draft-ietf-avtcore-monarch-04.txt   draft-ietf-avtcore-monarch-05.txt 
Audio/Video Transport Working Group Q. Wu, Ed. Audio/Video Transport Working Group Q. Wu, Ed.
Internet-Draft Huawei Internet-Draft Huawei
Intended status: Informational G. Hunt Intended status: Informational G. Hunt
Expires: March 3, 2012 Unaffiliated Expires: April 27, 2012 Unaffiliated
P. Arden P. Arden
BT BT
August 31, 2011 October 25, 2011
Monitoring Architectures for RTP Monitoring Architectures for RTP
draft-ietf-avtcore-monarch-04.txt draft-ietf-avtcore-monarch-05.txt
Abstract Abstract
This memo proposes an architecture for extending RTCP with a new RTCP This memo proposes an architecture for extending RTCP with a new RTCP
XR (RFC3611) block type to report new metrics regarding media XR (RFC3611) block type to report new metrics regarding media
transmission or reception quality, as proposed in RFC5968. This memo transmission or reception quality, following RTCP guideline
suggests that a new block should contain a single metric or a small established in RFC5968. This memo suggests that a new block should
number of metrics relevant to a single parameter of interest or contain a single metric or a small number of metrics relevant to a
concern, rather than containing a number of metrics which attempt to single parameter of interest or concern, rather than containing a
provide full coverage of all those parameters of concern to a number of metrics which attempt to provide full coverage of all those
specific application. Applications may then "mix and match" to parameters of concern to a specific application. Applications may
create a set of blocks which covers their set of concerns. Where then "mix and match" to create a set of blocks which covers their set
possible, a specific block should be designed to be re-usable across of concerns. Where possible, a specific block should be designed to
more than one application, for example, for all of voice, streaming be re-usable across more than one application, for example, for all
audio and video. of voice, streaming audio and video.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 3, 2012. This Internet-Draft will expire on April 27, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 22 skipping to change at page 2, line 22
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 4 2. Requirements notation . . . . . . . . . . . . . . . . . . . . 4
3. RTP monitoring architecture . . . . . . . . . . . . . . . . . 5 3. RTP monitoring architecture . . . . . . . . . . . . . . . . . 5
3.1. RTCP Metric Block Report and associated parameters . . . . 7 3.1. RTCP Metric Block Report and associated parameters . . . . 7
4. Issues with reporting metric block using RTCP XR extension . . 9 4. Issues with reporting metric block using RTCP XR extension . . 9
5. Guideline for reporting block format using RTCP XR . . . . . . 11 5. Guideline for reporting metric block using RTCP XR . . . . . . 11
5.1. Using small blocks . . . . . . . . . . . . . . . . . . . . 11 5.1. Using single metric blocks . . . . . . . . . . . . . . . . 11
5.2. Correlating identity information with the non-RTP data . . 11 5.2. Correlating RTCP XR with the non-RTP data . . . . . . . . 11
5.3. Reducing Measurement information repetition . . . . . . . 12
6. An example of a metric block . . . . . . . . . . . . . . . . . 13 6. An example of a metric block . . . . . . . . . . . . . . . . . 13
7. Application to RFC 5117 topologies . . . . . . . . . . . . . . 14 7. Application to RFC 5117 topologies . . . . . . . . . . . . . . 14
7.1. Applicability to MCU . . . . . . . . . . . . . . . . . . . 14 7.1. Applicability to MCU . . . . . . . . . . . . . . . . . . . 14
7.2. Applicability to Translators . . . . . . . . . . . . . . . 14 7.2. Applicability to Translators . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18
11. Informative References . . . . . . . . . . . . . . . . . . . . 19 11. Informative References . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 21 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 21
A.1. draft-ietf-avtcore-monarch-00 . . . . . . . . . . . . . . 21 A.1. draft-ietf-avtcore-monarch-00 . . . . . . . . . . . . . . 21
A.2. draft-ietf-avtcore-monarch-01 . . . . . . . . . . . . . . 21 A.2. draft-ietf-avtcore-monarch-01 . . . . . . . . . . . . . . 21
A.3. draft-ietf-avtcore-monarch-02 . . . . . . . . . . . . . . 21 A.3. draft-ietf-avtcore-monarch-02 . . . . . . . . . . . . . . 21
A.4. draft-ietf-avtcore-monarch-03 . . . . . . . . . . . . . . 22 A.4. draft-ietf-avtcore-monarch-03 . . . . . . . . . . . . . . 22
A.5. draft-ietf-avtcore-monarch-04 . . . . . . . . . . . . . . 22 A.5. draft-ietf-avtcore-monarch-04 . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 A.6. draft-ietf-avtcore-monarch-05 . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
As more users and subscribers rely on real time application services, As more users and subscribers rely on real time application services,
uncertainties in the performance and availability of these services uncertainties in the performance and availability of these services
are driving the need to support new standard methods for gathering are driving the need to support new standard methods for gathering
performance metrics from RTP applications. These rapidly emerging performance metrics from RTP applications. These rapidly emerging
standards, such as RTCP XR [RFC3611]and other RTCP extension to standards, such as RTCP XR [RFC3611] and other RTCP extension to
Sender Reports(SR), Receiver Reports (RR) [RFC3550]are being Sender Reports (SR), Receiver Reports (RR) [RFC3550] are being
developed for the purpose of collecting and reporting performance developed for the purpose of collecting and reporting performance
metrics from endpoint devices that can be used to correlate the metrics from endpoint devices that can be used to correlate the
metrics, provide end to end service visibility and measure and metrics, provide end to end service visibility and measure and
monitor QoE. monitor Quality of Experience (QoE).
