wdiff rfc6792.original rfc6792.txt

Audio/Video Transport Working Group
Internet Engineering Task Force (IETF) Q. Wu, Ed.
Internet-Draft
Request for Comments: 6792 Huawei
Intended status:
Category: Informational G. Hunt
Expires: March 29, 2013
ISSN: 2070-1721 Unaffiliated
P. Arden
BT
September 25,
November 2012

Guidelines for Use of the RTP Monitoring Framework
draft-ietf-avtcore-monarch-22.txt

Abstract

This memo proposes an extensible Real-Time Real-time Transport Protocol (RTP)
monitoring framework for extending the RTP Control Protocol (RTCP)
with a new RTCP Extended Reports (XR) block type to report new
metrics regarding media transmission or reception quality. In this
framework, a new XR block should contain a single metric or a small
number of metrics relevant to a single parameter of interest or
concern, rather than containing a number of metrics which that attempt to
provide full coverage of all those parameters of concern to a
specific application. Applications may then "mix and match" to
create a set of blocks which
covers that cover their set of concerns. Where
possible, a specific block should be designed to be re-usable reusable across
more than one application, for example, for all of voice, streaming audio
audio, and video.

Status of this This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
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Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a maximum candidate for any level of Internet
Standard; see Section 2 of RFC 5741.

Information about the current status of six months this document, any errata,
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This Internet-Draft will expire on March 29, 2013.
http://www.rfc-editor.org/info/rfc6792.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 ....................................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 .....................................................3
3. RTP Monitoring Framework . . . . . . . . . . . . . . . . . . . 7 ........................................5
3.1. Overview of the RTP Monitoring Framework . . . . . . . . . 7 ...................5
3.2. Location of Monitors . . . . . . . . . . . . . . . . . . . 9 .......................................7
4. Issues With with Reporting Metric Block Metrics Blocks Using RTCP XR Extension . . 10 Extensions ...8
4.1. Using compound metrics block . . . . . . . . . . . . . . . 10 a Compound Metrics Block .............................8
4.2. Correlating RTCP XR with the non-RTP data . . . . . . . . 10 Non-RTP Data ......................8
4.3. Measurement Information duplication . . . . . . . . . . . 10 Duplication ........................9
4.4. Consumption of XR block code points . . . . . . . . . . . 11 Block Code Points ........................9
5. Guidelines For for Reporting Metric Block Metrics Blocks Using RTCP XR . . . . . 12 ...........9
5.1. Contain the single metrics Use a Single Metric in the Metric Metrics Block . . . . . . 12 ...................9
5.2. Include the payload type Payload Type in the Metric Metrics Block . . . . . . . 12 .............10
5.3. Use RTCP SDES to correlate XR reports Correlate XRs with non-RTP data . 13 Non-RTP Data ..........10
5.4. Reduce Measurement information repetition Information Repetition across
metric blocks . . . . . . . . . . . . . . . . . . . . . . 13
Metrics Blocks ............................................11
6. An Example of a Metric Metrics Block . . . . . . . . . . . . . . . . . 15 ..................................11
7. Application To to RFC 5117 Topologies . . . . . . . . . . . . . . 16 .............................12
7.1. Applicability to Translators . . . . . . . . . . . . . . . 16 ..............................13
7.2. Applicability to MCU . . . . . . . . . . . . . . . . . . . 17 MCUs .....................................13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 ........................................14
9. Acknowledgements ...............................................14
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 20
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 ........................................15

1. Introduction

Multimedia services using the Real-Time Real-time Transport Protocol (RTP) are
seeing increased use. Standard methods for gathering RTP performance
metrics from these applications are needed to manage uncertainties in
the behavior and availability of their services. Standards , such as
RTP
"RTP Control Protocol Extended Reports (RTCP XR)[RFC3611] and XR)" [RFC3611] as well
as other RTCP extension extensions to Sender Reports (SR), Receiver Reports (RR) sender reports (SRs) and receiver reports
(RRs) [RFC3550] are being developed for the purpose of collecting and
reporting performance metrics from endpoint devices that can be used
to correlate the metrics, provide end to end end-to-end service visibility visibility, and
measure and monitor Quality of Experience (QoE) [RFC6390].

