draft-ietf-avtcore-monarch-22.txt   rfc6792.txt 
Audio/Video Transport Working Group Q. Wu, Ed. Internet Engineering Task Force (IETF) Q. Wu, Ed.
Internet-Draft Huawei Request for Comments: 6792 Huawei
Intended status: Informational G. Hunt Category: Informational G. Hunt
Expires: March 29, 2013 Unaffiliated ISSN: 2070-1721 Unaffiliated
P. Arden P. Arden
BT BT
September 25, 2012 November 2012
Guidelines for Use of the RTP Monitoring Framework Guidelines for Use of the RTP Monitoring Framework
draft-ietf-avtcore-monarch-22.txt
Abstract Abstract
This memo proposes an extensible Real-Time Protocol (RTP) monitoring This memo proposes an extensible Real-time Transport Protocol (RTP)
framework for extending RTP Control Protocol (RTCP) with a new RTCP monitoring framework for extending the RTP Control Protocol (RTCP)
Extended Reports (XR) block type to report new metrics regarding with a new RTCP Extended Reports (XR) block type to report new
media transmission or reception quality. In this framework, a new XR metrics regarding media transmission or reception quality. In this
block should contain a single metric or a small number of metrics framework, a new XR block should contain a single metric or a small
relevant to a single parameter of interest or concern, rather than number of metrics relevant to a single parameter of interest or
containing a number of metrics which attempt to provide full coverage concern, rather than containing a number of metrics that attempt to
of all those parameters of concern to a specific application. provide full coverage of all those parameters of concern to a
Applications may then "mix and match" to create a set of blocks which specific application. Applications may then "mix and match" to
covers their set of concerns. Where possible, a specific block create a set of blocks that cover their set of concerns. Where
should be designed to be re-usable across more than one application, possible, a specific block should be designed to be reusable across
for example, for all of voice, streaming audio and video. more than one application, for example, for all of voice, streaming
audio, and video.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is not an Internet Standards Track specification; it is
Task Force (IETF). Note that other groups may also distribute published for informational purposes.
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
This Internet-Draft will expire on March 29, 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/rfc6792.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology .....................................................3
3. RTP Monitoring Framework . . . . . . . . . . . . . . . . . . . 7 3. RTP Monitoring Framework ........................................5
3.1. Overview of the RTP Monitoring Framework . . . . . . . . . 7 3.1. Overview of the RTP Monitoring Framework ...................5
3.2. Location of Monitors . . . . . . . . . . . . . . . . . . . 9 3.2. Location of Monitors .......................................7
4. Issues With Reporting Metric Block Using RTCP XR Extension . . 10 4. Issues with Reporting Metrics Blocks Using RTCP XR Extensions ...8
4.1. Using compound metrics block . . . . . . . . . . . . . . . 10 4.1. Using a Compound Metrics Block .............................8
4.2. Correlating RTCP XR with the non-RTP data . . . . . . . . 10 4.2. Correlating RTCP XR with Non-RTP Data ......................8
4.3. Measurement Information duplication . . . . . . . . . . . 10 4.3. Measurement Information Duplication ........................9
4.4. Consumption of XR block code points . . . . . . . . . . . 11 4.4. Consumption of XR Block Code Points ........................9
5. Guidelines For Reporting Metric Block Using RTCP XR . . . . . 12 5. Guidelines for Reporting Metrics Blocks Using RTCP XR ...........9
5.1. Contain the single metrics in the Metric Block . . . . . . 12 5.1. Use a Single Metric in the Metrics Block ...................9
5.2. Include the payload type in the Metric Block . . . . . . . 12 5.2. Include the Payload Type in the Metrics Block .............10
5.3. Use RTCP SDES to correlate XR reports with non-RTP data . 13 5.3. Use RTCP SDES to Correlate XRs with Non-RTP Data ..........10
5.4. Reduce Measurement information repetition across 5.4. Reduce Measurement Information Repetition across
metric blocks . . . . . . . . . . . . . . . . . . . . . . 13 Metrics Blocks ............................................11
6. An Example of a Metric Block . . . . . . . . . . . . . . . . . 15 6. An Example of a Metrics Block ..................................11
7. Application To RFC 5117 Topologies . . . . . . . . . . . . . . 16 7. Application to RFC 5117 Topologies .............................12
7.1. Applicability to Translators . . . . . . . . . . . . . . . 16 7.1. Applicability to Translators ..............................13
7.2. Applicability to MCU . . . . . . . . . . . . . . . . . . . 17 7.2. Applicability to MCUs .....................................13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 8. Security Considerations ........................................14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9. Acknowledgements ...............................................14
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 20 10. Informative References ........................................15
11. Informative References . . . . . . . . . . . . . . . . . . . . 21
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 23
A.1. draft-ietf-avtcore-monarch-22 . . . . . . . . . . . . . . 23
A.2. draft-ietf-avtcore-monarch-20 . . . . . . . . . . . . . . 23
A.3. draft-ietf-avtcore-monarch-19 . . . . . . . . . . . . . . 23
A.4. draft-ietf-avtcore-monarch-18 . . . . . . . . . . . . . . 23
A.5. draft-ietf-avtcore-monarch-17 . . . . . . . . . . . . . . 23
A.6. draft-ietf-avtcore-monarch-16 . . . . . . . . . . . . . . 24
A.7. draft-ietf-avtcore-monarch-15 . . . . . . . . . . . . . . 24
A.8. draft-ietf-avtcore-monarch-14 . . . . . . . . . . . . . . 24
A.9. draft-ietf-avtcore-monarch-13 . . . . . . . . . . . . . . 24
A.10. draft-ietf-avtcore-monarch-12 . . . . . . . . . . . . . . 25
A.11. draft-ietf-avtcore-monarch-11 . . . . . . . . . . . . . . 25
A.12. draft-ietf-avtcore-monarch-10 . . . . . . . . . . . . . . 25
A.13. draft-ietf-avtcore-monarch-09 . . . . . . . . . . . . . . 25
A.14. draft-ietf-avtcore-monarch-08 . . . . . . . . . . . . . . 26
A.15. draft-ietf-avtcore-monarch-07 . . . . . . . . . . . . . . 26
A.16. draft-ietf-avtcore-monarch-06 . . . . . . . . . . . . . . 26
A.17. draft-ietf-avtcore-monarch-05 . . . . . . . . . . . . . . 26
A.18. draft-ietf-avtcore-monarch-04 . . . . . . . . . . . . . . 26
A.19. draft-ietf-avtcore-monarch-03 . . . . . . . . . . . . . . 27
A.20. draft-ietf-avtcore-monarch-02 . . . . . . . . . . . . . . 27
A.21. draft-ietf-avtcore-monarch-01 . . . . . . . . . . . . . . 27
A.22. draft-ietf-avtcore-monarch-00 . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
Multimedia services using the Real-Time Protocol (RTP) are seeing Multimedia services using the Real-time Transport Protocol (RTP) are
increased use. Standard methods for gathering RTP performance seeing increased use. Standard methods for gathering RTP performance
metrics from these applications are needed to manage uncertainties in metrics from these applications are needed to manage uncertainties in
the behavior and availability of their services. Standards , such as the behavior and availability of their services. Standards such as
RTP Control Protocol Extended Reports (RTCP XR)[RFC3611] and other "RTP Control Protocol Extended Reports (RTCP XR)" [RFC3611] as well
RTCP extension to Sender Reports (SR), Receiver Reports (RR) as other RTCP extensions to sender reports (SRs) and receiver reports
[RFC3550] are being developed for the purpose of collecting and (RRs) [RFC3550] are being developed for the purpose of collecting and
reporting performance metrics from endpoint devices that can be used reporting performance metrics from endpoint devices that can be used
to correlate the metrics, provide end to end service visibility and to correlate the metrics, provide end-to-end service visibility, and
measure and monitor Quality of Experience (QoE) [RFC6390]. measure and monitor Quality of Experience (QoE) [RFC6390].
