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

From: Mark Allman <[email-masked]>
Date: Mon, 09 Nov 1998 16:03:23 -0500

> (1) Increase cwnd by 1 segment once cwnd segments are ACKed,
> 
> or
> 
> (2) Increase cwnd by 1 segment once cwnd ACKs are received.

According to 2001.bis (we just submitted version -01, so it should
be in the archive soon), either of these are allowed.  That is, the
spirit of the congestion avoidance algorithm is that it should
increase cwnd by one segment per RTT.  You can do this using the
traditional method, which is basically adding 1/cwnd for every ACK.
This method adds about 1 segment to cwnd every RTT if delayed ACKs
are not used and roughly 1 segment for every 2 RTTs if delayed ACKs
are used.  Or, you can use another method (such as method (1)
outlined above).  There are two or three methods outlined in
2001.bis, but the basic idea is that you are allowed to somehow add
1 segment to cwnd every RTT.

However, a TCP that is more conservative and only increases the
window by 1 segment every other RTT is also specifically allowed by
2001.bis (i.e., if a TCP implementer thinks any of the algorithms is
too aggressive, throttling the window to something less than what
the standard algorithms would use is allowed).

allman

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From: Amr A Awadallah <[email-masked]>
Date: Mon, 09 Nov 1998 15:46:21 -0800

> be in the archive soon), either of these are allowed.  That is, the

  So which is more popular in current implementations ?

Thanks in advance,

-- Amr

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From: Neal Cardwell <[email-masked]>
Date: Mon, 9 Nov 1998 18:20:00 -0800 (PST)

>   So which is more popular in current implementations ?

Linux (2.0,2.1), (Free)BSD and Win95/NT use approach (2), i believe.

neal