From: Chris Friesen <chris.friesen@genband.com>
To: Ben Greear <greearb@candelatech.com>
Cc: rick.jones2@hp.com, Stephen Hemminger <shemminger@vyatta.com>,
netdev <netdev@vger.kernel.org>
Subject: Re: TCP funny-ness when over-driving a 1Gbps link (and wifi)
Date: Thu, 26 May 2011 09:28:16 -0600 [thread overview]
Message-ID: <4DDE7190.3080503@genband.com> (raw)
In-Reply-To: <4DD6DE1C.8090607@candelatech.com>
On 05/20/2011 03:33 PM, Ben Greear wrote:
> I tried a different test today: 3 TCP connections between two
> wifi station interfaces (using ath9k). Each connection is
> endpoint configured to send 100Mbps of traffic to the peer.
>
> With a single connection, it does OK (maybe 250ms round-trip time max).
> With 3 of them running, round-trip user-space to user-space latency
> often goes above 3 seconds.
<snip>
> So, seems a general issue with over-driving links with multiple TCP
> connections. Doesn't seem like a regression, and probably not really
> a bug, but maybe the buffer-bloat project will help this sort of
> thing...
Given that one rule of thumb for the send buffer size is twice the
bandwidth delay product, it seems clear that on a wifi connection 3
seconds worth of buffering is excessive. I think I'd classify that as a
bug.
Chris
--
Chris Friesen
Software Developer
GENBAND
chris.friesen@genband.com
www.genband.com
prev parent reply other threads:[~2011-05-26 15:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 22:47 TCP funny-ness when over-driving a 1Gbps link Ben Greear
2011-05-19 23:18 ` Stephen Hemminger
2011-05-19 23:20 ` Ben Greear
2011-05-19 23:42 ` Ben Greear
2011-05-20 0:05 ` Rick Jones
2011-05-20 0:12 ` Ben Greear
2011-05-20 0:24 ` Rick Jones
2011-05-20 0:37 ` Ben Greear
2011-05-20 0:46 ` Rick Jones
2011-05-20 3:39 ` Ben Greear
2011-05-20 21:33 ` TCP funny-ness when over-driving a 1Gbps link (and wifi) Ben Greear
2011-05-26 15:28 ` Chris Friesen [this message]
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