However the proliferation of RTP/RTCP specific metrics for transport However, the proliferation of RTP-/RTCP-specific metrics for
and application quality monitoring has been identified as a potential transport and application quality monitoring has been identified as a
problem for interoperability when using RTP/RTCP to communicate all potential problem for interoperability when using RTP/RTCP to
the parameters of concern to a specific application. Given that communicate all the parameters of concern to a specific application.
different applications layered on RTP may have some monitoring Given that different applications layered on RTP may have some
requirements in common, these metrics should be satisfied by a common monitoring requirements in common, these metrics should be satisfied
design. by a common design.
The objective of this document is to describe an extensible RTP The objective of this document is to describe an extensible RTP
monitoring framework to provide a small number of re-usable Quality monitoring framework to provide a small number of reusable Quality of
of Service (QoS) / QoE metrics which facilitate reduced Service (QoS) / QoE metrics that facilitate reduced implementation
implementation costs and help maximize inter-operability. The costs and help maximize interoperability. "Guidelines for Extending
"Guidelines for Extending the RTP Control Protocol (RTCP)" [RFC5968] the RTP Control Protocol (RTCP)" [RFC5968] has stated that where RTCP
has stated that, where RTCP is to be extended with a new metric, the is to be extended with a new metric, the preferred mechanism is by
preferred mechanism is by the addition of a new RTCP XR [RFC3611] the addition of a new RTCP XR [RFC3611] block. This memo assumes
block. This memo assumes that all the guidelines from RFC 5968 must that all the guidelines from RFC 5968 must apply on top of the
apply on top of the guidelines in this document. Guidelines for guidelines in this document. Guidelines for developing new
developing new performance metrics are specified in [RFC6390]. New performance metrics are specified in [RFC6390]. New RTCP XR report
RTCP XR report block definitions should not define new performance block definitions should not define new performance metrics but
metrics, but should rather refer to metrics defined elsewhere. should rather refer to metrics defined elsewhere.
2. Terminology 2. Terminology
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 that characterize the three transport impairments
impairments of packet loss, packet delay, jitter (also known as of packet loss, packet delay, and jitter (also known as delay
delay variation). These metrics should be usable by any variation). These metrics should be usable by any application
application which uses RTP transport. that uses RTP transport.
Application level metrics Application-level metrics
Metrics relating to application specific parameters or QoE related Metrics relating to application-specific parameters or QoE-related
parameters. Application specific parameters are measured at the parameters. Application-specific parameters are measured at the
application level and focus on quality of content rather than application level and focus on quality of content rather than
network performance. QoE related parameters reflect the end-to- network performance. QoE-related parameters reflect the end-to-
end performance at the services level and are usually measured at end performance at the services level and are usually measured at
the user endpoint. One example of such metrics is the QoE Metric the user endpoint. One example of such metrics is the QoE metric
specified in QoE metric reporting Block [QOE_BLOCK]. as specified in the QoE Metrics Report Block; see [QOE_BLOCK].
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.
Direct metrics Direct metrics
Metrics that can be directly measured or calculated and are not Metrics that can be directly measured or calculated and are not
dependent on other metrics. dependent on other metrics.
Interval metrics Interval metrics
Metrics measured over the course of a single reporting interval Metrics measured over the course of a single reporting interval
between two successive report blocks. This may be the most recent between two successive report blocks. This may be the most recent
RTCP reporting interval ([RFC3550], section 6.2) or some other RTCP reporting interval ([RFC3550], Section 6.2) or some other
interval signalled using an RTCP Measurement Information XR Block interval signaled using an RTCP Measurement Information XR Block
[MEASI]. An example interval metric is the count of the number of [RFC6776]. An example interval metric is the count of the number
RTP packets lost over the course of the last RTCP reporting of RTP packets lost over the course of the last RTCP reporting
interval. interval.
Cumulative metrics Cumulative metrics
Metrics measured over several reporting intervals for accumulating Metrics measured over several reporting intervals for accumulating
statistics. The time period over which measurements are statistics. The time period over which measurements are
accumulated can be the complete RTP session, or some other accumulated can be the complete RTP session, or some other
interval signalled using an RTCP Measurement Information XR Block interval signaled using an RTCP Measurement Information XR Block
[MEASI]. An example cumulative metric is the total number of RTP [RFC6776]. An example cumulative metric is the total number of
packets lost since the start of the RTP session. RTP packets lost since the start of the RTP session.
Sampled metrics Sampled metrics
Metrics measured at a particular time instant and sampled from the Metrics measured at a particular time instant and sampled from the
values of a continuously measured or calculated metric within a values of a continuously measured or calculated metric within a
reporting interval (generally the value of some measurement as reporting interval (generally, the value of some measurement as
taken at the end of the reporting interval). An example is the taken at the end of the reporting interval). An example is the
inter-arrival jitter reported in RTCP SR and RR packets, which is inter-arrival jitter reported in RTCP SR and RR packets, which is
continually updated as each RTP data packet arrives, but only continually updated as each RTP data packet arrives but is only
reported based on a snapshot of the value which is sampled at the reported based on a snapshot of the value that is sampled at the
instant the reporting interval ends. instant the reporting interval ends.
3. RTP Monitoring Framework 3. RTP Monitoring Framework
There are many ways in which the performance of an RTP session can be There are many ways in which the performance of an RTP session can be
monitored. These include RTP-based mechanisms such as the RTP MIB monitored. These include RTP-based mechanisms such as the RTP MIB
module [RFC2959], or the Session Initiation Protocol (SIP) event module [RFC2959]; or the Session Initiation Protocol (SIP) event
package for RTCP summary reports [RFC6035], or non-RTP mechanisms package for RTCP summary reports [RFC6035]; or non-RTP mechanisms
such as generic MIBs, NetFlow [RFC3954], IPFIX [RFC5101][RFC5102], such as generic MIBs, NetFlow [RFC3954], IP Flow Information Export
and so on. Together, these provide useful mechanisms for exporting (IPFIX) [RFC5101] [RFC5102], and so on. Together, these provide
data on the performance of an RTP session to non-RTP network useful mechanisms for exporting data on the performance of an RTP
management systems. It is desirable to also perform in-session session to non-RTP network management systems. It is desirable to
monitoring of RTP performance. RTCP provides the means to do this. also perform in-session monitoring of RTP performance. RTCP provides
In the following, we review the RTP Monitoring Framework, and give the means to do this. In the following, we review the RTP Monitoring
guidance for using and extending RTCP for monitoring RTP sessions. Framework, and give guidance for using and extending RTCP for
One major benefit of such framework is ease of integration with other monitoring RTP sessions. One major benefit of such a framework is
RTP/RTCP mechanisms. ease of integration with other RTP/RTCP mechanisms.
3.1. Overview of the RTP Monitoring Framework 3.1. Overview of the RTP Monitoring Framework
The RTP monitoring Framework comprises the following two key The RTP monitoring Framework comprises the following two key
functional components described below: functional components described below:
o Monitor o Monitor
o RTP Metric Block o RTP Metrics Block
Monitor is the functional component defined in the Real-time "Monitor" is the functional component defined in the RTP
Transport Protocol [RFC3550]. It acts as a repository of information specification [RFC3550]. It acts as a repository of information
gathered for monitoring purposes. gathered for monitoring purposes.