However

However, the proliferation of RTP/RTCP specific RTP-/RTCP-specific metrics for
transport and application quality monitoring has been identified as a
potential problem for interoperability when using RTP/RTCP to
communicate all the parameters of concern to a specific application.
Given that different applications layered on RTP may have some
monitoring requirements in common, these metrics should be satisfied
by a common design.

The objective of this document is to describe an extensible RTP
monitoring framework to provide a small number of re-usable reusable Quality of
Service (QoS) / QoE metrics which that facilitate reduced implementation
costs and help maximize inter-operability. The interoperability. "Guidelines for Extending
the RTP Control Protocol (RTCP)" [RFC5968] has stated that, that where RTCP
is to be extended with a new metric, the preferred mechanism is by
the addition of a new RTCP XR [RFC3611] block. This memo assumes
that all the guidelines from RFC 5968 must apply on top of the
guidelines in this document. Guidelines for developing new
performance metrics are specified in [RFC6390]. New RTCP XR report
block definitions should not define new performance
metrics, metrics but
should rather refer to metrics defined elsewhere.

2. Terminology

This memo is informative and as such contains no normative
requirements.

In addition, the following terms are defined:

Transport level

Transport-level metrics

A set of metrics which characterise that characterize the three transport impairments
of packet loss, packet delay, and jitter (also known as delay
variation). These metrics should be usable by any application which
that uses RTP transport.

Application level

Application-level metrics

Metrics relating to application specific application-specific parameters or QoE related QoE-related
parameters. Application specific Application-specific parameters are measured at the
application level and focus on quality of content rather than
network performance. QoE related QoE-related parameters reflect the end-to-
end performance at the services level and are usually measured at
the user endpoint. One example of such metrics is the QoE Metric metric
as specified in the QoE metric reporting Block Metrics Report Block; see [QOE_BLOCK].

End System

End-system metrics

Metrics relating to the way a terminal deals with transport
impairments affecting the incident RTP stream. These may include
de-jitter buffering, packet loss concealment, and the use of
redundant streams (if any) for correction of error or loss.

Direct metrics

Metrics that can be directly measured or calculated and are not
dependent on other metrics.

Interval metrics

Metrics measured over the course of a single reporting interval
between two successive report blocks. This may be the most recent
RTCP reporting interval ([RFC3550], section Section 6.2) or some other
interval signalled signaled using an RTCP Measurement Information XR Block
[MEASI].
[RFC6776]. An example interval metric is the count of the number
of RTP packets lost over the course of the last RTCP reporting
interval.

Cumulative metrics

Metrics measured over several reporting intervals for accumulating
statistics. The time period over which measurements are
accumulated can be the complete RTP session, or some other
interval signalled signaled using an RTCP Measurement Information XR Block
[MEASI].
[RFC6776]. An example cumulative metric is the total number of
RTP packets lost since the start of the RTP session.

Sampled metrics

Metrics measured at a particular time instant and sampled from the
values of a continuously measured or calculated metric within a
reporting interval (generally (generally, the value of some measurement as
taken at the end of the reporting interval). An example is the
inter-arrival jitter reported in RTCP SR and RR packets, which is
continually updated as each RTP data packet arrives, arrives but is only
reported based on a snapshot of the value which that is sampled at the
instant the reporting interval ends.

3. RTP Monitoring Framework

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
module [RFC2959], [RFC2959]; or the Session Initiation Protocol (SIP) event
package for RTCP summary reports [RFC6035], [RFC6035]; or non-RTP mechanisms
such as generic MIBs, NetFlow [RFC3954], IPFIX [RFC5101][RFC5102],
and so on. Together, these IP Flow Information Export
(IPFIX) [RFC5101] [RFC5102], and so on. Together, these provide
useful mechanisms for exporting data on the performance of an RTP
session to non-RTP network management systems. It is desirable to
also perform in-session monitoring of RTP performance. RTCP provides
the means to do this. In the following, we review the RTP Monitoring
Framework, and give guidance for using and extending RTCP for
monitoring RTP sessions. One major benefit of such a framework is
ease of integration with other RTP/RTCP mechanisms.

