Network Working Group H. Asaeda
Internet-Draft Keio University
Intended status: Standards Track R. Huang
Expires: December 17, 2011 Q. Wu
Huawei
June 15, 2011
RTCP XR Blocks for Synchronization Delay and Offset Metrics Reporting
draft-asaeda-xrblock-rtcp-xr-synchronization-01
Abstract
This document defines an RTCP XR Report Block and associated SDP
parameters that allows the reporting of synchronization delay and
offset metrics for use in a range of RTP applications.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. RTP Flows Initial Synchronization Delay Report Block . . . . . 4
4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 4
4.2. Definition of Fields in RTP Flow Initial
Synchronization Delay Metrics Block . . . . . . . . . . . . 4
5. RTP Flows General Synchronization Offset Metrics Block . . . . 5
5.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5
5.2. Definition of Fields in RTP Flow General
Synchronization Offset Metrics Block . . . . . . . . . . . 6
6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . . 9
A.1. draft-asaeda-xrblock-rtcp-xr-syncronization-00 . . . . . . 9
A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-01 . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
This draft defines a new block type to augment those defined in
[RFC3611], for use in a range of RTP applications.
This new block type supports reporting of Initial synchronization
delay. Information is recorded about the difference between the
start of RTP sessions and the time the RTP receiver acquires all
components of RTP sessions [RFC6051]. It also supports reporting of
the general Synchronization offset status of an arbitrary number of
streams, with the same RTCP CNAME. Information is recorded about the
synchronization offset time of each RTP stream relative to the
reference RTP stream with the same CNAME and General Synchronization
Offset of zero.
The metrics belong to the class of transport level metrics defined in
[MONARCH] (work in progress).
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].
3. Applicability
The report blocks defined in this document could be used by dedicated
network monitoring applications.
When joining a layered video session in such an application, a
receiver may not synchronize playout across the multimedia session
until RTCP SR packets have been received on all of the component RTP
sessions. For unicast session, the delay due to negotiation of NAT
pinholes, firewall holes, quality-of-service, and media security keys
is contributed to such initial synchronization playout. For
multicast session, such initial synchronization delay varies with the
session bandwidth and the number of members, the number of senders in
the session. The RTP flow synchronization delay block can be used to
report the initial synchronization delay of these RTP streams beyond
the information carried in the standard RTCP packet format. In the
absence of packet loss, the initial synchronization delay equals to
the average time taken to receive the first RTCP packet in the RTP
session with the longest RTCP reporting interval. In the presence of
packet loss, the media synchronization needs to wait until the
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reporting interval has passed, and the next RTCP SR packet is sent.
In an RTP multimedia session, there can be an arbitrary number of
streams, with the same RTCP CNAME. The RTP Flows General
Synchronization Offset block can be used to report the general
Synchronization offset status of these RTP streams beyond the
information carried in the standard RTCP packet format. For layered
session or multimedia session, the first RTP packet can be chosen as
the basic packet of reference RTP stream.
4. RTP Flows Initial Synchronization Delay Report Block
This block reports Initial synchronization delay beyond the
information carried in the standard RTCP packet format. Information
is recorded about the the difference between the start of RTP
sessions and the time the RTP receiver acquires all components of RTP
sessions [RFC6051]. The components of RTP session are referred to as
one RTP session for each media type or the media content in each
layer contained in RTP Control Protocol (RTCP) sender report (SR)
packets [RFC3550].
4.1. Metric Block Structure
The RTP Flows Initial Synchronization Delay Report Block has the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=TBD | Reserved | Block length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Sender |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initial Synchronization Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2. Definition of Fields in RTP Flow Initial Synchronization Delay
Metrics Block
Block type (BT): 8 bits
The Statistics Summary Report Block is identified by the constant
<RFISD>.
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Block length: 16 bits
The constant 2, in accordance with the definition of this field in
Section 3 of RFC 3611 [RFC3611].
SSRC of Sender: 32 bits
The SSRC of the RTP data packet source being reported upon by this
report block. (Section 4.1 of [RFC3611]).
Initial Synchronization Delay: 32 bits
The average delay, expressed in units of 1/65536 seconds, between
the RTCP packets received on all of the components RTP sessions
and the beginning of session [RFC6051]. The value is calculated
as follows:
The average time, expressed in units of 1/65536 seconds, taken
to receive the first RTCP packet in the RTP session with the
longest RTCP reporting interval [RFC6051].
5. RTP Flows General Synchronization Offset Metrics Block
In an RTP multimedia session, there can be an arbitrary number of
streams, with the same RTCP CNAME. This block reports the general
Synchronization offset status of these RTP streams beyond the
information carried in the standard RTCP packet format. Information
is recorded about the synchronization offset time of each RTP stream
relative to the reference RTP stream with the same CNAME and General
Synchronisation Offset of zero.
