draft-ietf-xrblock-rtcp-xr-discard-06.txt   draft-ietf-xrblock-rtcp-xr-discard-07.txt 
Audio/Video Transport Working Group A. Clark Audio/Video Transport Working Group A. Clark
Internet-Draft Telchemy Internet-Draft Telchemy
Intended status: Standards Track G. Zorn Intended status: Standards Track G. Zorn
Expires: February 25, 2013 Network Zen Expires: March 15, 2013 Network Zen
Q. Wu Q. Wu
Huawei Huawei
August 24, 2012 September 11, 2012
RTCP XR Report Block for Discard Count metric Reporting RTCP XR Report Block for Discard Count metric Reporting
draft-ietf-xrblock-rtcp-xr-discard-06.txt draft-ietf-xrblock-rtcp-xr-discard-07.txt
Abstract Abstract
This document defines an RTCP XR Report Block that allows the This document defines an RTCP XR Report Block that allows the
reporting of a simple discard count metric for use in a range of RTP reporting of a simple discard count metric for use in a range of RTP
applications. applications.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 25, 2013. This Internet-Draft will expire on March 15, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Discard Count Report Block . . . . . . . . . . . . . . . . 3 1.1. Discard Count Report Block . . . . . . . . . . . . . . . . 3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5
3. Discard Count Metric Report Block . . . . . . . . . . . . . . 6 3. Discard Count Metric Report Block . . . . . . . . . . . . . . 6
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6
3.2. Definition of Fields in Discard Count Metric Report 3.2. Definition of Fields in Discard Count Metric Report
Block . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Block . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10
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correctly but are never played out, typically because they arrive too correctly but are never played out, typically because they arrive too
late to be played out (buffer underflow) or too early (buffer late to be played out (buffer underflow) or too early (buffer
overflow). The metric is applicable both to systems which use packet overflow). The metric is applicable both to systems which use packet
loss repair techniques (such as forward error correction [RFC5109] or loss repair techniques (such as forward error correction [RFC5109] or
retransmission [RFC4588]) and to those which do not. retransmission [RFC4588]) and to those which do not.
This metric is useful for identifying the existence, and This metric is useful for identifying the existence, and
characterising the severity, of a packet transport problem which may characterising the severity, of a packet transport problem which may
affect users' perception of a service delivered over RTP. affect users' perception of a service delivered over RTP.
This block may be used in conjunction with [BGDISCARD] which provides
additional information on the pattern of discarded packets. However
the metric in [BGDISCARD] may be used independently of the metrics in
this block.
In case of Discard count metric block sent together with Burst gap
discard metric block defined in [BGDISCARD] to the media sender or
RTP based network management system, information carried in the
discard count metric block and Burst gap discard metric block allows
them calculate the some bust gap summary statistics, e.g., gap
discard rate.
The metric belongs to the class of transport-related terminal metrics The metric belongs to the class of transport-related terminal metrics
defined in [MONARCH]. defined in [MONARCH].
1.2. RTCP and RTCP XR Reports 1.2. RTCP and RTCP XR Reports
The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] The use of RTCP for reporting is defined in [RFC3550]. [RFC3611]
defined an extensible structure for reporting using an RTCP Extended defined an extensible structure for reporting using an RTCP Extended
Report (XR). This document defines a new Extended Report block. The Report (XR). This document defines a new Extended Report block. The
use of Extended Report blocks is defined by [RFC3611]. use of Extended Report blocks is defined by [RFC3611].
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Monitoring Architectures [MONARCH] provides guideline for reporting Monitoring Architectures [MONARCH] provides guideline for reporting
block format using RTCP XR. The Metrics Block described in this block format using RTCP XR. The Metrics Block described in this
document are in accordance with the guidelines in [RFC6390] and document are in accordance with the guidelines in [RFC6390] and
[MONARCH]. [MONARCH].
1.4. Applicability 1.4. Applicability
This metric is believed to be applicable to a large class of RTP This metric is believed to be applicable to a large class of RTP
applications which use a jitter buffer. applications which use a jitter buffer.
In case of Discard count metric block sent together with Burst gap Discards due to late or early arriving packets affects user
discard metric block defined in [BGDISCARD] to the media sender or experience. The reporting of discards alerts senders and other
RTP based network management system, information carried in the receivers to the need to adjust their transmission or reception
discard count metric block and Burst gap discard metric block allows strategies. The reports allow network managers to diagnose these
them calculate the some bust gap summary statistics,e.g., gap discard user experience problems.
rate.
