[xrblock] proposed change to discard draft for the issue: duplication packet discards

Qin Wu <bill.wu@huawei.com> Thu, 16 August 2012 03:28 UTC

Message-ID: <53777A58EAB149DDA8395907307F29B0@china.huawei.com>
From: Qin Wu <bill.wu@huawei.com>
To: xrblock@ietf.org
Date: Thu, 16 Aug 2012 11:26:40 +0800
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Subject: [xrblock] proposed change to discard draft for the issue: duplication packet discards
Precedence: list

Hi,
Discard count metric block draft
(http://tools.ietf.org/html/draft-ietf-xrblock-rtcp-xr-discard-05)
supports reporting discards due to packet duplication.

It was suggested on the list to provide backgound information for duplication packet discards.
In the Vancouver meeting,we re-discussed duplication packet discards issue. It was pointed out
RTP packet duplication is not standard method and may break RTCP rules when we do RTCP
statistics reporting.

Combining these comments and incorporated proposed change from Varun earlier on the list,
I propose the following change to the defintion part of Discard Type.

OLD TEXT:
"
An endpoint MAY send only one of the discard types (early, late,
duplication packets discard) in one RTCP report or choose to
report early (DT=1) and late (DT=2), duplication packets discard
(DT=0) in separate block. It MAY also send the combined early and
late discard type (DT=2) in one RTCP compound packet, but not any
other combination of the three Discard Types. The endpoint MUST
not report the the total number of discarded packets covering all
three discard types. Instead, two separate report blocks should
be used to carry duplication packets discard and the combined
early and late discard respectively.
"
NEW TEXT:
"
An endpoint MAY report only one of the above four discard types

blocks in an compound RTCP report in a reporting interval. It MAY

also report a combination of discard types in a compound RTCP report

but not all combinations are valid. The endpoint MAY report

duplicate packet discard (DT=0) block with any other discard (DT=1,

2, or 3) block. Additionally, an endpoint MUST NOT report combined

discard (DT=3) block with early discard (DT=1) or late discard (DT=2)

report block. Note that duplicating RTP packets using RTP

replication may lead to breakage of RTP media streams or RTCP rules.

In order not to disrupt all the RTCP statistics, it is recommended

to duplicate RTP packets as described in [draft-ietf-avtext-rtp-duplication-00]

which will not cause breakage.

Also in the meeting, Kevin raised we should add some text to clarify the use cases and suggest to put into the section 1.4 applicability section.
I propose the following change to the section 1.4 as follows:
OLD TEXT:
"
1.4. Applicability

This metric is believed to be applicable to a large class of RTP
applications which use a jitter buffer.

"
NEW TEXT:
"
1.4. Applicability

This metric is believed to be applicable to a large class of RTP

applications which use a jitter buffer. For example, in one reporting

interval, when packets were received but dropped from the jitter buffer

due to either buffer underflow or buffer overflow or both, the discard count

metric can be used to report such packet discards. In some other cases(e.g.,

desktop video conferencing), duplicating RTP packets using RTP replication

may be used by media receiver for error concealment.

These duplicated packets can be counted as discards when they are not used and

dropped by application from jitter buffer, in such cases, the discard count

metric can be used to report such packet discards due to packet duplication.

"
Regards!
-Qin

[xrblock] proposed change to discard draft for th… Qin Wu
Re: [xrblock] proposed change to discard draft fo… Colin Perkins
Re: [xrblock] proposed change to discard draft fo… Alan Clark
Re: [xrblock] proposed change to discard draft fo… Colin Perkins
Re: [xrblock] proposed change to discard draft fo… Kevin Gross
Re: [xrblock] proposed change to discard draft fo… Colin Perkins
Re: [xrblock] proposed change to discard draft fo… Qin Wu
Re: [xrblock] proposed change to discard draft fo… Qin Wu
Re: [xrblock] proposed change to discard draft fo… Colin Perkins
Re: [xrblock] proposed change to discard draft fo… Qin Wu
Re: [xrblock] proposed change to discard draft fo… Colin Perkins