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Date: Mon, 24 Mar 2014 01:07:28 -0700
Message-ID: <CALCpEUESZP5ZpN5gw2Xpe-Yi4BARObKKmAnO9pe39nObxXMQ_w@mail.gmail.com>
Subject: hostcache's effect on initcwnd calculation
From: hiren panchasara <hiren.panchasara@gmail.com>
To: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
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Host A:10000 talks to Host B:20000 (10000 and 20000 being ports) and
it gets logged in tcp's hostcache.

Now if a new connection happens between A:10001 and Host B:20000, the
initcwnd (initial congestion window) would not look at the CWND from
hostcache but will always use what we've set as tp->snd_cwnd in
cc_conn_init() of tcp_input.c - is this a correct assumption?

What I want to confirm is, whether hostcache has any effect on initial
congestion window of a new connection being setup.

>From my reading of the code, cc_conn_init() always happens before we
call tcp_hc_get() to get data out of hostcache to update other
parameters of a connection.

I do not see hc_entry->rmx_cwnd being actually used anywhere in
tcp_input.c while connection bring up.

Am I missing anything?

cheers,
Hiren