Audio/Video Transport Working Group G. Hunt
Internet-Draft Unaffiliated
Intended status: Standards Track A. Clark
Expires: October 23, 2012 Telchemy
K. Gross
AVA Networks
Q. Wu
Huawei
April 21, 2012
RTCP XR Report Block for Delay metric Reporting
draft-ietf-xrblock-rtcp-xr-delay-03.txt
Abstract
This document defines an RTCP XR Report Block that allows the
reporting of Delay metrics for use in a range of RTP applications.
Status of this Memo
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Packet Delay Metrics Block . . . . . . . . . . . . . . . . 3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 4
3. Delay Block . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5
3.2. Definition of Fields in Delay Metrics Report Block . . . . 5
4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 9
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 9
5.3. Contact information for registrations . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 13
A.1. draft-ietf-xrblock-rtcp-xr-delay-03 . . . . . . . . . . . 13
A.2. draft-ietf-xrblock-rtcp-xr-delay-02 . . . . . . . . . . . 13
A.3. draft-ietf-xrblock-rtcp-xr-delay-01 . . . . . . . . . . . 13
A.4. draft-ietf-xrblock-rtcp-xr-delay-00 . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
1.1. Packet Delay 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
supports the reporting of the mean, minimum and maximum values of the
network round-trip delay between RTP interfaces in peer RTP end
systems as measured, for example, using the RTCP method described in
[RFC3550]. It also supports reporting of the component of the round-
trip delay internal to the local RTP system.
The network metrics belong to the class of packet transport delay
metrics defined in [MONARCH] (work in progress).
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 [RFC6390] 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
[RFC6390].
1.4. Applicability
These metrics are applicable to a range of RTP applications in which
this report block would be useful, such as multimedia conferencing
and streaming audio and video.
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2. Terminology
2.1. Standards Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. Delay Block
Metrics in this block report on packet delay in the stream arriving
at the RTP system. Instances of this Metrics Block refer by SSRC to
the separate auxiliary Measurement Information block [MEASI] which
contains measurement intervals. This metric block relies on the
measurement interval in the Measurement Information block indicating
the span of the report. If the measurement interval is not received
in the same compound RTCP packet as this metric block, this metric
block should be discarded.
3.1. Report Block Structure
Delay 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=NDEL | I | resv. | block length = 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mean Network Round Trip Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Min Network Round Trip Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Network Round Trip Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End System Delay - Seconds (bit 0-31) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End System Delay - Fraction (bit 0-31) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure
3.2. Definition of Fields in Delay Metrics Report Block
Block type (BT): 8 bits
A Delay Report Block is identified by the constant NDEL.
[Note to RFC Editor: please replace NDEL with the IANA provided
RTCP XR block type for this block.]
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Interval Metric flag (I): 2 bit
This field is used to indicate whether the Delay metrics are
Sampled, Interval or Cumulative metrics, that is, whether the
reported values applies to the most recent measurement interval
duration between successive metrics reports (I=10) (the Interval
Duration) or to the accumulation period characteristic of
cumulative measurements (I=11) (the Cumulative Duration) or to the
value of a continuously measured or calculated that has been
sampled at end of the interval (I=01) (Sampled Value).
Reserved (resv): 6 bits
These bits are reserved. They MUST be set to zero by senders and
SHOULD be ignored by receivers.
block length: 16 bits
The length of this report block in 32-bit words, minus one. For
the Delay block, the block length is equal to 6.
SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611].
Mean Network Round Trip Delay: 32 bits
The Mean Network Round Trip Delay is the mean value of the RTP-to-
RTP interface round trip delay over the measurement period,
expressed in units of 1/65536 seconds. This value is typically
determined using RTCP SR/RR.
If only one measurement of Round Trip Delay is available for the
timespan of the report (whether Interval or Cumulative), this
single value should be reported as the mean value.
If the measurement is unavailable, the value 0xFFFFFFFF SHOULD be
reported.
