Internet DRAFT - draft-ietf-xrblock-rtcp-xr-pdv
draft-ietf-xrblock-rtcp-xr-pdv
Audio/Video Transport Working Group A. Clark
Internet-Draft Telchemy
Intended status: Standards Track Q. Wu
Expires: March 30, 2013 Huawei
September 26, 2012
RTP Control Protocol (RTCP) Extended Report (XR) Block for Packet Delay
Variation Metric Reporting
draft-ietf-xrblock-rtcp-xr-pdv-08.txt
Abstract
This document defines an RTP Control Protocol (RTCP) Extended Report
(XR) block that allows the reporting of Packet Delay Variation
metrics for a range of RTP applications.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on March 30, 2013.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Packet Delay Variation 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
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Packet Delay Variation Metrics Block . . . . . . . . . . . . . 5
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5
3.2. Definition of Fields in PDV Metrics Block . . . . . . . . 5
3.3. Guidance on use of PDV metrics . . . . . . . . . . . . . . 9
3.4. Examples of use . . . . . . . . . . . . . . . . . . . . . 9
4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 12
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 12
5.3. Contact information for registrations . . . . . . . . . . 12
5.4. New registry of PDV types . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 19
A.1. draft-ietf-xrblock-rtcp-xr-pdv-08 . . . . . . . . . . . . 19
A.2. draft-ietf-xrblock-rtcp-xr-pdv-06 . . . . . . . . . . . . 19
A.3. draft-ietf-xrblock-rtcp-xr-pdv-05 . . . . . . . . . . . . 19
A.4. draft-ietf-xrblock-rtcp-xr-pdv-04 . . . . . . . . . . . . 19
A.5. draft-ietf-xrblock-rtcp-xr-pdv-03 . . . . . . . . . . . . 19
A.6. draft-ietf-xrblock-rtcp-xr-pdv-02 . . . . . . . . . . . . 20
A.7. draft-ietf-xrblock-rtcp-xr-pdv-01 . . . . . . . . . . . . 20
A.8. draft-ietf-xrblock-rtcp-xr-pdv-00 . . . . . . . . . . . . 20
A.9. draft-ietf-avt-rtcp-xr-pdv-03 . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
1.1. Packet Delay Variation 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 provides information on Packet Delay Variation
(PDV) using one of several standard metrics,, for example, Mean
Absolute Packet Delay Variation 2 (MAPDV2) (Clause 6.2.3.2 of
[G.1020]), or 2-point PDV (Clause 6.2.4 of [Y.1540]).
The 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 draft 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 XR Block described in this document
are in accordance with the guidelines in [RFC6390] and [MONARCH].
1.4. Applicability
These metrics are applicable to a wide range of RTP applications in
which the application streams are sensitive to delay
variation[RFC5481]. For example, applications could use the
measurements of these metrics to help adjust the size of adaptive
jitter buffers to improve performance. Network managers can use
these metrics to compare actual delay variation to targets (i.e., a
numerical objective or Service Level Agreement) to help ensure the
quality of real-time application performance.
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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].
2.2. Notations
This report block makes use of binary fractions. The terminology
used is
Numeric formats S X:Y
where S indicates a two's complement signed representation, X
the number of bits prior to the decimal place and Y the number
of bits after the decimal place.
Hence 8:8 represents an unsigned number in the range 0.0 to
255.996 with a granularity of 0.0039. S7:8 would represent the
range -127.996 to +127.996. 0:16 represents a proper binary
fraction with range
0.0 to 1 - 1/65536 = 0.9999847
though note that use of flag values at the top of the numeric
range slightly reduces this upper limit. For example, if the
16- bit values 0xfffe and 0xffff are used as flags for "over-
range" and "unavailable" conditions, a 0:16 quantity has range
0.0 to 1 - 3/65536 = 0.9999542
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3. Packet Delay Variation Metrics Block
Metrics in this block report on packet delay variation in the stream
arriving at the RTP system. The measurement of these metrics are
made at the receiving end of the RTP stream. Instances of this
metric block refer by Synchronization Source (SSRC) to the separate
auxiliary Measurement Information Block [MEASI] which contains
measurement intervals. This metric block relies on the measurement
interval given by the value of the "Measurement Duration (Interval)"
field in the Measurement Information Block to indicate the span of
the report and MUST be sent in the same compound RTCP packet as the
Measurement Information Block. If the measurement interval is not
received for this metric block, this metric block MUST be discarded.