According to the definition of monitor in the RTP Protocol [RFC3550], According to the definition of "monitor" in [RFC3550], the end system
the end system that runs an application program that sends or that runs an application program that sends or receives RTP data
receives RTP data packets, an intermediate-system that forwards RTP packets, an intermediate system that forwards RTP packets to end
packets to End-devices or a third party that observes the RTP and devices, or a third party that observes the RTP and RTCP traffic but
RTCP traffic but does not make itself visible to the RTP Session does not make itself visible to the RTP Session participants can play
participants can play the role of the monitor within the RTP the role of the monitor within the RTP monitoring framework. As
monitoring Framework. As shown in Figure 1, the third party monitor shown in Figure 1, the third-party monitor can be a passive monitor
can be a passive monitor that sees the RTP/RTCP stream pass it, or a that sees the RTP/RTCP stream pass it, or a system that gets sent
system that gets sent RTCP reports but not RTP and uses that to RTCP reports but not RTP and uses that to collect information. The
collect information. The third party monitor should be placed on the third-party monitor should be placed on the RTP/RTCP path between the
RTP/RTCP path between the sender, intermediate and the receiver. sender, the intermediate system, and the receiver.
The RTP Metric Block (MB) conveys real time Application QoS/QoE The RTP Metrics Block (MB) conveys real-time application QoS/QoE
metric information and is used by the monitor to exchange with other metric information and is used by the monitor to exchange information
monitors in the appropriate report block format. The information with other monitors in the appropriate report block format. The
contained in the RTP MBs is collected by monitors and can be information contained in the RTP MBs is collected by monitors and can
formulated as various types of metrics, e.g., direct metrics/composed be formulated as various types of metrics, e.g., direct metrics/
performance metrics [RFC6390]or interval metrics/ cumulative metrics/ composed performance metrics [RFC6390] or interval metrics/cumulative
sampled metrics, etc. Both the RTCP or RTCP XR can be extended to metrics/sampled metrics, etc. Both the RTCP and RTCP XR can be
transport these metrics, e.g., the basic RTCP Reception Report (RR) extended to transport these metrics, e.g., the basic RTCP reception
[RFC3550] that conveys reception statistics (i.e., transport level report [RFC3550] that conveys reception statistics (i.e., transport-
statistics) for multiple RTP media streams, the RTCP XRs [RFC3611] level statistics) for multiple RTP media streams, the RTCP XRs
that supplement the existing RTCP packets and provide more detailed [RFC3611] that supplement the existing RTCP packets and provide more
feedback on reception quality, and RTCP NACK [RFC4585] that provides detailed feedback on reception quality, and an RTCP NACK [RFC4585]
feedback on the RTP sequence numbers for a subset of the lost packets that provides feedback on the RTP sequence numbers for a subset of
or all the currently lost packets. Ultimately the metric information the lost packets or all the currently lost packets. Ultimately, the
collected by monitors within the RTP monitoring framework may go to metric information collected by monitors within the RTP monitoring
the network management tools beyond the RTP monitoring framework, framework may go to the network management tools beyond the RTP
e.g., as shown Figure 1, the monitors may export the metric monitoring framework; e.g., as shown in Figure 1, the monitors may
information derived from the RTP monitoring framework to the export the metric information derived from the RTP monitoring
management system using non-RTP means. framework to the management system using non-RTP means.
+-----------+ +----------+ +-----------+ +----------+
|Third Party| |Management| |Third-Party| |Management|
| Monitor | >>>>>>>>| System |<<<<< | Monitor | >>>>>>>>| System |<<<<<
+-----------+ ^ +----------+ ^ +-----------+ ^ +----------+ ^
: ^ ^ ^ : ^ ^ ^
: | ^ ^ : | ^ ^
+---------------+ : | +-------------+ +-------------+ +---------------+ : | +-------------+ +-------------+
| +-----------+ | : | |+-----------+| |+-----------+| | +-----------+ | : | |+-----------+| |+-----------+|
| | Monitor | |..:...|.......|| Monitor ||........|| Monitor || | | Monitor | |..:...|.......|| Monitor ||........|| Monitor ||
| +-----------+ | | |+-----------+| |+-----------+| | +-----------+ | | |+-----------+| |+-----------+|
| |------+------>| |------->| | | |------+------>| |------->| |
| RTP Sender | |RTP Mixer or | |RTP Receiver | | RTP Sender | |RTP Mixer or | |RTP Receiver |
| | |Translator | | | | | |Translator | | |
+---------------+ +-------------+ +-------------+ +---------------+ +-------------+ +-------------+
----> RTP media traffic ----> RTP media traffic
..... RTCP control channel ..... RTCP control channel
>>>>> Non-RTP/RTCP management flows >>>>> Non-RTP/RTCP management flows
Figure 1: Example showing the components of the RTP monitoring Figure 1: Example Showing the Components
framework of the RTP Monitoring Framework
RTP may be used with multicast groups, both Any Source Multicast RTP may be used with multicast groups: both Any-Source Multicast
(ASM) and Source Specific Multicast (SSM). These groups can be (ASM) and Source-Specific Multicast (SSM). These groups can be
monitored using RTCP. In the ASM case, the monitor is a member of monitored using RTCP. In the ASM case, the monitor is a member of
the multicast group and listens to RTCP reports from all members of the multicast group and listens to RTCP reports from all members of
the ASM group. In the SSM case, there is a unicast feedback target the ASM group. In the SSM case, there is a unicast feedback target
that receives RTCP feedback from receivers and distributes it to that receives RTCP feedback from receivers and distributes it to
other members of the SSM group (see Figure 1 of [RFC5760] ). The other members of the SSM group (see Figure 1 of [RFC5760]). The
monitor will need to be co-located with the feedback target to monitor will need to be co-located with the feedback target to
receive all feedback from the receivers (this may also be an receive all feedback from the receivers (this may also be an
intermediate-system). In both ASM and SSM scenarios, receivers can intermediate system). In both ASM and SSM scenarios, receivers can
send RTCP reports to enhance the reception quality reporting. send RTCP reports to enhance reception-quality reporting.
3.2. Location of Monitors 3.2. Location of Monitors
As shown in Figure 1, there are several possible locations from where As shown in Figure 1, there are several possible locations from which
RTP sessions can be monitored. These include end systems that RTP sessions can be monitored. These include end systems that
terminate RTP sessions, intermediate-systems that are an active part terminate RTP sessions, intermediate systems that are an active part
of an RTP session, and third-party devices that passively monitor an of an RTP session, and third-party devices that passively monitor an
RTP session. Not every RTP sessions will include monitoring, and RTP session. Not every RTP session will include monitoring, and
those sessions that are monitored will not all include each type of those sessions that are monitored will not all include each type of
monitor. The performance metrics collected by monitors can be monitor. The performance metrics collected by monitors can be
divided into end system metrics, application level metrics, and divided into end-system metrics, application-level metrics, and
transport level metrics. Some of these metrics may be specific to transport-level metrics. Some of these metrics may be specific to
the measurement point of the monitor, or depend on where the monitors the measurement point of the monitor or may depend on where the
are located in the network, while others are more general and can be monitors are located in the network, while others are more general
collected in any monitoring location. and can be collected in any monitoring location.