3.1. Overview of the RTP Monitoring Framework

The RTP monitoring Framework comprises the following two key
functional components described below:

o Monitor

o RTP Metric Metrics Block

Monitor

"Monitor" is the functional component defined in the Real-time
Transport Protocol RTP
specification [RFC3550]. It acts as a repository of information
gathered for monitoring purposes.

According to the definition of monitor "monitor" in the RTP Protocol [RFC3550], the end system
that runs an application program that sends or receives RTP data
packets, an intermediate-system intermediate system that forwards RTP packets to End-devices end
devices, or a third party that observes the RTP and RTCP traffic but
does not make itself visible to the RTP Session participants can play
the role of the monitor within the RTP monitoring Framework. framework. As
shown in Figure 1, the third party third-party monitor can be a passive monitor
that sees the RTP/RTCP stream pass it, or a system that gets sent
RTCP reports but not RTP and uses that to collect information. The third party
third-party monitor should be placed on the RTP/RTCP path between the
sender, the intermediate system, and the receiver.

The RTP Metric Metrics Block (MB) conveys real time Application real-time application QoS/QoE
metric information and is used by the monitor to exchange information
with other monitors in the appropriate report block format. The
information contained in the RTP MBs is collected by monitors and can
be formulated as various types of metrics, e.g., direct metrics/composed metrics/
composed performance metrics [RFC6390]or [RFC6390] or interval metrics/ cumulative metrics/
sampled metrics/cumulative
metrics/sampled metrics, etc. Both the RTCP or and RTCP XR can be
extended to transport these metrics, e.g., the basic RTCP Reception Report (RR) reception
report [RFC3550] that conveys reception statistics (i.e., transport transport-
level statistics) for multiple RTP media streams, the RTCP XRs
[RFC3611] that supplement the existing RTCP packets and provide more
detailed feedback on reception quality, and an RTCP NACK [RFC4585]
that provides feedback on the RTP sequence numbers for a subset of
the lost packets or all the currently lost packets. Ultimately Ultimately, the
metric information collected by monitors within the RTP monitoring
framework may go to the network management tools beyond the RTP
monitoring framework, framework; e.g., as shown in Figure 1, the monitors may
export the metric information derived from the RTP monitoring
framework to the management system using non-RTP means.

+-----------+ +----------+
|Third Party|
|Third-Party| |Management|
| Monitor | >>>>>>>>| System |<<<<<
+-----------+ ^ +----------+ ^
: ^ ^ ^
: | ^ ^
+---------------+ : | +-------------+ +-------------+
| +-----------+ | : | |+-----------+| |+-----------+|
| | Monitor | |..:...|.......|| Monitor ||........|| Monitor ||
| +-----------+ | | |+-----------+| |+-----------+|
| |------+------>| |------->| |
| RTP Sender | |RTP Mixer or | |RTP Receiver |
| | |Translator | | |
+---------------+ +-------------+ +-------------+

----> RTP media traffic
..... RTCP control channel
>>>>> Non-RTP/RTCP management flows

Figure 1: Example showing Showing the components Components
of the RTP monitoring
framework Monitoring Framework

RTP may be used with multicast groups, groups: both Any Source Any-Source Multicast
(ASM) and Source Specific Source-Specific Multicast (SSM). These groups can be
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 ASM group. In the SSM case, there is a unicast feedback target
that receives RTCP feedback from receivers and distributes it to
other members of the SSM group (see Figure 1 of [RFC5760] ). [RFC5760]). The
monitor will need to be co-located with the feedback target to
receive all feedback from the receivers (this may also be an
intermediate-system).
intermediate system). In both ASM and SSM scenarios, receivers can
send RTCP reports to enhance the reception quality reception-quality reporting.

3.2. Location of Monitors

As shown in Figure 1, there are several possible locations from where which
RTP sessions can be monitored. These include end systems that
terminate RTP sessions, intermediate-systems intermediate systems that are an active part
of an RTP session, and third-party devices that passively monitor an
RTP session. Not every RTP sessions session will include monitoring, and
those sessions that are monitored will not all include each type of
monitor. The performance metrics collected by monitors can be
divided into end system end-system metrics, application level application-level metrics, and
transport level
transport-level metrics. Some of these metrics may be specific to
the measurement point of the monitor, monitor or may depend on where the
monitors are located in the network, while others are more general
and can be collected in any monitoring location.

