Internet DRAFT - draft-ietf-xrblock-rtcp-xr-delay
draft-ietf-xrblock-rtcp-xr-delay
Audio/Video Transport Working Group A. Clark
Internet-Draft Telchemy
Intended status: Standards Track K. Gross
Expires: May 23, 2013 AVA Networks
Q. Wu
Huawei
November 19, 2012
RTP Control Protocol (RTCP) Extended Report (XR) Block for Delay metric
Reporting
draft-ietf-xrblock-rtcp-xr-delay-12.txt
Abstract
This document defines an RTP Control Protocol(RTCP) Extended Report
(XR) Block that allows the reporting of Delay metrics for use in a
range of Real-time Transport Protocol 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 . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 9
4.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10
5.3. Contact information for registrations . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 15
A.1. draft-ietf-xrblock-rtcp-xr-delay-12 . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
1.1. Packet Delay Metrics Block
This document 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 transport metrics defined
in [MONARCH].
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 document defines a new Extended Report block for
use with[RFC3550] and [RFC3611].
1.3. Performance Metrics Framework
The Performance Metrics Framework [RFC6390] provides guidance on the
definition and specification of performance metrics. The RTP
Monitoring Architectures [MONARCH] provides guideline for reporting
block format using RTCP XR. The Metrics Block described in this
document are in accordance with the guidelines in [RFC6390] and
[MONARCH].
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. Knowledge of the round-trip delay and
delay characteristics can aid other receivers in sizing their receive
buffers and selecting a playout delay. The same information is also
valuable to network managers in troubleshooting network and user
experience issues.
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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. The measurement of these metrics are made either
at the receiving end of the RTP stream or at the sending end of the
RTP stream. Instances of this Metrics Block refer by Synchronization
source (SSRC) to the separate auxiliary Measurement Information block
[RFC6776] which contains measurement periods (see RFC6776 section
4.2). This metric block relies on the measurement period in the
Measurement Information block indicating the span of the report and
SHOULD be sent in the same compound RTCP packet as the measurement
information block. If the measurement period is not received in the
same compound RTCP packet as this metric block, this metric block
MUST 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:
I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive
metrics reports.
I=11: Cumulative Duration - the reported value applies to the
accumulation period characteristic of cumulative measurements.
I=01: Sampled Value - the reported value is a sampled
instantaneous value.
Reserved (resv): 6 bits
These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See RFC6709 section 4.2).
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 NTP timestamp field in the RTCP SR and LSR field
and DLSR field in the RTCP RR (See RFC 3550 section 6.4.1 and
figure 2). It also can be determined using NTP timestamp field in
the RTCP Receiver Reference Time Report Block and LRR field and
DLRR field in the DLRR Report Block (See RFC3611 section 4.5).
If only one measurement of Round Trip Delay is available for the
timespan of the report (i.e.,the measurement period) (whether
Interval or Cumulative), this single value SHOULD be reported as
the mean value.
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If the measurement is unavailable, the value of this field with
all bits set to 1 MUST 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,
expressed in units of 1/65536 seconds. This value is typically
determined using NTP timestamp field in the RTCP SR and LSR field
and DLSR field in the RTCP RR. It also can be determined using
NTP timestamp field in the RTCP Receiver Reference Time Report
Block and LRR field and DLRR field in the DLRR Report Block.
If only one measurement of Round Trip Delay is available for the
timespan of the report (i.e.,the measurement period) (whether
Interval or Cumulative), this single value SHOULD be reported as
the minimum value.
If the measurement is unavailable, the value of this field with
all bits set to 1 MUST 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 NTP timestamp field in the RTCP SR and LSR field
and DLSR field in the RTCP RR. It also can be determined using
NTP timestamp field in the RTCP Receiver Reference Time Report
Block and LRR field and DLRR field in the DLRR Report Block.
If only one measurement of Round Trip Delay is available for the
timespan of the report (i.e.,the measurement period) (whether
Interval or Cumulative), this single value SHOULD be reported as
the maximum value.
If the measurement is unavailable, the value of this field with
all bits set to 1 MUST 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
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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 of this field with
all bits set to 1 MUST 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.
4.1. SDP rtcp-xr-attrib Attribute Extension
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.
xr-format =/ xr-delay-block
xr-delay-block ="delay"
4.2. Offer/Answer Usage
When SDP is used in offer-answer context, the SDP Offer/Answer usage
defined in [RFC3611] applies.
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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:
Qin Wu (sunseawq@huawei.com)
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
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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. Contributors
Geoff Hunt wrote the initial version of this document.
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8. 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,Jing
Zhao,Kevin Gross, Colin Perkins, Charles Eckel, Glen Zorn,Shida
Schubert,Barry Leiba,Sean Turner,Robert Sparks,Benoit Claise,Stephen
Farrell.
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9. References
9.1. 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.
[RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design
Considerations for Protocol Extensions", RFC 6709,
September 2012.
9.2. Informative References
[MONARCH] Hunt, G., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-22, September 2012.
[RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric
Development", RFC 6390, October 2011.
[RFC6776] Hunt, G., "Measurement Identity and information Reporting
using SDES item and XR Block", RFC 6776, October 2012.
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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-12
The following are the major changes to previous version :
o Remove SHOULD from reserved field and add reference to RFC6709.
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Authors' Addresses
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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