[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-clark-avt-rtcphr) 00 01 02 03

Internet Engineering Task Force                                 A. Clark
Internet-Draft                                     Telchemy Incorporated
Expires: 4 January 2008                                     A. Pendleton
                                                                  Nortel
                                                                R. Kumar
                                                               K. Connor
                                                           Cisco Systems
                                                                 G. Hunt
                                                                      BT
                                                               July 2007



             RTCP HR - High Resolution VoIP Metrics Report Blocks
                     draft-ietf-avt-rtcphr-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on 4th January 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document defines extensions to the RTCP XR extended report
   packet type blocks to support Voice over IP (VoIP) monitoring
   for services that require higher resolution or more detailed
   metrics than those supported by RFC3611 [3].





Clark                                                          [Page  1]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.   Definitions  . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.   High Resolution VoIP Metrics Report Block    . . . . . . . . 4
   4.   RTCP HR Configuration Block  . . . . . . . . . . . . . . . . 19
   5.   Application of RTCP HR to RTP translators  . . . . . . . . . 22
   6.   RTCP HR Block Multiplexing . . . . . . . . . . . . . . . . . 24
   7.   SDP Signaling    . . . . . . . . . . . . . . . . . . . . . . 28
   8.   Practical applications   . . . . . . . . . . . . . . . . . . 28
   9.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 31
   10.  Security Considerations  . . . . . . . . . . . . . . . . . . 31
   11.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . 31
   12.  Informative References . . . . . . . . . . . . . . . . . . . 31
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 32
        Intellectual Property and Copyright Statements . . . . . . . 33


1.  Introduction

   This draft defines several new block types to augment those defined
   in RFC3611 for use in Quality of Service reporting for Voice over IP.
   The new block types support the reporting of metrics to a higher
   resolution to support certain applications, for example carrier
   backbone networks.

   For certain types of VoIP service it is desirable to report VoIP
   performance metrics to a higher resolution than provided in the
   RFC3611 [3] VoIP Metrics block or RFC3550 [2] Receiver Reports.
   The report blocks described in this section provide both interval
   based and cumulative metrics with a higher resolution than that
   provided in the RFC3611 VoIP metrics report block[3].

   The new block types defined in this draft are the High Resolution
   VoIP Metrics Report Block, and the High Resolution VoIP Metrics
   Configuration Block.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.


2.  Definitions

2.1 Cumulative and Interval Metrics

   Cumulative metrics relate to the entire duration of the call to the
   point at which metrics are determined and reported, and are typically
   used to report call quality.  Cumulative metrics generally result in
   a lower volume of data that may need to be stored, as each report
   supersedes earlier reports.


Clark                                                          [Page  2]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   Interval metrics relate to the period since the last Interval report.
   Interval data may be easier to correlate with specific network events
   for which timing is known, and may also be used as a basis for
   threshold crossing alerts.

   Note that interval metrics for the start and end of calls may be
   unreliable due to factors such as irregular start and end interval
   length and the difficulty in knowing when packet transmission started
   and ended.

2.2 Bursts, Gaps, and Concealed Seconds

   The terms Burst and Gap are used in a manner consistent with that of
   RTCP XR (RFC3611). RTCP XR views a call as being divided into bursts,
   which are periods during which the combined packet loss and discard
   rate is high enough to cause noticeable call quality degradation
   (generally over 5 percent loss/discard rate), and gaps, which are
   periods during which lost or discarded packets are infrequent and
   hence call quality is generally acceptable.

   The recommended value for Gmin in RFC3611 results in a Burst being a
   period of time during which the call quality is degraded to a similar
   extent to a typical PCM Severely Errored Second.

   The term Concealed Seconds defines a count of seconds during which
   some proportion of the media stream was lost through packet loss and
   discard. The term Severely Concealed Seconds defines a count of
   seconds during which the proportion of the media stream lost through
   packet loss and discardeds a specified threshold.

2.3 Numeric formats

   This report block makes use of binary fractions.  The terminology
   used is

   S X:Y, where S indicates a signed representation,
                X the number of bits prior to the decimal place and
                Y the number of bits after the decimal place.

   Hence 8:8 represents an unsigned number in the range 0.0 to
   255.996 with a granulatity of 0.0039.
   S7:8 would represent the range -127.996 to +127.996.












Clark                                                          [Page  3]
draft-ietf-avt-rtcphr-01.txt                                   July 2007



3   High Resolution VoIP Metrics Report Block

3.1 Block Description

   This block comprises a header and a series of sub-blocks.  The
   Map field in the header defines which sub-blocks are present.

   Header sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     BT=N      |   Map         |        block length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        SSRC of source                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Duration                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Basic Loss/Discard Metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Loss Proportion         |      Discard Proportion       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Number of frames expected                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Burst/Gap metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Threshold     |             Burst Duration (ms)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Gap Duration (ms)                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Burst Loss/Disc Proportion    |  Gap Loss/Disc Proportion     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Playout metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 On-time Playout Duration                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              On-time Active Speech Playout Duration           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Loss Concealment Duration                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Buffer Adjustment Concealment Duration           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


Clark                                                          [Page  4]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   Concealed Seconds metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Unimpaired Seconds                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Concealed Seconds                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Severely Concealed Seconds    | RESERVED      | SCS Threshold |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Delay and PDV metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Network Round Trip Delay      |       End System Delay        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       External Delay          |           Mean PDV            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Pos Threshold/Peak PDV     |     Pos PDV Percentile        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Neg Threshold/Peak PDV     |     Neg PDV Percentile        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   PDV Type    | JB/PLC config |          JB nominal           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          JB maximum           |          JB abs max           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     JB high water mark        |      JB low water mark        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Call Quality metrics sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               R-LQ            |             R-CQ              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              MOS-LQ           |            MOS-CQ             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | R-LQ Ext In   | R-LQ Ext Out  |RFC3550 Payload| Media Type    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | RxSigLev (IP) |RxNoiseLev (IP)|  Local RERL   |  Remote RERL  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | RxSigLev (Ext)|RxNoiseLev(Ext)|       Metric Status           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Vendor specific extension sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Vendor ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Vendor ID Src |Manuf Code Src |     Extension Block Length    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Clark                                                          [Page  5]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   |                    Vendor-specific extension data             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.2 Header
   Implementations MUST send the Header block within each High
   Resolution Metrics report.

   3.2.1 Block type
   Nine High Resolution VoIP Metrics blocks are defined

   mmm   = HR Metrics- Cumulative, Locally Generated
   mmm+1 = HR Metrics- Cumulative, Relayed from Remote IP Endpoint
   mmm+2 = HR Metrics- Cumulative, Relayed from Remote Ext Endpoint
   mmm+3 = HR Metrics- Cumulative,TBD
   mmm+4 = HR Metrics- Interval, Locally Generated
   mmm+5 = HR Metrics- Interval, Relayed from Remote IP Endpoint
   mmm+6 = HR Metrics- Interval, Relayed from Remote Ext Endpoint
   mmm+7 = HR Metrics- Interval, TBD
   mmm+7 = HR Metrics- Alert, Locally Generated
   mmm+9 = HR Metrics- Alert, Relayed from Remote IP Endpoint
   mmm+10 = HR Metrics- Alert, Relayed from Remote Ext Endpoint
   mmm+11 = HR Metrics- Alert, TBD

   The time interval associated with these report blocks is left to the
   implementation.  Spacing of RTCP reports should be in accordance
   with RFC3550. The specific timing of RTCP HR reports may be
   determined in response to an internally derived alert such as a
   threshold violation however the spacing of RTCP HR reports must not
   exceed that defined in RFC3550.

