Audio/Video Transport Working Group                           Q. Wu, Ed.
Internet-Draft                                                    Huawei
Intended status: Informational                                   G. Hunt
Expires: December 18, 2011 March 3, 2012                                      Unaffiliated
                                                                P. Arden
                                                                      BT
                                                           June 16,
                                                         August 31, 2011

                    Monitoring Architectures for RTP
                   draft-ietf-avtcore-monarch-03.txt
                   draft-ietf-avtcore-monarch-04.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, as proposed 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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on December 18, 2011. March 3, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  4
   3.  RTP monitoring architecture  . . . . . . . . . . . . . . . . .  5
     3.1.  RTCP Metric Block Report and associated parameters . . . .  7
   4.  Issues with reporting metric block using RTCP XR extension . .  9
   5.  Guideline for reporting block format using RTCP XR . . . . . . 11
     5.1.  Using small blocks . . . . . . . . . . . . . . . . . . . . 11
     5.2.  Reducing the identity information repetition . . . . . . . 11
     5.3.  Correlating identity information with the non-RTP data . . 13 11
   6.  An example of a metric block . . . . . . . . . . . . . . . . . 14 13
   7.  Application to RFC 5117 topologies . . . . . . . . . . . . . . 15 14
     7.1.  Applicability to MCU . . . . . . . . . . . . . . . . . . . 15 14
     7.2.  Applicability to Translators . . . . . . . . . . . . . . . 15 14
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17 16
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18 17
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 19 18
   11. Informative References . . . . . . . . . . . . . . . . . . . . 20 19
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 21
     A.1.  draft-ietf-avtcore-monarch-00  . . . . . . . . . . . . . . 21
     A.2.  draft-ietf-avtcore-monarch-01  . . . . . . . . . . . . . . 21
     A.3.  draft-ietf-avtcore-monarch-02  . . . . . . . . . . . . . . 21
     A.4.  draft-ietf-avtcore-monarch-03  . . . . . . . . . . . . . . 22
     A.5.  draft-ietf-avtcore-monarch-04  . . . . . . . . . . . . . . 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23

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 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 QoS/QoE
   metrics which facilitate reduced implementation costs and help
   maximize inter-operability.  [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 Multimedia Quality Metric specified in [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.

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 a functional component defined in RFC3550 that acts as a
   source of information gathered for monitoring purposes.  It may also
   collect statistics from multiple source, stores such information
   reported by RTCP XR or other RTCP extension appropriately as base
   metric or calculates composite metric.  According to the definition
   of monitor in 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 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 Quality information in
   the appropriate report block format to monitor the Monitor within the RTP
   monitoring architecture.  Both the RTCP or RTCP XR can be extended to
   convey such information.  The details on transport protocol for
   metric block is described in Section 3.1.

                                                |---------------+
                                                | Management    |
                +-------------------+           |   System      |
                | RTP Sender        |           |  +----------+ |
                |   +-----------+   |           |  |          | |
   ---------------->|  Monitor  |---------5------->|  Monitor | |
   |            |   |           |   |           |  |          | |
   |            |   +-----------+   |           |  +----\-----+ |
   |            |+-----------------+|           |       |       |
   |            ||Application      ||           --------|-------+
   |            ||-Streaming video ||                   |
   |   |---------|-VOIP            ||                   5
   |   |        ||-Video conference||                   |
   |   |        ||-Telepresence    ||       +---------------+
   |   |        ||-Ad insertion    ||       |  Third Party  |
   5   |        |+-----------------+|       |    Monitor    |
   |   |        +-------------------+       +---------------+
   |   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 applications.

