Re: [Lsvr] [Tsv-art] Tsvart early review of draft-ietf-lsvr-l3dl-03

Joerg Ott <ott@in.tum.de> Tue, 26 May 2020 05:51 UTC

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To: Randy Bush <randy@psg.com>
Cc: tsv-art@ietf.org, lsvr@ietf.org, draft-ietf-lsvr-l3dl.all@ietf.org
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From: Joerg Ott <ott@in.tum.de>
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Subject: Re: [Lsvr] [Tsv-art] Tsvart early review of draft-ietf-lsvr-l3dl-03
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On 26.05.20 07:35, Randy Bush wrote:
>>>>>> 3. When the protocol applies fragmentation, should there be a note on
>>>>>> preventing bursts?
>>>>> likely part of this is our fault, as we did not mean 'fragmentation' in
>>>>> the classic "oops!  we found a hop with a small mtu."
>>>> I didn't take it to mean classic fragmentation but rather ALF-style
>>>> operation.  Still, this could generate bursts depending on how much
>>>> information there is to 'fragment'.
>>> yes, it is app level framing.  perhaps we should call it that explicitly
>>> or even segmentataion or some term less well known.
>>> do you perhaps have a specific suggestion?
>> Not really.  This all appears artificial if you need two or three
>> packets for app layer fragmentation.  Maybe one could write something
>> substantially improved along the lines of:
>> To prevent packet bursts, a sender SHOULD pace the transmission of
>> application layer fragmented data units as follows: A sender MAY
>> transmit up to K packets containing fragments in a burst and SHOULD
>> pace bursts ... (but how?)
> 
> ok.  i have stared at this three times today and have no bright ideas.
> i do not want to start pacing by measuring rtt or other known deep
> holes.  so i will try to think some more.
> 

One option could be to just have a note of warning.  Any ideas how big
your application layer messages will usually get...?