Subject: Quick question on delayed-ACKs and updating the congestion window.

From: "Amr A. Awadallah" <[email-masked]>
Date: Mon, 09 Nov 1998 12:35:11 -0800

Hi,

  Just wondering what is the "correct" way of increasing the congestion
window during congestion avoidance when delayed-ACKs are used, is it:

(1) Increase cwnd by 1 segment once cwnd segments are ACKed,

or

(2) Increase cwnd by 1 segment once cwnd ACKs are received.

They are both equivalent if delayed ACKs are not used. But if ACKs are
for every other received packet, then (2) will increase cwnd at half the
rate of one.

Which is correct, (1) or (2) ?

Thanks,

-- Amr

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From: Mark Allman <[email-masked]>
Date: Mon, 09 Nov 1998 22:58:44 -0500

>   So which is more popular in current implementations ?

I haven't surveyed implementations, but I think that most TCPs use
the MSS*MSS/cwnd formula, which effectivly yields option (2).
Certainly the BSD varieties (and decendants) that I play with often
do.

allman