Subject: [Tsvwg] SCTP counters during zero-window probing.

From: Karoline Malmkjær <[email-masked]>
Date: Wed, 24 Sep 2008 12:24:07 +0200

Hello list.

I have been asked to take my questions here after posting them on
sctp-impl.

I have been looking in RFC4960 for a rule that allows me the
clear the error counters during zero-window probing.

Basically, I can only find a rule that SCTP should not *increase*
the error counters if it receives packets from peer while
probing.  If no packets are received when the probe times out,
the counters are increased as usual.  And I cannot find any rule
that allows *clearing* the counters.

This would be fine, except that most people expect zero-window
probing to go on indefinitely.  However, if there is an
occasional loss on the line, the errors will accumulate, and
eventually, SCTP will time out.

So, when would the counters be cleared?  And, if there is a way
to clear the counters, why is the rule about not incrementing the
counters needed?  Would it be non-compliant to skip it (it is
rather messy to implement, so I would rather be rid of it)?

Thanks for your help.
  Karoline

-- 
Karoline Malmkjær, Software Developer
TietoEnator A/S, IP Solutions
www.tietoenator.com

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From: Randy Stewart <[email-masked]>
Date: Wed, 24 Sep 2008 07:01:29 -0400

Karoline:

The overall error counter should be cleared
when a SACK is received.. i.e. the one indicating
that you have a rwnd=0.

The actual destination counter should probably not
be cleared... as long as you are handling the dormant
case by still allowing sending of data to one of
the destinations. If you don't then I would also
suggest clearing the destination  error counter when you get
a probe response with rwnd=0 as well.

R

> rather messy to implement, so I would rather be rid of it)?

-----
Randall Stewart
[email-masked]

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From: Michael Tüxen <[email-masked]>
Date: Wed, 24 Sep 2008 14:42:42 +0200

Hi Randy,

I agree with you (as stated earlier on the implemeters list)...
Should we add an errata to RFC 4960?

Best regards
Michael