   Note that interval data may be derived by subtracting successive
   cumulative reports, which provides increased tolerance to potential
   loss of RTCP reports.

   When these block types are used in SDP offer-answer, semantics are
   as defined in RFC3611 [3], see clause 6. In particular, for
   "sendrecv" unicast connections, a block type in an offer indicates
   the offerer's wish to receive the specified block type. A block type
   in an answer indicates the answerer's wish to receive the specified
   block type.

   <Authors' note: need to review idea of negotiation of sub-blocks by
   SDP offer-answer?>

   3.2.2 Map field
   A Map field indicates the optional sub-blocks present in this
   report. A 1 indicates that the sub-block is present, and a 0 that
   the block is absent.  If present, the sub-blocks must be in the
   sequence defined in this document.
   The bits have the following definitions:

   0 Burst/Gap Metrics block
   1 Playout Metrics block

Clark                                                          [Page  6]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   2 Concealed Seconds Metrics block
   3 Call Quality Metrics
   4 Vendor specific extension block
   5-7 Reserved, set to 0

   3.2.3 Block Length
   The block length indicates the length of this report in 32 bit
   words and includes the header and any extension octets.

   3.2.4 SSRC
   The SSRC of the stream to which this report relates.  The value
   of this field shall follow the rules defined in RFC3550 with
   regard to the forwarding of RTP and RTCP messages.

   3.2.5 Duration
   The duration of time for which this report applies expressed in
   milliseconds.  For cumulative reports this would be the call
   duration. For interval reports this would be the duration of the
   interval.

3.3 Basic Loss/ Discard Metrics

   The Basic Loss/Discard Metrics sub-block MUST be present.

   This block reports the proportion of frames lost by the network and
   the proportion of frames discarded due to jitter.

   For sample-based codecs such as G.711, a frame shall be defined as
   an RTP frame. For endpoints that incorporate jitter buffers capable
   of fractional frame discard the proportion of frames discarded MAY
   be determined on the basis of the proportion of samples discarded.
   If Voice Activity Detection is used then the proportion of frames
   lost and discarded shall be determined based on transmitted packets,
   i.e. frames that contained silence and were not transmitted shall
   not be considered.

   A frame shall be regarded as lost if it fails to arrive within an
   implementation-specific time window.  A frame that arrives within
   this time window but is too early or late to be played out shall
   be regarded as discarded.  A frame shall be classified as one of
   received (or OK), discarded or lost.

   The Loss and Discard metrics are determined after the effects of
   FEC, redundancy (RFC2198) or other similar process.

   3.3.1 Loss Proportion
   Proportion of frames lost within the network expressed as a binary
   fraction in 0:16 format.  Duplicate frames shall be disregarded.

   3.3.2 Discard Proportion
   Proportion of voice frames received but discarded due to late or
   early arrival, expressed as a binary fraction in 0:16 format.


Clark                                                          [Page  7]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   3.3.3 Dead connection detection
   If no RTP, SID or RTP no-op packets have been received for a pre-
   specified time interval(for example ten seconds) then an RTCP HR
   dead connection indication MUST be sent.  This time interval may
   be changed during the connection, for example being longer at the
   start of a call.  Dead connection detection may be temporarily
   disabled during silence periods if VAD is used.
   A dead connection is indicated by setting both the frames lost
   and frames discarded fields above to 0xFFFF (equivalent to
   indicating 99.99% of packets have been both lost and discarded).
   Receipt of an RTCP HR block with either field set to a value other
   than 0xFFFF shall indicate that the remote endpoint HAS received
   some valid RTP packets.

   3.3.4 Number of frames expected
   A count of the number of frames expected, estimated if necessary.
   If no frames have been received then this count shall be set to
   zero, however if a dead connection is indicated then this count
   shall be regarded as undefined.

3.4 Burst/Gap metrics sub-block

   The Burst/Gap metrics sub-block MAY be present and if present MUST
   be indicated in the Map field.

   This block provides information on transient IP problems and is
   able to represent the combined effect of packet loss and packet
   discard. Burst/Gap metrics are typically used in Cumulative reports
   however MAY be used in Interval reports.

   The definition of Burst and Gap is consistent with that defined in
   the RFC3611 VoIP Metrics block, with the clarification that Loss
   and Discard are defined in terms of frames (as described in 3.3
   above). To accomodate the range of jitter buffer algorithms and
   packet discard logic that may be used by implementors, the method
   used to distinguish between bursts and gaps may be an equivalent
   method to that defined in RFC3611.  The method used SHOULD produce
   the same result as that defined in RFC3611 for conditions of burst
   packet loss, but MAY produce different results for conditions of
   time varying jitter.

   If Voice Activity Detection is used the Burst and Gap Duration
   shall be determined as if silence frames had been sent, i.e. a
   period of silence in excess of Gmin frames MUST terminate a burst
   condition.

   The Burst/Gap Metrics sub-block contains the following elements.

   3.4.1 Threshold
   The Threshold is equivalent to Gmin in RFC3611, i.e. the number of
   successive frames that must be received and not discarded prior to
   and following a lost or discarded frame in order for this lost or
   discarded frame to be regarded as part of a gap.

Clark                                                          [Page  8]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   3.4.2 Burst Duration (ms)
   The average duration of a burst of lost and discarded frames.

   3.4.3 Gap Duration (ms)
   The average duration of periods between bursts.

   3.4.4 Burst Loss/Discard Proportion
   The proportion of Lost and Discarded frames during Bursts expressed
   as a binary fraction expressed in 0:16 format.

   3.4.5 Gap Loss/Discard Proportion
   The proportion of Lost and Discarded frames during Gaps expressed
   as a binary fraction expressed in 0:16 format.

3.5 Playout Metrics sub-block

   The Playout Duration metrics sub-block MAY be present and
   if present MUST be indicated in the Map field.

   At any instant, the audio output at a receiver may be classified
   as either 'normal' or 'concealed'.  'Normal' refers to playout of
   audio payload received from the remote end, and also includes locally
   generated signals such as announcements, tones and comfort noise.
   Concealment refers to playout of locally-generated signals used to
   mask the impact of network impairments or to reduce the audibility
   of jitter buffer adaptations.

   This sub-block accounts for the source of the output audio, in
   millisecond units.  The on-time and active speech playout durations
   allow calculation of the voice activity fraction.  The on-time, and
   concealment durations allow calculation of concealment ratios. This
   sub-block distinguishes between reactive (due to effective packet
   loss) and proactive (due to buffer adaptation) concealment.

   3.5.1 On-time Playout Duration

   'On-time' playout is the uninterrupted, in-sequence playout of valid
   decoded audio information originating from the remote endpoint.
   This includes comfort noise during periods of remote talker silence,
   if VAD is used, and locally generated or regenerated tones and
   announcements.

   An equivalent definition is that on-time playout is playout of any
   signal other than those used for concealment.

   On-time playout duration MUST include both speech and silence
   intervals, whether VAD is used or not.  This duration is reported
   in millisecond units.

