wdiff rfc6798.original rfc6798.txt

Audio/Video Transport Working Group
Internet Engineering Task Force (IETF) A. Clark
Internet-Draft
Request for Comments: 6798 Telchemy
Intended status:
Category: Standards Track Q. Wu
Expires: March 30, 2013
ISSN: 2070-1721 Huawei
September 26,
November 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 packet delay variation
metrics for a range of RTP applications.

Status of this This Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on March 30, 2013.
http://www.rfc-editor.org/info/rfc6798.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 ....................................................3
1.1. Packet Delay Variation Metrics Block . . . . . . . . . . . 3 .......................3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 ...................................3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 ..............................3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 ..............................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 .....................................................3
2.1. Standards Requirements Language . . . . . . . . . . . . . . . . . . . . 4 ......................................3
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 4 ..................................................4
3. Packet Delay Variation Metrics Block . . . . . . . . . . . . . 5 ............................4
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 .....................................4
3.2. Definition of Fields in PDV Metrics Block . . . . . . . . 5 ..................5
3.3. Guidance on use Use of PDV metrics . . . . . . . . . . . . . . 9 Metrics .............................8
3.4. Examples of use . . . . . . . . . . . . . . . . . . . . . 9 Use ............................................9
4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 11 ...................................................9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 ............................................10
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 12 Value ..............................10
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 12 .................................10
5.3. Contact information Information for registrations . . . . . . . . . . 12 Registrations .....................11
5.4. New registry Registry of PDV types . . . . . . . . . . . . . . . . 12 Types .................................11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 ........................................11
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15 ...................................................12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 ................................................12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 .....................................................12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 ......................................12
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 ....................................13

1. Introduction

1.1. Packet Delay Variation Metrics Block

This draft document 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,, metrics, for example, Mean
Absolute Packet Delay Variation 2 (MAPDV2) (Clause 6.2.3.2 of
[G.1020]),
[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 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
monitoring architectures [MONARCH] provides guideline guidelines for reporting
block format using RTCP XR. The XR Block block described in this document
are
is 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]. 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.

2. Terminology

2.1. Standards Requirements 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 place, and Y the number
of bits after the decimal place.

Hence

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 represents the
range -127.996 to +127.996. 0:16 represents a proper binary
fraction with range as follows:

0.0 to 1 - 1/65536 = 0.9999847

though

however, note that use of flag values at the top of the numeric
range slightly reduces this upper limit. For example, if the
16- bit
16-bit values 0xfffe and 0xffff are used as flags for "over-
range" and "unavailable" conditions, a 0:16 quantity has a
range as follows:

0.0 to 1 - 3/65536 = 0.9999542

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 is made
at the receiving end of the RTP stream. Instances of this metric
block refer by Synchronization Source synchronization source (SSRC) to the separate
auxiliary Measurement Information Block [MEASI] [RFC6776], 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 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 BT=15 | 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.] 15.

Interval Metric flag (I): 2 bit

This field is used to indicate whether the Packet Delay variation Variation
metrics are Sampled, Interval Interval, or Cumulative metrics [MONARCH],
that is, whether the reported values applies apply to the most recent
measurement interval duration between successive metrics reports
(I=10) (the Interval Duration) Duration), or they apply to the accumulation
period characteristic of cumulative measurements (I=11) (the
Cumulative
Duration) Duration), or is they are a sampled instantaneous value
(I=01) (Sampled Value). The value I=00 is reserved, 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.:

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:

block length: 16 bits

The length of this report block is in 32-bit words, minus one.
For the Packet Delay Variation Metrics block, Block, the block length is
equal to 4.

SSRC of source: 32 bits

This field is as defined in Section 4.1 of [RFC3611].

Positive PDV Threshold/Peak: 16 bits

This field is associated with the Positive PDV percentile and
expressed in Milliseconds milliseconds with numeric format S11:4. The term
Positive
"Positive" represents that the packets are arriving later than the
expected time.

If the measured value is less than -2047.9375 (the value which that
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 that would be coded as
0x7FFD), the value 0x7FFE SHOULD be reported to indicate an
over-range over-
range positive measurement. If the measurement is unavailable,
the value 0x7FFF MUST be reported.

Positive PDV Percentile: 16 bits

The

This field indicates 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 milliseconds with numeric format S11:4. The term
Negative
"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
that 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 that
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

This field indicates 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 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 percentiles are set to 100.0 100.0, 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 MAPDV2, this value is generated according to Clause 6.2.3.2 of
[G.1020]. For interval reports 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 signaling packets due to
head-of-line blocking.

Reserved: 16 bits

These bits are reserved for future definition. They MUST be set
to zero by the sender and ignored by the receiver.

3.3. Guidance on use Use of PDV metrics 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 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
that 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 . delay.
Note that the reference packet is generally selected as the packet
with minimum delay based on the most common criterion (See section (see Sections 1
and section 5.1 of [RFC5481] ). [RFC5481]). In an RTP context, the two "points" are at
the sender (the synchronization source which that 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] [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 networks
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 example, where the network carries
ISDN data traffic over RTP [RFC4040]. The metric is likely to be
useful in networks which that 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) Use

(a) To report MAPDV2 [G.1020]:

Pos PDV Threshold = 50.0; Pos PDV Percentile = 95.3; Neg PDV
Threshold = 50.0 (note this implies -50ms); -50 ms); 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 may fix the reported
percentile and calculate the associated PDV level or may fix a
threshold PDV level and calculate the associated percentile.
From a practical implementation perspective 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); +60 ms); 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.

4. SDP Signaling

[RFC3611] defines the use of SDP (Session the Session Description Protocol) Protocol (SDP)
[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, 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, 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.

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 Value

This document assigns the block type value NPDV 15 in the IANA "RTCP XR
Block Type Registry" 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". Parameters" registry.

5.3. Contact information Information for registrations 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 Registry of PDV types 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" 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".

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.

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 3, of [RFC3611]
does not apply.

7. Contributors

Geoff Hunt wrote the initial version of this document.

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 Farrel, and Pete Resnick.

9. References

9.1. Normative References

[G.1020] ITU-T, "ITU-T ITU-T Rec. G.1020, Performance 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", 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.

[RFC4040] Kreuter, R., "RTP Payload Format for a 64 kbit/s
Transparent Call", RFC 4040, April 2005.

[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.

[RFC5226] Narten, T., T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.

BCP 26

[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.

[RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information
Reporting Using a Source Description (SDES) Item and an
RTCP Extended Report (XR) Block", RFC 6776, October 2012.

[Y.1540] ITU-T, "ITU-T ITU-T Rec. Y.1540, IP "IP packet transfer and availability
performance parameters", November 2007.

9.2. Informative References

[MONARCH] Wu, W., Hunt, G., "Monitoring Architectures and P. Arden, "Guidelines for RTP",
ID draft-ietf-avtcore-monarch-22, Use of the
RTP Monitoring Framework", Work in Progress,
September 2012.

[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009.

[RFC6390] Clark, A. and B. Claise, "Framework "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
October 2011.

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.

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.

Authors' Addresses

Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, GA 30097
USA

Email:

EMail: alan.d.clark@telchemy.com

Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China

Email:

EMail: sunseawq@huawei.com