In case of replication being kept "on", reporting duplicate packets The ability to detect duplicate packets can be used by managers to
discards allows the media sender or network management system detect network layer or sender behavior which may indicate network or
determine what proportion of lost packets are being concealed by the device issues. Based on the reports, these issues may be addressed
process and calculate the actual loss rate which is helpful to know prior to any impact on user experience.
that there are some network issues that need to be investigated.
2. Terminology 2. Terminology
2.1. Standards Language 2.1. Standards Language
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 RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
In addition, the following terms are defined: In addition, the following terms are defined:
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Block type (BT): 8 bits Block type (BT): 8 bits
A Discard Count Metric Report Block is identified by the constant A Discard Count Metric Report Block is identified by the constant
PDC. PDC.
[Note to RFC Editor: please replace PDC with the IANA provided [Note to RFC Editor: please replace PDC with the IANA provided
RTCP XR block type for this block.] RTCP XR block type for this block.]
Interval Metric flag (I): 2 bits Interval Metric flag (I): 2 bits
This field is used to indicate whether the Discard Count Metric is This field indicates whether the reported metric is an interval,
an Interval or Cumulative metric, Sample metric [MONARCH],that is, cumulative, or sampled metric [MONARCH]. The Discard Count Metric
whether the reported values applies to the most recent measurement value can be reported as either an interval metric (I=10) or a
interval duration between successive metrics reports (I=10) (the cumulative metric (I=11). It does not make sense to report the
Interval Duration) or to the accumulation period characteristic of Discard Count Metric as a sampled metric, so the value I=01 MUST
cumulative measurements (I=11) (the Cumulative Duration) or is a NOT be used. The value I=00 is reserved, and MUST NOT be used.
sampled instantaneous value (I=01) (Sampled Value). In this
document, Discard Count Metric is not measured at a particular
time instant but over one or several reporting intervals.
Therefore Discard Count Metric MUST not be chosen as Sampled
Metric.
Discard Type (DT): 2bits Discard Type (DT): 2bits
This field is used to identify the discard type used in this This field is used to identify the discard type used in this
report block. The discard type is defined as follows: report block. The discard type is defined as follows:
00: Report packet discarded or being thrown away before playout 00: Report packet discarded or being thrown away before playout
due to packets duplication. due to packets duplication.
01: Report packet discarded due to too early to be played out. 01: Report packet discarded due to too early to be played out.
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An endpoint MAY report only one of the above four discard types An endpoint MAY report only one of the above four discard types
blocks in an compound RTCP report in a reporting interval. It MAY blocks in an compound RTCP report in a reporting interval. It MAY
also report a combination of discard types in a compound RTCP also report a combination of discard types in a compound RTCP
report but not all combinations are valid. The endpoint MAY report but not all combinations are valid. The endpoint MAY
report duplicate packet discard (DT=0) block with any other report duplicate packet discard (DT=0) block with any other
discard (DT=1, 2, or 3) block. Additionally, an endpoint MUST NOT discard (DT=1, 2, or 3) block. Additionally, an endpoint MUST NOT
report combined discard (DT=3) block with early discard (DT=1) or report combined discard (DT=3) block with early discard (DT=1) or
late discard (DT=2) report block. late discard (DT=2) report block.
Note that duplicating RTP packets is for robustness or error Some systems send duplicate RTP packets for robustness or error
resilience but disrupts RTCP statitics. In order to tackle this, resilience. This is NOT RECOMMENDED since it breaks RTCP packet
the mechanism described in [RTPDUP] can be used which will not statistics. If duplication is desired for error resilience, the
cause breakage of RTP streams or RTCP rules. mechanism described in [RTPDUP] can be used, since this will not
cause breakage of RTP streams or RTCP statistics.
Reserved (resv): 4 bits Reserved (resv): 4 bits
These bits are reserved. They SHOULD be set to zero by senders These bits are reserved. They MUST be set to zero by senders and
and MUST be ignored by receivers. ignored by receivers.
block length: 16 bits block length: 16 bits
The length of this report block in 32-bit words, minus one. For The length of this report block in 32-bit words, minus one. For
the Discard Count block, the block length is equal to 2. the Discard Count block, the block length is equal to 2.
SSRC of source: 32 bits SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611]. As defined in Section 4.1 of [RFC3611].
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