End system

End-system monitoring is monitoring that is deployed on devices that
terminate RTP flows. Flows can be terminated in user equipment, such
as phones, video conferencing videoconferencing systems, or IPTV set-top boxes.
Alternatively, they can be terminated in devices that gateway between
RTP and other transport protocols. Transport and end Transport-level metrics, end-
system metrics,
application level and application-level metrics that don't reflect end to end the
end-to-end user experience may be collected at all types of end system,
systems, but some
application level application-level metrics (i.e.,quality (i.e., quality of
experience (QoE) metrics) may only be applicable for user-facing end
systems.

RTP sessions can include intermediate-systems intermediate systems that are an active part
of the system. These intermediate-systems intermediate systems include RTP mixers and
translators, Multipoint Control Units (MCUs), retransmission servers,
etc. If the intermediate-system intermediate system establishes separate RTP sessions to
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
single RTP session traverses the intermediate-system, intermediate system, then the
intermediate-system
intermediate system can be assigned an Synchronization a synchronization source (SSRC)
in that session session, which it can use for its reports. Transport level Transport-level
metrics may be collected at such intermediate-system. an intermediate system.

Third-party monitors may be deployed that passively monitor RTP
sessions for network management purposes. Third-party monitors often
do not send reports into the RTP session being monitored, monitored but instead
collect transport level transport-level metrics, end-system metrics, end system metrics and application application-
level metrics. In some cases, however, third-party monitors can send
reports to some or all participants in the session being monitored.

For example, in a media streaming scenario, third-party monitors may
be deployed that passively monitor the session and send reception reception-
quality reports to the media source, source but not to the receivers.

4. Issues With with Reporting Metric Block Metrics Blocks Using RTCP XR Extension Extensions

The following sections discuss four issues that have come up in the
past with reporting metric block metrics blocks using RTCP XR extensions.

4.1. Using compound metrics block a Compound Metrics Block

A compound metrics block is designed to contain a large number of
parameters from different classes for a specific application in a
single block. For example, the RTCP "RTP Control Protocol Extended Reports (XRs)
(RTCP XR)" [RFC3611] defines seven report block formats for network
management and quality monitoring. Some of these block types defined
in the RTCP XRs [RFC3611] are only specifically designed for
conveying multicast inference of network characteristics (MINC) or
voice over IP (VoIP) monitoring. However However, different applications
layered on RTP may have different monitoring requirements. Designing
a compound metrics block only for specific applications may increase
implementation cost costs and minimize interoperability.

4.2. Correlating RTCP XR with the non-RTP data Non-RTP Data

The Canonical End-Point Identifier SDES Item (CNAME), as defined in the
RTP
Protocol [RFC3550], is an example of an existing tool that allows binding
an SSRC that may change to a name that is fixed within one RTP
session. The CNAME may be also be fixed across multiple RTP sessions
from the same source. However However, there may be situations where RTCP
reports are sent to other participating endpoints using a non-RTP
protocol in a session. For example, as described in the SIP RTCP
Summary Report Protocol [RFC6035], [RFC6035] in
relation to summary reports, the data contained in RTCP XR VoIP
metrics reports [RFC3611] are is forwarded to a central collection server systems
system using SIP. In such a case, there is a large portfolio of
quality parameters that can be associated with real time
application, real-time
applications, e.g., VOIP application, applications, but only a minimal number of
parameters are included on in the RTCP-XR reports. RTCP XRs. With these this minimal number of
RTCP statistics statistical parameters mapped to non-RTCP measurements, it is
hard to provide accurate measures measurements of real time real-time application
quality, conduct detailed data analysis analysis, and creates alerts create timely to
the alerts for
users. Therefore Therefore, a correlation between RTCP XR XRs and non-RTP data
should be provided.

