Active work within IETF AVT related to QOSMON

Alan Clark alan at TELCHEMY.COM
Tue Oct 8 14:53:56 EDT 2002


The IETF AVT group is the responsible standards group for RTP/RTCP
(RFC1889).  RTCP already provides some end-to-end statistics on packet loss
and jitter and is in use within the industry to support VoIP management.  It
was recognized within AVT that RTCP does not provide enough information to
support monitoring of VoIP calls and diagnosis of typical problems.  Several
individual drafts related to the use of RTCP for extended metrics reporting
were combined together at the last (Yokohama) meeting to form a working
group draft.

The RTCP Reporting Extensions provides a series of useful metrics to
specifically support Voice over IP call management.  These include:-

- Packets lost (cumulative)
- Packets discarded due to jitter (cumulative)
- For loss and discard combined
  - mean burst length
  - mean burst density
  - mean gap length
  - mean gap density
- Round trip delay (mS) to RTP terminating points
- End system delay (mS) from RTP terminating point through to "analog"
interface
- Mean signal level during silence periods (dBo)
- Mean signal level during talkspurts (dBo)
- Doubletalk ratio
- R factor
- External network R factor (supports interconnection to other networks)
- MOS-LQ (estimated listening quality MOS)
- MOS-CQ (estimated conversational quality MOS)
- Jitter buffer parameters (fixed/adaptive, size)
- Packet loss concealment (silence insertion, simple extrapolation, robust)

Attached is a recent working draft of this document, this will be updated
and released in the very near future.

Alan Clark
Telchemy



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