End system monitoring is monitoring that is deployed on devices that End-system monitoring is monitoring that is deployed on devices that
terminate RTP flows. Flows can be terminated in user equipment, such terminate RTP flows. Flows can be terminated in user equipment, such
as phones, video conferencing systems, or IPTV set-top boxes. as phones, videoconferencing systems, or IPTV set-top boxes.
Alternatively, they can be terminated in devices that gateway between Alternatively, they can be terminated in devices that gateway between
RTP and other transport protocols. Transport and end system metrics, RTP and other transport protocols. Transport-level metrics, end-
application level metrics that don't reflect end to end user system metrics, and application-level metrics that don't reflect the
experience may be collected at all types of end system, but some end-to-end user experience may be collected at all types of end
application level metrics (i.e.,quality of experience (QoE) metrics) systems, but some application-level metrics (i.e., quality of
may only be applicable for user-facing end systems. experience (QoE) metrics) may only be applicable for user-facing end
systems.
RTP sessions can include intermediate-systems that are an active part RTP sessions can include intermediate systems that are an active part
of the system. These intermediate-systems include RTP mixers and of the system. These intermediate systems include RTP mixers and
translators, Multipoint Control Units (MCUs), retransmission servers, translators, Multipoint Control Units (MCUs), retransmission servers,
etc. If the intermediate-system establishes separate RTP sessions to etc. If the intermediate system establishes separate RTP sessions to
the other participants, then it must act as an end system in each of the other participants, then it must act as an end system in each of
those separate RTP sessions for the purposes of monitoring. If a those separate RTP sessions for the purposes of monitoring. If a
single RTP session traverses the intermediate-system, then the single RTP session traverses the intermediate system, then the
intermediate-system can be assigned an Synchronization source (SSRC) intermediate system can be assigned a synchronization source (SSRC)
in that session which it can use for its reports. Transport level in that session, which it can use for its reports. Transport-level
metrics may be collected at such intermediate-system. metrics may be collected at such an intermediate system.
Third-party monitors may be deployed that passively monitor RTP Third-party monitors may be deployed that passively monitor RTP
sessions for network management purposes. Third-party monitors often sessions for network management purposes. Third-party monitors often
do not send reports into the RTP session being monitored, but instead do not send reports into the RTP session being monitored but instead
collect transport level metrics, end system metrics and application collect transport-level metrics, end-system metrics, and application-
level metrics. In some cases, however, third-party monitors can send level metrics. In some cases, however, third-party monitors can send
reports to some or all participants in the session being monitored. reports to some or all participants in the session being monitored.
For example, in a media streaming scenario, third-party monitors may For example, in a media streaming scenario, third-party monitors may
be deployed that passively monitor the session and send reception be deployed that passively monitor the session and send reception-
quality reports to the media source, but not to the receivers. quality reports to the media source but not to the receivers.
4. Issues With Reporting Metric Block Using RTCP XR Extension 4. Issues with Reporting Metrics Blocks Using RTCP XR Extensions
The following sections discuss four issues that have come up in the The following sections discuss four issues that have come up in the
past with reporting metric block using RTCP XR extensions. past with reporting metrics blocks using RTCP XR extensions.
4.1. Using compound metrics block 4.1. Using a Compound Metrics Block
A compound metrics block is designed to contain a large number of A compound metrics block is designed to contain a large number of
parameters from different classes for a specific application in a parameters from different classes for a specific application in a
single block. For example, the RTCP Extended Reports (XRs) [RFC3611] single block. For example, "RTP Control Protocol Extended Reports
defines seven report block formats for network management and quality (RTCP XR)" [RFC3611] defines seven report block formats for network
monitoring. Some of these block types defined in the RTCP XRs management and quality monitoring. Some of these block types defined
[RFC3611] are only specifically designed for conveying multicast in the RTCP XRs [RFC3611] are only specifically designed for
inference of network characteristics (MINC) or voice over IP (VoIP) conveying multicast inference of network characteristics (MINC) or
monitoring. However different applications layered on RTP may have voice over IP (VoIP) monitoring. However, different applications
different monitoring requirements. Designing compound metrics block layered on RTP may have different monitoring requirements. Designing
only for specific applications may increase implementation cost and a compound metrics block only for specific applications may increase
minimize interoperability. implementation costs and minimize interoperability.
4.2. Correlating RTCP XR with the non-RTP data 4.2. Correlating RTCP XR with Non-RTP Data
Canonical End-Point Identifier SDES Item (CNAME), defined in the RTP The Canonical End-Point Identifier SDES Item (CNAME), as defined in
Protocol [RFC3550], is an example of an existing tool that allows RTP [RFC3550], is an example of an existing tool that allows binding
binding an SSRC that may change to a name that is fixed within one an SSRC that may change to a name that is fixed within one RTP
RTP session. CNAME may be also fixed across multiple RTP sessions session. The CNAME may also be fixed across multiple RTP sessions
from the same source. However there may be situations where RTCP from the same source. However, there may be situations where RTCP
reports are sent to other participating endpoints using non-RTP reports are sent to other participating endpoints using a non-RTP
protocol in a session. For example, as described in the SIP RTCP protocol in a session. For example, as described in [RFC6035] in
Summary Report Protocol [RFC6035], the data contained in RTCP XR VoIP relation to summary reports, the data contained in RTCP XR VoIP
metrics reports [RFC3611] are forwarded to a central collection metrics reports [RFC3611] is forwarded to a central collection server
server systems using SIP. In such case, there is a large portfolio system using SIP. In such a case, there is a large portfolio of
of quality parameters that can be associated with real time quality parameters that can be associated with real-time
application, e.g., VOIP application, but only a minimal number of applications, e.g., VOIP applications, but only a minimal number of
parameters are included on the RTCP-XR reports. With these minimal parameters are included in the RTCP XRs. With this minimal number of
number of RTCP statistics parameters mapped to non-RTCP measurements, RTCP statistical parameters mapped to non-RTCP measurements, it is
it is hard to provide accurate measures of real time application hard to provide accurate measurements of real-time application
quality, conduct detailed data analysis and creates alerts timely to quality, conduct detailed data analysis, and create timely alerts for
the users. Therefore correlation between RTCP XR and non-RTP data users. Therefore, a correlation between RTCP XRs and non-RTP data
should be provided. should be provided.
4.3. Measurement Information duplication 4.3. Measurement Information Duplication
We may set a measurement interval for the session and monitor RTP We may set a measurement interval for the session and monitor RTP
packets within one or several consecutive report intervals. In such packets within one or several consecutive report intervals. In such
case, the extra measurement information (e.g., extended sequence a case, extra measurement information (e.g., extended sequence number
number of 1st packet, measurement period) may be expected. However of the first packet, measurement period) may be expected. However,
if we put such extra measurement information into each metric block, if we put such extra measurement information into each metrics block,
there may be situations where an RTCP XR packet containing multiple there may be situations where an RTCP XR packet that contains
metric blocks, reports on the same streams from the same source. In multiple metrics blocks will report on the same streams from the same
other words, duplicated data for the measurement is provided multiple source. In other words, duplicated data for the measurement is
times, once in every metric block. Though this design ensures provided multiple times, once in every metrics block. Though this
immunity to packet loss, it may bring more packetization complexity design ensures immunity to packet loss, it may result in more
and the processing overhead is not completely trivial in some cases. packetization complexity, and this processing overhead is not
Therefore compromise between processing overhead and reliability completely trivial in some cases. Therefore, a compromise between
should be taken into account. processing overhead and reliability should be taken into account.