   3.5.2 On-time Active Speech Playout Duration

   The duration, in milliseconds, of the on-time playout duration

Clark                                                          [Page  9]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   corresponding to playout of active speech signals, if known. If
   not known, then this field is set to all ones (0x FFFF FFFF).

   In the absence of silence suppression, on-time active speech playout
   equals on-time playout (section 3.5.1).

   3.5.3 Loss Concealment Duration

   The duration, in milliseconds, of audio playout corresponding to
   Loss-type concealment.

   Loss-type concealment is reactive insertion or deletion of samples
   in the audio playout stream due to effective frame loss at the audio
   decoder. "Effective frame loss" is the event in which a frame of
   coded audio is simply not present at the audio decoder when
   required.  In this case, substitute audio samples are generally
   formed, at the decoder or elsewhere, to reduce audible impairment.

   Only loss-type concealment is necessary to form Concealed and
   Severely Concealed Seconds counts, in Section 3.6.

   3.5.4 Buffer Adjustment Concealment Duration (optional)

   The duration, in milliseconds, of audio playout corresponding to
   Buffer Adjustment-type concealment, if known. If not known, then
   this field is set to all ones (0x FFFF FFFF).

   Buffer Adjustment-type concealment is proactive or controlled
   insertion or deletion of samples in the audio playout stream due to
   jitter buffer adaptation, re-sizing or re-centering decisions within
   the endpoint.

   Because this insertion is controlled, rather than occurring randomly
   in response to losses, it is typically less audible than loss-type
   concealment (section 3.5.3).  For example, jitter buffer adaptation
   events may be constrained to occur during periods of talker silence,
   in which case only silence duration is affected, or sophisticated
   time-stretching methods for insertion/deletion during favorable
   periods in active speech may be employed.  For these reasons, buffer
   adjustment-type concealment MAY be exempted from inclusion in
   calculations of Concealed Seconds and Severely Concealed Seconds.

   However, an implementation SHOULD include buffer-type concealment in
   counts of Concealed Seconds and Severely Concealed Seconds if the
   event occurs at an 'inopportune' moment, with an emergency or large,
   immediate adaptation during active speech, or for unsophisticated
   adaptation during speech without regard for the underlying signal, in
   which cases the assumption of low-audibility cannot hold.  In other
   words, jitter buffer adaptation events which may be presumed to be
   audible SHOULD be included in Concealed Seconds and Severely
   Concealed Seconds counts.

   Concealment events which cannot be classified as Buffer Adjustment-

Clark                                                         [Page  10]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   type MUST be classified as Loss-type.

3.6 Concealed Seconds metrics sub-block

   The Concealed Seconds metrics sub-block MAY be present and if
   present MUST be indicated in the Map field.

   This sub-block provides a description of potentially audible
   impairments due to lost and discarded packets at the endpoint,
   expressed on a time basis analogous to a traditional PSTN T1/E1
   errored seconds metric.

   The following metrics are based on successive one second intervals as
   declared by a local clock.  This local clock does NOT need to be
   synchronized to any external time reference. The starting time of
   this clock is unspecified.  Note that this implies that the same loss
   pattern could result in slightly different count values, depending on
   where the losses occur relative to the particular one-second
   demarcation points. For example, two loss events occurring 50ms apart
   could result in either one concealed second or two, depending on the
   particular 1000 ms boundaries used.

   The seconds in this sub-block are not necessarily calendar seconds.
   At the tail end of a call, periods of time of less than 1000ms shall
   be incorporated into these counts if they exceed 500mS and shall be
   disregarded if they are less than 500mS.

   3.6.1 Unimpaired Seconds
   A count of the number of unimpaired Seconds that have occurred.

   An unimpaired Second is defined as a continuous period of
   1000ms during which no frame loss or discard due to late arrival has
   occurred.  Every second in a call must be classified as either
   OK or Concealed.

   Normal playout of comfort noise or other silence concealment
   signal during periods of talker silence, if VAD is used, shall be
   counted as unimpaired seconds.

   3.6.2 Concealed Seconds

   A count of the number of Concealed Seconds that have occurred.

   A Concealed Second is defined as a continuous period of 1000ms
   during which any frame loss or discard due to late arrival has
   occurred.

   Equivalently, a concealed second is one in which
   some Loss-type concealment (defined in section 3.6) has occurred.
   Buffer adjustment-type concealment SHALL not cause Concealed
   Seconds to be incremented, with the following exception. An
   implementation MAY cause Concealed Seconds to be incremented for
   'emergency' buffer adjustments made during talkspurts.

Clark                                                         [Page  11]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   For clarification, the count of Concealed Seconds MUST
   include the count of Severely Concealed Seconds.

   3.6.3 Severely Concealed Seconds
   A count of the number of Severely Concealed Seconds.

   A Severely Concealed Second is defined as a non-overlapping period
   of 1000 ms during which the cumulative amount of time that has been
   subject to frame loss or discard due to late arrival, exceeds the
   SCS Threshold.

   3.6.4 SCS Threshold
   The SCS Threshold defines the amount of time corresponding to lost
   or discarded frames that must occur within a one second period in
   order for the second to be classified as a Severely Concealed
   Second.  This is expressed in milliseconds and hence can represent
   a range of 0.1 to 25.5 percent loss/ discard.

   A default threshold of 50ms (5% effective frame loss per second)
   is suggested.

3.7 Delay and Packet Delay Variation (PDV) metrics sub-block

   The Delay and PDV metrics sub-block MUST be present.  This sub-block
   contains a number of parameters related to overall delay (latency),
   delay variation and the current jitter buffer configuration.

   3.7.1 Network Round Trip Delay (ms)
   The Network Round Trip Delay is the most recently measured value
   of the RTP-to-RTP interface round trip delay, typically determined
   using RTCP SR/RR. If no measured delay is available then this
   field shall be set to 0xFFFF.

   3.7.2 End System Delay (ms)
   The End System Delay is the internal round trip delay within the
   reporting endpoint, calculated using the nominal value of the jitter
   buffer delay plus the accumulation/ encoding and decoding / playout
   delay associated with the codec being used.

   3.7.3 External Delay (ms)
   The External Network Delay parameter indicates external network
   round trip delay through cellular, satellite or other types of
   network with significant delay impact, if known.  A value of
   0xFFFF shall indicate that the delay is unknown.
   If the external network is IP based then this parameter is
   typically determined using RTCP SR/RR.  If the external network delay
   is known and does not vary materially then this value may be
   provisioned.





Clark                                                         [Page  12]
draft-ietf-avt-rtcphr-01.txt                                   July 2007



   3.7.4 PDV/ Jitter Metrics

   Jitter metrics defined are:

    (i)  Mean PDV -
         For MAPDV this value is generated according to ITU-T G.1020.
         For interval reports the MAPDV value is reset at the start of
         the interval.
         For PPDV the value reported is the value of J(i) calculated
         according to RFC3550 at the time the report is generated.

         (16 bit, S11:4 format) expressed in milliseconds

    (ii) Positive Threshold/Peak PDV - the PDV associated with the
         Positive PDV percentile (16 bit, S11:4 format) expressed in
         milliseconds.  The term Positive is associated with packets
         arriving later than the expected time.

    (iii) Negative Threshold/Peak PDV - the PDV associated with the
          Negative PDV percentile (16 bit, S11:4 format) expressed in
          milliseconds. The term Negative is associated with packets
          arriving earler than the expected time.

