Subject: RE: [Tsvwg] SCTP: Data chunk in flight when a_rwnd = 0

From: [email-masked]
Date: Tue, 6 Nov 2001 01:15:51 +0200

Hi all,

	I think that the problem here is that the people understands the RFC
in the right way, but there is just that typo in section 6.2.

	For me, it is quite obvious that one shouldn't acknowledge a TSN if
it is unable to take it because there isn't any buffer space, and I guess
that this is what everybody thinks... But Brian is right when saying that
the first paragraph of section 6.2:

"
   The SCTP endpoint MUST always acknowledge the reception of each valid
   DATA chunk.
"

together with the case when a_rwnd = 0, is wrong... And I think that this is
a very nice catch and that Randall's Note right after that text will fix
this all... :-0

	It doesn't really matter if the receiver sends back a SACK or not,
as far as in that SACK it *doesn't* acknowledge the received (but dropped)
TSN. And that's in my opinion a quite simple modification to current RFC...
The probing mechanism should be still be there to avoid a deathlock when we
are not able to send, and the receiver is not sending us any SACK simply
because we are not sending any DATA...

	And about lowering cwnd... Well... Isn't it the whole problem that
the receiver wants the sender to stop sending data (probably as a precursor
to a changeover)? In that case, the intention is to tear down the
association later on, so why that matters? The TSNs are not lost since they
weren't ever acknowledged and it should be possible to retrieve them and
resend them through the new association created right after the changeover
has taken place... shouldn't them? :-/

	I might be loosing lots of things, but I think we are making a
mountain out of a molehill... :-0

	BR Iván Arias Rodríguez

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