3.1. Report Block Structure
PDV metrics block
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=NPDV | I |pdvtyp |Rsv| block length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pos PDV Threshold/Peak | Pos PDV Percentile |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neg PDV Threshold/Peak | Neg PDV Percentile |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mean PDV | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure
3.2. Definition of Fields in PDV Metrics Block
Block type (BT): 8 bits
A Packet Delay Variation Metrics Report Block is identified by the
constant NPDV.
[Note to RFC Editor: please replace NPDV 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 Packet Delay variation
metrics are Sampled, Interval or Cumulative metrics [MONARCH],
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 is a sampled instantaneous value (I=01) (Sampled
Value). The value I=00 is reserved, and MUST NOT be used. If the
value I=00 is received, then the XR block MUST be ignored by the
receiver.
Packet Delay Variation Metric Type (pdvtyp): 4 bits
Packet Delay Variation Metric Type is of type enumerated and is
interpreted as an unsigned, 4-bit integer. This field is used to
identify the Packet Delay Variation Metric Type used in this
report block, according to the following code:
bits 014-011
0: MAPDV2, Clause 6.2.3.2 of [G.1020],
1: 2-point PDV, Clause 6.2.4 of [Y.1540].
Rsv.: 2 bits
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
ignored by the receiver.
Block Length: 16 bits
The length of this report block in 32-bit words, minus one. For
the Packet Delay Variation Metrics block, the block length is
equal to 4.
SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611].
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Positive PDV Threshold/Peak: 16 bits
This field is associated with the Positive PDV percentile and
expressed in Milliseconds with numeric format S11:4. The term
Positive represents that the packets are arriving later than the
expected time.
If the measured value is less than -2047.9375 (the value which
would be coded as 0x8001), the value 0x8000 SHOULD be reported to
indicate an over-range negative measurement. If the measured
value is greater than +2047.8125 (the value which would be coded
as 0x7FFD), the value 0x7FFE SHOULD be reported to indicate an
over-range positive measurement. If the measurement is
unavailable, the value 0x7FFF MUST be reported.
Positive PDV Percentile: 16 bits
The percentages of packets in the RTP stream for which individual
packet delays were less than the Positive PDV Threshold. It is
expressed in numeric format 8:8 with values from 0 to 100th
percentile.
If the measurement is unavailable, the value 0xFFFF MUST be
reported.
Negative PDV Threshold/Peak: 16 bits
This field is associated with the Negative PDV percentile and
expressed in Milliseconds with numeric format S11:4. The term
Negative represents that the packets are arriving earlier than the
expected time.
If the measured value is more negative than -2047.9375 (the value
which would be coded as 0x8001), the value 0x8000 SHOULD be
reported to indicate an over-range negative measurement. If the
measured value is more positive than +2047.8125 (the value which
would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to
indicate an over-range positive measurement. If the measurement
is unavailable, the value 0x7FFF MUST be reported.
Negative PDV Percentile: 16 bits
The percentages of packets in the RTP stream for which individual
packet delays were more than the Negative PDV Threshold. It is
expressed in numeric format 8:8 with values from 0 to 100th
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percentile.
If the measurement is unavailable, the value 0xFFFF MUST be
reported.
If the PDV Type indicated is 2-point PDV and the Positive and
Negative PDV Percentiles are set to 100.0 then the Positive and
Negative Threshold/Peak PDV values are the peak values measured
during the reporting interval (which may be from the start of the
call for cumulative reports). In this case, the difference
between the Positive and Negative Threshold/Peak values defines
the range of 2-point PDV.
Mean PDV: 16 bits
The mean PDV value of data packets is expressed in milliseconds
with Numeric format S11:4 format.
For MAPDV2 this value is generated according to Clause 6.2.3.2 of
[G.1020]. For interval reports the MAPDV2 value is reset at the
start of the interval.
For 2-point PDV, the value reported is the mean of per-packet
2-point PDV values. This metric indicates the arrival time of the
first media packet of the session with respect to the mean of the
arrival times of every packet of the session. A single value of
the metric (for a single session) may not be useful by itself, but
its average over a number of sessions may be useful in diagnosing
media delay at session startup. For example, this might occur if
media packets are often delayed behind signalling packets due to
head-of-line blocking.