    (iv) Positive PDV Percentile - the percentage of packets on the
         call for which individual packet delays were less than the
         Positive Threshold PDV expressed in 8:8 format.

    (v) Negative PDV Percentile - the percentage of packets on the call
        for which individual packet delays were more than the Negative
        Threshold PDV expressed in 8:8 format.

   If the PDV Type indicated is IPDV and the Positive and Negative PDV
   Percentiles are set to 100.0 then the Positive and Negative
   Threshold/Peak PDV values are the peak values measured during the
   reporting interval (which may be from the start of the call for
   cumulative reports).  In this case, the difference between the
   Positive and Negative Threshold/Peak values defines the range of
   IPDV.

   3.7.5 PDV Type
   Indicates the type of algorithm used to calculate PDV:

      PPDV  (0) according to RFC3550 [2],
      MAPDV (1) according to ITU-T G.1020 [4],
      IPDV  (2) according to ITU-T Y.1540 [6]
      Other values reserved

   For example:-

     (a) To report PPDV (RFC3550):
         Mean PDV = PPDV

Clark                                                         [Page  13]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

         Threshold PDV = Undefined (FF FF)
         PDV Percentile = Undefined (FFF)
         PDV type = 0 PPDV

     (b) To report MAPDV (G.1020):
         Mean PDV = average MAPDV
         Pos Threshold PDV = 50.0
         Pos PDV Percentile = 95.3
         Neg Threshold PDV = 50.0 (note - implies -50ms)
         Neg PDV Percentile = 98.4
         PDV type = 1 MAPDV

   Note that implementations may either fix the reported percentile
   and calculate the associated PDV level OR may fix a threshold PDV
   level and calculate the associated percentile. From a practical
   implementation perspective it is simpler to use the second of these
   approaches (except of course in the extreme case of a 100%
   percentile).

   IPDV, according to Y.1540 is the difference in delay between the
   i-th packet and the first packet of the stream.  If the sending
   and receiving clocks are not synchronized, this metrics includes
   the effect of relative timing drift.

   3.7.6 Jitter Buffer / PLC Configuration
   Indicates the configuration of the jitter buffer and the type of PLC
   algorithm in use.

        bits 0-3
              0 = silence insertion
              1 = simple replay, no attenuation
              2 = simple replay, with attenuation
              3 = enhanced
              Other values reserved

        bits 4-7
              0 = Fixed jitter buffer
              1 = Adaptive jitter buffer
              Other values reserved

   3.7.7 Jitter Buffer Size parameters
   Current nominal, maximum and absolute maximum jitter buffer size
   expressed in milliseconds, as defined in RFC3611.


3.8 Call Quality Metrics sub-block

   The Call Quality Metrics sub-block MAY be present and if present
   MUST be indicated in the Header Map field. This sub-block reports
   call quality metrics and estimates of signal, noise and echo levels.

   Signal, noise and echo metrics should be long term averages and
   should not be instantaneous values.

Clark                                                         [Page  14]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   3.8.1 Listening and Conversation Quality R Factors - R-LQ, R-CQ
   Expresses listening and conversational quality in terms of R factor,
   a 0-120 scaled parameter in 8:8 format.  The algorithm used to
   calculate R factor MAY be defined in the RTCP HR Configuration block
   (see Section 4).

   3.8.2 Listening and Conversation Quality MOS - MOS-LQ, MOS-CQ
   Expresses listening and conversational quality in terms of MOS,
   a 1-5 scaled parameter in 8:8 format.  The algorithm used to
   calculate MOS MAY be defined in the RTCP HR Configuration block.

   Note that R factors and MOS scores may be defined for both narrow
   and wide-band VoIP calls.  R Factors are continuous for narrow and
   wideband, hence the R factor for a wideband call may be higher than
   that for a narrowband call.  MOS scores are scaled relative to
   reference conditions and hence both narrow and wideband MOS occupy
   the same 1-5 scale; this can lead to a wideband MOS being lower than
   a narrowband MOS even though the listening quality may be higher.

   3.8.3 R-LQ Ext In and Out.
   These parameters provide call quality information for external
   networks - for example an external PCM or cellular network - or for
   a reporting call quality from the "other" side of a transcoding
   device or mixer - for example a conference bridge.

     R-LQ Ext In - measured by this endpoint for incoming
                        connection on "other" side of this endpoint

     R-LQ Ext Out - copied from RTCP XR message received from
                      remote endpoint on "other" side of this endpoint

   e.g. Phone A <---> Bridge <----> Phone B

   In XR message from Bridge to Phone A:-

        - R-LQ = quality for PhoneA ----> Bridge path

        - R-LQ-ExtIn = quality for Bridge <---- Phone B path

        - R-LQ-ExtOut = quality for Bridge -----> Phone B path

   This allows PhoneA to assess

     (i) received quality from the combination of

         R-LQ measured at A
               and
         R-LQ-ExtIn reported by the Bridge to A

     (ii) remote endpoint quality from the combination of

         R-LQ reported by the Bridge

Clark                                                         [Page  15]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

               and
         R-LQ-ExtOut reported by the Bridge

   3.8.4 RFC3550 RTP Payload Type

   The RTP Payload type field - as per RFC3551 and
   http://www.iana.org/assignments/rtp-parameters


   3.8.5 Media Type
      Media type -
                  0 = No media present
                  1 = Narrowband audio
                  2 = Wideband audio

   3.8.6 Received Signal and Noise Levels - IP side
   The received signal level during talkspurts and the noise level
   expressed in dBm0, for the decoded packet stream.

   3.8.7 Received Signal and Noise Levels - External
   The received signal level during talkspurts and the noise level
   expressed in dBm0, for the PCM side of a gateway, audio input
   from a handset or decoded packet stream for an IP-to-IP gateway.

   3.8.8 Local and Remote Residual Echo Return Loss
   The Local and Remote Residual Echo Return Loss (RERL) expressed in
   dB. The Local RERL is the echo level that would be reflected into the
   IP path due to line echo on the circuit switched element side of this
   IP endpoint if a gateway or acoustic echo if a handset or wireless
   terminal.

   The Remote RERL is the echo level that would be reflected into the
   remote IP endpoint from the network "behind" it, and would typically
   be measured at and reported from the remote endpoint. This value is
   included as it may be used in calculating the R-CQ and MOS-CQ values
   expressed in this report block.

   3.8.9 Metric Status
   Indicates the source of parameter values used in call quality
   calculation:

   Bit      Description                 Source

   0-1    Local IP side Signal/Noise Levels measured on the incoming
          decoded VoIP stream to this endpoint

              00 = assumed
              01 = measured for this call
              10 = measured across multiple calls on this port
              11 = measured across multiple ports

   2-3    Remote IP side Signal/Noise Levels reported by the remote
          IP endpoint through RTCP XR or equivalent

Clark                                                         [Page  16]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


              00 = assumed
              01 = measured for this call
              10 = measured across multiple calls on this port
              11 = measured across multiple ports

   4-5    Local Trunk side Signal/Noise Levels measured on the incoming
          PCM, Audio or non-IP side of this endpoint

              00 = assumed
              01 = measured for this call
              10 = measured across multiple calls on this port
              11 = measured across multiple ports

   6-7    Local Echo level measured in the incoming line/ trunk/
          handset direction at this endpoint after the effects of echo
          cancellation

              00 = assumed
              01 = measured for this call
              10 = measured across multiple calls on this port
              11 = measured across multiple ports

   8      Remote Echo level measured in the incoming line/ trunk/
          handset direction at the remote endpoint after the effects of
          echo cancellation and reported to this endpoint via RTCP XR
          or equivalent.

