draft-ietf-xrblock-rtcp-xr-pdv-08.txt   rfc6798.txt 
Audio/Video Transport Working Group A. Clark Internet Engineering Task Force (IETF) A. Clark
Internet-Draft Telchemy Request for Comments: 6798 Telchemy
Intended status: Standards Track Q. Wu Category: Standards Track Q. Wu
Expires: March 30, 2013 Huawei ISSN: 2070-1721 Huawei
September 26, 2012 November 2012
RTP Control Protocol (RTCP) Extended Report (XR) Block for Packet Delay RTP Control Protocol (RTCP) Extended Report (XR) Block
Variation Metric Reporting for Packet Delay Variation Metric Reporting
draft-ietf-xrblock-rtcp-xr-pdv-08.txt
Abstract Abstract
This document defines an RTP Control Protocol (RTCP) Extended Report This document defines an RTP Control Protocol (RTCP) Extended Report
(XR) block that allows the reporting of Packet Delay Variation (XR) block that allows the reporting of packet delay variation
metrics for a range of RTP applications. metrics for a range of RTP applications.
Status of this Memo 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 This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on March 30, 2013. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6798.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................3
1.1. Packet Delay Variation Metrics Block . . . . . . . . . . . 3 1.1. Packet Delay Variation Metrics Block .......................3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 1.2. RTCP and RTCP XR Reports ...................................3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 1.3. Performance Metrics Framework ..............................3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 1.4. Applicability ..............................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology .....................................................3
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Language ......................................3
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Notations ..................................................4
3. Packet Delay Variation Metrics Block . . . . . . . . . . . . . 5 3. Packet Delay Variation Metrics Block ............................4
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 3.1. Report Block Structure .....................................5
3.2. Definition of Fields in PDV Metrics Block . . . . . . . . 5 3.2. Definition of Fields in PDV Metrics Block ..................5
3.3. Guidance on use of PDV metrics . . . . . . . . . . . . . . 9 3.3. Guidance on Use of PDV Metrics .............................8
3.4. Examples of use . . . . . . . . . . . . . . . . . . . . . 9 3.4. Examples of Use ............................................9
4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 11 4. SDP Signaling ...................................................9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 5. IANA Considerations ............................................10
5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 12 5.1. New RTCP XR Block Type Value ..............................10
5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 12 5.2. New RTCP XR SDP Parameter .................................10
5.3. Contact information for registrations . . . . . . . . . . 12 5.3. Contact Information for Registrations .....................11
5.4. New registry of PDV types . . . . . . . . . . . . . . . . 12 5.4. New Registry of PDV Types .................................11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. Security Considerations ........................................11
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15 7. Contributors ...................................................12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 8. Acknowledgments ................................................12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9. References .....................................................12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 9.1. Normative References ......................................12
9.2. Informative References . . . . . . . . . . . . . . . . . . 17 9.2. Informative References ....................................13
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
1. Introduction 1. Introduction
1.1. Packet Delay Variation Metrics Block 1.1. Packet Delay Variation Metrics Block
This draft defines a new block type to augment those defined in This document defines a new block type to augment those defined in
[RFC3611], for use in a range of RTP applications. [RFC3611], for use in a range of RTP applications.
The new block type provides information on Packet Delay Variation The new block type provides information on Packet Delay Variation
(PDV) using one of several standard metrics,, for example, Mean (PDV) using one of several standard metrics, for example, Mean
Absolute Packet Delay Variation 2 (MAPDV2) (Clause 6.2.3.2 of 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]). [G.1020]) or 2-point PDV (Clause 6.2.4 of [Y.1540]).
The metrics belong to the class of transport metrics defined in The metrics belong to the class of transport metrics defined in
[MONARCH]. [MONARCH].
1.2. RTCP and RTCP XR Reports 1.2. RTCP and RTCP XR Reports
The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] The use of RTCP for reporting is defined in [RFC3550]. [RFC3611]
defined an extensible structure for reporting using an RTCP Extended defined an extensible structure for reporting using an RTCP Extended
Report (XR). This draft defines a new Extended Report block for use Report (XR). This document defines a new Extended Report block for
with [RFC3550] and [RFC3611]. use with [RFC3550] and [RFC3611].
