Re: TCP receive window behavior

From: James Knott (james.knott_at_rogers.com)
Date: 06/13/05 

Date: Sun, 12 Jun 2005 21:58:43 -0400

Anant Padmanath Mudambi wrote:

> Let me try and explain my question better. Suppose that the receiving
> application is fast enough that the receiver window is never reduced.
> Say the receiver has a receive buffer space of R bytes. Linux starts off
> by advertising a rcv wnd smaller than R and as the data comes in
> increases it to eventually settle at R. In this case I think min(cwnd,
> receiver wnd) should equal cwnd for all 'receiver wnd' < R. Otherwise the
> sender is throttled because of the way Linux increases 'receiver wnd',
> even though the receiver may have enough space to accept more data.
> If that's right then the receiver might as well start off by advertising a
> receive window of R.

As far as I know, the ramp up is controlled by the sender, not the receiver.
The receive windows is simply how much data the receiver is prepared to
leave unacknowledged. It is the senders responsibility to gradually
increase to that receive window value. There's a good description in one
of the books by Commer (IIRC), about the process. It describes not only
the ramp up of the transmit window, but also determining how long to wait
for acks and resetting the values should some data not be acked in time
etc. It pretty well covers all you're looking for.

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