              0 = assumed
              1 = reported from remote endpoint

   9-15  Reserved

   For example, if this endpoint is "C" in the diagram below then the
   following definitions would apply.

   Endpoint B -----RTP-------> Gateway C <-----PCM-------> D
   "Remote"                    "Local"        "Trunk/PCM/External"

      Reporting endpoint is "C"

      Local IP side signal/noise metrics relate to signal/noise levels
      from decoded RTP packets received by C from B

      Remote IP side signal/noise metrics relate to signal/noise levels
      from decoded RTP packets received by B from C, and reported by B
      to C through RTCP XR or RTCP HR VoIP Metrics blocks

      Local Trunk side signal/noise metrics relate to signal/noise
      levels from the PCM signal received by C from D

      Local Echo level relates to the proportion of the signal passing
      from B to C to D that is reflected back to C at some point

Clark                                                         [Page  17]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

      between C and D or on the far side of D.  This would typically be
      electrical echo or acoustic echo.

      Remote Echo level relates to the proportion of the signal passing
      from D to C to B that is reflected back to B at some point
      between B and the user.  This echo level is typically measured at
      B and reported to C via RTCP XR or RTCP HR VoIP Metrics blocks.

3.9 Vendor Extension sub-block

   One or more Vendor Extension sub-blocks MAY be present and if present
   MUST be indicated in the Header Map field. Note that the map
   field does not indicate the number of vendor extension sub-blocks.
   This must be deduced from the length of the overall report block and
   the lengths of the Vendor Extension sub-blocks.

   Each vendor extension sub-block consists of an extension header and
   vendor-specific extension data. The extension header has the form
   Vendor ID, Vendor ID Source and Extension Block Length. The Extension
   Block Length is defined as including these extension header and
   extension data octets but does not include any subsequent vendor
   extension sub-blocks.  An implementation can skip over a
   vendor extension sub-block that it does not understand.

   The Vendor ID Source field indicates whether the four-octet Vendor ID
   is based on ITU T.35 or is an IANA private enterprise number. The
   designated values for these options are 1 and 2 respectively. If the
   Vendor ID Source field is assigned a value of 0, then all of the
   fields in the vendor extension sub-block with the exception of the
   Vendor ID Source field and the Extension Block Length field have
   proprietary definitions.

   If the Vendor ID is based on ITU-T Recommendation T.35, its first two
   octets either contain a country code from Annex A of ITU-T Rec. T.35
   followed by 0x00, or an escape code of 0xFF followed by a country
   code from Annex B of ITU-T Rec. T.35. The next two octets comprise a
   terminal provider code allocated by a national assignment authority
   (http://people.itu.int/~campos/t35/t35db.htm). This field is padded
   with leading zeros if necessary. If a vendor has multiple
   terminal provider codes in different registries (e.g. the H-series,
   T-series and V-series registries for the USA), then this provenance
   shall be indicated in the Manufacturer Code Source field. Possible
   values of the Manufacturer Code Source field are:

    0 Unspecified/don't care (may be used if there is no conflict)
    1 G-series registry
    2 H-series registry
    3 T-series registry
    4 V-series registry
    5-255 Reserved.

   If the four-octet Vendor ID is an IANA private enterprise number,
   then it is padded with leading zeros as necessary. Current private

Clark                                                         [Page  18]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   enterprise numbers (www.iana.org/assignments/enterprise-numbers)
   can be accommodated within two octets. The additional two octets
   provide for future growth.

4. RTCP HR Configuration Block

   This block type provides a flexible means to describe the algorithms
   used for call quality calculation and other data.  This block need
   only be exchanged occasionally, for example sent once at the start
   of a call.

   Header sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     BT=N      |   Map         |        block length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        SSRC of source                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Correlation Tag sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Tag Type      |  Tag length   |      Correlation Tag...       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   ... Correlation Tag                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Algorithm sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Alg type      | Descriptor len|       Algorithm descriptor... |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   ... Algorithm descriptor                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Vendor Specific Extensions sub-block
    0               1               2               3
    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Vendor ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Vendor ID Src |Manuf Code Src |     Extension Block Length    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Vendor-specific extension data             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


4.1 Header

   Implementations MUST send the Header block within each RTCP HR

Clark                                                         [Page  19]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   Configuration report.

   4.2.1 Block type

   One RTCP HR Configuration block is defined

   mmm+12   = RTCP HR Configuration Block

   The time interval associated with these report blocks is left to the
   implementation.  Spacing of RTCP reports should be in accordance
   with RFC3550 however the specific timing of RTCP HR reports may
   be determined in response to an internally derived alert such as a
   threshold crossing.

   4.2.2 Map field
   A Map field indicates the optional sub-blocks present in this
   report. A '1' indicates that the sub-block is present, and a '0' that
   the block is absent.  If present, the sub-blocks must be in the
   sequence defined in this document.
   The bits have the following definitions:

   0 Correlation Tag
   1 Algorithm Descriptor 1
   2 Algorithm Descriptor 2
   3 Algorithm Descriptor 3
   4 Algorithm Descriptor 4
   5 Vendor Specific Extension
   6-7 Reserved, set to '0'

   4.2.3 Block Length
   The block length indicates the length of this report in 32 bit
   words and includes the header and any extension octets.

   4.2.4 SSRC
   The SSRC of the stream to which this report relates.

4.3 Correlation Tag

   The Correlation Tag sub-block MAY be present and if present
   MUST be indicated in the map field. This tag facilitates the
   correlation of the high resolution VoIP metrics report blocks
   with other call-related data, session-related data or endpoint data.

   An example use case is for an endpoint to convey its version of a
   call identifier or a global call identifier via this tag. A
   flow measurement tool (sniffer) that is not call-aware can then
   forward the RTCP-HR reports along with this correlation tag to
   network management. Network management can then use this tag to
   correlate this report with other diagnostic information such as
   call detail records.

   The Tag Type indicates the use of the correlation tag. The following
   values are defined:

Clark                                                         [Page  20]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


     0:  IMS Charging Identity (ICID) subfield of the
         P-Charging-Vector header specified in RFC 3455 [7].

     1:  Globally unique ID as specified in ITU-T H.225.0
         (Table 20/H.225.0) [8].

     2:  Conference Identifier, per ITU-T H.225.0
         (Table 20/H.225.0) [8].

     3:  SIP Call-ID as defined in RFC 3261 [9].

     4:  PacketCable Billing Call ID (BCID) [10].

     5:  Text string using the US-ASCII character set [11].

     6:  Octet string.

     7-255: Future growth.

   Although the intent of this RFC is to list all currently known
   values of usable correlation tags, it is possible that new values
   may be defined in the future. An IANA registry of correlation
   tags is recommended.

   The tag length indicates the overall length of the sub-block in
   32 bit words and includes the tag type and length fields.

4.4 Algorithm descriptor

   The Algorithm Type sub-block MAY be present and if present
   MUST be indicated in the map field
   The Algorithm Type is a bit field which indicates which
   algorithm is being described.  The bits are defined as:-

      Bit 0:      MOS-LQ Algorithm
      Bit 1:      MOS-CQ Algorithm
      Bit 2:      R-LQ Algorithm
      Bit 3:      R-CQ Algorithm
      Bit 4-7:    Reserved and set to '0'

   The descriptor length gives the overall length of the descriptor in
   32 bit words and includes the algorithm descriptor and length fields.