1.3. Performance Metrics Framework 1.3. Performance Metrics Framework
The Performance Metrics Framework [RFC6390] provides guidance on the The Performance Metrics Framework [RFC6390] provides guidance on the
definition and specification of performance metrics. The RTP definition and specification of performance metrics. The RTP
Monitoring Architectures [MONARCH] provides guideline for reporting monitoring architectures [MONARCH] provides guidelines for reporting
block format using RTCP XR. The XR Block described in this document block format using RTCP XR. The XR block described in this document
are in accordance with the guidelines in [RFC6390] and [MONARCH]. is in accordance with the guidelines in [RFC6390] and [MONARCH].
1.4. Applicability 1.4. Applicability
These metrics are applicable to a wide range of RTP applications in These metrics are applicable to a wide range of RTP applications in
which the application streams are sensitive to delay which the application streams are sensitive to delay variation
variation[RFC5481]. For example, applications could use the [RFC5481]. For example, applications could use the measurements of
measurements of these metrics to help adjust the size of adaptive these metrics to help adjust the size of adaptive jitter buffers to
jitter buffers to improve performance. Network managers can use improve performance. Network managers can use these metrics to
these metrics to compare actual delay variation to targets (i.e., a compare actual delay variation to targets (i.e., a numerical
numerical objective or Service Level Agreement) to help ensure the objective or Service Level Agreement) to help ensure the quality of
quality of real-time application performance. real-time application performance.
2. Terminology 2. Terminology
2.1. Standards Language 2.1. Requirements 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].
2.2. Notations 2.2. Notations
This report block makes use of binary fractions. The terminology This report block makes use of binary fractions. The terminology
used is used is
Numeric formats S X:Y Numeric formats S X:Y
where S indicates a two's complement signed representation, X where S indicates a two's complement signed representation, X
the number of bits prior to the decimal place and Y the number the number of bits prior to the decimal place, and Y the number
of bits after the decimal place. of bits after the decimal place.
Hence 8:8 represents an unsigned number in the range 0.0 to 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 255.996 with a granularity of 0.0039. S7:8 represents the
range -127.996 to +127.996. 0:16 represents a proper binary range -127.996 to +127.996. 0:16 represents a proper binary
fraction with range fraction with range as follows:
0.0 to 1 - 1/65536 = 0.9999847 0.0 to 1 - 1/65536 = 0.9999847
though note that use of flag values at the top of the numeric however, note that use of flag values at the top of the numeric
range slightly reduces this upper limit. For example, if the range slightly reduces this upper limit. For example, if the
16- bit values 0xfffe and 0xffff are used as flags for "over- 16-bit values 0xfffe and 0xffff are used as flags for "over-
range" and "unavailable" conditions, a 0:16 quantity has range range" and "unavailable" conditions, a 0:16 quantity has a
range as follows:
0.0 to 1 - 3/65536 = 0.9999542 0.0 to 1 - 3/65536 = 0.9999542
3. Packet Delay Variation Metrics Block 3. Packet Delay Variation Metrics Block
Metrics in this block report on packet delay variation in the stream Metrics in this block report on packet delay variation in the stream
arriving at the RTP system. The measurement of these metrics are arriving at the RTP system. The measurement of these metrics is made
made at the receiving end of the RTP stream. Instances of this at the receiving end of the RTP stream. Instances of this metric
metric block refer by Synchronization Source (SSRC) to the separate block refer by synchronization source (SSRC) to the separate
auxiliary Measurement Information Block [MEASI] which contains auxiliary Measurement Information Block [RFC6776], which contains
measurement intervals. This metric block relies on the measurement measurement intervals. This metric block relies on the measurement
interval given by the value of the "Measurement Duration (Interval)" interval given by the value of the "Measurement Duration (Interval)"
field in the Measurement Information Block to indicate the span of 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 the report and MUST be sent in the same compound RTCP packet as the
Measurement Information Block. If the measurement interval is not Measurement Information Block. If the measurement interval is not
received for this metric block, this metric block MUST be discarded. received for this metric block, this metric block MUST be discarded.