4.4. Consumption of XR block code points 4.4. Consumption of XR Block Code Points
The RTCP XR block namespace is limited by the 8-bit block type field The RTCP XR block namespace is limited by the 8-bit block type field
in the RTCP XR header. Space exhaustion may be a concern in the in the RTCP XR header. Space exhaustion may be a concern in the
future. Anticipating the potential need to extend the block type future. In anticipation of the potential need to extend the block
space, it is noted that Block Type 255 is reserved for future type space, it is noted that Block Type 255 is reserved for future
extensions in [RFC3611]. extensions in [RFC3611].
5. Guidelines For Reporting Metric Block Using RTCP XR 5. Guidelines for Reporting Metrics Blocks Using RTCP XR
5.1. Contain the single metrics in the Metric Block 5.1. Use a Single Metric in the Metrics Block
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 Source
are sufficient. For other applications additional metrics may be Description (SDES) packets) are sufficient. For other applications,
required or at least sufficiently useful to justify the overhead, additional metrics may be required or at least may be sufficiently
both of processing in endpoints and of increased session bandwidth. useful to justify the overhead, in terms of both processing in
For example an IPTV application using Forward Error Correction (FEC) endpoints and of increased session bandwidth. For example, an IPTV
might use either a metric of post-repair loss or a metric giving application using Forward Error Correction (FEC) might use either a
detailed information about pre-repair loss bursts to optimise payload metric of post-repair loss or a metric giving detailed information
bandwidth and the strength of FEC required for changing network about pre-repair loss bursts to optimize payload bandwidth and the
conditions. However there are many metrics available. It is likely strength of FEC required for changing network conditions. However,
that different applications or classes of applications will wish to there are many metrics available. It is likely that different
use different metrics. Any one application is likely to require applications or classes of applications will wish to use different
metrics for more than one parameter but if this is the case, metrics. Any one application is likely to require metrics for more
different applications will almost certainly require different than one parameter, but if this is the case, different applications
combinations of metrics. If larger blocks are defined containing will almost certainly require different combinations of metrics. If
multiple metrics to address the needs of each application, it becomes larger blocks are defined containing multiple metrics to address the
likely that many different such larger blocks are defined, which needs of each application, it becomes likely that many such different
becomes a danger to interoperability. larger blocks are defined, which poses a danger to interoperability.
To avoid this pitfall, this memo recommends the definition of metrics To avoid this pitfall, this memo recommends the definition of metrics
blocks containing a very small number of individual metrics blocks containing a very small number of individual metrics
characterizing only one parameter of interest to an application characterizing only one parameter of interest to an application
running over RTP. For example, at the RTP transport layer, the running over RTP. For example, at the RTP transport layer, the
parameter of interest might be packet delay variation, and parameter of interest might be packet delay variation, and
specifically the metric "IP Packet Delay Variation (IPDV)" defined by specifically the metric "IP Packet Delay Variation (IPDV)" defined by
[Y1540]. See Section 6 for architectural considerations for a [Y1540]. See Section 6 for architectural considerations for a
metrics block, using as an example a metrics block to report packet metrics block, using as an example a metrics block to report packet
delay variation. Further, it is appropriate to not only define delay variation. Further, it is appropriate to not only define
report blocks separately, but also to do so in separate documents report blocks separately but also to do so in separate documents
where possible. This makes it easier to evolve the reports (i.e., to where possible. This makes it easier to evolve the reports (i.e., to
update each type of report block separately), and also makes it update each type of report block separately) and also makes it easier
easier to require compliance with a particular report block. to require compliance with a particular report block.
5.2. Include the payload type in the Metric Block 5.2. Include the Payload Type in the Metrics Block
There are some classes of metrics that can only be interpreted with There are some classes of metrics that can only be interpreted with
knowledge of the media codec that is being used (audio mean opinion knowledge of the media codec that is being used (audio mean opinion
scores (MOS) were the triggering example, but there may be others). scores (MOSs) were the triggering example, but there may be others).
In such cases the correlation of RTCP XR with RTP data is needed. In such cases, the correlation of an RTCP XR with RTP data is needed.
Report blocks that require such correlation need to include the Report blocks that require such correlation need to include the
payload type of the reported media. In addition, it is necessary to payload type of the reported media. In addition, it is necessary to
signal the details and parameters of the payload format to which that signal the details and parameters of the payload format to which that
payload type is bound using some out-of-band means (e.g., as part of payload type is bound using some out-of-band means (e.g., as part of
an SDP offer/answer exchange). a Session Description Protocol (SDP) offer/answer exchange).
5.3. Use RTCP SDES to correlate XR reports with non-RTP data 5.3. Use RTCP SDES to Correlate XRs with Non-RTP Data
There may be situations where more than one media transport protocol There may be situations where more than one media transport protocol
is used by one application to interconnect to the same session in the is used by one application to interconnect to the same session in the
gateway. For example, one RTCP XR Packet is sent to the gateway. For example, one RTCP XR packet is sent to the
participating endpoints using non-RTP-based media transport (e.g., participating endpoints using non-RTP-based media transport (e.g.,
using SIP) in a VoIP session. One crucial factor lies in how to using SIP) in a VoIP session. One crucial factor lies in how to
handle their different identities that are corresponding to different handle the different identities that correspond to these different
media transport. media transport protocols.
This memo recommends an approach to facilitate the correlation of the This memo recommends an approach to facilitate the correlation of the
RTCP Session with other session-related non-RTP data. That is to say RTCP session with other session-related non-RTP data. That is to
if there is a need to correlate RTP sessions with non-RTP sessions, say, if there is a need to correlate RTP sessions with non-RTP
then the correlation information needed should be conveyed in a new sessions, then the correlation information needed should be conveyed
RTCP Source Description (SDES) item, since such correlation in a new RTCP SDES item, since such correlation information describes
information describes the source, rather than providing a quality the source rather than providing a quality report. An example use
report. An example use case is for a participant endpoint may convey case is where a participant endpoint may convey a call identifier or
a call identifier or a global call identifier associated with the a global call identifier associated with the SSRC of a measured RTP
SSRC of measured RTP stream. In such case, the participant endpoint stream. In such a case, the participant endpoint uses the SSRC to
uses the SSRC to bind the call identifier using SDES item in the SDES bind the call identifier using the SDES item in the SDES RTCP packet
RTCP packet and send such correlation to the network management and sends this correlation to the network management system. A flow
system. A flow measurement tool that is configured with the 5-tuple measurement tool that is configured with the 5-tuple and is not call-
and not call-aware then forwards the RTCP XR reports along with the aware then forwards the RTCP XRs along with the SSRC of the measured
SSRC of the measured RTP stream which is included in the XR Block RTP stream, which is included in the XR Block header and 5-tuple to
header and 5-tuple to the network management system. Network the network management system. The network management system can
management system can then correlate this report using SSRC with then correlate this report using SSRC with other diagnostic
other diagnostic information such as call detail records. information, such as call detail records.