However the proliferation of RTP/RTCP specific metrics for transport However the proliferation of RTP/RTCP specific metrics for transport
and application quality monitoring has been identified as a potential and application quality monitoring has been identified as a potential
problem for RTP/RTCP interoperability, which attempt to provide full problem for RTP/RTCP interoperability, which attempt to provide full
coverage of all those parameters of concern to a specific coverage of all those parameters of concern to a specific
application. Since different applications layered on RTP may have application. Since different applications layered on RTP may have
some monitoring requirements in common, therefore these metrics some monitoring requirements in common, therefore these metrics
should be satisfied by a common design. should be satisfied by a common design.
The objective of this document is to define an extensible RTP The objective of this document is to define an extensible RTP
monitoring framework to provide a small number of re-usable QoS/QoE monitoring framework to provide a small number of re-usable Quality
metrics which facilitate reduced implementation costs and help of Service (QoS)/QoE metrics which facilitate reduced implementation
maximize inter-operability. [RFC5968] has stated that, where RTCP is costs and help maximize inter-operability. RTCP Guideline [RFC5968]
to be extended with a new metric, the preferred mechanism is by the has stated that, where RTCP is to be extended with a new metric, the
addition of a new RTCP XR [RFC3611] block. This memo assumes that preferred mechanism is by the addition of a new RTCP XR [RFC3611]
any requirement for a new metric to be transported in RTCP will use a block. This memo assumes that any requirement for a new metric to be
new RTCP XR block. transported in RTCP will use a new RTCP XR block.
2. Requirements notation 2. Requirements notation
This memo is informative and as such contains no normative This memo is informative and as such contains no normative
requirements. requirements.
In addition, the following terms are defined: In addition, the following terms are defined:
Transport level metrics Transport level metrics
A set of metrics which characterise the three transport A set of metrics which characterise the three transport
impairments of packet loss, packet delay, and packet delay impairments of packet loss, packet delay, and packet delay
variation. These metrics should be usable by any application variation. These metrics should be usable by any application
which uses RTP transport. which uses RTP transport.
Application level metrics Application level metrics
Metrics relating to QoE related parameters. These metrics are Metrics relating to QoE related parameters. These metrics are
measured at the application level and focus on quality of content measured at the application level and focus on quality of content
rather than network parameters. One example of such metrics is rather than network parameters. One example of such metrics is
the Multimedia Quality Metric specified in [MQ]. the QoE Metric specified in QoE metric reporting Block [MQ].
End System metrics End System metrics
Metrics relating to the way a terminal deals with transport Metrics relating to the way a terminal deals with transport
impairments affecting the incident RTP stream. These may include impairments affecting the incident RTP stream. These may include
de-jitter buffering, packet loss concealment, and the use of de-jitter buffering, packet loss concealment, and the use of
redundant streams (if any) for correction of error or loss. redundant streams (if any) for correction of error or loss.
3. RTP monitoring architecture 3. RTP monitoring architecture
The RTP monitoring architecture comprises the following two key The RTP monitoring architecture comprises the following two key
functional components shown below: functional components shown below:
o Monitor o Monitor
o Metric Block Structure o Metric Block Structure
Monitor is a functional component defined in RFC3550 that acts as a Monitor is the functional component defined in the Real-time
source of information gathered for monitoring purposes. It may also Transport Protocol (RTP) [RFC3550] that acts as a source of
collect statistics from multiple source, stores such information information gathered for monitoring purposes. It may gather such
reported by RTCP XR or other RTCP extension appropriately as base information reported by RTCP XR or other RTCP extension and calculate
metric or calculates composite metric. According to the definition statistics from multiple source. According to the definition of
of monitor in RFC3550, the end system that source RTP streams, an monitor in the RTP Protocol [RFC3550], the end system that source RTP
intermediate-system that forwards RTP packets to End-devices or a streams, an intermediate-system that forwards RTP packets to End-
third party that does not participate RTP session (i.e., the third devices or a third party that does not participate in the RTP session
party monitor depicted in figure 1) can be envisioned to act as the (i.e., the third party monitor depicted in figure 1) can be
Monitor within the RTP monitoring architecture. envisioned to act as the Monitor within the RTP monitoring
architecture.