   The algorithm descriptor is a text field that contains the
   description or name of the algorithm.  If the algorithm name is
   shorter than the length of the field then the trailing octets
   must be set to 0x00.

   For example, an implementation may report:

      Algorithm descriptor = 0xF0   - R and MOS algorithms
      Descriptor length = 3         - 3 words

Clark                                                         [Page  21]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

      Descriptor = "Alg X" 0x00     - description

   Call quality estimation algorithms may be defined for listening or
   conversational quality MOS or R factor.


4.5 Vendor Extension field

   One or more vendor specific extension blocks may be added, as defined
   in Section 3.10

5. Application of RTCP HR to RTP translators

   RFC3550 [2] defines three types of RTP systems which may source and
   sink RTP streams. These types are RTP end systems, RTP mixers, and
   RTP translators. 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. Translators have a wide range of possible reporting
   behaviours. This section describes in more detail the application of
   RTCP HR to RTP translators.

   An RTP translator is defined in RFC3550 [2] as "An intermediate
   system that forwards RTP packets with their synchronization source
   identifier intact". RFC3550 gives the following examples of
   translators: devices that convert encodings without mixing;
   replicators from multicast to unicast; and application-level filters
   in firewalls.

   For each session, an RTP translator has at least two RTP connections
   via different logical interfaces to network clouds, with logical
   separation based on a transport layer identifier (e.g. by UDP port)
   or at a lower layer (e.g. IP address, Ethernet VLAN identifier, ATM
   VCI, or physical interface). RTP traffic streams flowing via these
   two connections may be unicast or multicast, and may be
   unidirectional or bidirectional. Section 7 of RFC3550 [2] defines
   the RTCP processing in the translator which is required to maintain
   correct semantics for the RTCP communication between the RTP end
   systems involved in the connection.

   Where the RTP translator makes its own measurements of the incoming
   packet stream, section 7 of RFC3550 [2] allows it to send RTCP
   reception reports about what it has received. To do this, it is
   allowed to allocate an SSRC and a CNAME for itself.

   An RTP translator has several potential sources of information about
   transport and application quality in a session. These include

      o RTCP (including XR and HR) reports received from RTP end
       systems and mixers


Clark                                                         [Page  22]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

      o RTCP (including XR and HR) reports received from other
       translators

      o Measurements made locally on incoming RTP streams at the
       translators' interfaces

   In general, it is a matter of policy whether each of these types of
   information should be reported or forwarded by the translator towards
   neighbouring RTP systems involved in the same session. The objective
   of this policy may be to ensure that sufficient information is
   available to support network and service management at RTP systems,
   whilst avoiding excessive RTCP processing.

   Where a translator forms a boundary between service providers'
   domains, a provider may wish to apply policy to restrict the release
   of network performance information towards the provider's peer. This
   suggests that policy controlling reporting and forwarding of RTCP
   information (including XR and HR) MAY be configurable differently
   for each network interface, and may be chosen differently for each
   session if the translator is capable of this level of control. This
   allows certain types of RTCP reports for the session
   to be sent outwards via one subset of the translator's interfaces
   involved in the session, whilst restricting reporting and forwarding
   outwards via another subset.

   The following behaviours are potentially useful at a translator:

     o RTCP [2] reports received from an upstream RTP end system
      or mixer SHOULD be forwarded towards the downstream RTP end
      systems or mixers involved in the session. This behaviour is
      RECOMMENDED to maintain the integrity of the RTCP connection
      between the RTP end systems involved in the connection. We call
      this behaviour "a" to aid discussion below of the examples of
      end-to-end capabilities.

     o RTCP XR and RTCP HR reports received from an upstream RTP end
      system or mixer MAY be forwarded towards the downstream RTP
      end systems or mixers involved in the session. We call this
      behaviour "b".

     o The results of measurements made on an RTP stream received at
      one of the translator's network interfaces MAY be sent out
      as RTCP reports towards neighbouring RTP systems, either
      upstream in the direction towards the RTP system which
      originated the RTP stream (behaviour "c1"), or downstream in the
      direction towards the RTP system(s) which will receive the
      translated RTP stream (behaviour "c2"), or both upstream and
      downstream (described as behaviour "c1+c2").

     o RTCP XR and RTCP HR reports received from an upstream RTP
      translator MAY be forwarded towards the downstream RTP
      end systems or mixers involved in the session. We call this
      behaviour "d".

Clark                                                         [Page  23]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   NOTE: Behaviour "a", "b", "c" and "d" may be further classified in
      a) transparent forwarding ("a_t", "b_t", "c_t", "d_t") and
      b) forwarding with modification of RTCP fields ("a_m", "b_m",
         c_m", "d_t"), dependent on the specific, VoIP call-individual
         mode of operation of the RTP translator (see also below note
         at the end of clause 5.1.1). The detailed behaviour is
         inherent to the RTP translator configuration, thus orthogonal
         to the applied measurement mode.

   Material in section 6 illustrates how policies may be applied to
   control these behaviours and hence achieve potentially useful end-
   to-end reporting modes.

6. RTCP HR Report Multiplexing

   For RTP sessions that traverse one or more RTP translators,
   implementations MAY concatenate RTCP HR Report Blocks. The order
   of concatenated RTCP HR blocks shall be the same as the order
   in which network segments are traversed.

   This behaviour is described below with respect to the following
   example of a bidirectional unicast connection between RTP end
   systems A and Z using three translators J, K, and L:


             ----     -----     -----     -----     ----
            |   T|-->|1R 2T|-->|1R 2T|-->|1R 2T|-->|R   |
            | A  |   |  J  |   |  K  |   |  L  |   |  Z |
            |   R|<--|1T 2R|<--|1T 2R|<--|1T 2R|<--|T   |
             ----     -----     -----     -----     ----


   [Editors notes:
    (a) In above example, if segment A->J does not support HR then
        reports from K, L, Z should not be forwarded to A - for
        further study.
    (b) Suggest three options -
         - local only, i.e. (A->J) only
         - endpoint only, .e. (A->Z) only
         - all segments (A->J) and (J->K)....]

   In the first example (Figure 1) translators implement policies "a",
   "b", "c1+c2" and "d" of section 5. The result is that the connection
   operates in a mode called "Global Reporting" in which all
   measurements by translators are forwarded to end systems. Without
   concatenation, this set of policies results in a large number of
   separate RTCP packets.

   In Figure 2, concatenation is applied to reduce the number of
   separate RTCP packets, here to 3. The packet labelled "RTCP(A.R)"
   is the report from the end system, identified because its SSRC is
   the same as the SSRC of the RTP flow in the same direction. This is

Clark                                                         [Page  24]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   forwarded without concatenation. The packet labelled RTCP(J.1R,
   K.1R, L.1R) contains translator reports of measurements made on the
   RTP flow from A to Z, identified because they report the measured
   flow having SSRC equal to the SSRC of A. The packet labelled RTCP
   (J.2R,K.2R,L.2R) contains translator reports of measurements
   made on the RTP flow from Z to A, identified because they report
   the measured flow having SSRC equal to the SSRC of Z.