   2.  Application level metrics collection.

   3.  Transport level metrics collection.

   4.  End System metrics collection.

   5.  Reporting Session- metrics transmitted over specified interfaces interfaces.

3.1.  RTCP Metric Block Report and associated parameters

   The basic RTCP Reception Report (RR) conveys reception statistics in
   metric block report format for multiple RTP media streams including

   o  transport level statistics

   o  the fraction of packet lost since the last report

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

   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]

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, RFC 3611 [RFC3611] defines
      seven report block formats for network management and quality
      monitoring.  However some of these block types defined in
      [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 some monitoring requirements in common, design large block
      only for specific applications may increase implementation cost
      and minimize interoperability.

   o  Correlating RTCP XR with the non-RTP data.  CNAME [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 is 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 [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 hardly 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  Identity Information duplication.  Identity information is used to
      identify an instance of a metric block.  The SSRC of the measured
      stream as part of the metric block is one example of Identity
      information.  However in some cases, Identity information may be
      not part of metric and include information more than one the SSRC in
      the metric block,e.g., block, e.g., when we set a metric interval for the
      session and monitor RTP packets within one or several consecutive
      metric interval, extra identity information is expected.  In such case, (e.g., sequence number
      of 1st packet) is expected, if we put such extra identity
      information into each metric block
      or create standalone block containing extra identity information, block, there may be situations where
      an RTCP XR packet containing more than two metric blocks and other standalone block containing including
      the duplicated extra identity information, reports on the same
      streams from the same source. each block have the same extra
      identity information for measurement, if each metric block carry
      such duplicated data for the measurement, it leads to redundant
      information in this design since equivalent information is
      provided multiple times, once in *every* metric block and other block containing identity
      information. block.  Though
      this ensures immunity to packet loss, the design may bring more
      complexity and the overhead is not completely
      trivial.

   o  Correlating RTCP XR with the non-RTP data.  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 [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 hardly to provide accurate measures of real
      time application quality with a minimal number of parameters
      included on the RTCP-XR reports trivial in such case. some
      cases.

5.   Guideline for reporting block format using RTCP XR

5.1.  Using small 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.  Reducing the  Correlating identity information repetition

   Any measurement must be identified.  For example, an instance of a
   metric must be identified using information which is likely to
   include most of the following:

   o  the node at which it was measured,

   o with the source of non-RTP data

   When more than one media transport protocols are used by one
   application to interconnected to the measured stream (for example, its CNAME),

   o  the SSRC of the measured stream,
   o  the sequence number of the first packet of the RTP session,

   o  the extended sequence numbers of the first packet of the current
      measurement interval, and the last packet included in the
      measurement,

   o  the duration of the most recent measurement interval and

   o  the duration of the interval applicable to cumulative measurements
      (which may be the duration of the RTP session to date).

   Note that this set of information (identity information) may overlap
   with, but is more extensive than, that in the union of similar
   information in RTCP RR packets.  However we can not assume that RR
   information is always present when XR is sent, since they may have
   different measurement intervals.  Also the reason for the additional
   information carried in the XR is the perceived difficulty of
   "locating" the *start* of the RTP session (sequence number of 1st
   packet, duration of interval applicable to cumulative measurements)
   using only RR.  Therefore this set of information can provide more
   detailed identity information relevant to the measurement report.
   However if such detailed identity information are all put into each
   metric and the metric are delivered in small blocks there is a danger
   of inefficiency arising from repeating this information in a number
   of metrics blocks within the same RTCP packet, in cases where the
   same identification information applies to multiple metrics blocks.

   This memo proposes an approach to minimise the inefficiency of
   providing this identification information, assuming that an
   architecture based on small blocks means that a typical RTCP packet
   will contain more than one metrics block needing the same
   identification.  The choice of identification information to be
   provided is discussed in [IDENTITY].  The approach is to define a
   stand-alone block containing only identification information within
   the scope of the containing RTCP XR packet.  The "containing RTCP XR
   packet" is defined here as the RTCP XR header with PT=XR=207 defined
   in Section 2 of [RFC3611] and the associated payload defined by the
   length field of this RTCP XR header.  The RTCP XR header itself
   includes the SSRC of the node at which all of the contained metrics
   were measured, hence this SSRC need not be repeated in the stand-
   alone identity block.  A single RTCP XR packet containing multiple
   metric block may contain multiple identity blocks.  Typically there
   will be one identity block per monitored source SSRC, but the use of
   more than one identification block for a single monitored source SSRC
   within a single containing RTCP XR packet is not ruled out.  In order
   to further reduce identity information repeatition, This stand-alone
   block is recommended to only be exchanged occasionally, for example
   sent once at the start of a session.