3.1. Report Block Structure 3.1. Report Block Structure
PDV metrics block PDV metrics block:
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=NPDV | I |pdvtyp |Rsv| block length=4 | | BT=15 | I |pdvtyp |Rsv| block length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source | | SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pos PDV Threshold/Peak | Pos PDV Percentile | | Pos PDV Threshold/Peak | Pos PDV Percentile |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neg PDV Threshold/Peak | Neg PDV Percentile | | Neg PDV Threshold/Peak | Neg PDV Percentile |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mean PDV | Reserved | | Mean PDV | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure Figure 1: Report Block Structure
3.2. Definition of Fields in PDV Metrics Block 3.2. Definition of Fields in PDV Metrics Block
Block type (BT): 8 bits Block type (BT): 8 bits
A Packet Delay Variation Metrics Report Block is identified by the A Packet Delay Variation Metrics Block is identified by the
constant NPDV. constant 15.
[Note to RFC Editor: please replace NPDV with the IANA provided
RTCP XR block type for this block.]
Interval Metric flag (I): 2 bit Interval Metric flag (I): 2 bit
This field is used to indicate whether the Packet Delay variation This field is used to indicate whether the Packet Delay Variation
metrics are Sampled, Interval or Cumulative metrics [MONARCH], metrics are Sampled, Interval, or Cumulative metrics [MONARCH],
that is, whether the reported values applies to the most recent that is, whether the reported values apply to the most recent
measurement interval duration between successive metrics reports measurement interval duration between successive metrics reports
(I=10) (the Interval Duration) or to the accumulation period (I=10) (the Interval Duration), or they apply to the accumulation
characteristic of cumulative measurements (I=11) (the Cumulative period characteristic of cumulative measurements (I=11) (the
Duration) or is a sampled instantaneous value (I=01) (Sampled Cumulative Duration), or they are a sampled instantaneous value
Value). The value I=00 is reserved, and MUST NOT be used. If the (I=01) (Sampled Value). The value I=00 is reserved and MUST NOT
value I=00 is received, then the XR block MUST be ignored by the be used. If the value I=00 is received, then the XR block MUST be
receiver. ignored by the receiver.
Packet Delay Variation Metric Type (pdvtyp): 4 bits Packet Delay Variation Metric Type (pdvtyp): 4 bits
Packet Delay Variation Metric Type is of type enumerated and is Packet Delay Variation Metric Type is of type enumerated and is
interpreted as an unsigned, 4-bit integer. This field is used to interpreted as an unsigned, 4-bit integer. This field is used to
identify the Packet Delay Variation Metric Type used in this identify the Packet Delay Variation Metric Type used in this
report block, according to the following code: report block, according to the following code:
bits 014-011 bits 014-011
0: MAPDV2, Clause 6.2.3.2 of [G.1020], 0: MAPDV2, Clause 6.2.3.2 of [G.1020],
1: 2-point PDV, Clause 6.2.4 of [Y.1540]. 1: 2-point PDV, Clause 6.2.4 of [Y.1540].
Rsv.: 2 bits Rsv: 2 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
ignored by the receiver. ignored by the receiver.
Block Length: 16 bits block length: 16 bits
The length of this report block in 32-bit words, minus one. For The length of this report block is in 32-bit words, minus one.
the Packet Delay Variation Metrics block, the block length is For the Packet Delay Variation Metrics Block, the block length is
equal to 4. equal to 4.
SSRC of source: 32 bits SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611]. This field is as defined in Section 4.1 of [RFC3611].
Positive PDV Threshold/Peak: 16 bits Positive PDV Threshold/Peak: 16 bits
This field is associated with the Positive PDV percentile and This field is associated with the Positive PDV percentile and
expressed in Milliseconds with numeric format S11:4. The term expressed in milliseconds with numeric format S11:4. The term
Positive represents that the packets are arriving later than the "Positive" represents that the packets are arriving later than the
expected time. expected time.