 A.R/A.T------>J.1R/J.2T---->K.1R/K.2T---->L.1R/L.2T------>Z.R/Z.T

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)    |
    |- - - - - - >|- - - - - - >|- - - - - - >|- - - - - - > |
    |             | RTCP(J.1R)  | RTCP(J.1R)  | RTCP(J.1R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |
    |             | RTCP(J.2R)  | RTCP(J.2R)  | RTCP(J.2R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |
    |             |             | RTCP(K.1R)  | RTCP(K.1R)   |
    |             |             |- - - - - - >|- - - - - - > |
    |             |             | RTCP(K.2R)  | RTCP(K.2R)   |
    |             |             |- - - - - - >|- - - - - - > |
    |             |             |             | RTCP(L.2R)   |
    |             |             |             |- - - - - - > |
    |             |             |             | RTCP(L.2R)   |
    |             |             |             |- - - - - - > |
    |             |             |             |              |

 A.T/A.R<------J.1T/J.2R<----K.1T/K.2R<----L.1T/L.2R<------Z.T/Z.R

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)    |
    |< - - - - - -|< - - - - - -|< - - - - - -|< - - - - - - |
    | RTCP(L.1R)  | RTCP(L.1R)  | RTCP(L.1R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    | RTCP(L.2R)  | RTCP(L.2R)  | RTCP(L.2R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    | RTCP(K.1R)  | RTCP(K.1R)  |             |              |
    |< - - - - - -|< - - - - - -|             |              |
    | RTCP(K.2R)  | RTCP(K.2R)  |             |              |
    |< - - - - - -|< - - - - - -|             |              |
    | RTCP(J.1R)  |             |             |              |
    |< - - - - - -|             |             |              |
    | RTCP(J.2R)  |             |             |              |
    |< - - - - - -|             |             |              |
    |             |             |             |              |

               Figure 1 The Global reporting mode



Clark                                                         [Page  25]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


 A.R/A.T------>J.1R/J.2T---->K.1R/K.2T---->L.1R/L.2T------>Z.R/Z.T

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)    |
    |- - - - - - >|- - - - - - >|- - - - - - >|- - - - - - > |
    |             |             |             | RTCP(J.1R,   |
    |             |             | RTCP(J.1R,  |      K.1R,   |
    |             | RTCP(J.1R)  |      K.1R)  |      L.1R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |
    |             |             |             | RTCP(J.2R,   |
    |             |             | RTCP(J.2R,  |      K.2R,   |
    |             | RTCP(J.2R)  |      K.2R)  |      L.2R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |

 A.T/A.R<------J.1T/J.2R<----K.1T/K.2R<----L.1T/L.2R<------Z.T/Z.R

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)    |
    |< - - - - - -|< - - - - - -|< - - - - - -|< - - - - - - |
    | RTCP(L.1R,  |             |             |              |
    |      K.1R,  | RTCP(L.1R,  |             |              |
    |      J.1R)  |      K.1R)  | RTCP(L.1R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    | RTCP(L.2R,  |             |             |              |
    |      K.2R,  | RTCP(L.2R,  |             |              |
    |      J.2R)  |      K.2R)  | RTCP(L.2R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    |             |             |             |              |

 Figure 2 Proposed multiplexing scheme of the Global reporting mode

   In the second example, (Figure 3) translators implement policies
   "a", "b", and "c1+c2" of section 5. The result is that the connection
   operates in a mode called "Local Reporting" in which measurements by
   each translator are sent to the nearest-neighbour RTP system in each
   direction but are not forwarded further. Even without concatenation,
   this set of policies results in a maximum of three RTCP packets in
   each direction on each link (per RTCP measurement cycle).
   Concatenation does not occur in this mode.


  A.R/A.T------>J.1R/J.2T---->K.1R/K.2T---->L.1R/L.2T------>Z.R/Z.T

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)   | RTCP(A.R)    |
    |- - - - - - >|- - - - - - >|- - - - - - >|- - - - - - > |

Clark                                                         [Page  26]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

    |             | RTCP(J.1R)  | RTCP(K.1R)  | RTCP(L.1R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |
    |             | RTCP(J.2R)  | RTCP(K.2R)  | RTCP(L.2R)   |
    |             |- - - - - - >|- - - - - - >|- - - - - - > |
    |             |             |             |              |
    |             |             |             |              |

  A.T/A.R<------J.1T/J.2R<----K.1T/K.2R<----L.1T/L.2R<------Z.T/Z.R

    |     RTP     |             |             |              |
    |<------------|-------------|-------------|------------->|
    |             |             |             |              |
    | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)   | RTCP(Z.R)    |
    |< - - - - - -|< - - - - - -|< - - - - - -|< - - - - - - |
    | RTCP(J.1R)  | RTCP(K.1R)  | RTCP(L.1R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    | RTCP(J.2R)  | RTCP(K.2R)  | RTCP(L.2R)  |              |
    |< - - - - - -|< - - - - - -|< - - - - - -|              |
    |             |             |             |              |

                  Figure 3 Local reporting mode



   Figure 4 depicts an example of the RTCP reports configuration of
   the proposed multiplexing scheme.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Header                            |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                          Sender info                          |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                       Report block of SSRC 1                  |
   |                                                               |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                            Chunk 1                            |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                           HR header                           |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                      Report blocks (Chunk 1)                  |
   |                                                               |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                                                               |
   |                             ...                               |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                            Chunk N                            |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                           HR header                           |

Clark                                                         [Page  27]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                      Report blocks (Chunk N)                  |
   |                                                               |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+

    Figure 4 An example of the multiplexed RTCP reports packet


7. SDP Signaling

7.1 Block type values: assignment of initial value "mmm"

   The assignment of the initial value "mmm" is under responsibility of
   "non-RTP means" (definition see clause 3/RFC 3550), which is
   typically SDP signalling.

7.2 Applicability for single port RTP/RTCP sessions
   The selection of a value range for HR block types is independent of
   the fact, whether RTP and RTCP using different ports or a single port
   (see draft-ietf-avt-rtp-and-rtcp-mux).

   Single port RTP/RTCP applications must ensure that RTP payload type
   79 is NOT used (because in conflict with RTCP XR packet type 207,
   see clause 4/draft-ietf-avt-rtp-and-rtcp-mux).

7.3 The SDP attribute "rtcp-hr"

   The "rtcp-hr" attribute is complementing/extending the "rtcp-xr" SDP
   attribute as defined in clause 5.1/RFC3611.

   <Note: this clause is so far a placeholder, assuming that
   the rtcp-xr attribute is not sufficient for RTCP HR. For further
   study.>

7.4 Usage in Offer/Answer

   See clause 5.2/RFC3611.

   <Note: a correspondent modification would be required
    dependent on "rtcp-hr" attribute. For further study.>

7.5 Usage Outside of Offer/Answer

   See clause 5.3/RFC3611.

   <Note: a correspondent modification would be required dependent on
   "rtcp-hr" attribute. For further study.>

8. Practical Applications

8.1 Overview

Clark                                                         [Page  28]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   The objective of this section is to identify a number of cases in
   which there could potentially be some ambiguity in the application
   of the report blocks defined above or some exceptions to the
   defined operation of the metrics.

