Re: [xrblock] Benoit Claise's Discuss on draft-ietf-xrblock-rtcp-xr-post-repair-loss-count-10: (with DISCUSS and COMMENT)

Benoit Claise <bclaise@cisco.com> Mon, 16 February 2015 09:55 UTC

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Date: Mon, 16 Feb 2015 10:55:23 +0100
From: Benoit Claise <bclaise@cisco.com>
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To: Varun Singh <varun@comnet.tkk.fi>
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Cc: xrblock-chairs@ietf.org, The IESG <iesg@ietf.org>, xrblock@ietf.org, draft-ietf-xrblock-rtcp-xr-post-repair-loss-count.all@ietf.org
Subject: Re: [xrblock] Benoit Claise's Discuss on draft-ietf-xrblock-rtcp-xr-post-repair-loss-count-10: (with DISCUSS and COMMENT)
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On 16/02/2015 10:31, Varun Singh wrote:
> Hi Benoit,
>
> Thank you for reviewing the proposal, comments inline.
>
>
>> On 16 Feb 2015, at 11:14, Benoit Claise <bclaise@cisco.com 
>> <mailto:bclaise@cisco.com>> wrote:
>>
>>
>> ----------------------------------------------------------------------
>> DISCUSS:
>> ----------------------------------------------------------------------
>>
>> The following MUST versus RECOMMENDED is still an issue
>>
>>  post-repair loss count: 16 bits
>>
>>      Total number of packets finally lost after applying one or more
>>      loss-repair methods, e.g., FEC and/or retransmission, during the
>>      actual sequence number range indicated by begin_seq and end_seq.
>>      This metric MUST NOT count the lost packets for which repair might
>>      still be possible.
>>
>> This goes against
>>
>> 2. Interval report
>>
>>   Some implementations may align the begin_seq and end_seq number with
>>   the highest sequence numbers of consecutive RTCP RRs (RTCP interval).
>>   This is NOT RECOMMENDED as packets that are not yet repaired in this
>>   current RTCP interval and may repaired in the future will not be
>>   reported in subsequent reports.
>>
>
>
> The not recommended is if the receiver strictly aligns the begin_seq 
> and end_seq to
> the HSNs of consecutive reports.
> Example below:
>
> a) HSN is 20, begin_seq is 10 end_seq is 20.
> b) HSN is 30, begin_seq is 20 end_seq is 30.
> If 17 and 19 were packets lost and not yet repaired in a) and
> subsequently repaired in b) then it won't be reported because the
> sequence numbers do not belong in b)’s interval, but to the previous
> begin and end seq,
But you can not do that (Interval report, i.e. align the begin_seq and 
end_seq number with the highest sequence numbers of consecutive RTCP 
RRs, as in your example) according to that sentence ": This metric MUST 
NOT count the lost packets for which repair might still be possible.", 
right? What do I miss?
> therefore it is not recommended to align the begin_seq
> and end_seq to HSN of consecutive RTCP reports, unless repairs occur
> within that interval.
>
> Hence, (hopefully the next paragraph in the section clarifies) receivers
> should prefer begin_ and end_seq use longer than an RTCP interval.
>
>
Regards, Benoit