre-repair Loss RLE cannot indicate which source packets were
recovered and which are still missing. Thus, the pre-repair Loss RLE recovered and which are still missing. Thus, the pre-repair Loss RLE
cannot specify how well the error repair performed. cannot specify how well the loss repair performed.
This issue can be addressed by generating an additional report block This issue can be addressed by generating an additional report block
(within the same RTCP XR report), which reflects the packet receipt/ (within the same RTCP XR report), which reflects the packet receipt/
loss events after all error-repair techniques are applied. This loss events after all loss-repair methods are applied. This report
report block, which we refer to as the Post-repair Loss RLE, block, which we refer to as the Post-repair Loss RLE, indicates the
indicates the remaining missing, i.e., unrepairable, source packets. remaining missing, i.e., unrepairable, source packets. When the pre-
When the pre- and post-repair Loss RLEs are compared, the RTP sender repair and post-repair Loss RLEs are compared, the RTP sender or
or another third party entity can evaluate the effectiveness of the another third party entity can evaluate the effectiveness of the
error-repair techniques in an aggregated fashion. loss-repair methods (at the packet level) in an aggregated fashion.
To avoid any ambiguity in the evaluation, it is RECOMMENDED that the
post-repair Loss RLE is generated for the source packets that have no
further chance of being repaired. If the loss-repair method(s) may
still recover one or more missing source packets, the post-repair
Loss RLE SHOULD NOT be sent until the loss-recovery process has been
completed.
Note that the idea of using pre- and post-repair Loss RLEs can be Note that the idea of using pre-repair and post-repair Loss RLEs can
further extended when multiple sequential error-repair techniques are be further extended when multiple sequential loss-repair methods are
applied to the primary source stream. Reporting the Loss RLEs before applied to the primary source stream. Reporting the Loss RLEs before
and after each error-repair technique can provide specific and after each loss-repair method can provide specific information
information about the individual performances of these techniques. about the individual performances of these methods. However, it can
However, it can be a difficult task to quantify the specific be a difficult task to quantify the specific contribution made by
contribution made by each error-repair technique in hybrid systems, each loss-repair method in hybrid systems, where different methods
where different techniques collectively work together to repair the collectively work together to repair the lost source packets. Thus,
lost source packets. Thus, in this specification we only consider in this specification we only consider reporting the Loss RLE after
reporting the Loss RLE after all error-repair techniques are applied. all loss-repair methods are applied.
This document registers a new report block type to cover the Post-
repair Loss RLE within the framework of RTCP XR. This document registers a new report block type to cover the post-
repair Loss RLE within the framework of RTCP XR. Applications that
are employing one or more loss-repair methods MAY use Post-repair
Loss RLE Reports for every packet they receive or for a set of
specific packets they have received. In other words, the coverage of
the post-repair Loss RLEs may or may not be contiguous.
2. Requirements Notation 2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Post-Repair Loss RLE Report Block 3. Post-Repair Loss RLE Report Block
The Post-repair Loss RLE Report Block is similar to the existing Loss The Post-repair Loss RLE Report Block is similar to the existing Loss
RLE Report Block defined in [RFC3611]. The report is formatted as RLE Report Block defined in [RFC3611]. The report format is shown in
sketched in Figure 1. Figure 1. Using the same structure for reporting both pre-repair and
post-repair Loss RLEs allows the implementations to compare the Loss
RLEs very efficiently.
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=10 | rsvd. | T | block length | | BT=10 | rsvd. | T | block length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source | | SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| begin_seq | end_seq | | begin_seq | end_seq |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The last sequence number that this block reports on plus one. The last sequence number that this block reports on plus one.
o chunk i: 16 bits o chunk i: 16 bits
There are three chunk types: run length, bit vector, and There are three chunk types: run length, bit vector, and
terminating null, defined in [RFC3611] (Section 4). If the chunk terminating null, defined in [RFC3611] (Section 4). If the chunk
is all zeroes, then it is a terminating null chunk. Otherwise, is all zeroes, then it is a terminating null chunk. Otherwise,
the left most bit of the chunk determines its type: 0 for run the left most bit of the chunk determines its type: 0 for run
length and 1 for bit vector. length and 1 for bit vector.
Note that the sequence numbers that are included in the report refer
to the primary source stream.
4. Session Description Protocol Signaling 4. Session Description Protocol Signaling
A new parameter is defined for the Post-repair Loss RLE Report Block A new parameter is defined for the Post-repair Loss RLE Report Block
to be used with Session Description Protocol (SDP) [RFC4566]. It has to be used with Session Description Protocol (SDP) [RFC4566]. It has
the following syntax within the "rtcp-xr" attribute: the following syntax within the "rtcp-xr" attribute:
rtcp-xr-attrib = "a=rtcp-xr:" [xr-format *(SP xr-format)] CRLF rtcp-xr-attrib = "a=rtcp-xr:" [xr-format *(SP xr-format)] CRLF
xr-format = "post-repair-loss-rle" ["=" max-size] xr-format = "post-repair-loss-rle" ["=" max-size]
 End of changes. 14 change blocks. 
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