Min Network Round Trip Delay: 32 bits
The Min Network Round Trip Delay is the minimum value of the RTP-
to-RTP interface round trip delay over the measurement period,
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expressed in units of 1/65536 seconds. This value is typically
determined using RTCP SR/RR.
If only one measurement of Round Trip Delay is available for the
timespan of the report (whether Interval or Cumulative), this
single value should be reported as the minimum value.
If the measurement is unavailable, the value 0xFFFFFFFF SHOULD be
reported.
Max Network Round Trip Delay: 32 bits
The Max Network Round Trip Delay is the maximum value of the RTP-
to-RTP interface round trip delay over the measurement period,
expressed in units of 1/65536 seconds. This value is typically
determined using RTCP SR/RR.
If only one measurement of Round Trip Delay is available for the
timespan of the report (whether Interval or Cumulative), this
single value should be reported as the maximum value.
If the measurement is unavailable, the value 0xFFFFFFFF SHOULD be
reported.
End System Delay: 64 bits
The End System Delay is the internal round trip delay within the
reporting endpoint, calculated using the nominal value of the
jitter buffer delay plus the accumulation/encoding and decoding/
playout delay associated with the codec being used. The value of
this field is represented using a 64-bit NTP-format timestamp as
defined in [RFC5905], which is 64-bit unsigned fixed-point number
with the integer part in the first 32 bits and the fractional part
in the last 32 bits.
If the measurement is unavailable, the value 0xFFFFFFFF SHOULD be
reported.
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4. 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-delay-block
xr-delay-block ="delay"
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5. 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].
5.1. New RTCP XR Block Type value
This document assigns the block type value NDEL in the IANA "RTCP XR
Block Type Registry" to the "Delay Metrics Block".
[Note to RFC Editor: please replace NDEL with the IANA provided RTCP
XR block type for this block.]
5.2. New RTCP XR SDP Parameter
This document also registers a new parameter "delay" in the "RTCP XR
SDP Parameters Registry".
5.3. Contact information for registrations
The contact information for the registrations is:
Geoff Hunt (r.geoff.hunt@gmail.com)
Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United
Kingdom
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6. 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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7. Acknowledgments
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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8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
Applications", RFC 3550, July 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", November 2003.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", July 2006.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
8.2. Informative References
[MEASI] Hunt, G., "Measurement Identity and information Reporting
using SDES item and XR Block",
ID draft-ietf-xrblock-rtcp-xr-meas-identity-06,
April 2012.
[MONARCH] Hunt, G., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-12, April 2012.
[RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric
Development", RFC 6390, October 2011.
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Appendix A. Change Log
Note to the RFC-Editor: please remove this section prior to
publication as an RFC.
A.1. draft-ietf-xrblock-rtcp-xr-delay-03
The following are the major changes to previous version :
o Allocate 64 bit for end system delay and represent it using 64 bit
NTP-Timestamp.
o Other editorial changes.
A.2. draft-ietf-xrblock-rtcp-xr-delay-02
The following are the major changes to previous version :
o Allocate 32bits for each metrics and change unit for each metric
from ms to 1/65536 seconds.
A.3. draft-ietf-xrblock-rtcp-xr-delay-01
The following are the major changes to previous version :
o Updated references.
o Allocate one more bit for Interval metric flag to indicate sampled
metric can be used.
o add a few clarification text for failure mode.
A.4. draft-ietf-xrblock-rtcp-xr-delay-00
The following are the major changes to previous version :
o Changed BNF for SDP following Christian Groves' and Tom Taylor's
comments (4th and 5th May 2009).
o Updated references.
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Authors' Addresses
Geoff Hunt
Unaffiliated
Email: r.geoff.hunt@gmail.com
Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, GA 30097
USA
Email: alan.d.clark@telchemy.com
Kevin Gross
AVA Networks
Email: kevin.gross@avanw.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
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