If the measured value is more negative than -2047.9375 (the value
which would be coded as 0x8001), the value 0x8000 SHOULD be
reported to indicate an over-range negative measurement. If the
measured value is more positive than +2047.8125 (the value which
would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to
indicate an over-range positive measurement. If the measurement
is unavailable, the value 0x7FFF MUST be reported.
Reserved: 16 bits
These bits are reserved for future definition. They MUST be set
to zero by the sender and ignored by the receiver.
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3.3. Guidance on use of PDV metrics
This subsection provides informative guidance on when it might be
appropriate to use each of the PDV metric types.
MAPDV2 (Clause 6.2.3.2 of [G.1020]) is the envelope of instantaneous
(per-packet) delay when compared to the short term moving average
delay. This metric could be useful in determining residual
impairment when an RTP end system uses an adaptive de-jitter buffer
which tracks the average delay variation, provided that the averaging
behavior of the adaptive algorithm is similar to that of the MAPDV2
algorithm.
2-point PDV (Clause 6.2.4 of [Y.1540]) reports absolute packet delay
variation with respect to a defined reference packet transfer delay .
Note that the reference packet is generally selected as the packet
with minimum delay based on the most common criterion (See section 1
and section 5.1 of [RFC5481] ). In an RTP context, the two "points"
are at the sender (the synchronization source which applies RTP
timestamps) and at the receiver. The value of this metric for the
packet with index j is identical to the quantity D(i,j) defined in
Section 6.4.1 of [RFC3550] and the packet index i should be set equal
to the index of the reference packet for the metric in practice. The
metric includes the effect of the frequency offsets of clocks in both
the sender and receiver end systems, so it is useful mainly in
network where synchronization is distributed. As well as measuring
packet delay variation in such networks, it may be used to ensure
that synchronization is effective, for example where the network
carries ISDN data traffic over RTP [RFC4040]. The metric is likely
to be useful in networks which use fixed de-jitter buffering, because
it may be used to determine the length of the required de-jitter
buffer, or to determine if network performance has deteriorated such
that existing de-jitter buffers are too small to accommodate the
observed delay variation.
3.4. Examples of use
(b) To report MAPDV2 [G.1020]:
Pos PDV Threshold = 50.0; Pos PDV Percentile = 95.3; Neg PDV
Threshold = 50.0 (note this implies -50ms); Neg PDV Percentile
= 98.4; PDV type = 0 (MAPDV2)
causes average MAPDV2 to be reported in the Mean PDV field.
Note that implementations may either fix the reported
percentile and calculate the associated PDV level or may fix a
threshold PDV level and calculate the associated percentile.
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From a practical implementation perspective it is simpler to
use the second of these approaches (except of course in the
extreme case of a 100% percentile).
(b) To report 2-point PDV [Y.1540]:
Pos PDV Threshold = 60 (note this implies +60ms); Pos PDV
Percentile = 96.3; Neg PDV Threshold = 0; Neg PDV Percentile =
0; PDV type = 1 (2-point PDV)
causes 2-point PDV to be reported in the Mean PDV field.
2-point PDV, according to [Y.1540] is the difference in delay
between the current packet and the referenced packet of the
stream. If the sending and receiving clocks are not
synchronized, this metric includes the effect of relative
timing drift.
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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.
xr-format =/ xr-pdv-block
xr-pdv-block = "pkt-dly-var" [ "," pdvtype ] [ "," nspec "," pspec ]
pdvtype = "pdv=" ( "0" ; MAPDV2 ITU-T G.1020
/ "1" ; 2-point PDV ITU-T Y.1540
/ 1*2DIGIT ) ;Value 2~15 are valid and
;reserved for future use
nspec = ("nthr=" fixpoint) ; negative PDV threshold (ms)
/ ("npc=" fixpoint ) ; negative PDV percentile
pspec = ("pthr=" fixpoint) ; positive PDV threshold (ms)
/ ("ppc=" fixpoint) ; positive PDV percentile
fixpoint = 1*DIGIT "." 1*DIGIT ; fixed point decimal
DIGIT = <as defined in Section 3.4 of [RFC5234]>
When SDP is used in offer-answer, a system sending SDP may request a
specific type of PDV measurement. In addition, they may state a
specific percentile or threshold value, and expect to receive the
corresponding threshold or percentile metric, respectively. The
system receiving the SDP SHOULD send the PDV metrics requested, but
if the metric is not available, the system receiving the SDP MUST
send the metric block with the flag value indicating that the metric
is unavailable.
