Audio/Video Transport Working Group                           Q. Wu, Ed.
Internet-Draft                                                    Huawei
Intended status: Informational                                   G. Hunt
Expires: June 1, 2012                                       Unaffiliated
                                                                P. Arden
                                                                      BT
                                                       November 29, 2011

                    Monitoring Architectures for RTP
                   draft-ietf-avtcore-monarch-07.txt
                   draft-ietf-avtcore-monarch-08.txt

Abstract

   This memo proposes an architecture for extending RTCP with a new RTCP
   XR (RFC3611) block type to report new metrics regarding media
   transmission or reception quality, following RTCP guideline
   established in RFC5968.  This memo suggests that a new 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 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 their set
   of concerns.  Where possible, a specific block should be designed to
   be re-usable across 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
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 1, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  4
   3.  RTP monitoring architecture  . . . . . . . . . . . . . . . . .  6
     3.1.  RTCP Metric Block Report and associated parameters . . . .  8
   4.  Issues with reporting metric block using RTCP XR extension . . 10
   5.  Guideline for reporting metric block using RTCP XR . . . . . . 12
     5.1.  Using single metrics blocks  . . . . . . . . . . . . . . . 12
     5.2.  Correlating RTCP XR with the non-RTP data  . . . . . . . . 12
     5.3.  Reducing Measurement information repetition  . . . . . . . 13
     5.4.  Expanding the RTCP XR block namespace  . . . . . . . . . . 13
   6.  An example of a metric block . . . . . . . . . . . . . . . . . 14
   7.  Application to RFC 5117 topologies . . . . . . . . . . . . . . 15
     7.1.  Applicability to MCU . . . . . . . . . . . . . . . . . . . 15
     7.2.  Applicability to Translators . . . . . . . . . . . . . . . 16
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 19
   11. Informative References . . . . . . . . . . . . . . . . . . . . 20
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 22
     A.1.  draft-ietf-avtcore-monarch-00  . . . . . . . . . . . . . . 22
     A.2.  draft-ietf-avtcore-monarch-01  . . . . . . . . . . . . . . 22
     A.3.  draft-ietf-avtcore-monarch-02  . . . . . . . . . . . . . . 22
     A.4.  draft-ietf-avtcore-monarch-03  . . . . . . . . . . . . . . 23
     A.5.  draft-ietf-avtcore-monarch-04  . . . . . . . . . . . . . . 23
     A.6.  draft-ietf-avtcore-monarch-05  . . . . . . . . . . . . . . 23
     A.7.  draft-ietf-avtcore-monarch-06  . . . . . . . . . . . . . . 24
     A.8.  draft-ietf-avtcore-monarch-07  . . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25

1.  Introduction

   As more users and subscribers rely on real time application services,
   uncertainties in the performance and availability of these services
   are driving the need to support new standard methods for gathering
   performance metrics from RTP applications.  These rapidly emerging
   standards, such as RTCP XR [RFC3611] and other RTCP extension to
   Sender Reports (SR), Receiver Reports (RR) [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 service visibility and measure and
   monitor Quality of Experience (QoE).

   However the proliferation of RTP/RTCP specific metrics for transport
   and application quality monitoring has been identified as a potential
   problem for RTP/RTCP interoperability, which attempt to provide full
   coverage of all those parameters of concern to a specific
   application.  Since different applications layered on RTP may have
   some monitoring requirements in common, therefore these metrics
   should be satisfied by a common design.

   The objective of this document is to define an extensible RTP
   monitoring framework to provide a small number of re-usable Quality
   of Service (QoS)/QoE metrics which facilitate reduced implementation
   costs and help maximize inter-operability.  RTCP Guideline [RFC5968]
   has stated 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 any requirement for a new metric to be
   transported in RTCP will use a new RTCP XR block.

2.  Requirements notation

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

   In addition, the following terms are defined:

   Transport level metrics

      A set of metrics which characterise the three transport
      impairments of packet loss, packet delay, and packet delay
      variation.  These metrics should be usable by any application
      which uses RTP transport.

   Application level metrics

      Metrics relating to QoE related parameters.  These metrics are
      measured at the application level and focus on quality of content
      rather than network parameters.  One example of such metrics is
      the QoE Metric specified in QoE metric reporting Block [MQ].

   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 metric.

   Composed metrics

      Metrics that are calculated based on direct metric or combination
      of direct metric and derived metrics.

   Interval metrics

      It is referred to as the metrics of which the reported values
      apply to the most recent measurement interval duration between
      successive metrics reports

   Cumulative metrics

      It is referred to as the metrics of which the reported values
      apply to the accumulation period characteristic of cumulative
      measurements

   Sampled metrics

      It is referred to as the metrics of which the reported values only
      apply to the value of a continuously measured or calculated that
      has been sampled at end of the interval.