The Metric Block exposes real time Application Quality information in The Metric Block exposes real time Application Quality information in
the appropriate report block format to the Monitor within the RTP the appropriate report block format to the management system within
monitoring architecture. Both the RTCP or RTCP XR can be extended to the RTP monitoring architecture. Such information can be formulated
convey such information. The details on transport protocol for as:
metric block is described in Section 3.1.
|---------------+ o The basic metric that is directly measured.
| Management |
+-------------------+ | System | o or the composed metric that is derived from one or more basic
| RTP Sender | | +----------+ | metrics.
| +-----------+ | | | | |
---------------->| Monitor |---------5------->| Monitor | | Both the RTCP or RTCP XR can be extended to convey these metrics.
| | | | | | | | | The details on transport protocols for metric blocks are described in
| | +-----------+ | | +----\-----+ | Section 3.1.
| |+-----------------+| | | |
| ||Application || --------|-------+ +-------------------+
| ||-Streaming video || | | RTP Sender | +----------+
| |---------|-VOIP || 5 | +-----------+ | |Management|
| | ||-Video conference|| | ---------------->| Monitor |---------5------->| System |
| | ||-Telepresence || +---------------+ | | | | | | |
| | ||-Ad insertion || | Third Party | | | +-----------+ | +----------+
5 | |+-----------------+| | Monitor | | |+-----------------+|
| | +-------------------+ +---------------+ | ||Application || --------------|
| ||-Streaming video || | |
| |---------|-VOIP || | +--------V------+
| | ||-Video conference|| ------ Third Party |
| | ||-Telepresence || | Monitor |
| | ||-Ad insertion || +---------------+
5 | |+-----------------+|
| | +-------------------+
| 1 | 1
| | +Intermediate------------+ |-------------- ---- ----+ | | +Intermediate------------+ |-------------- ---- ----+
| | | RTP System Report Block | RTP Receiver >--4-| | | | | RTP System Report Block | RTP Receiver >--4-| |
| | | +---------- transported over| +-----------+ | | | | | +---------- transported over| +-----------+ | |
| | | | RTCP extension | | Monitor |<-- | | | | | RTCP extension | | Monitor |<-- |
|------------- Monitor |<--------5------|----| |<------| |------------- Monitor |<--------5------|----| |<------|
| | | | Report Block +----/------+ || | | | | Report Block +----/------+ ||
| | +----------+ transported over | || | | +----------+ transported over | ||
| | RTCP XR | |2 || | | RTCP XR | |2 ||
| | +-----------------+ | | +-------/---------+ || | | +-----------------+ | | +-------/---------+ ||
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2. Application level metrics collection. 2. Application level metrics collection.
3. Transport level metrics collection. 3. Transport level metrics collection.
4. End System metrics collection. 4. End System metrics collection.
5. Reporting Session- metrics transmitted over specified interfaces. 5. Reporting Session- metrics transmitted over specified interfaces.
3.1. RTCP Metric Block Report and associated parameters 3.1. RTCP Metric Block Report and associated parameters
The basic RTCP Reception Report (RR) conveys reception statistics in The basic RTCP Reception Report (RR) [RFC3550] conveys reception
metric block report format for multiple RTP media streams including statistics (i.e., transport level statistics) in metric block report
format for multiple RTP media streams including
o transport level statistics
o the fraction of packet lost since the last report o the fraction of packet lost since the last report
o the cumulative number of packets lost o the cumulative number of packets lost
o the highest sequence number received o the highest sequence number received
o an estimate of the inter-arrival jitter o an estimate of the inter-arrival jitter
o and information to allow senders to calculate the network round o and information to allow senders to calculate the network round
skipping to change at page 7, line 44 skipping to change at page 7, line 39
o Loss and duplicate RLE reports o Loss and duplicate RLE reports
o Packet-receipt times reports o Packet-receipt times reports
o Round-trip time reports o Round-trip time reports
o Statistics Summary Reports o Statistics Summary Reports
There are also various other scenarios in which it is desirable to There are also various other scenarios in which it is desirable to
send RTCP Metric reports more frequently. The Audio/Video Profile send RTCP Metric reports more frequently. For example, the Audio/
with Feedback [RFC4585]extends the standard A/V Profile[RFC3551] to Video Profile with Feedback [RFC4585] extends the standard A/V
allow RTCP reports to be sent early provided RTCP bandwidth Profile [RFC3551] to allow RTCP reports to be sent early provided
allocation is respected. There are four use cases but are not RTCP bandwidth allocation is respected. The following are four use
limited to: cases but are not limited to:
o RTCP NACK is used to provide feedback on the RTP sequence number o RTCP NACK is used to provide feedback on the RTP sequence number
of the lost packets. [RFC4585] of the lost packets [RFC4585].
o RTCP XR is extended to provide feedback on multicast acquisition
statistics information and parameters.[RFC6332]
o RTCP is extended to convey requests for full intra-coded frames or o RTCP is extended to convey requests for full intra-coded frames or
select the reference picture, and signalchanges in the desired select the reference picture, and signalchanges in the desired
temporal/spatial trade-off and maximum media bit rate. [RFC5104] temporal/spatial trade-off and maximum media bit rate [RFC5104].
o RTCP or RTCP XR is extended to provide feedback on ECN statistics o RTCP or RTCP XR is extended to provide feedback on ECN statistics
information. [ECN] information [ECN].
o RTCP XR is extended to provide feedback on multicast acquisition
statistics information and parameters [RFC6332].