5.4. Reduce Measurement information repetition across metric blocks 5.4. Reduce Measurement Information Repetition across Metrics Blocks
When multiple metric blocks are carried in one RTCP XR packet, When multiple metrics blocks are carried in one RTCP XR packet,
reporting on the same stream from the same source for the same time reporting on the same stream from the same source for the same time
period, RTCP should use the SSRC to identify and correlate the period, RTCP should use the SSRC to identify and correlate the
multiple metric blocks between metric blocks. "Measurement Identity multiple metrics blocks placed between Measurement Information
and information Reporting using SDES item and XR Block" [MEASI] Blocks; see "Measurement Identity and Information Reporting Using a
enables an RTCP sender to convey the common time period and the Source Description (SDES) Item and an RTCP Extended Report (XR)
number of packets sent during this period. If the measurement Block" [RFC6776]. [RFC6776] enables an RTCP sender to convey the
interval for a metric is different from the RTCP reporting interval, common time period and the number of packets sent during this period.
then this measurement duration in the Measurement information block If the measurement interval for a metric is different from the RTCP
should be used to specify the interval. When there may be multiple reporting interval, then this measurement duration in the Measurement
measurements information blocks with the same SSRC in one RTCP XR Information Block should be used to specify the interval. When there
compound packet, the measurement information block should be put in may be multiple Measurement Information Blocks with the same SSRC in
order and followed by all the metric blocks associated with this one RTCP XR compound packet, the Measurement Information Block should
measurement information block. New RTCP XR metric blocks that rely be put in order and followed by all the metrics blocks associated
on the Measurement information block [MEASI] must specify the with this Measurement Information Block. New RTCP XR metrics blocks
response in case the new RTCP XR metric block is received without an that rely on the Measurement Information Block must specify the
associated measurement information block. In most cases, it is response in case the new RTCP XR metrics block is received without an
associated Measurement Information Block. In most cases, it is
expected that the correct response is to discard the received metric. expected that the correct response is to discard the received metric.
In order to reduce measurement information repetition in one RTCP XR In order to reduce measurement information repetition in one RTCP XR
compound packet containing multiple metric blocks, the measurement compound packet containing multiple metrics blocks, the measurement
information shall be sent before the related metric blocks that are information shall be sent before the related metrics blocks that are
from the same reporting interval. Note that for packet loss from the same reporting interval. Note that for packet loss
robustness if the report blocks for the same interval span over more robustness, if the report blocks for the same interval span more than
than one RTCP packet, then each must have the measurement identity one RTCP packet, then each block must have the measurement identity
information even though they will be the same. information sent together with itself in the same RTCP compound
packet, even though the information will be the same.
6. An Example of a Metric Block 6. An Example of a Metrics 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 Section 5. to illustrate the application of the principles set out in Section 5.
The example [PDV] is a block to convey information about packet delay The example [RFC6798] is a block to convey information about packet
variation (PDV) only, consistent with the principle that a metrics delay variation (PDV) only, consistent with the principle that a
block should address only one parameter of interest. One simple metrics block should address only one parameter of interest. One
metric of PDV is available in the RTCP RR packet as the "interarrival simple metric of PDV is available in the RTCP RR packet as the
jitter" field. There are other PDV metrics with a certain similarity "inter-arrival jitter" field. There are other PDV metrics with a
in metric structure which may be more useful to certain applications. certain similarity in metric structure that may be more useful to
Two such metrics are the IPDV metric ([Y1540], [RFC3393]) and the certain applications. Two such metrics are the IPDV metric ([Y1540]
mean absolute packet delay variation 2 (MAPDV2) metric [G1020]. Use [RFC3393]) and the mean absolute packet delay variation 2 (MAPDV2)
of these metrics is consistent with the principle in Section 5 of metric [G1020]. The use of these metrics is consistent with the
RTCP guideline [RFC5968] that metrics should usually be defined principle in Section 5 of the RTCP guidelines document [RFC5968] that
elsewhere, so that RTCP standards define only the transport of the metrics should usually be defined elsewhere, so that RTCP standards
metric rather than its nature. The purpose of this section is to define only the transport of the metric rather than its nature. The
illustrate the architectural consideration using the example of [PDV] purpose of this section is to illustrate the architectural
rather than to document the design of the PDV metrics block or to considerations, using the example of [RFC6798], rather than to
provide a tutorial on PDV in general. document the design of the PDV metrics block or to provide a tutorial
on PDV in 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 that 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 an identifier to inform the receiving RTP
system of the specific metric being conveyed system of the specific metric being conveyed.
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 the use of additional RTCP XR blocks, which may consume
limited namespace for RTCP XR blocks at an unacceptable rate. The the limited namespace for RTCP XR blocks at an unacceptable rate.
second option is not extensible, so could be rejected on that basis, The second option is not extensible and so could be rejected on that
but in any case a single application is quite unlikely to require basis, but in any case a single application is quite unlikely to
transport of more than one metric for PDV. Hence the third option require the transport of more than one metric for PDV. Hence, the
was chosen. This implies the creation of a subsidiary namespace to third option was chosen. This implies the creation of a subsidiary
enumerate the PDV metrics which may be transported by this block, as namespace to enumerate the PDV metrics that may be transported by
discussed further in [PDV]. this block, as discussed further in [RFC6798].
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 as well as combinations
the two), and Topo-Mixer. These topologies use RTP end systems, RTP of the two), and Topo-Mixer. These topologies use RTP end systems,
mixers and RTP translators defined in the RTP protocol [RFC3550]. RTP mixers, and RTP translators as defined in [RFC3550]. For the
For purposes of reporting connection quality to other RTP systems, purposes of reporting connection quality to other RTP systems, RTP
RTP mixers and RTP end systems are very similar. Mixers mixers and RTP end systems are very similar. Mixers resynchronize
resynchronize packets and do not relay RTCP reports received from one packets and do not relay RTCP reports received from one cloud towards
cloud towards other cloud(s). Translators do not resynchronize other cloud(s). Translators do not resynchronize packets and should
packets and should forward certain RTCP reports between clouds. In forward certain RTCP reports between clouds. In this category, the
this category, the RTP system (end system, mixer or translator) which RTP system (end system, mixer, or translator) that originates,
originates, terminates or forwards RTCP XR blocks is expected to terminates, or forwards RTCP XR blocks is expected to handle RTCP,
handle RTCP, including RTCP XR, according to the RTP protocol including RTCP XR, according to RTP [RFC3550]. Provided this
[RFC3550]. Provided this expectation is met, an RTP system using expectation is met, an RTP system using RTCP XR is architecturally no
RTCP XR is architecturally no different from an RTP system of the different from an RTP system of the same class (end system, mixer, or
same class (end system, mixer, or translator) which does not use RTCP translator) that does not use RTCP XR. The second category relates
XR. The second category relates to deployed system models used in to deployed system models used in many H.323 [H323] videoconferences.
many H.323 [H323] video conferences. The topologies in this category The topologies in this category are Topo-Video-switch-MCU and
are Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU. Such Topo-RTCP-terminating-MCU. Such topologies based on systems (e.g.,
topologies based on systems (e.g.,MCUs) do not behave according to MCUs) do not behave according to RTP [RFC3550].
the RTP protocol [RFC3550].
Considering the translator and MCU are two typical intermediate- Considering that the translator and MCU are two typical intermediate
systems in these two categories mentioned above, this document will systems in these two categories mentioned above, this document will
take them as two typical examples to explain how RTCP XR report works take them as two typical examples to explain how RTCP XR works in
in different RFC5117 topologies. different [RFC5117] topologies.