8.2 Supplementary Services: Call Hold and Transfer

   8.2.1 General
   Supplementary services are under control of call/session control
   protocols like SIP. Such signaling protocols are acting also as
   "non-RTP means" (definition see clause 3/RFC 3550) in such service
   scenarios.
   The "northbound" served user instance for RTCP HR data is typically
   "co-located" to the served user instance of the call/session
   control protocol controlling the supplementary service. This allows
   to correlate in principle supplementary service control events with
   RTCP HR measurements in such network elements (like a SIP UA, SIP
   proxy, application server, etc.).
   Thus, the correlation between RTP/RTCP session control and
   supplementary service control allows basically the minimization of
   potential ambiguity.

   Below sub-clause providing some additional notes dependent on
   specific supplementary services.

   8.2.2 Supplementary Service: Call Transfer
   A successful call transfer means that an initial call between A and
   B is transferred to a call between C and B. This means that the RTP
   end system A is "replaced" by RTP end system C, accompanied by all
   correspondent changes in a RTP/RTCP endpoint (e.g., SSRC for A
   "replaced" by SSRC for B).

   In the scope of RTCP HR, it is therefore recommended to consider
   the two call phases (1st phase: call A-B, 2nd phase: call C-B) as
   separate measurement phases.
   Separate measurement phases could be e.g. based on interval metrics
   and the derivation of call phase-individual cumulative metrics by
   the "northbound" served user instance of RTCP HR, or by "resetting"
   the cumulative metrics in each call phase.

   8.2.3 Supplementary Service: Call Hold
   Call hold enables the served (holding) user A to put user B (with
   whom user A has an active call) into a hold condition (held user)
   and subsequently to retrieve that user again.
   During this hold condition, user B may be provided with media on
   hold (MoH). The served (holding) user A may perform other actions
   while user B is being held, e.g. consulting with another user C.

   In the scope of RTCP HR, it is recommended to consider the
   different call phases firstly as separate measurement phases (see
   also 8.2.2).


Clark                                                         [Page  29]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

8.3 Bitrate efficiency improvements: VAD/Silence Suppression based
   on Voice Activity Detection (VAD)Elimination

   A VoIP call is either enabled or disabled for silence suppression.
   This is typically a call-individual configuration parameter,
   negotiated during call establishment phase, and not changed anymore
   during the remaining call phase.
   An enabled silence suppression mode is basically affecting almost
   all high resolution VoIP metrics.
   The "northbound" served user instance of RTCP HR may require access
   to the information, whether silence suppression was enabled or
   disabled for that call, in order to indicate that mode of operation
   in the VoIP measurement data.

8.4 Endpoint configuration changes mid-call

   An endpoint relates to an RTP end system, which can be either
      a) located in VoIP user/terminal equipment (e.g. SIP UA), or
      b) located in VoIP gateway equipment (e.g. PSTN-to-RTP H.248
         media gateway), or
      c) located in VoIP media server equipment.

   8.4.1 Changes due to mid-call transitions between different voice
   codec types
   Voice codec type changes are reflected in RTP payload type changes,
   which are visible in the Call Quality metrics sub-block (see clause
   3.1).

   8.4.2 Changes due to mid-call transitions from VoIP to RTP-based
   VBDoIP
   There might be mid-call transitions from VoIP to dedicated modes of
   operation for voiceband data services support in case that at least
   one RTP end system is located in type (b) equipment.
   Mode transitions should be again reflected in RTP payload type
   changes in case of RTP-based VBD transport (e.g. like ITU-T Rec.
   V.152 for VBDoIP).

   Details are for further study.

   8.4.3 Changes due to mid-call transitions from VoIP to non-RTP
   -based VBDoIP
   UDPTL/UDP based realtime facsimile according ITU-T Rec. T.38 is an
   example for RTP-less transport of facsimile/modem signals.
   Any mid-call transition to T.38 would inherently terminated the
   RTP/RTCP session, thus the measurement phase.

   Details are for further study.

8.5 SSRC changes mid-call
   An SSRC change may be e.g. the consequence of a mid-call transport
   address change.

   Details are for further study.

Clark                                                         [Page  30]
draft-ietf-avt-rtcphr-01.txt                                   July 2007



9. IANA Considerations

   This document defines a series of new RTCP Extended Report (XR)
   block types within the existing Internet Assigned Numbers
   Authority (IANA) registry of RTP RTCP XR block types.  In
   addition, this document defines the need for an IANA registry
   of correlation tag types (Section 4.3)

10.  Security Considerations

   RTCP reports can contain sensitive information since they can provide
   information about the nature and duration of a session established
   between two endpoints.  As a result, any third party wishing to
   obtain this information should be properly authenticated and the
   information transferred securely.

11.  Contributors

   The authors gratefully acknowledge the comments and contributions
   made by Jim Frauenthal, Mike Ramalho, Paul Jones, Claus Dahm, Bob
   Biskner, Mohamed Mostafa, Tom Hock, Albert Higashi, Shane Holthaus,
   Amit Arora, Bruce Adams, Albrecht Schwarz, Keith Lantz, Randy Ethier,
   Philip Arden, Ravi Raviraj and Hideaki Yamada.

12.  Informative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119,   June 1997.

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

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

   [4]  "Performance parameter definitions for quality of speech and
        other voiceband applications utilizing IP networks"
        ITU-T Rec. G.1020, November 2003

   [5]  Annex A to G.1020: "VoIP Gateway specific reference points and
        performance parameters", Amendment 1 to ITU-T Rec. G.1020
        May 2004

   [6]  "Internet protocol data communication service - IP packet
        transfer and availability performance parameters:,
        ITU-T Rec. Y.1540, December 2002

   [7]  M. Garcia-Martin, E. Henrikson and D. Mills, "Private Header
         (P-Header) Extensions to the Session Initiation Protocol
         (SIP) for the 3rd-Generation Partnership Project (3GPP)",

Clark                                                         [Page  31]
draft-ietf-avt-rtcphr-01.txt                                   July 2007

        RFC 3455, January 2003.

   [8]  ITU-T H.225.0, "Call signalling protocols and media stream
        packetization for packet-based multimedia communication
        systems", July 2003.

   [9]  J. Rosenberg,  H. Schulzrinne, G. Camarillo, A. Johnston,
        J. Peterson, J. Peterson, R. Sparks, M. Handley, E. Schooler,
        "SIP: Session Initiation Protocol", June 2002.

   [10]   PacketCable(TM) Multimedia Specification,
         PKT-SP-MM-I02-040930, September 2004.

   [11]  Coded Character Set--7-Bit American Standard Code for
        Information Interchange, ANSI X3.4-1986.


Authors' Addresses

   Alan Clark
   Telchemy Incorporated
   2905 Premiere Parkway, Suite 280
   Duluth, GA  30097
   Email: alan@telchemy.com

   Amy Pendleton
   Nortel
   2380 Performance Drive
   Richardson, TX  75081
   Email: aspen@nortel.com

   Rajesh Kumar
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134
   Email: rkumar@cisco.com

   Kevin Connor
   Cisco Systems
   5590 Whitehorn Way
   Blaine, WA 98230
   Email: kconnor@cisco.com

   Geoff Hunt
   BT
   BT Adastral Park
   Martlesham Heath
   Ipswich IP5 3RE
   UK
   Email: geoff.hunt@bt.com


Full Copyright Statement

Clark                                                         [Page  32]
draft-ietf-avt-rtcphr-01.txt                                   July 2007


   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at ietf-
   ipr@ietf.org.

Acknowledgement

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).










Clark                                                         [Page  33]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/