4. Issues with reporting metric block using RTCP XR extension 4. Issues with reporting metric block using RTCP XR extension
Issues that have come up in the past with reporting metric block Issues that have come up in the past with reporting metric block
using RTCP XR extensions include (but are probably not limited to) using RTCP XR extensions include (but are probably not limited to)
the following: the following:
o Using large block. A single report block or metric is designed to o Using large block. A single report block or metric is designed to
contain a large number of parameters in different classes for a contain a large number of parameters in different classes for a
specific application. For example, RFC 3611 [RFC3611] defines specific application. For example, the RTCP Extended Reports
seven report block formats for network management and quality (XRs) [RFC3611] defines seven report block formats for network
monitoring. However some of these block types defined in management and quality monitoring. Some of these block types
[RFC3611] are only specifically designed for conveying multicast defined in the RTCP XRs [RFC3611] are only specifically designed
inference of network characteristics(MINC) or voice over IP (VoIP) for conveying multicast inference of network characteristics
monitoring. However different applications layered on RTP may (MINC) or voice over IP (VoIP) monitoring. However different
have some monitoring requirements in common, design large block applications layered on RTP may have different monitoring
only for specific applications may increase implementation cost requirements, design large block only for specific applications
and minimize interoperability. may increase implementation cost and minimize interoperability.
o Correlating RTCP XR with the non-RTP data. CNAME [RFC3550] is an o Correlating RTCP XR with the non-RTP data. CNAME defined in the
example of existing tool that allows to bind an SSRC that may RTP Protocol [RFC3550] is an example of existing tool that allows
change to a fixed source name in one RTP session. It is also to bind an SSRC that may change to a fixed source name in one RTP
fixed across multiple RTP sessions from the same source. However session. It may be also fixed across multiple RTP sessions from
there may be situations where RTCP reports are sent to other the same source. However there may be situations where RTCP
participating endpoints using non-RTP protocol in a session. For reports are sent to other participating endpoints using non-RTP
example, as described in [RFC6035], the data contained in RTCP XR protocol in a session. For example, as described in the SIP RTCP
Summary Report Protocol [RFC6035], the data contained in RTCP XR
VoIP metrics reports [RFC3611] are forwarded to a central VoIP metrics reports [RFC3611] are forwarded to a central
collection server systems using SIP. In such case, there is a collection server systems using SIP. In such case, there is a
large portfolio of quality parameters that can be associated with large portfolio of quality parameters that can be associated with
real time application,e.g., VOIP application, but only a minimal real time application,e.g., VOIP application, but only a minimal
number of parameters are included on the RTCP-XR reports. number of parameters are included on the RTCP-XR reports.
Therefore correlation between RTCP XR and non-RTP data should be Therefore correlation between RTCP XR and non-RTP data should be
concerned if administration or management systems need to rely on concerned if administration or management systems need to rely on
the mapping RTCP statistics to non-RTCP measurements to conducts the mapping RTCP statistics to non-RTCP measurements to conducts
data analysis and creates alerts to the users. Without such data analysis and creates alerts to the users. Without such
correlation, it is hardly to provide accurate measures of real correlation, it is hardly to provide accurate measures of real
time application quality with a minimal number of parameters time application quality with a minimal number of parameters
included on the RTCP-XR reports in such case. included on the RTCP-XR reports in such case.
o Identity Information duplication. Identity information is used to o Measurement Information duplication. Measurement information
identify an instance of a metric block. The SSRC of the measured provides information relevant to a measurement reported in one or
stream as part of the metric block is one example of Identity more other block types For example,we may set a metric interval
information. However in some cases, Identity information may be for the session and monitor RTP packets within one or several
not part of metric and include information more than the SSRC in consecutive metric interval. In such case, the extra meaurement
the metric block, e.g., when we set a metric interval for the information (e.g., extended sequence number of 1st packet,
session and monitor RTP packets within one or several consecutive measurement period) may be expected. However if we put such extra
metric interval, extra identity information (e.g., sequence number measurement information into each metric block, there may be
of 1st packet) is expected, if we put such extra identity situations where an RTCP XR packet containing multiple metric
information into each metric block, there may be situations where blocks, reports on the same streams from the same source. In
an RTCP XR packet containing more than two metric blocks including other words, duplicated data for the measurement is provided
the duplicated extra identity information, reports on the same multiple times, once in every metric block. Though this design
streams from the same source. each block have the same extra ensures immunity to packet loss, it may bring more packetization
identity information for measurement, if each metric block carry complexity and the processing overhead is not completely trivial
such duplicated data for the measurement, it leads to redundant in some cases. Therefore compromise between processing overhead
information in this design since equivalent information is and reliability should be taken into account.
provided multiple times, once in *every* metric block. Though
this ensures immunity to packet loss, the design may bring more
complexity and the overhead is not completely trivial in some
cases.
5. Guideline for reporting block format using RTCP XR 5. Guideline for reporting metric block using RTCP XR
5.1. Using small blocks 5.1. Using single metric blocks
Different applications using RTP for media transport certainly have Different applications using RTP for media transport certainly have
differing requirements for metrics transported in RTCP to support differing requirements for metrics transported in RTCP to support
their operation. For many applications, the basic metrics for their operation. For many applications, the basic metrics for
transport impairments provided in RTCP SR and RR packets [RFC3550] transport impairments provided in RTCP SR and RR packets [RFC3550]
(together with source identification provided in RTCP SDES packets) (together with source identification provided in RTCP SDES packets)
are sufficient. For other applications additional metrics may be are sufficient. For other applications additional metrics may be
required or at least sufficiently useful to justify the overheads, required or at least sufficiently useful to justify the overheads,
both of processing in endpoints and of increased session bandwidth. both of processing in endpoints and of increased session bandwidth.
