From: Stephen Hemminger <shemminger@linux-foundation.org>
To: Lachlan Andrew <lachlan.andrew@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Herbert Xu <herbert@gondor.apana.org.au>,
shaoliu@princeton.edu, Douglas Leith <doug.leith@nuim.ie>,
Robert Shorten <robert.shorten@nuim.ie>,
netdev@vger.kernel.org
Subject: Re: [PATCH] tcp-illinois: incorrect beta usage
Date: Wed, 28 Nov 2007 16:43:31 -0800 [thread overview]
Message-ID: <474E0B33.2060108@linux-foundation.org> (raw)
In-Reply-To: <aa7d2c6d0711281625m44bf3ca3me188a7041d3421da@mail.gmail.com>
Lachlan Andrew wrote:
> Thanks Stephen.
>
> A related problem (largely due to the published algorithm itself) is
> that Illinois is very aggressive when it over-estimates the maximum
> RTT.
>
> At high load (say 200Mbps and 200ms RTT), a backlog of packets builds
> up just after a loss, causing the RTT estimate to become large. This
> makes Illinois think that *all* losses are due to corruption not
> congestion, and so only back off by 1/8 instead of 1/2.
>
> I can't think how to fix this except by better RTT estimation, or
> changes to Illinois itself. Currently, I ignore RTT measurements when
> sacked_out != 0 and have a heuristic "RTT aging" mechanism, but
> that's pretty ugly.
>
> Cheers,
> Lachlan
>
>
Ageing the RTT estimates needs to be done anyway.
Maybe something can be reused from H-TCP. The two are closely related.
next prev parent reply other threads:[~2007-11-29 0:44 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <aa7d2c6d0711261023m3d2dd850o76a8f44aef022f39@mail.gmail.com>
[not found] ` <001001c83063$9adbc9d0$d5897e82@csp.uiuc.edu>
2007-11-28 23:47 ` [PATCH] tcp-illinois: incorrect beta usage Stephen Hemminger
2007-11-29 0:25 ` Lachlan Andrew
2007-11-29 0:43 ` Stephen Hemminger [this message]
2007-11-29 5:26 ` Shao Liu
2007-12-03 22:52 ` [RFC] TCP illinois max rtt aging Stephen Hemminger
2007-12-03 23:06 ` Lachlan Andrew
2007-12-03 23:59 ` Shao Liu
2007-12-04 0:32 ` Stephen Hemminger
2007-12-04 1:23 ` Lachlan Andrew
2007-12-04 8:37 ` Ilpo Järvinen
2007-12-07 3:27 ` Lachlan Andrew
2007-12-07 11:05 ` Ilpo Järvinen
2007-12-07 12:41 ` David Miller
2007-12-07 13:05 ` Ilpo Järvinen
2007-12-07 18:27 ` Ilpo Järvinen
2007-12-08 1:32 ` David Miller
2007-12-11 11:59 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one (Was: Re: [RFC] TCP illinois max rtt aging) Ilpo Järvinen
2007-12-11 12:32 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one David Miller
2007-12-12 0:14 ` Lachlan Andrew
2007-12-12 15:11 ` David Miller
2007-12-12 23:35 ` Lachlan Andrew
2007-12-12 23:38 ` David Miller
2007-12-13 0:00 ` Stephen Hemminger
2007-12-15 9:51 ` SACK scoreboard (Was: Re: [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one) Ilpo Järvinen
2008-01-08 7:36 ` SACK scoreboard David Miller
2008-01-08 12:12 ` Ilpo Järvinen
2008-01-09 7:58 ` David Miller
2008-01-08 16:51 ` John Heffner
2008-01-08 22:44 ` David Miller
2008-01-09 1:34 ` Lachlan Andrew
2008-01-09 6:35 ` David Miller
2008-01-09 2:25 ` Andi Kleen
2008-01-09 4:27 ` John Heffner
2008-01-09 6:41 ` David Miller
2008-01-09 14:56 ` John Heffner
2008-01-09 18:14 ` SANGTAE HA
2008-01-09 18:23 ` John Heffner
2008-01-09 12:55 ` Ilpo Järvinen
2008-01-09 6:39 ` David Miller
2008-01-09 7:03 ` Andi Kleen
2008-01-09 7:16 ` David Miller
2008-01-09 9:47 ` Evgeniy Polyakov
2008-01-09 14:02 ` Andi Kleen
2007-11-29 14:12 ` [PATCH] tcp-illinois: incorrect beta usage Herbert Xu
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