5.1. Metric Block Structure
The RTP Flow General Synchronization Offset Report Block has the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=TBD | Reserved | Block length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| General Synchronization Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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5.2. Definition of Fields in RTP Flow General Synchronization Offset
Metrics Block
Block type (BT): 8 bits
The RTP Flow General Synchronization Offset Report Block is
identified by the constant <RFGSO>.
Block length: 16 bits
The constant 3, in accordance with the definition of this field in
Section 3 of RFC 3611 [RFC3611].
SSRC of Source: 32 bits
The SSRC of the RTP data packet source being reported upon by this
report block. (Section 4.1 of [RFC3611]).
General synchronization offset: 32 bits
This field represents the synchronization offset time of one RTP
stream in milliseconds relative to the reference RTP stream with
the same CNAME and General Synchronisation Offset of zero
[RFC6051] This value is calculated based on the interarrival time
between arbitray RTP packet and the reference RTP packet with the
same CNAME , and timestamps of this arbitray RTP packet and the
reference RTP packet with the same CNAME.
6. SDP Signaling
Two new parameters are defined for the two report blocks defined in
this document to be used with Session Description Protocol (SDP)
[RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234].
They have the following syntax within the "rtcp-xr" attribute
[RFC3611]:
rtcp-xr-attrib = "a=rtcp-xr:"
[xr-format *(SP xr-format)] CRLF
xr-format = RTP-flows-init-syn
/ RTP-flows-general-syn
RTP-flows-init-syn = "RTP-flows-init-syn"
["=" max-size]
max-size = 1*DIGIT ; maximum block size in octets
RTP-flow-general-syn = "RTP-flows-general-syn"
["=" max-size]
max-size = 1*DIGIT ; maximum block size in octets
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Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description
and the full syntax of the "rtcp-xr" attribute.
7. IANA Considerations
New report block types for RTCP XR are subject to IANA registration.
For general guidelines on IANA allocations for RTCP XR, refer to
Section 6.2 of [RFC3611].
This document assigns two new block type values in the RTCP XR Block
Type Registry:
Name: RFISD
Long Name: RTP Flows Initial Synchronization Delay
Value <RFISD>
Reference: Section 4
Name: RFGSO
Long Name: RTP Flows General Synchronization Offset Metrics Block
Value <RFGSO>
Reference: Section 5
This document also registers two new SDP [RFC4566] parameters for the
"rtcp-xr" attribute in the RTCP XR SDP Parameters Registry:
* "RTP-flows-init-syn"
* "RTP-flows-general-syn"
The contact information for the registrations is:
Qin Wu
sunseawq@huawei.com
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012, China
8. Security Considerations
The new RTCP XR report blocks proposed in this document introduces no
new security considerations beyond those described in [RFC3611].
9. Acknowledgements
The authors would like to thank Bill Ver Steeg, David R Oran, Ali
Begen, Colin Perkins, Roni Even, Youqing Yang, Wenxiao Yu and
Yinliang Hu for their valuable comments and suggestions on this
document.
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10. References
10.1. Normative References
[I-D.ietf-avt-rtp-svc]
Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis,
"RTP Payload Format for Scalable Video Coding",
draft-ietf-avt-rtp-svc-27 (work in progress),
February 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2250] Hoffman, D., Fernando, G., Goyal, V., and M. Civanlar,
"RTP Payload Format for MPEG1/MPEG2 Video", RFC 2250,
January 1998.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
Flows", RFC 6051, November 2010.
10.2. Informative References
[MEASIDENT]
Hunt, G. and A. Clark, "RTCP XR Measurement Identifier
Block", ID draft-ietf-avt-rtcp-xr-meas-identity-02,
May 2009.
[MONARCH] Wu, Q., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-00, April 2011.
[PMOL] Clark, A., "Framework for Performance Metric Development",
ID draft-ietf-pmol-metrics-framework-08, January 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-asaeda-xrblock-rtcp-xr-syncronization-00
This document is separated from
draft-wu-xrblock-rtcp-xr-quality-monitoring-01 with some editorial
changes and focuses on RTP Flow Initial Synchronization Delay and RTP
Flows General Synchronization Offset.
A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-01
Separate Synchronization Delay and Offset Metrics Block into two
independent block based on comments on the list.
Authors' Addresses
Hitoshi Asaeda
Keio University
Graduate School of Media and Governance
5322 Endo
Fujisawa, Kanagawa 252-0882
Japan
Email: asaeda@wide.ad.jp
Rachel Huang
Huawei Technologies Co., Ltd.
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: Rachel@huawei.com
Qin Wu
Huawei Technologies Co., Ltd.
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
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