draft-ietf-xrblock-rtcp-xr-synchronization-01.txt   draft-ietf-xrblock-rtcp-xr-synchronization-02.txt 
Network Working Group H. Asaeda Network Working Group H. Asaeda
Internet-Draft NICT Internet-Draft NICT
Intended status: Standards Track R. Huang Intended status: Standards Track R. Huang
Expires: April 21, 2013 Q. Wu Expires: August 5, 2013 Q. Wu
Huawei Huawei
October 18, 2012 February 1, 2013
RTP Control Protocol (RTCP) Extended Report (XR) Blocks for RTP Control Protocol (RTCP) Extended Report (XR) Blocks for
Synchronization Delay and Offset Metrics Reporting Synchronization Delay and Offset Metrics Reporting
draft-ietf-xrblock-rtcp-xr-synchronization-01 draft-ietf-xrblock-rtcp-xr-synchronization-02
Abstract Abstract
This document defines two RTP Control Protocol (RTCP) Extended Report This document defines two RTP Control Protocol (RTCP) Extended Report
(XR) Blocks and associated with SDP parameters that allow the (XR) Blocks that allow the reporting of synchronization delay and
reporting of synchronization delay and offset metrics for use in a offset metrics for use in a range of RTP applications.
range of RTP applications.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2013. This Internet-Draft will expire on August 5, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Synchronization Delay and Offset Metrics Reporting
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 3 Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3
4. RTP Flows Initial Synchronization Delay Report Block . . . . . 4 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3
4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Definition of Fields in RTP Flow Initial 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 4
3. RTP Flows Initial Synchronization Delay Report Block . . . . . 5
3.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5
3.2. Definition of Fields in RTP Flow Initial
Synchronization Delay Metrics Block . . . . . . . . . . . 5 Synchronization Delay Metrics Block . . . . . . . . . . . 5
5. RTP Flows Synchronization Offset Metrics Block . . . . . . . . 6 4. RTP Flows Synchronization Offset Metrics Block . . . . . . . . 6
5.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 6 4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 7
5.2. Definition of Fields in RTP Flow General 4.2. Definition of Fields in RTP Flow General
Synchronization Offset Metrics Block . . . . . . . . . . . 7 Synchronization Offset Metrics Block . . . . . . . . . . . 7
6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 8 5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 8
6.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 8 5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 10 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 11
A.1. draft-ietf-xrblock-rtcp-xr-syncronization-01 . . . . . . . 10 A.1. draft-ietf-xrblock-rtcp-xr-syncronization-02 . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
1.1. Synchronization Delay and Offset Metrics Reporting Blocks
This draft defines two new block types to augment those defined in This draft defines two new block types to augment those defined in
[RFC3611], for use in a range of RTP applications. [RFC3611], for use in a range of RTP applications.
The first new block type supports reporting of Initial The first new block type supports reporting of Initial
Synchronization Delay to establish multimedia session. Information Synchronization Delay to establish multimedia session. Information
is recorded about time difference between the start of RTP sessions is recorded about time difference between the start of RTP sessions
and the time the RTP receiver acquires all components of RTP sessions and the time the RTP receiver acquires all components of RTP sessions
in the multimedia session [RFC6051]. in the multimedia session [RFC6051].
The second new block type supports reporting of the relative The second new block type supports reporting of the relative
synchronization offset time of two arbitrary streams (e.g., between synchronization offset time of two arbitrary streams (e.g., between
audio and video streams), with the same RTCP CNAME included in RTCP audio and video streams), with the same RTCP CNAME included in RTCP
SDES packets [RFC3550]. Information is recorded about the SDES packets [RFC3550]. Information is recorded about the
synchronization offset time of each RTP stream relative to the synchronization offset time of each RTP stream relative to the
reference RTP stream with the same CNAME and General Synchronization reference RTP stream with the same CNAME and General Synchronization
Offset of zero. Offset of zero.
These metrics belong to the class of transport level metrics defined These metrics belong to the class of transport level metrics defined
in [MONARCH]. in [RFC6792].
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 RTP Monitoring Architectures [RFC6792] provides guideline for
reporting block format using RTCP XR. The new report block described
in this memo is in compliance with the monitoring architecture
specified in [RFC6792].
