From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-24-ewr.dyndns.com (mxout-024-ewr.mailhop.org [216.146.33.24]) by lists.bufferbloat.net (Postfix) with ESMTP id 064FC2E034F for ; Wed, 2 Feb 2011 08:05:16 -0800 (PST) Received: from scan-21-ewr.mailhop.org (scan-21-ewr.local [10.0.141.243]) by mail-24-ewr.dyndns.com (Postfix) with ESMTP id CA6BD5D0109 for ; Wed, 2 Feb 2011 16:05:13 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 74.125.82.47 Received: from mail-ww0-f47.google.com (mail-ww0-f47.google.com [74.125.82.47]) by mail-24-ewr.dyndns.com (Postfix) with ESMTP id CEADE5D00B0 for ; Wed, 2 Feb 2011 16:05:06 +0000 (UTC) Received: by wwb39 with SMTP id 39so105019wwb.28 for ; Wed, 02 Feb 2011 08:05:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=XOiilFAVx/x8oDEtPJpaBFpF773d9EOAaP75NkIhOe4=; b=pnu1j1gx4XBFEqMTeOCgUHnzFGJuDnbuDjB9svbbGkZ25/Ua4jWswXRcwd8OUSq1J1 OXAHHI2l2F4hYpbsHNpdqaEzUM3R1kU/QMBnMc9KTvQR978wR6fHEacx5aUsqJ/pwtzw NTpNLLbfq4i7xSovwbp+W3A5OdVObo4DF4rSE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=f9Tq5qjzuYwCjQl87hEz33M0960S5H2uT191tkzqEZCotbdrL6rckWFKzGD74EPWSn 2gcJUiQrfFq47sXEBLqVF4ZqPe7eGx1YeDCxhMRHElbk2CpyRk/IsM/luvAUmdQFqgH0 hD2z/U4KsFMfKny8Cyz8oJcNeYRnZ9SgjkIhk= MIME-Version: 1.0 Received: by 10.227.134.69 with SMTP id i5mr9304974wbt.139.1296662705530; Wed, 02 Feb 2011 08:05:05 -0800 (PST) Received: by 10.227.2.208 with HTTP; Wed, 2 Feb 2011 08:05:04 -0800 (PST) In-Reply-To: <87bp2upinw.fsf@cruithne.co.teklibre.org> References: <87bp2upinw.fsf@cruithne.co.teklibre.org> Date: Wed, 2 Feb 2011 11:05:04 -0500 Message-ID: From: Justin McCann To: =?ISO-8859-1?Q?Dave_T=E4ht?= Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: bloat Subject: Re: [Bloat] TCP vegas vs TCP cubic X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Feb 2011 16:05:17 -0000 On Wed, Feb 2, 2011 at 10:20 AM, Dave T=E4ht wrote: > Can I surmise that TCP cubic is like a dragster, able to go really fast > in one direction down a straightaway, and TCP vegas more like an 80s > model MR2, maneuverable, but underpowered? There are some parameters to tune, essentially setting the number of packets you want queued in the network at any one time (see http://neal.nu/uw/linux-vegas/). I haven't messed with it much myself, but you might try to increase those just a bit -- if Vegas underestimates the queue size and the queue empties, you'll never get the throughput. Ideally there would always be exactly one packet in the bottleneck queue. But I think your results are pretty much expected with Vegas, since it uses the increase in queuing latency as an early congestion indicator. If everyone used it, we may be better off, but other congestion algorithms aren't fair to Vegas since they wait until there are packet drops to notice congestion. > On a failed hunch, I also re-ran the tests with a much larger > congestion window: > > echo /proc/sys/net/core/rmem_max > echo /proc/sys/net/core/wmem_max > > iperf -w8m -s > > To no net difference in effect. I think you mean larger send/receive buffers instead of congestion window? I'll bet the Vegas parameters are keeping the congestion window smaller than your send/receive buffer sizes, so they aren't limiting you in the first place, so no improvement. The web100 patches (web100.org) are great for getting into the details of how TCP is working. If you don't want to apply them yourself, you can try the Live CD of perfSONAR-PS (http://psps.perfsonar.net/). It might be useful to have an NDT (http://www.internet2.edu/performance/ndt/) server running on your home network, or use one at M-Lab. It doesn't need much resource-wise but the web100 patches. Justin