4.3. Measurement Information duplication Duplication

We may set a measurement interval for the session and monitor RTP
packets within one or several consecutive report intervals. In such
a case, the extra measurement information (e.g., extended sequence number
of 1st the first packet, measurement period) may be expected. However However,
if we put such extra measurement information into each metric metrics block,
there may be situations where an RTCP XR packet containing that contains
multiple
metric blocks, reports metrics blocks will report on the same streams from the same
source. In other words, duplicated data for the measurement is
provided multiple times, once in every metric metrics block. Though this
design ensures immunity to packet loss, it may bring result in more
packetization complexity complexity, and the this processing overhead is not
completely trivial in some cases.
Therefore Therefore, a compromise between
processing overhead and reliability should be taken into account.

4.4. Consumption of XR block code points Block Code Points

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
future. Anticipating In anticipation of the potential need to extend the block
type space, it is noted that Block Type 255 is reserved for future
extensions in [RFC3611].

5. Guidelines For for Reporting Metric Block Metrics Blocks Using RTCP XR

5.1. Contain the single metrics Use a Single Metric in the Metric Metrics Block

Different applications using RTP for media transport certainly have
differing requirements for metrics transported in RTCP to support
their operation. For many applications, the basic metrics for
transport impairments provided in RTCP SR and RR packets [RFC3550]
(together with source identification provided in RTCP SDES Source
Description (SDES) packets) are sufficient. For other applications applications,
additional metrics may be required or at least sufficiently may be sufficiently
useful to justify the overhead,
both in terms of both processing in
endpoints and of increased session bandwidth. For example example, an IPTV
application using Forward Error Correction (FEC) might use either a
metric of post-repair loss or a metric giving detailed information
about pre-repair loss bursts to optimise optimize payload bandwidth and the
strength of FEC required for changing network conditions. However However,
there are many metrics available. It is likely that different
applications or classes of applications will wish to use different
metrics. Any one application is likely to require metrics for more
than one parameter parameter, but if this is the case, different applications
will almost certainly require different combinations of metrics. If
larger blocks are defined containing multiple metrics to address the
needs of each application, it becomes likely that many different such different
larger blocks are defined, which
becomes poses a danger to interoperability.

To avoid this pitfall, this memo recommends the definition of metrics
blocks containing a very small number of individual metrics
characterizing only one parameter of interest to an application
running over RTP. For example, at the RTP transport layer, the
parameter of interest might be packet delay variation, and
specifically the metric "IP Packet Delay Variation (IPDV)" defined by
[Y1540]. See Section 6 for architectural considerations for a
metrics block, using as an example a metrics block to report packet
delay variation. Further, it is appropriate to not only define
report blocks separately, separately but also to do so in separate documents
where possible. This makes it easier to evolve the reports (i.e., to
update each type of report block separately), separately) and also makes it easier
to require compliance with a particular report block.

5.2. Include the payload type Payload Type in the Metric Metrics Block

There are some classes of metrics that can only be interpreted with
knowledge of the media codec that is being used (audio mean opinion
scores (MOS) (MOSs) were the triggering example, but there may be others).
In such cases cases, the correlation of an RTCP XR with RTP data is needed.
Report blocks that require such correlation need to include the
payload type of the reported media. In addition, it is necessary to
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
an SDP
a Session Description Protocol (SDP) offer/answer exchange).

5.3. Use RTCP SDES to correlate XR reports Correlate XRs with non-RTP data Non-RTP Data

There may be situations where more than one media transport protocol
is used by one application to interconnect to the same session in the
gateway. For example, one RTCP XR Packet packet is sent to the
participating endpoints using non-RTP-based media transport (e.g.,
using SIP) in a VoIP session. One crucial factor lies in how to
handle their the different identities that are corresponding correspond to these different
media transport. transport protocols.

This memo recommends an approach to facilitate the correlation of the
RTCP Session session with other session-related non-RTP data. That is to say
say, if there is a need to correlate RTP sessions with non-RTP
sessions, then the correlation information needed should be conveyed
in a new RTCP Source Description (SDES) SDES item, since such correlation information describes
the source, source rather than providing a quality report. An example use
case is for where a participant endpoint may convey a call identifier or
a global call identifier associated with the SSRC of a measured RTP
stream. In such a case, the participant endpoint uses the SSRC to
bind the call identifier using the SDES item in the SDES RTCP packet
and send such sends this correlation to the network management system. A flow
measurement tool that is configured with the 5-tuple and is not call-aware call-
aware then forwards the RTCP XR reports XRs along with the SSRC of the measured
RTP stream stream, which is included in the XR Block header and 5-tuple to
the network management system. Network The network management system can
then correlate this report using SSRC with other diagnostic information
information, such as call detail records.