1.4. Applicability
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 components of 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 multicast session, the initial
synchronization delay metric varies with the session bandwidth, the
number of members, and the number of senders in the session. The RTP
flow Initial synchronization delay block defined in this document can
be used to report such metric, i.e., 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 should rely 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.
Receivers of the RTP flow initial synchronization delay block could
use this metric to compare with targets (i.e., Service Level
Agreement or thresholds of the system) to help ensure the quality of
real-time application performance.
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
the audio stream is transmitted lagging behind video stream for
multiple tens of milliseconds [TR-126]. The RTP Flows
Synchronization Offset block can be used to report such
synchronization offset between video stream and audio stream. The
metrics defined in the RTP flows synchronization Offset block can be
used by network manager for trouble shooting and dealing with user
experience issues.
2. Terminology 2. Terminology
2.1. Standards Language 2.1. Standards Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
In addition, the following terms are defined: In addition, the following terms are defined:
skipping to change at page 4, line 6 skipping to change at page 5, line 14
Synchronization Offset: Synchronization Offset:
Synchronization between two media streams must be maintained to Synchronization between two media streams must be maintained to
ensure satisfactory QoE. Two media streams can be of the same ensure satisfactory QoE. Two media streams can be of the same
media type belonging to one RTP session or in different media media type belonging to one RTP session or in different media
types belonging to one multimedia session. The Synchronization types belonging to one multimedia session. The Synchronization
Offset is the relative time difference of the two media streams Offset is the relative time difference of the two media streams
that need to be synchronized. that need to be synchronized.
3. Applicability 3. RTP Flows Initial Synchronization Delay Report Block
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 components of 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 [TR-126]. 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 This block is sent by RTP receivers and reports Initial
synchronization delay beyond the information carried in the standard synchronization delay beyond the information carried in the standard
RTCP packet format. Information is recorded about time difference RTCP packet format. Information is recorded about time difference
between the start of RTP sessions and the time the RTP receiver between the start of multimedia session and the time when the RTP
acquires all components of RTP sessions [RFC6051]. receiver acquires all components of RTP sessions [RFC6051].
4.1. Metric Block Structure 3.1. Metric Block Structure
The RTP Flows Initial Synchronization Delay Report Block has the The RTP Flows Initial Synchronization Delay Report Block has the
following format: following format:
0 1 2 3 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 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 | | BT=RFISD | Reserved | Block length=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source | | SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initial Synchronization Delay | | Initial Synchronization Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2. Definition of Fields in RTP Flow Initial Synchronization Delay 3.2. Definition of Fields in RTP Flow Initial Synchronization Delay
Metrics Block Metrics Block
Block type (BT): 8 bits Block type (BT): 8 bits
The RTP Flows Initial Synchronization Delay Report Block is The RTP Flows Initial Synchronization Delay Report Block is
identified by the constant <RFISD>. identified by the constant <RFISD>.
Reserved: 8 bits Reserved: 8 bits
This field is reserved for future definition. In the absence of This field is reserved for future definition. In the absence of
skipping to change at page 5, line 48 skipping to change at page 6, line 19
SSRC of source: 32 bits SSRC of source: 32 bits
The SSRC of the media source SHALL be set to the value of the SSRC The SSRC of the media source SHALL be set to the value of the SSRC
identifier carried in any arbitrary component of RTP sessions identifier carried in any arbitrary component of RTP sessions
belonging to the same multimedia session. belonging to the same multimedia session.
Initial Synchronization Delay: 32 bits Initial Synchronization Delay: 32 bits
The average delay, expressed in units of 1/65536 seconds, from the 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 multimedia session [RFC6051] to the time when RTCP
beginning of session [RFC6051]. The value is calculated based on packets are received on all of the components RTP sessions. It is
received RTCP SR packets or the RTP header extension containing recommended that the beginning of multimedia session is chosen as
in-band mapping of RTP and NTP-format timestamps [RFC6051]. If the time when the receiver has joined the first RTP session of the
there is no packet loss, the initial synchronization delay is multimedia session. The value of the initial synchronization
expected to be equal to the average time taken to receive the delay is calculated based on received RTCP SR packets or the RTP
first RTCP packet in the RTP session with the longest RTCP header extension containing in-band mapping of RTP and NTP-format
reporting interval or the average time taken to receive the first timestamps [RFC6051]. If there is no packet loss, the initial
RTP header extension containing in-band mapping of RTP and NTP- synchronization delay is expected to be equal to the average time
format timestamps. taken to receive the first RTCP packet in the RTP session with the
longest RTCP reporting interval or the average time taken to
receive the first RTP header extension containing in-band mapping
of RTP and NTP- format timestamps.