7.1. Applicability to Translators 7.1. Applicability to Translators
Section 7.2 of the RTP protocol [RFC3550] describes processing of Section 7.2 of the RTP specification [RFC3550] describes the
RTCP by translators. RTCP XR is within the scope of the processing of RTCP by translators. RTCP XR is within the scope of
recommendations of the RTP protocol [RFC3550]. Some RTCP XR metrics the recommendations of [RFC3550]. Some RTCP XR metrics blocks may
blocks may usefully be measured at, and reported by, translators. As usefully be measured at, and reported by, translators. As described
described in the RTP protocol [RFC3550] this creates a requirement in [RFC3550], this creates a requirement for the translator to
for the translator to allocate an SSRC for the monitor collocated allocate an SSRC for the monitor co-located with itself so that the
with itself so that the monitor may populate the SSRC in the RTCP XR monitor may populate the SSRC in the RTCP XR packet header as the
packet header as packet sender SSRC and send it out(although the packet sender SSRC and send it out (although the translator is not a
translator is not a Synchronisation Source in the sense of synchronization source in the sense of originating RTP media
originating RTP media packets). It must also supply this SSRC and packets). It must also supply this SSRC and the corresponding CNAME
the corresponding CNAME in RTCP SDES packets. 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-neighbor 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 behavior based on local policy, which might differ between
between different interfaces of the same translator. different interfaces of the same translator.
7.2. Applicability to MCU 7.2. Applicability to MCUs
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 speaking,
system can only conclude that its RTP has been lost in the network, the RTP end system can only conclude that its RTP has been lost in
though an RTP end system complying with the robustness principle of the network, though an RTP end system complying with the robustness
[RFC1122] should survive with essential functions (i.e.,media principle of [RFC1122] should survive with essential functions (i.e.,
distribution) unimpaired. media distribution) unimpaired.
8. IANA Considerations
There is no IANA action in this document.
9. Security Considerations 8. Security Considerations
This document focuses on the RTCP reporting extension using RTCP XR This document focuses on the RTCP reporting extension using RTCP XR
and should not give rise to any new security vulnerabilities beyond and should not give rise to any new security vulnerabilities beyond
those described in RTCP XRs [RFC3611]. However it also describes the those described in RTCP XRs [RFC3611]. However, it also describes
architectural framework to be used for monitoring at RTP layer. The the architectural framework to be used for monitoring at the RTP
security issues with monitoring needs to be considered. layer. The security issues with monitoring need to be considered.
In RTP sessions, a RTP system may use its own SSRC to send its
monitoring reports towards its next-neighbour RTP system. Other RTP
system in the session may have a choice as to whether they forward
this RTP system's RTCP packets. This present a security issue since
the information in the report may be exposed by the other RTP system
to any malicious node. Therefore if the information is considered as
sensitive, the monitoring reports SHOULD be secured to the same
extent as the RTP flows that they measure. If encryption is used and
the encrypted monitoring report is received by the RTP system that
deploy the third party monitor,the RTP system may decrypt the monitor
report for the third party monitor based on local policy(e.g.,third-
party monitors is allowed to access to the metric) and forward it to
the third party monitor, otherwise, the third party monitor SHOULD
discard the received encrypted monitoring report.
10. Acknowledgement
The authors would also like to thank Colin Perkins, Charles Eckel,
Robert Sparks, Salvatore Loreto, Graeme Gibbs, Debbie Greenstreet,
Keith Drage, Dan Romascanu, Ali C. Begen, Roni Even, Magnus
Westerlund,Meral Shirazipour,Tina Tsou,Barry Leiba,Benoit Claise,Russ
Housley,Stephen Farrell for their valuable comments and suggestions
on the early version of this document.
11. Informative References
[G1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter
definitions for quality of speech and other voiceband
applications utilizing IP networks", July 2006.
[H323] ITU-T, "ITU-T Rec. H.323, Packet-based multimedia
communications systems", June 2006.
[MEASI] Wu, Q., "Measurement Identity and information Reporting
using SDES item and XR Block",
ID draft-ietf-xrblock-rtcp-xr-meas-identity-10,
August 2012.
[PDV] Hunt, G., Clark, A., and Q. Wu, "RTCP XR Report Block for
Packet Delay Variation Metric Reporting",
ID draft-ietf-xrblock-rtcp-xr-pdv-05, August 2012.
[QOE_BLOCK]
Hunt, G., Clark, A., Wu, Q., Schott, R., and G. Zorn,
"RTCP XR Blocks for QoE Metric Reporting",
ID draft-ietf-xrblock-rtcp-xr-qoe-02, July 2012.
[RFC1122] Braden, R., "Requirements for Internet Hosts --
Communication Layers", RFC 1122, October 1989.
[RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time
Transport Protocol Management Information Base", RFC 2959,
October 2000.
[RFC3393] Demichelis, C., "IP Packet Delay Variation Metric for IP
Performance Metrics (IPPM)", RFC 3393, November 2002.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
Applications", RFC 3550, July 2003.
[RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP
XR)", RFC 3611, November 2003.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version
9", RFC 3954, October 2004.
[RFC4585] Ott, J. and S. Wenger, "Extended RTP Profile for Real-time
Transport Control Protocol (RTCP)-Based Feedback (RTP/
AVPF)", RFC 4585, July 2006.
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
[RFC5102] Quittek, J., , S., Claise, B., Aitken, P., and J. Meyer,
"Information Model for IP Flow Information Export",
RFC 5102, January 2008.
[RFC5117] Westerlund, M., "RTP Topologies", RFC 5117, January 2008.
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760, February 2010.
[RFC5968] Ott, J. and C. Perkins, "Guidelines for Extending the RTP
Control Protocol (RTCP)", RFC 5968, September 2010.
[RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich,
"Session Initiation Protocol Event Package for Voice
Quality Reporting", RFC 6035, November 2010.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", RFC 6390, October 2011.
[Y1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and
availability performance parameters", November 2007.
Appendix A. Change Log
Note to the RFC-Editor: please remove this section prior to
publication as an RFC.
A.1. draft-ietf-avtcore-monarch-22
The following are the major changes compared to 20,21:
o Editorial changes based on Benoit and WG Review.
A.2. draft-ietf-avtcore-monarch-20
The following are the major changes compared to 19:
o Editorial changes based on IESG Review.
o Some new text in the security section to clarify encryption issue
for third party monitoring.
o Some new text in introduction section to clarify the relationship
with RFC5968 and RFC6390.
A.3. draft-ietf-avtcore-monarch-19
The following are the major changes compared to 18:
o Editorial changes based on Meral Shirazipour's second Gen-Art
review.
o Transport level metrics definition simplifying based on Robert's
comment.
A.4. draft-ietf-avtcore-monarch-18
The following are the major changes compared to 17:
o Some Editorial changes based on Gen-Art review and Secdir Review.
A.5. draft-ietf-avtcore-monarch-17
The following are the major changes compared to 16:
o Some Editorial changes.
A.6. draft-ietf-avtcore-monarch-16
The following are the major changes compared to 15:
o A few modification to the figure 1.
o Change RTCP XR reports into RTCP reports in the section 3.1.
o References Update.
A.7. draft-ietf-avtcore-monarch-15
The following are the major changes compared to 14:
o Add figure 1 in section 3 to describe RTP monitoring framework.
o Change the title as Guidelines for Use of the RTP Monitoring
Framework.
o Other editorial change to get in line with the title change in the
section 3.
A.8. draft-ietf-avtcore-monarch-14
The following are the major changes compared to 13:
o Incorporate the key points in the section 3.2 into overview
section.
o Remove the figure 1 and use the description instead.
o Add description in the section 3.3 to discuss the possible
location of the monitors and the types of metric at that location.
o Add the description to make the definition of Interval metrics/
cumulative metrics/sampled metrics clear.
o Editorial Changes.