5.3.  Correlating identity information with the non-RTP data

   When more than one media transport protocols are used by one
   application to interconnected to the same session (in gateway),e.g.,
   one RTCP XR Packet is sent to same session (in gateway),e.g.,
   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 XR identity information Session with other session-related non-RTP data, i.e., using SSRC of source in if there
   is a need to correlate RTP sessions with non-RTP sessions, then the identity
   correlation information as the needed should be conveyed in RTCP SDES
   packets since such correlation tag to associate identity information with describes the non-RTP-
   based data. source,
   rather than providing a quality report.  An example use case is for an a
   participant endpoint may convey a call identifier or a global call
   identifier associated with the XR block
   identity information and use SSRC of measured RTP stream .  In such
   case, the participant endpoint uses SSRC of source in to bind the identity
   information as call
   identifier in each chunk of the SDES RTCP packet and send such
   correlation tag using the chunk containing SDES item to the call identifier. network
   management system.  A flow measurement tool that is not call-aware
   then forward the subsequent
   metric RTCP XR reports along with this correlation tag SSRC of the measured RTP
   stream which is included in the XR Block header to the network management.
   management system.  Network management system can then use this tag to correlate this
   report using SSRC with other diagnostic information such as call
   detail records.

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] (work in progress) 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 "jit" 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
   [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] (work in progress) 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] (work in progress).

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 [RFC3550].  For purposes of
   reporting connection quality to other RTP systems, RTP mixers and RTP
   end systems are very similar.  Mixers resynchronize audio 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 [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 [RFC3550].

   Considering the translator and MCU 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 unimpaired.

7.2.  Applicability to Translators

   Section 7.2 of [RFC3550] describes processing of RTCP by translators.
   RTCP XR is within the scope of the recommendations of [RFC3550].

   Some RTCP XR metrics blocks may usefully be measured at, and reported
   by, translators.  As described in [RFC3550] this creates a
   requirement for the translator to allocate an SSRC for the monitor
   within
   collocated with itself so that it the monitor may populate the SSRC in
   the RTCP XR packet header (although 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.

   For bidirectional unicast, an RTP system may usually detect RTCP XR
   from a translator by noting that the sending SSRC is not present in
   any RTP media packet.  However even for bidirectional unicast there is a possibility of a source
   sending RTCP XR before it has sent any RTP media (leading to
   transient mis-categorisation of an RTP end system or RTP mixer as a
   translator), and for multicast sessions - or unidirectional/streaming
   unicast - there is also a possibility of a receive-only end system
   being permanently mis-categorised as a translator sending XR report, i.e.,monitor collocated with
   transaltor.
   i.e.,the monitor sending XR report within the translator.  Hence it
   is desirable for a translator that sends XR report to have a way to
   declare itself explicitly.

8.  IANA Considerations

   None.

9.  Security Considerations

   This document itself contains no normative text and hence should not
   give rise to any new security considerations, to be confirmed.

10.  Acknowledgement

   The authors would also like to thank Colin Perkins, Graeme Gibbs,
   Debbie Greenstreet, Keith Drage,Dan Drage, Dan Romascanu, Ali C. Begen, Roni
   Even for 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.

   [IDENTITY]
              Hunt,

   [MQ]       Wu, Q., Zorn, G., Schott, R., and K. Lee, "RTCP XR Report Block Blocks
              for Measurement Identity", multimedia quality metric reporting",
              ID draft-ietf-avt-rtcp-xr-meas-identity-02, draft-wu-xrblock-rtcp-xr-quality-monitoring-02,
              May 2009. 2011.

   [PDV]      Hunt, G., "RTCP XR Report Block for Packet Delay Variation
              Metric Reporting", ID draft-ietf-avt-rtcp-xr-pdv-03,
              May 2009.

   [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  Separeate 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 01: 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.

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