If the measurement is unavailable, the value of this field with If the measurement is unavailable, the value of this field with
all bits set to 1 SHOULD be reported. all bits set to 1 MUST be reported.
5. RTP Flows Synchronization Offset Metrics Block 4. RTP Flows Synchronization Offset Metrics Block
In the RTP multimedia sessions, there can be an arbitrary number of In the RTP multimedia sessions, there can be an arbitrary number of
Media streams and each media stream (e.g., audio stream or video Media streams and each media stream (e.g., audio stream or video
stream) is sent in a separate RTP stream. The receiver associates stream) is sent in a separate RTP stream. The receiver associates
RTP streams to be synchronized by means of RTCP CNAME contained in RTP streams to be synchronized by means of RTCP CNAME contained in
the RTCP Source Description (SDES) packets [RFC3550]. the RTCP Source Description (SDES) packets [RFC3550].
This block is sent by RTP receivers and reports synchronization This block is sent by RTP receivers and reports synchronization
offset of the arbitrary two RTP streams that needs to be synchronized offset of the arbitrary two RTP streams that needs to be synchronized
in the RTP multimedia session. Information is recorded about the in the RTP multimedia session. Information is recorded about the
relative time difference between two media streams with the same relative average time difference between the reporting stream and the
CNAME. In two media streams, one media stream is the reference reference stream with the same CNAME. For multimedia session with
stream, which can be chosen as the arbitrary stream with minimum multiple media types (e.g., audio and video), it is recommended to
delay according to the common criterion defined in section 6.2.2.1 of choose the stream with the lower bandwidth as the reference stream.
[Y.1540]. For layered video sessions, it is recommended to use the base layer
stream as the reference stream.
5.1. Metric Block Structure 4.1. Metric Block Structure
The RTP Flow General Synchronization Offset Report Block has the The RTP Flow General Synchronization Offset Report Block has the
following format: following format:
0 1 2 3 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 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 |L| Reserved | Block length=4 | | BT=RFSO | Reserved | Block length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source | | SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of reference | | SSRC of reference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Synchronization Offset, most significant word | | Synchronization Offset, most significant word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Synchronization Offset, least significant word | | Synchronization Offset, least significant word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2. Definition of Fields in RTP Flow General Synchronization Offset 4.2. Definition of Fields in RTP Flow General Synchronization Offset
Metrics Block Metrics Block
Block type (BT): 8 bits Block type (BT): 8 bits
The RTP Flow General Synchronization Offset Report Block is The RTP Flow General Synchronization Offset Report Block is
identified by the constant <RFSO>. identified by the constant <RFSO>.
Lag and Lead Indication (L): 1 bit Reserved: 8 bits
This field is used to indicate whether the reporting stream lead
before the reference stream or lag behind the reference stream.
The value of this field is set to 1, if the reporting stream lead
before the reference stream, 0 otherwise.
Reserved: 7 bits
This field is reserved for future definition. In the absence of This field is reserved for future definition. In the absence of
such a definition, the bits in this field MUST be set to zero and such a definition, the bits in this field MUST be set to zero and
MUST be ignored by the receiver. MUST be ignored by the receiver.
Block length: 16 bits Block length: 16 bits
The constant 4, in accordance with the definition of this field in The constant 4, in accordance with the definition of this field in
Section 3 of RFC 3611 [RFC3611]. Section 3 of RFC 3611 [RFC3611].
skipping to change at page 7, line 47 skipping to change at page 8, line 16
The SSRC of the reference stream SHALL be set to the value of the The SSRC of the reference stream SHALL be set to the value of the
SSRC identifier of the reference RTP stream to which the XR SSRC identifier of the reference RTP stream to which the XR
relates. relates.
