Audio/Video Transport Working G. Hunt
Group BT
Internet-Draft A. Clark
Intended status: Standards Track Telchemy
Expires: August 29, 2009 February 25, 2009
RTCP XR Report Block for Jitter Buffer Metric Reporting
draft-ietf-avt-rtcp-xr-jb-01.txt
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Abstract
This document defines an RTCP XR Report Block that allows the
reporting of Jitter Buffer metrics for a range of RTP applications.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Jitter Buffer Metrics Block . . . . . . . . . . . . . . . 3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
2. Jitter Buffer Metrics Block . . . . . . . . . . . . . . . . . 4
2.1. Report Block Structure . . . . . . . . . . . . . . . . . . 4
2.2. Definition of Fields in Jitter Buffer Metrics Block . . . 4
3. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 8
4.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 8
4.3. Contact information for registrations . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Changes since previous version . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
1.1. Jitter Buffer Metrics Block
This draft defines a new block type to augment those defined in
[RFC3611], for use in a range of RTP applications.
The new block type provides information on jitter buffer
configuration and performance.
The metric belongs to the class of transport-related terminal metrics
defined in [MONARCH] (work in progress).
Instances of this Metrics Block refer by tag to the separate
auxiliary Measurement Identity block [MEASIDENT] which contains
information such as the SSRC of the measured stream, and RTP sequence
numbers and time intervals indicating the span of the report.
1.2. RTCP and RTCP XR Reports
The use of RTCP for reporting is defined in [RFC3550]. [RFC3611]
defined an extensible structure for reporting using an RTCP Extended
Report (XR). This draft defines a new Extended Report block that
MUST be used as defined in [RFC3550] and [RFC3611].
1.3. Performance Metrics Framework
The Performance Metrics Framework [PMOLFRAME] provides guidance on
the definition and specification of performance metrics. Metrics
described in this draft either reference external definitions or
define metrics generally in accordance with the guidelines in
[PMOLFRAME].
1.4. Applicability
These metrics are applicable to a range of RTP applications.
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2. Jitter Buffer Metrics Block
This block describes the configuration and operating parameters of
the jitter buffer in the receiver of the RTP end system or RTP mixer
which sends the report.
2.1. Report Block Structure
JB Metrics Block
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=NJB |I| tag |jb cfg | block length=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| JB nominal | JB maximum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| JB high water mark | JB low water mark |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure
2.2. Definition of Fields in Jitter Buffer Metrics Block
block type (BT): 8 bits
A Jitter Buffer Metrics Report Block is identified by the constant
NJB.
[Note to RFC Editor: please replace NJB with the IANA provided RTCP
XR block type for this block.]
Interval Metric flag (I): 1 bit
This field is used to indicate whether the Jitter Buffer Metrics
block is an Interval or a Cumulative report, that is, whether the
reported values apply to the most recent measurement interval
duration between successive metrics reports (I=1) (the Interval
Duration) or to the accumulation period characteristic of
cumulative measurements (I=0) (the Cumulative Duration).
Numerical values for both these intervals are provided in the
Measurement Identifier block referenced by the tag field below.
Measurement Identifier association (tag): 3 bits
This field is used to identify the Measurement Identifier block
[MEASIDENT] which describes this measurement. The relevant
Measurement Identifier block has the same tag value as the Jitter
Buffer Metrics block. Note that there may be more than one
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Measurement Identifier block per RTCP packet.
Jitter Buffer Configuration (jb cfg): 4 bits
This field is used to identify the jitter buffer method in use at
the receiver, according to the following code:
bits 014-017
0 = Fixed jitter buffer
1 = Adaptive jitter buffer
Other values reserved
block length: 16 bits
The length of this report block in 32-bit words, minus one. For
the Jitter Buffer block, the block length is equal to 2.
jitter buffer nominal delay (JB nominal): 16 bits
This is the current nominal jitter buffer delay in milliseconds,
which corresponds to the nominal jitter buffer delay for packets
that arrive exactly on time. This parameter MUST be provided for
both fixed and adaptive jitter buffer implementations.
If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be
reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF SHOULD be reported.
jitter buffer maximum delay (JB maximum): 16 bits
This is the current maximum jitter buffer delay in milliseconds
which corresponds to the earliest arriving packet that would not
be discarded. In simple queue implementations this may correspond
to the nominal size. In adaptive jitter buffer implementations,
this value may dynamically. This parameter MUST be provided for
both fixed and adaptive jitter buffer implementations.
If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be
reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF SHOULD be reported.
jitter buffer high water mark (JB high water mark): 16 bits
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This is the highest value of the jitter buffer nominal delay which
occurred at any time during the reporting interval.
If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be
reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF SHOULD be reported.
jitter buffer low water mark (JB low water mark): 16 bits
This is the lowest value of the jitter buffer nominal delay which
occurred at any time during the reporting interval.
If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be
reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF SHOULD be reported.
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3. SDP Signaling
[RFC3611] defines the use of SDP (Session Description Protocol)
[RFC4566] for signaling the use of XR blocks. XR blocks MAY be used
without prior signaling.
This section augments the SDP [RFC4566] attribute "rtcp-xr" defined
in [RFC3611] by providing an additional value of "xr-format" to
signal the use of the report block defined in this document.
rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF
(defined in [RFC3611])
xr-format = xr-format / xr-jb-block
xr-jb-block = "jitter-bfr"
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4. IANA Considerations
New block types for RTCP XR are subject to IANA registration. For
general guidelines on IANA considerations for RTCP XR, refer to
[RFC3611].
4.1. New RTCP XR Block Type value
This document assigns the block type value NJB in the IANA "RTCP XR
Block Type Registry" to the "JB Metrics Block".
[Note to RFC Editor: please replace NJB with the IANA provided RTCP
XR block type for this block.]
4.2. New RTCP XR SDP Parameter
This document also registers a new parameter "jitter-bfr" in the
"RTCP XR SDP Parameters Registry".
4.3. Contact information for registrations
The contact information for the registrations is:
Geoff Hunt (geoff.hunt@bt.com)
Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United
Kingdom
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5. Security Considerations
It is believed that this proposed RTCP XR report block introduces no
new security considerations beyond those described in [RFC3611].
This block does not provide per-packet statistics so the risk to
confidentiality documented in Section 7, paragraph 3 of [RFC3611]
does not apply.
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6. Contributors
The authors gratefully acknowledge the comments and contributions
made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin
Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert
Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith
Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho,
Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada.
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7. Changes since previous version
Expanded and clarified IANA Considerations section
Changed SDP tag for block to "jitter-bfr"
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8. References
8.1. Normative References
[MEASIDENT]
Hunt, G., "RTCP XR Measurement Identifier Block",
ID draft-ietf-avt-rtcp-xr-measid-01, February 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
Applications", RFC 3550, July 2003.
[RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP
XR)", RFC 3611, November 2003.
[RFC4566] Handley, M., "SDP: Session Description Protocol",
RFC 4566, July 2006.
8.2. Informative References
[MONARCH] Hunt, G., "Monitoring Architectures for RTP",
ID draft-hunt-avt-monarch-01, August 2008.
[PMOLFRAME]
Clark, A., "Framework for Performance Metric Development",
ID draft-ietf-pmol-metrics-framework-00, July 2008.
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Authors' Addresses
Geoff Hunt
BT
Orion 2 PP3
Adastral Park
Martlesham Heath
Ipswich, Suffolk IP5 3RE
United Kingdom
Phone: +44 1473 651704
Email: geoff.hunt@bt.com
Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, GA 30097
USA
Email: alan.d.clark@telchemy.com
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