5.4. Reduce Measurement information repetition Information Repetition across metric blocks Metrics Blocks

When multiple metric metrics blocks are carried in one RTCP XR packet,
reporting on the same stream from the same source for the same time
period, RTCP should use the SSRC to identify and correlate the
multiple metric metrics blocks placed between metric blocks. Measurement Information
Blocks; see "Measurement Identity and information Information Reporting using SDES item Using a
Source Description (SDES) Item and XR an RTCP Extended Report (XR)
Block" [MEASI] [RFC6776]. [RFC6776] enables an RTCP sender to convey the
common time period and the number of packets sent during this period.
If the measurement interval for a metric is different from the RTCP
reporting interval, then this measurement duration in the Measurement information block
Information Block should be used to specify the interval. When there
may be multiple
measurements information blocks Measurement Information Blocks with the same SSRC in
one RTCP XR compound packet, the measurement information block Measurement Information Block should
be put in order and followed by all the metric metrics blocks associated
with this
measurement information block. Measurement Information Block. New RTCP XR metric metrics blocks
that rely on the Measurement information block [MEASI] Information Block must specify the
response in case the new RTCP XR metric metrics block is received without an
associated measurement information block. Measurement Information Block. In most cases, it is
expected that the correct response is to discard the received metric.
In order to reduce measurement information repetition in one RTCP XR
compound packet containing multiple metric metrics blocks, the measurement
information shall be sent before the related metric metrics blocks that are
from the same reporting interval. Note that for packet loss
robustness
robustness, if the report blocks for the same interval span over more than
one RTCP packet, then each block must have the measurement identity
information sent together with itself in the same RTCP compound
packet, even though they the information will be the same.

6. An Example of a Metric 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.

The example [PDV] [RFC6798] is a block to convey information about packet
delay variation (PDV) only, consistent with the principle that a
metrics block should address only one parameter of interest. One
simple metric of PDV is available in the RTCP RR packet as the "interarrival
"inter-arrival jitter" field. There are other PDV metrics with a
certain similarity in metric structure which that may be more useful to
certain applications. Two such metrics are the IPDV metric ([Y1540], ([Y1540]
[RFC3393]) and the mean absolute packet delay variation 2 (MAPDV2)
metric [G1020]. Use The use of these metrics is consistent with the
principle in Section 5 of the RTCP guideline guidelines document [RFC5968] that
metrics should usually be defined elsewhere, so that RTCP standards
define only the transport of the metric rather than its nature. The
purpose of this section is to illustrate the architectural consideration
considerations, using the example of [PDV] [RFC6798], rather than to
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
design options for the allocation of metrics to RTCP XR blocks:

o provide Provide an RTCP XR block per metric metric.

o provide Provide a single RTCP XR block which that contains all three metrics metrics.

o provide Provide a single RTCP block to convey any one of the three
metrics, together with a an identifier to inform the receiving RTP
system of the specific metric being conveyed conveyed.

In choosing between these options, extensibility is important,
because additional metrics of PDV may well be standardized and
require inclusion in this framework. The first option is extensible
but only by the use of additional RTCP XR blocks, which may consume
the limited namespace for RTCP XR blocks at an unacceptable rate.
The second option is not extensible, extensible and so could be rejected on that
basis, but in any case a single application is quite unlikely to
require the transport of more than one metric for PDV. Hence Hence, the
third option was chosen. This implies the creation of a subsidiary
namespace to enumerate the PDV metrics which that may be transported by
this block, as discussed further in [PDV]. [RFC6798].