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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 NPDV in the IANA "RTCP XR
Block Type Registry" to the "Packet Delay Variation Metrics Block".
[Note to RFC Editor: please replace NPDV 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 "pkt-dly-var" 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
5.4. New registry of PDV types
This document creates a new registry to be called "RTCP XR PDV block
- PDV type" as a sub-registry of the "RTP Control Protocol Extended
Reports (RTCP XR) Block Type Registry". Policies for this new
registry are as follows:
o The information required to support an assignment is an
unambiguous definition of the new metric, covering the base
measurements and how they are processed to generate the reported
metric. This should include the units of measurement, how values
of the metric are reported in the three 16-bit fields "Pos PDV
Threshold/Peak", "Neg PDV Threshold/Peak" and "Mean PDV" within
the report block, and how the metric uses the two 16-bit fields
"Pos PDV Percentile" and "Neg PDV Percentile".
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o The review process for the registry is "Specification Required" as
described in Section 4.1 of [RFC5226].
o Entries in the registry are unsigned 4-bit integers. The valid
range is 0 to 15 corresponding to the 4-bit field "pdvtyp" in the
block. Values are to be recorded in decimal.
o Initial assignments are as follows:
* 0: MAPDV2, Clause 6.2.3.2 of [G.1020],
* 1: 2-point PDV, Clause 6.2.4 of [Y.1540],
* 2-15: Reserved for future use.
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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 reviews and feedback provided 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, Hideaki Yamada, Jing Zhao,
Kevin Gross, Colin Perkins, Charles Eckel, Glen Zorn, Shida Schubert,
Benoit Claise, Adrian Farrel and Pete Resnick.
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9. References
9.1. Normative References
[G.1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter
definitions for quality of speech and other voiceband
applications utilizing IP networks", July 2006.
[MEASI] Hunt, G., "Measurement Identity and information Reporting
using SDES item and XR Block",
ID draft-ietf-xrblock-rtcp-xr-meas-identity-10,
August 2012.
[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.
[RFC4040] Kreuter, R., "RTP Payload Format for a 64 kbit/s
Transparent Call", April 2005.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", July 2006.
[RFC5226] Narten, T., "Guidelines for Writing an IANA Considerations
Section in RFCs", May 2008.
BCP 26
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", January 2008.
[Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and
availability performance parameters", November 2007.
9.2. Informative References
[MONARCH] Hunt, G., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-22, September 2012.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009.
[RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric
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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-pdv-08
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-07,6:
o Editorial change based on IESG Review.
A.2. draft-ietf-xrblock-rtcp-xr-pdv-06
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-05:
o Editorial change based on IESG Review.
o SDP element update based on pete's suggestion.
o Clarify the value of PDV in the applicability section.
o Clarify measurement point and timing in section 3.
A.3. draft-ietf-xrblock-rtcp-xr-pdv-05
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-04:
o Move Geoff Hunt from author list to Contributors section based on
his suggestion.
A.4. draft-ietf-xrblock-rtcp-xr-pdv-04
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-03:
o Editorial changes based on Gen-Art Review and Secdir Review.
A.5. draft-ietf-xrblock-rtcp-xr-pdv-03
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-02:
o Make definition of pdvtype get alignment with IANA section.
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o Make Guidance on use of PDV metrics get alignment with RFC5481.
o Other Editorial changes.
A.6. draft-ietf-xrblock-rtcp-xr-pdv-02
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-01:
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.7. draft-ietf-xrblock-rtcp-xr-pdv-01
The following are the major changes to previous version
draft-ietf-xrblock-rtcp-xr-pdv-00:
o Fix typos or nits in the definition of Negative PDV Threshold/
Peak.
o Fix nits in Numeric format S7:8.
o remove the text that is relevant to tag field.
o Add text in SDP signaling section to clarify indicationof metric
unavailable.
A.8. draft-ietf-xrblock-rtcp-xr-pdv-00
The following are the major changes to previous version
draft-ietf-avt-rtcp-xr-pdv-03:
o Updated references.
A.9. draft-ietf-avt-rtcp-xr-pdv-03
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.
Clark & Wu Expires March 30, 2013 [Page 20]
Internet-Draft RTCP XR Packet Delay Variation September 2012
Authors' Addresses
Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, GA 30097
USA
Email: alan.d.clark@telchemy.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
Clark & Wu Expires March 30, 2013 [Page 21]