If the measured value is less than -2047.9375 (the value which If the measured value is less than -2047.9375 (the value that
would be coded as 0x8001), the value 0x8000 SHOULD be reported to would be coded as 0x8001), the value 0x8000 SHOULD be reported to
indicate an over-range negative measurement. If the measured indicate an over-range negative measurement. If the measured
value is greater than +2047.8125 (the value which would be coded value is greater than +2047.8125 (the value that would be coded as
as 0x7FFD), the value 0x7FFE SHOULD be reported to indicate an 0x7FFD), the value 0x7FFE SHOULD be reported to indicate an over-
over-range positive measurement. If the measurement is range positive measurement. If the measurement is unavailable,
unavailable, the value 0x7FFF MUST be reported. the value 0x7FFF MUST be reported.
Positive PDV Percentile: 16 bits Positive PDV Percentile: 16 bits
The percentages of packets in the RTP stream for which individual This field indicates the percentages of packets in the RTP stream
packet delays were less than the Positive PDV Threshold. It is for which individual packet delays were less than the Positive PDV
expressed in numeric format 8:8 with values from 0 to 100th Threshold. It is expressed in numeric format 8:8 with values from
percentile. 0 to 100th percentile.
If the measurement is unavailable, the value 0xFFFF MUST be If the measurement is unavailable, the value 0xFFFF MUST be
reported. reported.
Negative PDV Threshold/Peak: 16 bits Negative PDV Threshold/Peak: 16 bits
This field is associated with the Negative PDV percentile and This field is associated with the Negative PDV percentile and
expressed in Milliseconds with numeric format S11:4. The term expressed in milliseconds with numeric format S11:4. The term
Negative represents that the packets are arriving earlier than the "Negative" represents that the packets are arriving earlier than
expected time. the expected time.
If the measured value is more negative than -2047.9375 (the value If the measured value is more negative than -2047.9375 (the value
which would be coded as 0x8001), the value 0x8000 SHOULD be that would be coded as 0x8001), the value 0x8000 SHOULD be
reported to indicate an over-range negative measurement. If the reported to indicate an over-range negative measurement. If the
measured value is more positive than +2047.8125 (the value which measured value is more positive than +2047.8125 (the value that
would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to
indicate an over-range positive measurement. If the measurement indicate an over-range positive measurement. If the measurement
is unavailable, the value 0x7FFF MUST be reported. is unavailable, the value 0x7FFF MUST be reported.
Negative PDV Percentile: 16 bits Negative PDV Percentile: 16 bits
The percentages of packets in the RTP stream for which individual This field indicates the percentages of packets in the RTP stream
packet delays were more than the Negative PDV Threshold. It is for which individual packet delays were more than the Negative PDV
expressed in numeric format 8:8 with values from 0 to 100th Threshold. It is expressed in numeric format 8:8 with values from
percentile. 0 to 100th percentile.
If the measurement is unavailable, the value 0xFFFF MUST be If the measurement is unavailable, the value 0xFFFF MUST be
reported. reported.
If the PDV Type indicated is 2-point PDV and the Positive and 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 PDV percentiles are set to 100.0, then the Positive and
Negative Threshold/Peak PDV values are the peak values measured Negative Threshold/Peak PDV values are the peak values measured
during the reporting interval (which may be from the start of the during the reporting interval (which may be from the start of the
call for cumulative reports). In this case, the difference call for cumulative reports). In this case, the difference
between the Positive and Negative Threshold/Peak values defines between the Positive and Negative Threshold/Peak values defines
the range of 2-point PDV. the range of 2-point PDV.
Mean PDV: 16 bits Mean PDV: 16 bits
The mean PDV value of data packets is expressed in milliseconds The mean PDV value of data packets is expressed in milliseconds
with Numeric format S11:4 format. with Numeric format S11:4 format.