7. Application To to RFC 5117 Topologies

The topologies specified in [RFC5117] fall into two categories. The
first category relates to the RTP system model utilizing multicast
and/or unicast. The topologies in this category are specifically
Topo-Point-to-Point, Topo- Multicast, Topo-Multicast, Topo-Translator (both variants, variants
Topo-Trn-Translator and Topo-Media-Translator, and Topo-Media-Translator as well as combinations
of the two), and Topo-Mixer. These topologies use RTP end systems,
RTP
mixers mixers, and RTP translators as defined in the RTP protocol [RFC3550]. For the
purposes of reporting connection quality to other RTP systems, RTP
mixers and RTP end systems are very similar. Mixers resynchronize
packets and do not relay RTCP reports received from one cloud towards
other cloud(s). Translators do not resynchronize packets and should
forward certain RTCP reports between clouds. In this category, the
RTP system (end system, mixer mixer, or translator) which that originates, terminates
terminates, or forwards RTCP XR blocks is expected to handle RTCP,
including RTCP XR, according to the RTP protocol [RFC3550]. Provided this
expectation is met, an RTP system using RTCP XR is architecturally no
different from an RTP system of the same class (end system, mixer, or
translator) which that does not use RTCP XR. The second category relates
to deployed system models used in many H.323 [H323] video conferences. videoconferences.
The topologies in this category are Topo-Video-Switch-MCU Topo-Video-switch-MCU and
Topo-RTCP-terminating-MCU. Such topologies based on systems (e.g.,MCUs) (e.g.,
MCUs) do not behave according to
the RTP protocol [RFC3550].

Considering that the translator and MCU are two typical intermediate- intermediate
systems in these two categories mentioned above, this document will
take them as two typical examples to explain how RTCP XR report works in
different RFC5117 [RFC5117] topologies.

7.1. Applicability to Translators

Section 7.2 of the RTP protocol specification [RFC3550] describes the
processing of RTCP by translators. RTCP XR is within the scope of
the recommendations of the RTP protocol [RFC3550]. Some RTCP XR metrics blocks may
usefully be measured at, and reported by, translators. As described
in the RTP protocol [RFC3550] [RFC3550], this creates a requirement for the translator to
allocate an SSRC for the monitor collocated co-located with itself so that the
monitor may populate the SSRC in the RTCP XR packet header as the
packet sender SSRC and send it out(although out (although the translator is not a Synchronisation Source
synchronization source in the sense of originating RTP media
packets). It must also supply this SSRC and the corresponding CNAME
in RTCP SDES packets.

In RTP sessions where one or more translators generate any RTCP
traffic towards their next-neighbour next-neighbor RTP system, other translators in
the session have a choice as to whether they forward a translator's
RTCP packets. Forwarding may provide additional information to other
RTP systems in the connection but increases RTCP bandwidth and may in
some cases present a security risk. RTP translators may have
forwarding behaviour behavior based on local policy, which might differ between
different interfaces of the same translator.

7.2. Applicability to MCU

Topo-Video-Switch-MCU MCUs

Topo-Video-switch-MCU and Topo-RTCP-terminating-MCU, Topo-RTCP-terminating-MCU suffer from the
difficulties described in [RFC5117]. These difficulties apply to
systems sending, and expecting to receive, RTCP XR blocks as much as
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
stream is not selected for forwarding by the switch, neither RTCP RR
packets nor RTCP XR blocks referring to the end system's generated
stream will be received at the RTP end system. Strictly speaking,
the RTP end system can only conclude that its RTP has been lost in
the network, though an RTP end system complying with the robustness
principle of [RFC1122] should survive with essential functions (i.e.,media (i.e.,
media distribution) unimpaired.

8. IANA Considerations

There is no IANA action in this document.

9. Security Considerations

This document focuses on the RTCP reporting extension using RTCP XR
and should not give rise to any new security vulnerabilities beyond
those described in RTCP XRs [RFC3611]. However However, it also describes
the architectural framework to be used for monitoring at the RTP
layer. The security issues with monitoring needs need to be considered.

In RTP sessions, a an RTP system may use its own SSRC to send its
monitoring reports towards its next-neighbour next-neighbor RTP system. Other RTP
system
systems in the session may have a choice as to whether they forward
this RTP system's RTCP packets. This present presents a security issue issue,
since the information in the report may be exposed by the other RTP
system to any malicious node. Therefore Therefore, if the information is
considered as sensitive, the monitoring reports SHOULD 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 deploys the third-party monitor, the third party monitor,the RTP system may
decrypt the monitor report for the third party third-party monitor based on local policy(e.g.,third-
party
policy (e.g., third-party monitors is are allowed to access to the metric)
and forward it to the third party monitor, third-party monitor; otherwise, the third party third-party
monitor SHOULD should discard the received encrypted monitoring report.