For example an IPTV application using Forward Error Correction (FEC) For example an IPTV application using Forward Error Correction (FEC)
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To avoid this pitfall, this memo proposes the use of small RTCP XR To avoid this pitfall, this memo proposes the use of small RTCP XR
metrics blocks each containing a very small number of individual metrics blocks each containing a very small number of individual
metrics characterizing only one parameter of interest to an metrics characterizing only one parameter of interest to an
application running over RTP. For example, at the RTP transport application running over RTP. For example, at the RTP transport
layer, the parameter of interest might be packet delay variation, and layer, the parameter of interest might be packet delay variation, and
specifically the metric "IPDV" defined by [Y1540]. See Section 6 for specifically the metric "IPDV" defined by [Y1540]. See Section 6 for
architectural considerations for a metrics block, using as an example architectural considerations for a metrics block, using as an example
a metrics block to report packet delay variation. a metrics block to report packet delay variation.
5.2. Correlating identity information with the non-RTP data 5.2. Correlating RTCP XR with the non-RTP data
When more than one media transport protocols are used by one There may be situation where more than one media transport protocols
application to interconnected to the same session (in gateway),e.g., are used by one application to interconnect to the same session in
one RTCP XR Packet is sent to the participating endpoints using non- the gateway. For example, one RTCP XR Packet is sent to the
RTP-based media transport (e.g., using SIP) in a VOIP session, one participating endpoints using non- RTP-based media transport (e.g.,
crucial factor lies in how to handle their different identities that using SIP) in a VOIP session, one crucial factor lies in how to
are corresponding to different media transport. handle their different identities that are corresponding to different
media transport.
This memo proposes an approach to facilitate the correlation of the This memo proposes an approach to facilitate the correlation of the
RTCP Session with other session-related non-RTP data, i.e., if there RTCP Session with other session-related non-RTP data. That is to say
is a need to correlate RTP sessions with non-RTP sessions, then the if there is a need to correlate RTP sessions with non-RTP sessions,
correlation information needed should be conveyed in RTCP SDES then the correlation information needed should be conveyed in a new
packets since such correlation information describes the source, RTCP Source Description (SDES) item ,since such correlation
rather than providing a quality report. An example use case is for a information describes the source, rather than providing a quality
participant endpoint may convey a call identifier or a global call report. An example use case is for a participant endpoint may convey
identifier associated with the SSRC of measured RTP stream . In such a call identifier or a global call identifier associated with the
case, the participant endpoint uses SSRC of source to bind the call SSRC of measured RTP stream . In such case, the participant endpoint
identifier in each chunk of the SDES RTCP packet and send such uses the SSRC of source to bind the call identifier using SDES item
correlation using the chunk containing SDES item to the network in the SDES RTCP packet and send such correlation to the network
management system. A flow measurement tool that is not call-aware management system. A flow measurement tool that is configured with
then forward the RTCP XR reports along with SSRC of the measured RTP the 5-tuple and not call-aware then forward the RTCP XR reports along
stream which is included in the XR Block header to the network with the SSRC of the measured RTP stream which is included in the XR
management system. Network management system can then correlate this Block header and 5-tuple to the network management system. Network
report using SSRC with other diagnostic information such as call management system can then correlate this report using SSRC with
detail records. other diagnostic information such as call detail records.
5.3. Reducing Measurement information repetition
When multiple metric blocks are carried in one RTCP XR packet,
reporting on the same streams from the same source, RTCP should use
the SSRC to identify and correlate and group participants between
metric blocks. If extra measurement information (e.g., measurement
period) is expected and this information relates measurement data in
the different metric blocks to the same stream, and measurement
period, this memo propose to define new XR Block to convey it. In
order to reduce measurement information repetition in one RTCP XR
packet containing multiple metric blocks, the measurement information
should be sent together with the related metric block if measurement
information changes.
6. An example of a metric block 6. An example of a metric block
This section uses the example of an existing proposed metrics block This section uses the example of an existing proposed metrics block
to illustrate the application of the principles set out in to illustrate the application of the principles set out in
Section 5.1. Section 5.1.
The example [PDV] (work in progress) is a block to convey information The example [PDV] is a block to convey information about packet delay
about packet delay variation (PDV) only, consistent with the variation (PDV) only, consistent with the principle that a metrics
principle that a metrics block should address only one parameter of block should address only one parameter of interest. One simple
interest. One simple metric of PDV is available in the RTCP RR metric of PDV is available in the RTCP RR packet as the "interarrival
packet as the "jit" field. There are other PDV metrics which may be jitter" field. There are other PDV metrics which may be more useful
more useful to certain applications. Two such metrics are the IPDV to certain applications. Two such metrics are the IPDV metric
metric ([Y1540], [RFC3393]) and the MAPDV2 metric [G1020]. Use of ([Y1540], [RFC3393]) and the MAPDV2 metric [G1020]. Use of these
these metrics is consistent with the principle in Section 5 of metrics is consistent with the principle in Section 5 of RTCP
[RFC5968] that metrics should usually be defined elsewhere, so that guideline [RFC5968] that metrics should usually be defined elsewhere,
RTCP standards define only the transport of the metric rather than so that RTCP standards define only the transport of the metric rather
its nature. The purpose of this section is to illustrate the than its nature. The purpose of this section is to illustrate the
architecture using the example of [PDV] (work in progress) rather architecture using the example of [PDV] rather than to document the
than to document the design of the PDV metrics block or to provide a design of the PDV metrics block or to provide a tutorial on PDV in
tutorial on PDV in general. general.
