Internet DRAFT - draft-asaeda-xrblock-rtcp-xr-synchronization
draft-asaeda-xrblock-rtcp-xr-synchronization
Network Working Group H. Asaeda
Internet-Draft Keio University
Intended status: Standards Track R. Huang
Expires: January 17, 2013 Q. Wu
Huawei
July 16, 2012
RTCP XR Blocks for Synchronization Delay and Offset Metrics Reporting
draft-asaeda-xrblock-rtcp-xr-synchronization-07
Abstract
This document defines two RTCP XR Report Blocks and associated with
SDP parameters that allow the reporting of synchronization delay and
offset metrics for use in a range of RTP applications.
Status of this Memo
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This Internet-Draft will expire on January 17, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4
4. RTP Flows Initial Synchronization Delay Report Block . . . . . 4
4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5
4.2. Definition of Fields in RTP Flow Initial
Synchronization Delay Metrics Block . . . . . . . . . . . 5
5. RTP Flows Synchronization Offset Metrics Block . . . . . . . . 6
5.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 6
5.2. Definition of Fields in RTP Flow General
Synchronization Offset Metrics Block . . . . . . . . . . . 6
6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 9
A.1. draft-asaeda-xrblock-rtcp-xr-syncronization-07 . . . . . . 9
A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-06 . . . . . . 10
A.3. draft-asaeda-xrblock-rtcp-xr-syncronization-05 . . . . . . 10
A.4. draft-asaeda-xrblock-rtcp-xr-syncronization-04 . . . . . . 10
A.5. draft-asaeda-xrblock-rtcp-xr-syncronization-03 . . . . . . 10
A.6. draft-asaeda-xrblock-rtcp-xr-syncronization-02 . . . . . . 10
A.7. draft-asaeda-xrblock-rtcp-xr-syncronization-01 . . . . . . 10
A.8. draft-asaeda-xrblock-rtcp-xr-syncronization-00 . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
This draft defines two new block types to augment those defined in
[RFC3611], for use in a range of RTP applications.
The first new block type supports reporting of Initial
Synchronization Delay to establish multimedia session. Information
is recorded about time difference between the start of RTP sessions
and the time the RTP receiver acquires all components of RTP sessions
in the multimedia session [RFC6051].
The second new block type supports reporting of the relative
synchronization offset time of two arbitrary streams (e.g., between
audio and video streams), with the same RTCP CNAME included in RTCP
SDES packets [RFC3550]. 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.
These metrics belong to the class of terminal related transport level
metrics defined in [MONARCH].
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].
In addition, the following terms are defined:
Initial Synchronization Delay:
A multimedia session comprises a set of concurrent RTP sessions
among a common group of participants, using one RTP session for
each media type. Initial synchronization Delay is the average
time for receiver to synchronize the components of a multimedia
session [RFC6051].
Synchronization Offset:
The absolute delay variance of the measured RTP stream relative to
the reference RTP stream in the multimedia session.
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3. Applicability
The report blocks defined in this document could be used by dedicated
network monitoring applications.
When joining each session in layered video sessions [RFC6190] or the
multimedia session, a receiver may not synchronize playout across the
multimedia session or layered video session until RTCP SR packets
have been received on all of the component RTP sessions. The
component RTP session are referred to as each RTP session for each
media type in multimedia session or separate RTP session for each
layer in the layered video session. 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, the number
of members, and the number of senders in the session. The RTP flow
Initial synchronization delay block can be used to report the initial
synchronization delay to receive all the RTP streams belonging to the
same multimedia session or layered video session. 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 based on the in-band mapping of
RTP and NTP-format timestamps [RFC6051] or wait until the 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 carried in different RTP sessions, with the same RTCP CNAME.
These streams may be not synchronized with each other. For example,
one audio stream and one video stream belong to the same session and
audio stream are transmitted lag behind video stream for multiple
tens of milliseconds. The RTP Flows Synchronization Offset block can
be used to report such synchronization offset between video stream
and audio stream.
4. RTP Flows Initial Synchronization Delay Report Block
This block is sent by RTP receivers and reports Initial
synchronization delay beyond the information carried in the standard
RTCP packet format. Information is recorded about time difference
between the start of RTP sessions and the time the RTP receiver
acquires all components of RTP sessions [RFC6051].
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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=RFISD | Reserved | Block length=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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>.
Block length: 16 bits
The constant 2, in accordance with the definition of this field in
Section 3 of RFC 3611 [RFC3611].
SSRC of Source: 32 bits
The SSRC of the media source SHALL be set to the value of the SSRC
identifier carried in an arbitrary RTP stream belonging to the
same multimedia session.
