Date: Mon, 16 Jul 2007 07:03:05 -0400 From: Randall Stewart <rrs@cisco.com> To: James Healy <jhealy@swin.edu.au> Cc: freebsd-net@freebsd.org, Andrew <andybrand@swin.edu.au>, Lawrence Stewart <lastewart@swin.edu.au> Subject: Re: Odd congestion window behaviour [ was: Draft email to freebsd-net ] Message-ID: <469B5069.6080706@cisco.com> In-Reply-To: <469AFE80.2090304@swin.edu.au> References: <469AF916.6090901@swin.edu.au> <469AFE80.2090304@swin.edu.au>
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James Healy wrote: >>This behaviour seems a little odd to us - can anyone shed some light on >>it? Our assumption is that the use of the hostcache is designed to >>increase performance where appropriate by seeding the initial cwnd based >>on past experience. >> >>For this section of code to return a cwnd that is successfully >>influenced by the hostcache, it would seem that the use of tp->snd_wnd >>should be avoided when the connection is still being initialised: >> Oh, one other comment I have on this.. This is the code that used to be buried with comments about Alman et.al. says this is ok to do... if I am remembering right... I.e. where we keep past connection state and use that as a reference for the initial cwnd. I asked Mark about this in the past.. and he said that his paper was mis-interpreted and this is incorrect behavior. If you have no connections up to a peer you should not use any past value for the cwnd... Thats why we don't do it in SCTP. I know a lot of O/S's do this.. but it is not sanctified IMO from the CC experts :-D R -- Randall Stewart NSSTG - Cisco Systems Inc. 803-345-0369 <or> 803-317-4952 (cell)
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