A.9. draft-ietf-avtcore-monarch-13
The following are the major changes compared to 12:
o Editorial Changes.
A.10. draft-ietf-avtcore-monarch-12
The following are the major changes compared to 11:
o Editorial Changes based on Charles' Comments.
o Reference update.
o Add one new section 5.2 to discuss Correlating RTCP XR with RTP
data.
o Add text in section 5.1 to highlight it is more appropriate to
define each block in a separate draft.
A.11. draft-ietf-avtcore-monarch-11
The following are the major changes compared to 10:
o Editorial Changes.
A.12. draft-ietf-avtcore-monarch-10
The following are the major changes compared to 09:
o Discuss what exist already for monitoring in section 3.1.
o Provide benefit using RTCP XR based monitoring in section 3.1.
o add one new paragraph in section 3.1 to describe how monitoring
architecture is applied to ASM/SSM.
o Other Editorial Changes.
A.13. draft-ietf-avtcore-monarch-09
The following are the major changes compared to 07:
o Rephrase application level metric definition.
o Add one new section to clarify where to measure QoE related
parameters.
o Add text in section 5.3 to clarify the failure case when
measurement interval is not sent.
o Add text in section 5.3 to clarify how to deal with multiple
measurements information blocks carried in the same packet.
A.14. draft-ietf-avtcore-monarch-08
The following are the major changes compared to 07:
o Editorial change to the reference.
A.15. draft-ietf-avtcore-monarch-07
The following are the major changes compared to 06:
o Clarify the XR block code points consumption issue in the section
4 and new section 5.4.
o Other editorial changes.
A.16. draft-ietf-avtcore-monarch-06
The following are the major changes compared to 05:
o Some editorial changes.
A.17. 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.
A.18. draft-ietf-avtcore-monarch-04
The following are the major changes compared to 03:
o Update section 5.2 to clarify using SDES packet to carry
correlation information.
o Remove section 5.3 since additional identity information goes to
SDES packet and using SSRC to identify each block is standard RTP
feature.
o Swap the last two paragraphs in the section 4 since identity
information duplication can not been 100% avoided.
o Other editorial changes.
A.19. draft-ietf-avtcore-monarch-03
The following are the major changes compared to 02: In RTP sessions, an RTP system may use its own SSRC to send its
monitoring reports towards its next-neighbor RTP system. Other RTP
systems in the session may have a choice as to whether they forward
this RTP system's RTCP packets. This presents a security issue,
since the information in the report may be exposed by the other RTP
system to any malicious node. Therefore, if the information is
considered sensitive, the monitoring reports should be secured to the
same extent as the RTP flows that they measure. If encryption is
used and the encrypted monitoring report is received by the RTP
system that deploys the third-party monitor, the RTP system may
decrypt the monitor report for the third-party monitor based on local
policy (e.g., third-party monitors are allowed access to the metric)
and forward it to the third-party monitor; otherwise, the third-party
monitor should discard the received encrypted monitoring report.
o Update bullet 2 in section 4 to explain the ill-effect of Identity 9. Acknowledgements
Information duplication.
o Update bullet 3 in section 4 to explain why Correlating RTCP XR The authors would like to thank Colin Perkins, Charles Eckel, Robert
with the non-RTP data is needed. Sparks, Salvatore Loreto, Graeme Gibbs, Debbie Greenstreet, Keith
Drage, Dan Romascanu, Ali C. Begen, Roni Even, Magnus Westerlund,
Meral Shirazipour, Tina Tsou, Barry Leiba, Benoit Claise, Russ
Housley, and Stephen Farrell for their valuable comments and
suggestions on early versions of this document.
o Update section 5.2 to focus on how to reduce the identity 10. Informative References
information repetition
o Update section 5.3 to explain how to correlate identity [G1020] ITU-T, "Performance parameter definitions for quality of
information with the non-RTP data speech and other voiceband applications utilizing IP
networks", ITU-T Rec. G.1020, July 2006.
A.20. draft-ietf-avtcore-monarch-02 [H323] ITU-T, "Packet-based multimedia communications systems",
ITU-T Rec. H.323, December 2009.
The following are the major changes compared to 01: [QOE_BLOCK] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control
Protocol (RTCP) Extended Report (XR) Blocks for QoE
Metric Reporting", Work in Progress, October 2012.
o Deleting first paragraph of Section 1. [RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
o Deleting Section 3.1, since the interaction with the management [RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time
application is out of scope of this draft. Transport Protocol Management Information Base",
RFC 2959, October 2000.
o Separate identity information correlation from section 5.2 as new [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay
section 5.3. Variation Metric for IP Performance Metrics (IPPM)",
RFC 3393, November 2002.
o Remove figure 2 and related text from section 5.2. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
o Editorial changes in the section 4 and the first paragraph of [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
section 7. Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
A.21. draft-ietf-avtcore-monarch-01 [RFC3954] Claise, B., "Cisco Systems NetFlow Services Export
Version 9", RFC 3954, October 2004.
The following are the major changes compared to 00: [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J.
Rey, "Extended RTP Profile for Real-time Transport
Control Protocol (RTCP)-Based Feedback (RTP/AVPF)",
RFC 4585, July 2006.
o Restructure the document by merging section 4 into section 3. [RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
o Remove section 4.1,section 5 that is out of scope of this [RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
document. Meyer, "Information Model for IP Flow Information
Export", RFC 5102, January 2008.
o Remove the last bullet in section 6 and section 7.3 based on [RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies",
conclusion of last meeting. RFC 5117, January 2008.
o Update figure 1 and related text in section 3 according to the [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
monitor definition in RFC3550. Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760,
February 2010.
o Revise section 9 to address monitor declaration issue. [RFC5968] Ott, J. and C. Perkins, "Guidelines for Extending the
RTP Control Protocol (RTCP)", RFC 5968, September 2010.
o Merge the first two bullet in section 6. [RFC6035] Pendleton, A., Clark, A., Johnston, A., and H.
Sinnreich, "Session Initiation Protocol Event Package
for Voice Quality Reporting", RFC 6035, November 2010.
o Add one new bullet to discuss metric block association in section [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
6. Performance Metric Development", BCP 170, RFC 6390,
October 2011.
A.22. draft-ietf-avtcore-monarch-00 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and
Information Reporting Using a Source Description (SDES)
Item and an RTCP Extended Report (XR) Block", RFC 6776,
October 2012.
The following are the major changes compared to [RFC6798] Clark, A. and Q. Wu, "RTP Control Protocol (RTCP)
draft-hunt-avtcore-monarch-02: Extended Report (XR) Block for Packet Delay Variation
Metric Reporting", RFC 6798, November 2012.
o Move Geoff Hunt and Philip Arden to acknowledgement section. [Y1540] ITU-T, "IP packet transfer and availability performance
parameters", ITU-T Rec. Y.1540, March 2011.
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
Geoff Hunt Geoff Hunt
Unaffiliated Unaffiliated
Email: r.geoff.hunt@gmail.com EMail: r.geoff.hunt@gmail.com
Philip Arden Philip Arden
BT BT
Orion 3/7 PP4 Orion 3/7 PP4
Adastral Park Adastral Park
Martlesham Heath Martlesham Heath
Ipswich, Suffolk IP5 3RE Ipswich, Suffolk IP5 3RE
United Kingdom United Kingdom
Phone: +44 1473 644192 Phone: +44 1473 644192
Email: philip.arden@bt.com EMail: philip.arden@bt.com
 End of changes. 120 change blocks. 
724 lines changed or deleted 453 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/