Given the availability of at least three metrics for PDV, there are Given the availability of at least three metrics for PDV, there are
design options for the allocation of metrics to RTCP XR blocks: design options for the allocation of metrics to RTCP XR blocks:
o provide an RTCP XR block per metric o provide an RTCP XR block per metric
o provide a single RTCP XR block which contains all three metrics o provide a single RTCP XR block which contains all three metrics
o provide a single RTCP block to convey any one of the three o provide a single RTCP block to convey any one of the three
metrics, together with a identifier to inform the receiving RTP metrics, together with a identifier to inform the receiving RTP
skipping to change at page 13, line 47 skipping to change at page 13, line 47
In choosing between these options, extensibility is important, In choosing between these options, extensibility is important,
because additional metrics of PDV may well be standardized and because additional metrics of PDV may well be standardized and
require inclusion in this framework. The first option is extensible require inclusion in this framework. The first option is extensible
but only by use of additional RTCP XR blocks, which may consume the but only by use of additional RTCP XR blocks, which may consume the
limited namespace for RTCP XR blocks at an unacceptable rate. The limited namespace for RTCP XR blocks at an unacceptable rate. The
second option is not extensible, so could be rejected on that basis, second option is not extensible, so could be rejected on that basis,
but in any case a single application is quite unlikely to require but in any case a single application is quite unlikely to require
transport of more than one metric for PDV. Hence the third option transport of more than one metric for PDV. Hence the third option
was chosen. This implies the creation of a subsidiary namespace to was chosen. This implies the creation of a subsidiary namespace to
enumerate the PDV metrics which may be transported by this block, as enumerate the PDV metrics which may be transported by this block, as
discussed further in [PDV] (work in progress). discussed further in [PDV] .
7. Application to RFC 5117 topologies 7. Application to RFC 5117 topologies
The topologies specified in [RFC5117] fall into two categories. The The topologies specified in [RFC5117] fall into two categories. The
first category relates to the RTP system model utilizing multicast first category relates to the RTP system model utilizing multicast
and/or unicast. The topologies in this category are specifically and/or unicast. The topologies in this category are specifically
Topo-Point-to-Point, Topo- Multicast, Topo-Translator (both variants, Topo-Point-to-Point, Topo- Multicast, Topo-Translator (both variants,
Topo-Trn-Translator and Topo-Media-Translator, and combinations of Topo-Trn-Translator and Topo-Media-Translator, and combinations of
the two), and Topo-Mixer. These topologies use RTP end systems, RTP the two), and Topo-Mixer. These topologies use RTP end systems, RTP
mixers and RTP translators defined in [RFC3550]. For purposes of mixers and RTP translators defined in the RTP protocol [RFC3550].
reporting connection quality to other RTP systems, RTP mixers and RTP For purposes of reporting connection quality to other RTP systems,
end systems are very similar. Mixers resynchronize audio packets and RTP mixers and RTP end systems are very similar. Mixers
do not relay RTCP reports received from one cloud towards other resynchronize packets and do not relay RTCP reports received from one
cloud(s). Translators do not resynchronize packets and SHOULD cloud towards other cloud(s). Translators do not resynchronize
forward certain RTCP reports between clouds. In this category, the packets and SHOULD forward certain RTCP reports between clouds. In
RTP system (end system, mixer or translator) which originates, this category, the RTP system (end system, mixer or translator) which
terminates or forwards RTCP XR blocks is expected to handle RTCP, originates, terminates or forwards RTCP XR blocks is expected to
including RTCP XR, according to [RFC3550]. Provided this expectation handle RTCP, including RTCP XR, according to the RTP protocol
is met, an RTP system using RTCP XR is architecturally no different [RFC3550]. Provided this expectation is met, an RTP system using
from an RTP system of the same class (end system, mixer, or RTCP XR is architecturally no different from an RTP system of the
translator) which does not use RTCP XR. The second category relates same class (end system, mixer, or translator) which does not use RTCP
to deployed system models used in many H.323 [H323] video XR. The second category relates to deployed system models used in
conferences. The topologies in this category are Topo-Video-Switch- many H.323 [H323] video conferences. The topologies in this category
MCU and Topo-RTCP-terminating-MCU. Such topologies based on systems are Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU. Such
do not behave according to [RFC3550]. topologies based on systems do not behave according to the RTP
protocol [RFC3550].
Considering the translator and MCU are two typical topologies in the Considering the MCU and translator are two typical topologies in the
two categories mentioned above, this document will take them as two two categories mentioned above, this document will take them as two
typical examples to explain how RTCP XR report works in different typical examples to explain how RTCP XR report works in different
RFC5117 topologies. RFC5117 topologies.