Synchronization Offset: 64 bits Synchronization Offset: 64 bits
The synchronization offset of the reporting RTP stream relative to The synchronization offset of the reporting RTP stream relative to
the reference RTP stream with the same CNAME. The calculation of the reference RTP stream with the same CNAME. The calculation of
Synchronization Offset is similar to Difference D calculation in Synchronization Offset is similar to Difference D calculation in
the RFC3550. That is to say,if Si is the RTP timestamp from the the RFC3550. That is to say, if Si is the NTP timestamp from the
reporting RTP packet i, and Ri is the time of arrival in RTP reporting RTP packet i, and Ri is the time of arrival in NTP
timestamp units for reporting RTP packet i, Sj is the RTP timestamp units for reporting RTP packet i, Sj is the NTP
timestamp from the reference RTP packet j, and Rj is the time of timestamp from the reference RTP packet j, and Rj is the time of
arrival in RTP timestamp units for reference RTP packet j, then arrival in NTP timestamp units for reference RTP packet j, then
the value of the synchronization offset D may be expressed as the value of the synchronization offset D may be expressed as
D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si) D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si)
The value of the synchronization offset is represented using a 64-
bit NTP-format timestamp as defined in [RFC5905], which is 64-bit If in-band delivery of NTP-format timestamps is supported
unsigned fixed-point number with the integer part in the first 32 [RFC6051], Si and Sj should be obtained directly from the RTP
bits and the fractional part in the last 32 bits. packets where NTP timestamps are available. If not, Si and Sj
should be calculated from their corresponding RTP timestamps. The
value of the synchronization offset is represented using a 64- bit
signed NTP-format timestamp as defined in [RFC5905], which is 64-
bit signed fixed-point number with the integer part in the first
32 bits and the fractional part in the last 32 bits. A positive
value of the synchronization offset means that the reporting
stream leads before the reference stream, while a negative value
means that the reporting stream lags behind the reference stream.
If the measurement is unavailable, the value of this field with If the measurement is unavailable, the value of this field with
all bits set to 1 SHOULD be reported. all bits set to 1 MUST be reported.
6. SDP Signaling 5. SDP Signaling
[RFC3611] defines the use of SDP (Session Description Protocol) [RFC3611] defines the use of SDP (Session Description Protocol)
[RFC4566] for signaling the use of XR blocks. XR blocks MAY be used [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used
without prior signaling. without prior signaling.
6.1. SDP rtcp-xr-attrib Attribute Extension 5.1. SDP rtcp-xr-attrib Attribute Extension
Two new parameters are defined for the two report blocks defined in Two new parameters are defined for the two report blocks defined in
this document to be used with Session Description Protocol (SDP) this document to be used with Session Description Protocol (SDP)
[RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234]. [RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234].
They have the following syntax within the "rtcp-xr" attribute They have the following syntax within the "rtcp-xr" attribute
[RFC3611]:
rtcp-xr-attrib = "a=rtcp-xr:" [RFC3611]:
[xr-format *(SP xr-format)] CRLF
xr-format = RTP-flows-init-syn-delay xr-format = xr-rfisd-block
/ RTP-flows-syn-offset / xr-rfso-block
RTP-flows-init-syn-delay = "RTP-flows-init-syn-delay" xr-rfisd-block = " init-syn-delay"
RTP-flow-syn-offset = "RTP-flows-syn-offset" xr-rfso-block = " syn-offset"
Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description
and the full syntax of the "rtcp-xr" attribute. and the full syntax of the "rtcp-xr" attribute.
6.2. Offer/Answer Usage 5.2. Offer/Answer Usage
When SDP is used in offer-answer context, the SDP Offer/Answer usage When SDP is used in offer-answer context, the SDP Offer/Answer usage
defined in [RFC3611] applies. defined in [RFC3611] applies.
7. IANA Considerations 6. IANA Considerations
New report block types for RTCP XR are subject to IANA registration. New report block types for RTCP XR are subject to IANA registration.
For general guidelines on IANA allocations for RTCP XR, refer to For general guidelines on IANA allocations for RTCP XR, refer to
Section 6.2 of [RFC3611]. Section 6.2 of [RFC3611].