For MAPDV2 this value is generated according to Clause 6.2.3.2 of 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 [G.1020]. For interval reports, the MAPDV2 value is reset at the
start of the interval. start of the interval.
For 2-point PDV, the value reported is the mean of per-packet 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 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 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 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 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 its average over a number of sessions may be useful in diagnosing
media delay at session startup. For example, this might occur if media delay at session startup. For example, this might occur if
media packets are often delayed behind signalling packets due to media packets are often delayed behind signaling packets due to
head-of-line blocking. head-of-line blocking.
If the measured value is more negative than -2047.9375 (the value If the measured value is more negative than -2047.9375 (the value
which would be coded as 0x8001), the value 0x8000 SHOULD be that would be coded as 0x8001), the value 0x8000 SHOULD be
reported to indicate an over-range negative measurement. If the reported to indicate an over-range negative measurement. If the
measured value is more positive than +2047.8125 (the value which measured value is more positive than +2047.8125 (the value that
would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to
indicate an over-range positive measurement. If the measurement indicate an over-range positive measurement. If the measurement
is unavailable, the value 0x7FFF MUST be reported. is unavailable, the value 0x7FFF MUST be reported.
Reserved: 16 bits Reserved: 16 bits
These bits are reserved for future definition. They MUST be set These bits are reserved for future definition. They MUST be set
to zero by the sender and ignored by the receiver. to zero by the sender and ignored by the receiver.
3.3. Guidance on use of PDV metrics 3.3. Guidance on Use of PDV Metrics
This subsection provides informative guidance on when it might be This subsection provides informative guidance on when it might be
appropriate to use each of the PDV metric types. appropriate to use each of the PDV metric types.
MAPDV2 (Clause 6.2.3.2 of [G.1020]) is the envelope of instantaneous 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 (per-packet) delay when compared to the short-term moving average
delay. This metric could be useful in determining residual delay. This metric could be useful in determining residual
impairment when an RTP end system uses an adaptive de-jitter buffer impairment when an RTP end system uses an adaptive de-jitter buffer
which tracks the average delay variation, provided that the averaging that tracks the average delay variation, provided that the averaging
behavior of the adaptive algorithm is similar to that of the MAPDV2 behavior of the adaptive algorithm is similar to that of the MAPDV2
algorithm. algorithm.
2-point PDV (Clause 6.2.4 of [Y.1540]) reports absolute packet delay 2-point PDV (Clause 6.2.4 of [Y.1540]) reports absolute packet delay
variation with respect to a defined reference packet transfer delay . variation with respect to a defined reference packet transfer delay.
Note that the reference packet is generally selected as the packet Note that the reference packet is generally selected as the packet
with minimum delay based on the most common criterion (See section 1 with minimum delay based on the most common criterion (see Sections 1
and section 5.1 of [RFC5481] ). In an RTP context, the two "points" and 5.1 of [RFC5481]). In an RTP context, the two "points" are at
are at the sender (the synchronization source which applies RTP the sender (the synchronization source that applies RTP timestamps)
timestamps) and at the receiver. The value of this metric for the and at the receiver. The value of this metric for the packet with
packet with index j is identical to the quantity D(i,j) defined in index j is identical to the quantity D(i,j) defined in Section 6.4.1
Section 6.4.1 of [RFC3550] and the packet index i should be set equal of [RFC3550], and the packet index i should be set equal to the index
to the index of the reference packet for the metric in practice. The of the reference packet for the metric in practice. The metric
metric includes the effect of the frequency offsets of clocks in both includes the effect of the frequency offsets of clocks in both the
the sender and receiver end systems, so it is useful mainly in sender and receiver end systems, so it is useful mainly in networks
network where synchronization is distributed. As well as measuring where synchronization is distributed. As well as measuring packet
packet delay variation in such networks, it may be used to ensure delay variation in such networks, it may be used to ensure that
that synchronization is effective, for example where the network synchronization is effective, for example, where the network carries
carries ISDN data traffic over RTP [RFC4040]. The metric is likely ISDN data traffic over RTP [RFC4040]. The metric is likely to be
to be useful in networks which use fixed de-jitter buffering, because useful in networks that use fixed de-jitter buffering, because it may
it may be used to determine the length of the required de-jitter be used to determine the length of the required de-jitter buffer, or
buffer, or to determine if network performance has deteriorated such to determine if network performance has deteriorated such that
that existing de-jitter buffers are too small to accommodate the existing de-jitter buffers are too small to accommodate the observed
observed delay variation. delay variation.
