Subject: Re: fixing send(2) semantics (kern/29750)
To: Christos Zoulas <christos@zoulas.com>
From: Jonathan Stone <jonathan@dsg.stanford.edu>
List: tech-kern
Date: 03/26/2005 18:59:24
In message <20050326235313.E48372AC9C@beowulf.gw.com>,
Christos Zoulas writes:

>On Mar 27, 12:28am, manu@netbsd.org (Emmanuel Dreyfus) wrote:

[[ feedback points 1 through 6]]

You missed out:

7.  This whole suggestion is based on a fundamental misunderstanding
of how packet networks work, and of what SUS requires.  Not only is it
not necessary, its actively harmful in (for example) cases of
sustained congestion.

I don't have the prose skills to explain, to this audience, the
background behind this key conclusion in a short email.  For those who
understand Van Jacobson congestion avoidance (i.e., have read the
papers), one need say no more than repeat the observation that, under
heavy network load as evidenced by full queues, one is better off to
drop packets at their source than to try and resorces sending them
into the network, only to have them dropped later.

Or, much as Jason Thorpe commented recently about IP-over-TCP:
``Just don't do that''.