7.1. Applicability to MCU 7.1. Applicability to MCU
Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU, suffer from the Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU, suffer from the
difficulties described in [RFC5117]. These difficulties apply to difficulties described in [RFC5117]. These difficulties apply to
systems sending, and expecting to receive, RTCP XR blocks as much as systems sending, and expecting to receive, RTCP XR blocks as much as
to systems using other RTCP packet types. For example, a participant to systems using other RTCP packet types. For example, a participant
RTP end system may send media to a video switch MCU. If the media RTP end system may send media to a video switch MCU. If the media
stream is not selected for forwarding by the switch, neither RTCP RR stream is not selected for forwarding by the switch, neither RTCP RR
packets nor RTCP XR blocks referring to the end system's generated packets nor RTCP XR blocks referring to the end system's generated
stream will be received at the RTP end system. Strictly the RTP end stream will be received at the RTP end system. Strictly the RTP end
system can only conclude that its RTP has been lost in the network, system can only conclude that its RTP has been lost in the network,
though an RTP end system complying with the robustness principle of though an RTP end system complying with the robustness principle of
[RFC1122] should survive with essential functions unimpaired. [RFC1122] should survive with essential functions (i.e.,media
distribution) unimpaired.
7.2. Applicability to Translators 7.2. Applicability to Translators
Section 7.2 of [RFC3550] describes processing of RTCP by translators. Section 7.2 of the RTP protocol [RFC3550] describes processing of
RTCP XR is within the scope of the recommendations of [RFC3550]. RTCP by translators. RTCP XR is within the scope of the
recommendations of the RTP protocol [RFC3550]. Some RTCP XR metrics
Some RTCP XR metrics blocks may usefully be measured at, and reported blocks may usefully be measured at, and reported by, translators. As
by, translators. As described in [RFC3550] this creates a described in the RTP protocol [RFC3550] this creates a requirement
requirement for the translator to allocate an SSRC for the monitor for the translator to allocate an SSRC for the monitor collocated
collocated with itself so that the monitor may populate the SSRC in with itself so that the monitor may populate the SSRC in the RTCP XR
the RTCP XR packet header as packet sender SSRC and send it packet header as packet sender SSRC and send it out(although the
out(although the translator is not a Synchronisation Source in the translator is not a Synchronisation Source in the sense of
sense of originating RTP media packets). It must also supply this originating RTP media packets). It must also supply this SSRC and
SSRC and the corresponding CNAME in RTCP SDES packets. the corresponding CNAME in RTCP SDES packets.
In RTP sessions where one or more translators generate any RTCP In RTP sessions where one or more translators generate any RTCP
traffic towards their next-neighbour RTP system, other translators in traffic towards their next-neighbour RTP system, other translators in
the session have a choice as to whether they forward a translator's the session have a choice as to whether they forward a translator's
RTCP packets. Forwarding may provide additional information to other RTCP packets. Forwarding may provide additional information to other
RTP systems in the connection but increases RTCP bandwidth and may in RTP systems in the connection but increases RTCP bandwidth and may in
some cases present a security risk. RTP translators may have some cases present a security risk. RTP translators may have
forwarding behaviour based on local policy, which might differ forwarding behaviour based on local policy, which might differ
between different interfaces of the same translator. between different interfaces of the same translator.
For bidirectional unicast, an RTP system may usually detect RTCP XR For bidirectional unicast, an RTP system may check the presence of a
from a translator by noting that the sending SSRC is not present in translator by receiving RTCP XR and noting that the sending SSRC in
any RTP media packet. However there is a possibility of a source the XR packet is not present in any RTP media packet. However the
sending RTCP XR before it has sent any RTP media (leading to RTP system can't determine that an SSRC in the XR packet is
transient mis-categorisation of an RTP end system or RTP mixer as a associated with a translator rather than a receiving only end-point
translator), and for multicast sessions - or unidirectional/streaming unless the necessary session information on RTP node type is
unicast - there is also a possibility of a receive-only end system expected. This Checking may fail if a source sends RTCP XR before it
being permanently mis-categorised as a translator sending XR report, has sent any RTP media (leading to transient mis-categorisation of an
i.e.,the monitor sending XR report within the translator. Hence it RTP end system or RTP mixer as a translator). Another case is, for
is desirable for a translator that sends XR report to have a way to multicast sessions - or unidirectional/streaming unicast, there is
declare itself explicitly. also a possibility of a receive-only end system being permanently
mis-categorised as a translator sending XR report, i.e.,the monitor
sending XR report within the translator. Hence it is desirable for a
translator that sends XR report to have a way to announce its SSRC
and asscociated RTP node type explicitly to the management system.
8. IANA Considerations 8. IANA Considerations
None. There is no IANA action in this document.
9. Security Considerations 9. Security Considerations
This document itself contains no normative text and hence should not This document focuses on the RTCP reporting extension using RTCP XR
give rise to any new security considerations, to be confirmed. and should not give rise to any new security vulnerabilities beyond
those described in RTCP XRs [RFC3611]. However it also describes the
architectural framework to be used for monitoring at RTP layer. The
security issues with monitoring needs to be considered.