3.4. Examples of use 3.4. Examples of Use
(b) To report MAPDV2 [G.1020]: (a) To report MAPDV2 [G.1020]:
Pos PDV Threshold = 50.0; Pos PDV Percentile = 95.3; Neg PDV Pos PDV Threshold = 50.0; Pos PDV Percentile = 95.3; Neg PDV
Threshold = 50.0 (note this implies -50ms); Neg PDV Percentile Threshold = 50.0 (note this implies -50 ms); Neg PDV Percentile
= 98.4; PDV type = 0 (MAPDV2) = 98.4; PDV type = 0 (MAPDV2)
causes average MAPDV2 to be reported in the Mean PDV field. causes average MAPDV2 to be reported in the Mean PDV field.
Note that implementations may either fix the reported Note that implementations either may fix the reported
percentile and calculate the associated PDV level or may fix a percentile and calculate the associated PDV level or may fix a
threshold PDV level and calculate the associated percentile. threshold PDV level and calculate the associated percentile.
From a practical implementation perspective, it is simpler to
From a practical implementation perspective it is simpler to
use the second of these approaches (except of course in the use the second of these approaches (except of course in the
extreme case of a 100% percentile). extreme case of the 100th percentile).
(b) To report 2-point PDV [Y.1540]: (b) To report 2-point PDV [Y.1540]:
Pos PDV Threshold = 60 (note this implies +60ms); Pos PDV Pos PDV Threshold = 60 (note this implies +60 ms); Pos PDV
Percentile = 96.3; Neg PDV Threshold = 0; Neg PDV Percentile = Percentile = 96.3; Neg PDV Threshold = 0; Neg PDV Percentile =
0; PDV type = 1 (2-point PDV) 0; PDV type = 1 (2-point PDV)
causes 2-point PDV to be reported in the Mean PDV field. causes 2-point PDV to be reported in the Mean PDV field.
2-point PDV, according to [Y.1540] is the difference in delay 2-point PDV, according to [Y.1540] is the difference in delay
between the current packet and the referenced packet of the between the current packet and the referenced packet of the
stream. If the sending and receiving clocks are not stream. If the sending and receiving clocks are not
synchronized, this metric includes the effect of relative synchronized, this metric includes the effect of relative
timing drift. timing drift.
4. SDP Signaling 4. SDP Signaling
[RFC3611] defines the use of SDP (Session Description Protocol) [RFC3611] defines the use of the Session Description Protocol (SDP)
[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.
This section augments the SDP [RFC4566] attribute "rtcp-xr" defined This section augments the SDP [RFC4566] attribute "rtcp-xr" defined
in [RFC3611] by providing an additional value of "xr-format" to in [RFC3611] by providing an additional value of "xr-format" to
signal the use of the report block defined in this document. signal the use of the report block defined in this document.