3.  RTP monitoring architecture

   The RTP monitoring architecture comprises the following two key
   functional components shown below:

   o  Monitor

   o  Metric Block Structure

   Monitor is the functional component defined in the Real-time
   Transport Protocol (RTP) [RFC3550] that acts as a source of
   information gathered for monitoring purposes.  It may gather such
   information reported by RTCP XR or other RTCP extension and calculate
   statistics from multiple source.  According to the definition of
   monitor in the RTP Protocol [RFC3550], the end system that source RTP
   streams, an intermediate-system that forwards RTP packets to End-
   devices or a third party that does not participate in the RTP session
   (i.e., the third party monitor depicted in figure 1) can be
   envisioned to act as the Monitor within the RTP monitoring
   architecture.

   The Metric Block exposes real time Application QoS/QoE metric
   information in the appropriate report block format to the management
   system within the RTP monitoring architecture.  Such information can
   be formulated as:

   o  The direct metrics

   o  or the composed metrics.

   or formulated as

   o  The Interval metrics

   o  or cumulative metrics

   o  or sampled metrics.

   Both the RTCP or RTCP XR can be extended to convey these metrics.
   The details on transport protocols for metric blocks are described in
   Section 3.1.

                +-------------------+
                | RTP Sender        |              +----------+
                |   +-----------+   |              |Management|
   ---------------->|  Monitor  |---------5------->|  System  |
   |            |   |           |   |              |          |
   |            |   +-----------+   |              +----------+
   |            |+-----------------+|
   |            ||Application      ||    --------------|
   |            ||-Streaming video ||    |             |
   |   |---------|-VOIP            ||    |    +--------V------+
   |   |        ||-Video conference||    ------  Third Party  |
   |   |        ||-Telepresence    ||         |    Monitor    |
   |   |        ||-Ad insertion    ||         +---------------+
   5   |        |+-----------------+|
   |   |        +-------------------+
   |   1
   |   | +Intermediate------------+         |-------------- ---- ----+
   |   | | RTP System       Report Block    | RTP Receiver >--4-|    |
   |   | |      +---------- transported over|    +-----------+  |    |
   |   | |      |           RTCP extension  |    |  Monitor  |<--    |
   |-------------  Monitor |<--------5------|----|           |<------|
       | |      |          |   Report Block      +----/------+      ||
       | |      +----------+   transported over       |             ||
       | |                     RTCP XR      |         |2            ||
       | | +-----------------+    |         | +-------/---------+   ||
       | | |Application      |    |         | |Application      |   ||
       | | |-Streaming video |    |         | |-Streaming video |   ||
       | | |-VOIP            |    |    1    | |-VOIP            |   3|
       ---->-Video conference|--------------->|-Video conference    ||
         | |-Telepresence    |    |         | |-Telepresence    |   ||
         | |-Ad insertion    |    |         | |-Ad insertion    |   ||
         | +-----------------+    |         | +-----------------+   ||
         | +-----------------+    |         | +-----------------+   ||
         | |Transport        |    |         | |Transport        |   ||
         | |-IP/UDP/RTP      |    |         | |-IP/UDP/RTP      >---||
         | |-IP/TCP/RTP      |    |         | | -IP/TCP/RTP     |    |
         | |-IP/TCP/RTSP/RTP |    |         | |-IP/TCP/RTSP/RTP |    |
         | +-----------------+    |         | +-----------------+    |
         +------------------------+         +------------------------+

                   Figure 1: RTP Monitoring Architecture

   1.  RTP communication between real time applications.

   2.  Application level metrics collection.

   3.  Transport level metrics collection.

   4.  End System metrics collection.

   5.  Reporting Session- metrics transmitted over specified interfaces.

3.1.  RTCP Metric Block Report and associated parameters

   The basic RTCP Reception Report (RR) [RFC3550] conveys reception
   statistics (i.e., transport level statistics) in metric block report
   format for multiple RTP media streams including

   o  the fraction of packet lost since the last report

   o  the cumulative number of packets lost

   o  the highest sequence number received

   o  an estimate of the inter-arrival jitter

   o  and information to allow senders to calculate the network round
      trip time.

   The RTCP XRs [RFC3611] supplement the existing RTCP packets and
   provide more detailed feedback on reception quality in several
   categories:

   o  Loss and duplicate RLE reports

   o  Packet-receipt times reports

   o  Round-trip time reports

   o  Statistics Summary Reports

   There are also various other scenarios in which it is desirable to
   send RTCP Metric reports more frequently.  For example, the Audio/
   Video Profile with Feedback [RFC4585] extends the standard A/V
   Profile [RFC3551] to allow RTCP reports to be sent early provided
   RTCP bandwidth allocation is respected.  The following are four use
   cases but are not limited to:

   o  RTCP NACK is used to provide feedback on the RTP sequence number
      of the lost packets [RFC4585].

   o  RTCP is extended to convey requests for full intra-coded frames or
      select the reference picture, and signalchanges in the desired
      temporal/spatial trade-off and maximum media bit rate [RFC5104].

   o  RTCP or RTCP XR is extended to provide feedback on ECN statistics
      information [ECN].

   o  RTCP XR is extended to provide feedback on multicast acquisition
      statistics information and parameters [RFC6332].

