Date: Thu, 29 Oct 2015 23:24:23 -0700 From: hiren panchasara <hiren@strugglingcoder.info> To: Randall Stewart <rrs@netflix.com> Cc: FreeBSD Transports <transport@FreeBSD.org> Subject: Maintaining dupack counter per hole (was: The trouble with sack..) Message-ID: <20151030062423.GB5261@strugglingcoder.info> In-Reply-To: <DA8A5844-8F11-42D5-B923-3F329203B867@netflix.com> References: <DA8A5844-8F11-42D5-B923-3F329203B867@netflix.com>
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(Something Randall and I discussed today)
On 10/07/15 at 12:17P, Randall Stewart via freebsd-transport wrote:
>=20
> 3) When we have more than one hole the goal of SACK was to retransmit eve=
ry time that
> a hole had 3 dup-acks so that one could recover multiple blocks that =
were lost. We just
> plain don?t track dup-acks per hole. We do continue to count, but we =
will wait to retransmit
> anything until after we have drained 1/2 the data in flight from the =
network at a minimum. And only then
> do we start incrementing cwnd (remember we crashed it to 1 MTU) so th=
at we can retransmit. There
> may be some other twists in the code that we are missing but this is =
what we believe (this could could
> probably win the C obfuscation contest if someone were willing to ent=
er it :-D)
Wondering if we can add this dupack counter in struct sackhole {} and
every time we process acks with sack in tcp_sack_doack(), we increment
this counter if the same hole appears again. And retransmit it on (or
after?) 3rd dupack.
Cheers,
Hiren
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