xr-format =/ xr-pdv-block xr-format =/ xr-pdv-block
xr-pdv-block = "pkt-dly-var" [ "," pdvtype ] [ "," nspec "," pspec ] xr-pdv-block = "pkt-dly-var" [ "," pdvtype ] [ "," nspec "," pspec ]
skipping to change at page 11, line 31 skipping to change at page 10, line 21
/ 1*2DIGIT ) ;Value 2~15 are valid and / 1*2DIGIT ) ;Value 2~15 are valid and
;reserved for future use ;reserved for future use
nspec = ("nthr=" fixpoint) ; negative PDV threshold (ms) nspec = ("nthr=" fixpoint) ; negative PDV threshold (ms)
/ ("npc=" fixpoint ) ; negative PDV percentile / ("npc=" fixpoint ) ; negative PDV percentile
pspec = ("pthr=" fixpoint) ; positive PDV threshold (ms) pspec = ("pthr=" fixpoint) ; positive PDV threshold (ms)
/ ("ppc=" fixpoint) ; positive PDV percentile / ("ppc=" fixpoint) ; positive PDV percentile
fixpoint = 1*DIGIT "." 1*DIGIT ; fixed point decimal fixpoint = 1*DIGIT "." 1*DIGIT ; fixed point decimal
DIGIT = <as defined in Section 3.4 of [RFC5234]> DIGIT = <as defined in Section 3.4 of [RFC5234]>
When SDP is used in offer-answer, a system sending SDP may request a 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 type of PDV measurement. In addition, they may state a
specific percentile or threshold value, and expect to receive the specific percentile or threshold value and expect to receive the
corresponding threshold or percentile metric, respectively. The corresponding threshold or percentile metric, respectively. The
system receiving the SDP SHOULD send the PDV metrics requested, but system receiving the SDP SHOULD send the PDV metrics requested, but
if the metric is not available, the system receiving the SDP MUST if the metric is not available, the system receiving the SDP MUST
send the metric block with the flag value indicating that the metric send the metric block with the flag value indicating that the metric
is unavailable. is unavailable.
5. IANA Considerations 5. IANA Considerations
New block types for RTCP XR are subject to IANA registration. For New block types for RTCP XR are subject to IANA registration. For
general guidelines on IANA considerations for RTCP XR, refer to general guidelines on IANA considerations for RTCP XR, refer to
[RFC3611]. [RFC3611].
5.1. New RTCP XR Block Type value 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 This document assigns the block type value 15 in the IANA "RTCP XR
XR block type for this block.] Block Type" registry to the "Packet Delay Variation Metrics Block".
5.2. New RTCP XR SDP Parameter 5.2. New RTCP XR SDP Parameter
This document also registers a new parameter "pkt-dly-var" in the This document also registers a new parameter "pkt-dly-var" in the
"RTCP XR SDP Parameters Registry". "RTCP XR SDP Parameters" registry.
5.3. Contact information for registrations 5.3. Contact Information for Registrations
The contact information for the registrations is: The contact information for the registrations is:
Qin Wu (sunseawq@huawei.com) Qin Wu (sunseawq@huawei.com)
101 Software Avenue, Yuhua District 101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012 Nanjing, Jiangsu 210012
China China
5.4. New registry of PDV types 5.4. New Registry of PDV Types
This document creates a new registry to be called "RTCP XR PDV block 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 - PDV type" as a sub-registry of the "RTP Control Protocol Extended
Reports (RTCP XR) Block Type Registry". Policies for this new Reports (RTCP XR) Block Type Registry". Policies for this new
registry are as follows: registry are as follows:
o The information required to support an assignment is an o The information required to support an assignment is an
unambiguous definition of the new metric, covering the base unambiguous definition of the new metric, covering the base
measurements and how they are processed to generate the reported measurements and how they are processed to generate the reported
metric. This should include the units of measurement, how values metric. This should include the units of measurement, how values
of the metric are reported in the three 16-bit fields "Pos PDV of the metric are reported in the three 16-bit fields "Pos PDV
Threshold/Peak", "Neg PDV Threshold/Peak" and "Mean PDV" within Threshold/Peak", "Neg PDV Threshold/Peak", and "Mean PDV" within
the report block, and how the metric uses the two 16-bit fields the report block, and how the metric uses the two 16-bit fields
"Pos PDV Percentile" and "Neg PDV Percentile". "Pos PDV Percentile" and "Neg PDV Percentile".
o The review process for the registry is "Specification Required" as o The review process for the registry is "Specification Required" as
described in Section 4.1 of [RFC5226]. described in Section 4.1 of [RFC5226].
o Entries in the registry are unsigned 4-bit integers. The valid 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 range is 0 to 15 corresponding to the 4-bit field "pdvtyp" in the
block. Values are to be recorded in decimal. block. Values are to be recorded in decimal.
o Initial assignments are as follows: o Initial assignments are as follows:
* 0: MAPDV2, Clause 6.2.3.2 of [G.1020], * 0: MAPDV2, Clause 6.2.3.2 of [G.1020],
* 1: 2-point PDV, Clause 6.2.4 of [Y.1540], * 1: 2-point PDV, Clause 6.2.4 of [Y.1540],
* 2-15: Reserved for future use. * 2-15: Reserved for future use.
