Re: [tcpm] Comments on draft-blanton-tcpm-3517bis-01

[Alexander Zimmermann <[e-mail]>]

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Hi,

Am 13.04.2011 um 22:11 schrieb Ilpo Järvinen:

> On Wed, 13 Apr 2011, Mark Allman wrote:
> 
>>> 2)
>>> If the incoming ACK is a duplicate acknowledgment and the TCP is
>>> 
>>>   not currently in loss recovery, the TCP MUST increase DupAcks by
>>>   one and take the following steps:
>>> 
>>>   (1) If DupAcks >= DupThresh, go to step (4).
>>> 
>>>   (2) If DupAcks < DupThresh but IsLost (SND.UNA) returns
>>>       true---indicating at least three segments have arrived above
>>>       the current cumulative acknowledgment point, which is taken
>>>       to indicate loss---go to step (4).
>>> 
>>> can we combine (1) and (2)? go to steps (4) if IsLost(SND.UNA) is
>>> true. I guess it depends on your answer of my first question.
>> 
>> My first hit here is that this could indeed be tightened up by just
>> getting rid of DupAcks and consulting IsLost (SND.UNA).  If that returns
>> true we enter loss recovery, if not we don't.  Do I understand that to
>> be what you're saying?
> 
> ...I see, now we're back in discussing what this DupAcks counter is 
> for, right? It was added in sack-recovery-entry ID and had proper 
> explation of its purpose there in place. The DupAcks counter is to handle 
> case where the sender is sending smaller than SMSS sized segments. 
> ...Perhaps it would be useful to explain it like the sack-recovery-entry 
> did because otherwise this will just keep confusing people?

Yes, please. I really recommend to add section 3.1 of 
draft-ietf-tcpm-sack-recovery-entry-01.txt to the draft.

Alex

//
// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
// Ahornstr. 55, 52056 Aachen, Germany
// phone: [phone], fax: [phone]
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