4.  Issues with reporting metric block using RTCP XR extension

   Issues that have come up in the past with reporting metric block
   using RTCP XR extensions include (but are probably not limited to)
   the following:

   o  Using large block.  A single report block or metric is designed to
      contain a large number of parameters in different classes for a
      specific application.  For example, the RTCP Extended Reports
      (XRs) [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 different
      applications layered on RTP may have different monitoring
      requirements.  Design large block only for specific applications
      may increase implementation cost and minimize interoperability.

   o  Correlating RTCP XR with the non-RTP data.  CNAME defined in the
      RTP Protocol [RFC3550] is an example of existing tool that allows
      to bind an SSRC that may change to a fixed source name in one RTP
      session.  It may be also fixed across multiple RTP sessions from
      the same source.  However there may be situations where RTCP
      reports are sent to other participating endpoints using non-RTP
      protocol in a session.  For example, as described in the SIP RTCP
      Summary Report Protocol [RFC6035], the data contained in RTCP XR
      VoIP metrics reports [RFC3611] are forwarded to a central
      collection server systems using SIP.  In such case, there is a
      large portfolio of quality parameters that can be associated with
      real time application,e.g., VOIP application, but only a minimal
      number of parameters are included on the RTCP-XR reports.
      Therefore correlation between RTCP XR and non-RTP data should be
      concerned if administration or management systems need to rely on
      the mapping RTCP statistics to non-RTCP measurements to conducts
      data analysis and creates alerts to the users.  Without such
      correlation, it is hard to provide accurate measures of real time
      application quality with a minimal number of parameters included
      on the RTCP-XR reports in such case.

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

   o  Consumption of XR 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.  We therefore may
      need a way to extend the block type space, so that new
      specifications may continue to be developed.

5.  Guideline for reporting metric block using RTCP XR

5.1.  Using single metrics blocks

   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 packets)
   are sufficient.  For other applications additional metrics may be
   required or at least sufficiently useful to justify the overheads,
   both of processing in endpoints and of increased session bandwidth.
   For 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 payload
   bandwidth and the strength of FEC required for changing network
   conditions.  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 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 larger blocks are defined, which
   becomes a danger to interoperability.

   To avoid this pitfall, this memo proposes the use of small RTCP XR
   metrics blocks each 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 "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.

5.2.  Correlating RTCP XR with the non-RTP data

   There may be situation where more than one media transport protocols
   are used by one application to interconnect to the same session in
   the gateway.  For example, one RTCP XR 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 different identities that are corresponding to different
   media transport.

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

5.3.  Reducing Measurement information repetition

   When multiple metric blocks are carried in one RTCP XR packet,
   reporting on the same stream from the same source for the same time
   period, RTCP should use the SSRC to identify and correlate the
   multiple metric blocks between metric blocks.  This memo proposes to
   define a new XR Block that will be used to convey the common time
   period and the number of packets sent during this period [MI].  If
   the measurement interval for a metric is different from the RTCP
   reporting interval, then this measurement duration in the [MI] SHOULD
   be used to specify the interval.  In order to reduce measurement
   information repetition in one RTCP XR compound packet containing
   multiple metric blocks, the measurement information shall be sent
   before the related metric blocks that are from the same reporting
   interval.  Note that for packet loss robustness if the report blocks
   for the same interval span over more than one RTCP packet then each
   must have the measurement identity information even if though they
   will be the same.

5.4.  Expanding the RTCP XR block namespace

   The consumption of XR block code points isn't a major issue.  However
   if XR block codes points is really close to run out of space, it
   might be desirable to define new fields in the XR report block or
   define one XR block type for vendor-specific extensions, with an
   enterprise number included to identify the vendor making the
   extension.

6.  An example of a metric block

   This section uses the example of an existing proposed metrics block
   to illustrate the application of the principles set out in
   Section 5.1.

   The example [PDV] 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
   jitter" field.  There are other PDV metrics which may be more useful
   to certain applications.  Two such metrics are the IPDV metric
   ([Y1540], [RFC3393]) and the MAPDV2 metric [G1020].  Use of these
   metrics is consistent with the principle in Section 5 of RTCP
   guideline [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
   architecture using the example of [PDV] 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 an RTCP XR block per metric

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

   o  provide a single RTCP block to convey any one of the three
      metrics, together with a identifier to inform the receiving RTP
      system of the specific metric being 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 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, so could be rejected on that basis,
   but in any case a single application is quite unlikely to require
   transport of more than one metric for PDV.  Hence the third option
   was chosen.  This implies the creation of a subsidiary namespace to
   enumerate the PDV metrics which may be transported by this block, as
   discussed further in [PDV] .