6. Security Considerations 6. Security Considerations
It is believed that this proposed RTCP XR report block introduces no It is believed that this proposed RTCP XR block introduces no new
new security considerations beyond those described in [RFC3611]. security considerations beyond those described in [RFC3611]. This
This block does not provide per-packet statistics so the risk to block does not provide per-packet statistics so the risk to
confidentiality documented in Section 7, paragraph 3 of [RFC3611] confidentiality documented in Section 7, paragraph 3, of [RFC3611]
does not apply. does not apply.
7. Contributors 7. Contributors
Geoff Hunt wrote the initial version of this document. Geoff Hunt wrote the initial version of this document.
8. Acknowledgments 8. Acknowledgments
The authors gratefully acknowledge reviews and feedback provided by The authors gratefully acknowledge reviews and feedback provided by
Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor,
Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi,
Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz,
Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi
Raviraj, Albrecht Schwarz, Tom Taylor, Hideaki Yamada, Jing Zhao, Raviraj, Albrecht Schwarz, Tom Taylor, Hideaki Yamada, Jing Zhao,
Kevin Gross, Colin Perkins, Charles Eckel, Glen Zorn, Shida Schubert, Kevin Gross, Colin Perkins, Charles Eckel, Glen Zorn, Shida Schubert,
Benoit Claise, Adrian Farrel and Pete Resnick. Benoit Claise, Adrian Farrel, and Pete Resnick.
9. References 9. References
9.1. Normative References 9.1. Normative References
[G.1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter [G.1020] ITU-T Rec. G. 1020, "Performance parameter definitions for
definitions for quality of speech and other voiceband quality of speech and other voiceband applications
applications utilizing IP networks", July 2006. 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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Applications", RFC 3550, July 2003. 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 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", November 2003. Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
[RFC4040] Kreuter, R., "RTP Payload Format for a 64 kbit/s [RFC4040] Kreuter, R., "RTP Payload Format for a 64 kbit/s
Transparent Call", April 2005. Transparent Call", RFC 4040, April 2005.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", July 2006. Description Protocol", RFC 4566, July 2006.
[RFC5226] Narten, T., "Guidelines for Writing an IANA Considerations
Section in RFCs", May 2008.
BCP 26 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information
availability performance parameters", November 2007. Reporting Using a Source Description (SDES) Item and an
RTCP Extended Report (XR) Block", RFC 6776, October 2012.
[Y.1540] ITU-T Rec. Y.1540, "IP packet transfer and availability
performance parameters", November 2007.
9.2. Informative References 9.2. Informative References
[MONARCH] Hunt, G., "Monitoring Architectures for RTP", [MONARCH] Wu, W., Hunt, G., and P. Arden, "Guidelines for Use of the
ID draft-ietf-avtcore-monarch-22, September 2012. RTP Monitoring Framework", Work in Progress,
September 2012.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009. Applicability Statement", RFC 5481, March 2009.
[RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Development", RFC 6390, October 2011. 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 Authors' Addresses
Alan Clark Alan Clark
Telchemy Incorporated Telchemy Incorporated
2905 Premiere Parkway, Suite 280 2905 Premiere Parkway, Suite 280
Duluth, GA 30097 Duluth, GA 30097
USA USA
Email: alan.d.clark@telchemy.com EMail: alan.d.clark@telchemy.com
Qin Wu Qin Wu
Huawei Huawei
101 Software Avenue, Yuhua District 101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012 Nanjing, Jiangsu 210012
China China
Email: sunseawq@huawei.com EMail: sunseawq@huawei.com
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