Initial Synchronization Delay: 32 bits
The average delay, expressed in units of 1/65536 seconds, from the
RTCP packets received on all of the components RTP sessions to the
beginning of session [RFC6051]. The value is calculated based on
the information contained in RTCP SR packets or the in-band
mapping of RTP and NTP-format timestamps [RFC6051]. If there is
no packet loss, the initial synchronization delay is expected to
be equal to the average time taken to receive the first RTCP
packet in the RTP session with the longest RTCP reporting
interval.
If the measurement is unavailable, the value of this field with
all bits set to 1 SHOULD be reported.
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5. RTP Flows Synchronization Offset Metrics Block
In the RTP multimedia sessions, there can be an arbitrary number of
streams and each stream (e.g., audio stream or video stream) is sent
in a separate RTP stream. The receiver associates RTP streams to be
synchronized by means of RTCP CNAME contained in the RTCP Source
Description (SDES) packets [RFC3550].
This block is sent by RTP receivers and reports synchronization
offset of the arbitrary two RTP streams that needs to be synchronized
in the RTP multimedia session. Information is recorded about the
actual delay variance of the measured RTP stream relative to he
reference RTP stream with the same CNAME. The reference RTP stream
can be chosen as the arbitrary stream with minimum delay according to
the common criterion defined in section 6.2.2.1 of [Y.1540].
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=RFSO | Reserved | Block length=3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Synchronization Offset, most significant word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Synchronization Offset, least significant word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 <RFSO>.
Block length: 16 bits
The constant 3, in accordance with the definition of this field in
Section 3 of RFC 3611 [RFC3611].
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SSRC of Source: 32 bits
The SSRC of the media source SHALL be set to the value of the SSRC
identifier of the reference RTP stream to which the XR relates.
Synchronization Offset: 64 bits
The synchronization offset of one RTP stream relative to the
reference RTP stream with the same CNAME. The Synchronization
Offset of the reference stream should be zero. This value is
calculated based on the interarrival time between an arbitrary RTP
packet and the reference RTP packet with the same CNAME, and
timestamps of this arbitrary RTP packet and the reference RTP
packet with the same CNAME. 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 of this field with
all bits set to 1 SHOULD be reported.
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-delay
/ RTP-flows-syn-offset
RTP-flows-init-syn-delay = "RTP-flows-init-syn-delay"
["=" max-size]
RTP-flow-syn-offset = "RTP-flows-syn-offset"
["=" max-size]
max-size = 1*DIGIT ; maximum block size in octets
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.
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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: RFSO
Long Name: RTP Flows Synchronization Offset Metrics Block
Value <RFSO>
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-delay"
* "RTP-flows-syn-offset"
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, Kevin Gross, Jing Zhao, Fernando
Boronat Segui, Youqing Yang, Wenxiao Yu and Yinliang Hu for their
valuable comments and suggestions on this document.
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
Flows", RFC 6051, November 2010.
[RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis,
"RTP Payload Format for Scalable Video Coding", RFC 6190,
May 2011.
10.2. Informative References
[MONARCH] Wu, Q., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-13, May 2012.
[Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and
availability performance parameters", November 2007.
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-07
Editorial changes are made from the previous version 06.
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A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-06
The following are the major changes compared to previous version 05:
o Define synchronization offset as 64 bit NTP-format timestamp to
meet synchronization resolution requirements for some RTP
applications.
o Add the definition of Initial Synchronization Delay in section 2.
o Other editorial changes.
A.3. draft-asaeda-xrblock-rtcp-xr-syncronization-05
The following are the major changes compared to previous version 04:
o Remove per packet reporting and only report a single value of
general synchronization offset.
A.4. draft-asaeda-xrblock-rtcp-xr-syncronization-04
The following are the major changes compared to previous version 03:
o Add a definition for synchronization offset.
o Use additional text in applicability section to clarify the
difference between synchronization delay and offset.
o Add a reference to tell how to select the reference stream.
o Other Editorial Changes.
A.5. draft-asaeda-xrblock-rtcp-xr-syncronization-03
The following are the major changes compared to previous version 02:
o Support multiple general synchronization offset reporting.
o Other Editorial Changes.
A.6. draft-asaeda-xrblock-rtcp-xr-syncronization-02
The following are the major changes compared to previous version 01:
o Clarify which synchronization is reported in section 4 and 5.
o Allow calculating the synchronization delay based on RTP header
extension defined in RFC6051
o Explain what the components of RTP session are in section 3.
A.7. draft-asaeda-xrblock-rtcp-xr-syncronization-01
The following are the major changes compared to previous version:
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o Separate Synchronization Delay and Offset Metrics Block into two
independent block based on comments on the list.
A.8. draft-asaeda-xrblock-rtcp-xr-syncronization-00
The following are the major changes compared to previous version:
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.
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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