This document assigns two new block type values in the RTCP XR Block This document assigns two new block type values in the RTCP XR Block
Type Registry: Type Registry:
Name: RFISD Name: RFISD
Long Name: RTP Flows Initial Synchronization Delay Long Name: RTP Flows Initial Synchronization Delay
Value <RFISD> Value <RFISD>
Reference: Section 4 Reference: Section 3
Name: RFSO Name: RFSO
Long Name: RTP Flows Synchronization Offset Metrics Block Long Name: RTP Flows Synchronization Offset Metrics Block
Value <RFSO> Value <RFSO>
Reference: Section 5 Reference: Section 4
This document also registers two new SDP [RFC4566] parameters for the This document also registers two new SDP [RFC4566] parameters for the
"rtcp-xr" attribute in the RTCP XR SDP Parameters Registry: "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry:
* "RTP-flows-init-syn-delay" * "xr-rfisd "
* "RTP-flows-syn-offset" * "xr-rfso"
The contact information for the registrations is: The contact information for the registrations is:
Qin Wu Qin Wu
sunseawq@huawei.com sunseawq@huawei.com
101 Software Avenue, Yuhua District 101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012, China Nanjing, Jiangsu 210012, China
8. Security Considerations 7. Security Considerations
The new RTCP XR report blocks proposed in this document introduces no The new RTCP XR report blocks proposed in this document introduces no
new security considerations beyond those described in [RFC3611]. new security considerations beyond those described in [RFC3611].
9. Acknowledgements 8. Acknowledgements
The authors would like to thank Bill Ver Steeg, David R Oran, Ali The authors would like to thank Bill Ver Steeg, David R Oran, Ali
Begen, Colin Perkins, Roni Even, Kevin Gross, Jing Zhao, Fernando Begen, Colin Perkins, Roni Even, Kevin Gross, Jing Zhao, Fernando
Boronat Segui, Youqing Yang, Wenxiao Yu and Yinliang Hu for their Boronat Segui, Mario Montagud Climent, Youqing Yang, Wenxiao Yu and
valuable comments and suggestions on this document. Yinliang Hu for their valuable comments and suggestions on this
document.
10. References 9. References
10.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611, Protocol Extended Reports (RTCP XR)", RFC 3611,
skipping to change at page 10, line 33 skipping to change at page 11, line 12
[RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
Flows", RFC 6051, November 2010. Flows", RFC 6051, November 2010.
[RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, [RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis,
"RTP Payload Format for Scalable Video Coding", RFC 6190, "RTP Payload Format for Scalable Video Coding", RFC 6190,
May 2011. May 2011.
[TR-126] BBF Forum, "Triple-play Services Quality of Experience [TR-126] BBF Forum, "Triple-play Services Quality of Experience
(QoE) Requirements", December 2006. (QoE) Requirements", December 2006.
10.2. Informative References 9.2. Informative References
[MONARCH] Wu, Q., "Monitoring Architectures for RTP", [RFC6792] Wu, Q., "Guidelines for Use of the RTP Monitoring
ID draft-ietf-avtcore-monarch-22, September 2012. Framework", RFC 6792, November 2012.
[Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and [Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and
availability performance parameters", November 2007. availability performance parameters", November 2007.
Appendix A. Change Log Appendix A. Change Log
Note to the RFC-Editor: please remove this section prior to Note to the RFC-Editor: please remove this section prior to
publication as an RFC. publication as an RFC.
A.1. draft-ietf-xrblock-rtcp-xr-syncronization-01 A.1. draft-ietf-xrblock-rtcp-xr-syncronization-02
The following are the major changes compared to previous version: The following are the major changes compared to previous version:
Editorial change based on comments raised on the list. Editorial change based on comments raised on the list and in the
IETF85 meeting
Authors' Addresses Authors' Addresses
Hitoshi Asaeda Hitoshi Asaeda
National Institute of Information and Communications Technology National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi 4-2-1 Nukui-Kitamachi
Koganei, Tokyo 184-8795 Koganei, Tokyo 184-8795
Japan Japan
Email: asaeda@nict.go.jp Email: asaeda@nict.go.jp
 End of changes. 48 change blocks. 
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