10. Acknowledgement

9. Acknowledgements

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 Westerlund,
Meral Shirazipour, Tina Tsou, Barry Leiba, Benoit Claise, Russ
Housley, and Stephen Farrell for their valuable comments and
suggestions on the early version versions of this document.

11.

10. Informative References

[G1020] ITU-T, "ITU-T Rec. G.1020, Performance "Performance parameter definitions for quality of
speech and other voiceband applications utilizing IP
networks", ITU-T Rec. G.1020, July 2006.

[H323] ITU-T, "ITU-T Rec. H.323, Packet-based "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.
ITU-T Rec. H.323, December 2009.

[QOE_BLOCK]
Hunt, G., Clark, A., Wu, Q., Schott, R., and G. Zorn,
"RTCP XR "RTP Control
Protocol (RTCP) Extended Report (XR) Blocks for QoE
Metric Reporting",
ID draft-ietf-xrblock-rtcp-xr-qoe-02, July Work in Progress, October 2012.

[RFC1122] Braden, R., "Requirements for Internet Hosts -- -
Communication Layers", STD 3, 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., C. and P. Chimento, "IP Packet Delay
Variation Metric for IP Performance Metrics (IPPM)",
RFC 3393, November 2002.

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.

[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.

[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export
Version 9", RFC 3954, October 2004.

[RFC4585] Ott, J. and S. J., Wenger, S., Sato, N., Burmeister, C., and J.
Rey, "Extended RTP Profile for Real-time Transport
Control Protocol (RTCP)-Based Feedback (RTP/
AVPF)", (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., , Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information
Export", RFC 5102, January 2008.

[RFC5117] Westerlund, M., M. and S. Wenger, "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", BCP 170, RFC 6390,
October 2011.

[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.

[RFC6798] Clark, A. and Q. Wu, "RTP Control Protocol (RTCP)
Extended Report (XR) Block for Packet Delay Variation
Metric Reporting", RFC 6798, November 2012.

[Y1540] ITU-T, "ITU-T Rec. Y.1540, IP "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:

o Update bullet 2 in section 4 to explain the ill-effect of Identity
Information duplication.

o Update bullet 3 in section 4 to explain why Correlating RTCP XR
with the non-RTP data is needed.

o Update section 5.2 to focus on how to reduce the identity
information repetition

o Update section 5.3 to explain how to correlate identity
information with the non-RTP data

A.20. draft-ietf-avtcore-monarch-02

The following are the major changes compared to 01:

o Deleting first paragraph of Section 1.

o Deleting Section 3.1, since the interaction with the management
application is out of scope of this draft.

o Separate identity information correlation from section 5.2 as new
section 5.3.

o Remove figure 2 and related text from section 5.2.

o Editorial changes in the section 4 and the first paragraph of
section 7.

A.21. draft-ietf-avtcore-monarch-01

The following are the major changes compared to 00:

o Restructure the document by merging section 4 into section 3.

o Remove section 4.1,section 5 that is out of scope of this
document.

o Remove the last bullet in section 6 and section 7.3 based on
conclusion of last meeting.

o Update figure 1 and related text in section 3 according to the
monitor definition in RFC3550.

o Revise section 9 to address monitor declaration issue.

o Merge the first two bullet in section 6.

o Add one new bullet to discuss metric block association in section
6.

A.22. draft-ietf-avtcore-monarch-00

The following are the major changes compared to
draft-hunt-avtcore-monarch-02:

o Move Geoff Hunt and Philip Arden to acknowledgement section. ITU-T Rec. Y.1540, March 2011.

Authors' Addresses

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

Email:

EMail: sunseawq@huawei.com

Geoff Hunt
Unaffiliated

Email:

EMail: r.geoff.hunt@gmail.com

Philip Arden
BT
Orion 3/7 PP4
Adastral Park
Martlesham Heath
Ipswich, Suffolk IP5 3RE
United Kingdom

Phone: +44 1473 644192
Email:
EMail: philip.arden@bt.com