In RTP sessions, a translator may use its own SSRC to send its
monitoring reports towards its next-neighbour RTP system. Other
translators in the session may have a choice as to whether they
forward the translator's RTCP packets. This present a security issue
since the information in the report may be exposed by the other
translator to any malicious node. Therefore if the information is
considered as sensitive, the monitoring report should be encrypted.
Also note that the third party monitors are not visible at the RTP
layer since they do not send any RTCP packets. In order to prevent
any sensitive information leakage, the monitoring from the third
party monitors should be prohibited unless the security is in place
to authenticate them.
10. Acknowledgement 10. Acknowledgement
The authors would also like to thank Colin Perkins, Graeme Gibbs, The authors would also like to thank Colin Perkins, Graeme Gibbs,
Debbie Greenstreet, Keith Drage, Dan Romascanu, Ali C. Begen, Roni Debbie Greenstreet, Keith Drage, Dan Romascanu, Ali C. Begen, Roni
Even for their valuable comments and suggestions on the early version Even, Magnus Westerlundfor their valuable comments and suggestions on
of this document. the early version of this document.
11. Informative References 11. Informative References
[ECN] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., [ECN] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN) and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", ID draft-ietf-avtcore-ecn-for-rtp-04, for RTP over UDP", ID draft-ietf-avtcore-ecn-for-rtp-04,
July 2011. July 2011.
[G1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter [G1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter
definitions for quality of speech and other voiceband definitions for quality of speech and other voiceband
skipping to change at page 19, line 25 skipping to change at page 19, line 25
[H323] ITU-T, "ITU-T Rec. H.323, Packet-based multimedia [H323] ITU-T, "ITU-T Rec. H.323, Packet-based multimedia
communications systems", June 2006. communications systems", June 2006.
[MQ] Wu, Q., Zorn, G., Schott, R., and K. Lee, "RTCP XR Blocks [MQ] Wu, Q., Zorn, G., Schott, R., and K. Lee, "RTCP XR Blocks
for multimedia quality metric reporting", for multimedia quality metric reporting",
ID draft-wu-xrblock-rtcp-xr-quality-monitoring-02, ID draft-wu-xrblock-rtcp-xr-quality-monitoring-02,
May 2011. May 2011.
[PDV] Hunt, G., "RTCP XR Report Block for Packet Delay Variation [PDV] Hunt, G., "RTCP XR Report Block for Packet Delay Variation
Metric Reporting", ID draft-ietf-avt-rtcp-xr-pdv-03, Metric Reporting", ID draft-ietf-xrblock-rtcp-xr-pdv-00,
May 2009. September 2011.
[RFC1122] Braden, R., "Requirements for Internet Hosts -- [RFC1122] Braden, R., "Requirements for Internet Hosts --
Communication Layers", RFC 1122, October 1989. Communication Layers", RFC 1122, October 1989.
[RFC3393] Demichelis, C., "IP Packet Delay Variation Metric for IP [RFC3393] Demichelis, C., "IP Packet Delay Variation Metric for IP
Performance Metrics (IPPM)", RFC 3393, November 2002. Performance Metrics (IPPM)", RFC 3393, November 2002.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
Applications", RFC 3550, July 2003. Applications", RFC 3550, July 2003.
skipping to change at page 21, line 48 skipping to change at page 21, line 48
A.3. draft-ietf-avtcore-monarch-02 A.3. draft-ietf-avtcore-monarch-02
The following are the major changes compared to 01: The following are the major changes compared to 01:
o Deleting first paragraph of Section 1. o Deleting first paragraph of Section 1.
o Deleting Section 3.1, since the interaction with the management o Deleting Section 3.1, since the interaction with the management
application is out of scope of this draft. application is out of scope of this draft.
o Separeate identity information correlation from section 5.2 as new o Separate identity information correlation from section 5.2 as new
section 5.3. section 5.3.
o Remove figure 2 and related text from section 5.2. o Remove figure 2 and related text from section 5.2.
o Editorial changes in the section 4 and the first paragraph of o Editorial changes in the section 4 and the first paragraph of
section 7. section 7.
A.4. draft-ietf-avtcore-monarch-03 A.4. draft-ietf-avtcore-monarch-03
The following are the major changes compared to 02: The following are the major changes compared to 02:
skipping to change at page 23, line 5 skipping to change at page 22, line 40
o Remove section 5.3 since additional identity information goes to o Remove section 5.3 since additional identity information goes to
SDES packet and using SSRC to identify each block is standard RTP SDES packet and using SSRC to identify each block is standard RTP
feature. feature.
o Swap the last two paragraphs in the section 4 since identity o Swap the last two paragraphs in the section 4 since identity
information duplication can not been 100% avoided. information duplication can not been 100% avoided.
o Other editorial changes. o Other editorial changes.
A.6. draft-ietf-avtcore-monarch-05
The following are the major changes compared to 04:
o Replace "chunk" with "new SDES item".
o Add texts in security section to discussion potential security
issues.
o Add new sub-section 5.3 to discuss Reducing Measurement
information repetition.
o Other editorial changes.
Authors' Addresses Authors' Addresses
Qin Wu (editor) Qin Wu (editor)
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
 End of changes. 41 change blocks. 
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