7.  Application 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-Translator (both variants,
   Topo-Trn-Translator and Topo-Media-Translator, and combinations of
   the two), and Topo-Mixer.  These topologies use RTP end systems, RTP
   mixers and RTP translators defined in the RTP protocol [RFC3550].
   For 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 or translator) which
   originates, 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 does not use RTCP
   XR.  The second category relates to deployed system models used in
   many H.323 [H323] video conferences.  The topologies in this category
   are Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU.  Such
   topologies based on systems do not behave according to the RTP
   protocol [RFC3550].

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

7.1.  Applicability to MCU

   Topo-Video-Switch-MCU and 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 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
   distribution) unimpaired.

7.2.  Applicability to Translators

   Section 7.2 of the RTP protocol [RFC3550] describes 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] this creates a requirement
   for the translator to allocate an SSRC for the monitor collocated
   with itself so that the monitor may populate the SSRC in the RTCP XR
   packet header as packet sender SSRC and send it out(although the
   translator is not a Synchronisation 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 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 based on local policy, which might differ
   between different interfaces of the same translator.

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 it also describes the
   architectural framework to be used for monitoring at RTP layer.  The
   security issues with monitoring needs to be considered.

   In RTP sessions, a 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 report should be encrypted.

   Also note that the third party monitors are not visible at the RTP
   layer since they do not send any RTCP packets.  In order to prevent
   any sensitive information leakage, the monitoring from the third
   party monitors should be prohibited unless the security is in place
   to authenticate them.

10.  Acknowledgement

   The authors would also like to thank Colin Perkins, Graeme Gibbs,
   Debbie Greenstreet, Keith Drage, Dan Romascanu, Ali C. Begen, Roni
   Even, Magnus Westerlundfor their valuable comments and suggestions on
   the early version of this document.

11.  Informative References

   [ECN]      Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
              and K. Carlberg, "Explicit Congestion Notification (ECN)
              for RTP over UDP", ID draft-ietf-avtcore-ecn-for-rtp-04,
              July 2011.

   [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.

   [MI]       Wu, Q., "Measurement Identity and information Reporting
              using SDES item and XR Block",
              ID draft-ietf-xrblock-rtcp-xr-meas-identity-01,
              October 2011.

   [MQ]       Wu, Q., Zorn, G., Schott, R., and K. Lee, "RTCP XR Blocks
              for multimedia quality metric reporting",
              ID draft-wu-xrblock-rtcp-xr-quality-monitoring-02,
              May 2011.

   [PDV]      Hunt, G., "RTCP XR Report Block for Packet Delay Variation
              Metric Reporting", ID draft-ietf-xrblock-rtcp-xr-pdv-00,
              September 2011.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts --
              Communication Layers", RFC 1122, October 1989.

   [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.

   [RFC3551]  Schulzrinne , H. and S. Casner, "Extended RTP Profile for
              Real-time Transport Control Protocol (RTCP)-Based Feedback
              (RTP/AVPF)", RFC 3551, July 2003.

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

   [RFC4585]  Ott, J. and S. Wenger, "Extended RTP Profile for Real-time
              Transport Control Protocol (RTCP)-Based Feedback (RTP/
              AVPF)", RFC 4585, July 2006.

   [RFC5104]  Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
              "Session Initiation Protocol Event Package for Voice
              Quality Reporting", RFC 5104, February 2008.

   [RFC5117]  Westerlund, M., "RTP Topologies", RFC 5117, January 2008.

   [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.

   [RFC6332]  Begen, A. and E. Friedrich, "Multicast Acquisition Report
              Block Type for RTP Control Protocol (RTCP) Extended
              Reports (XRs)", RFC 6332, July 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-00

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

   o  Move Geoff Hunt and Philip Arden to acknowledgement section.

A.2.  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.3.  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.4.  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.5.  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.6.  draft-ietf-avtcore-monarch-05

   The following are the major changes compared to 04:

   o  Replace "chunk" with "new SDES item".

   o  Add texts in security section to discussion potential security
      issues.

   o  Add new sub-section 5.3 to discuss Reducing Measurement
      information repetition.

   o  Other editorial changes.

A.7.  draft-ietf-avtcore-monarch-06

   The following are the major changes compared to 05:

   o  Some editorial changes.

A.8.  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.

Authors' Addresses

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

   Email: sunseawq@huawei.com

   Geoff Hunt
   Unaffiliated

   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: philip.arden@bt.com