Subject: Re: initial window size

From: Mark Allman <[email-masked]>
Date: Thu, 29 Mar 2001 16:46:31 -0500

>  Iam new to this. My doubt is this. With what criteria the intial
> window for TCP is calculated and set. From the tcp code of linux,
> I can interpret that the allowable receive buffer is set to a
> value 32767. The initial window should be less than this
> value. Can any one of u explain me why the initial window is
> chosen less than 32767 and how is that calculation go.

See RFC 2581: 

    The initial window should be 1 or 2 segments (each up to an
    MSS).  (This document also provides the spec. for the congestion
    control algorithms used to increase the window size).

See RFC 2414:

    The initial window may be 3 or 4 segments, depending on the size
    of the segments (basically as long as the 3 or 4 segments do not
    exceed 4380 bytes).

2581 is a proposed standard; 2414 is experimental.

allman

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Mark Allman -- NASA GRC/BBN -- http://roland.grc.nasa.gov/~mallman/

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From: Lloyd Wood <[email-masked]>
Date: Fri, 30 Mar 2001 14:48:27 +0100 (BST)

> 2581 is a proposed standard; 2414 is experimental.

Am I right in thinking that we can blame the existence of this on:
a. the MTU of edge system (good old ethernet) not scaling upward?
b. TCP's back-to-back busrtiness behaviour?

Fix either one of those, and an initial window of more than one
segment looks less compelling.

L.

<[email-masked]>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>