From owner-freebsd-net@FreeBSD.ORG Sat Jan 4 20:41:01 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 37F2E754 for ; Sat, 4 Jan 2014 20:41:01 +0000 (UTC) Received: from mail-pa0-x22b.google.com (mail-pa0-x22b.google.com [IPv6:2607:f8b0:400e:c03::22b]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 036F51FE4 for ; Sat, 4 Jan 2014 20:41:00 +0000 (UTC) Received: by mail-pa0-f43.google.com with SMTP id bj1so17091568pad.2 for ; Sat, 04 Jan 2014 12:41:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wemm.org; s=google; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=ochH77LtGyaurLYIjeds6euOI4HA8nTOfG9FF7yviLI=; b=juxRLNYAAL6Q9w3NmeHNXLJ2nA+itDvusHUYjOhsXNgykA2WYkiAhQZTPNFfDMSXEp DZcVOQzi+1VSV0CYJUGZH2tVgxmYfjuWXhAevbiufo3QU9TRYj7tC5qChCW8ws/pCse1 Sy8O9AFsPCQZWqhpcRCV6Jq2nicKPO9L9+710= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=ochH77LtGyaurLYIjeds6euOI4HA8nTOfG9FF7yviLI=; b=F8vLBBkKhKDxOAQ1Sf+XW4J3jbUp+2kogmzO+2LJXsLUIOcS23sDtny3spym+Zy/Jv 99D/eJBuc4+0XiInOOjcVEBpX0Lp5ILI9VWCVBar0WsuqwBLFU9lbqMMPO0CB3cPQFTf /aT2VFo4qLUyBQe1tWFcOf+KU9YoFTMUNmOs9Kr7tzK4VZgvgVM9yTvBEK9kIy3IrTMp iMOsXIzRGmCrhCJ6fHe7qfdQ55D2NPkdMlZ/i+8ipx32glhy5K4ZH7zWMc+KyP3PIY4B jrDDczye/7W1LhoflfGKhUpnHNIUnYm9Nh3Hy6EDURT/N83P1j1fTk7y3Z0WdeTl4MPH moDw== X-Gm-Message-State: ALoCoQkUM1+CCMxDX2o6dxxZ8mB71ADphE3K5cxZ1ERCHHGCXyKMW+ylBAKamZvhfuiNRFVq4d62 MIME-Version: 1.0 X-Received: by 10.68.20.1 with SMTP id j1mr108912049pbe.148.1388868060497; Sat, 04 Jan 2014 12:41:00 -0800 (PST) Received: by 10.66.162.3 with HTTP; Sat, 4 Jan 2014 12:41:00 -0800 (PST) In-Reply-To: <52C85EED.801@wemm.org> References: <52C85537.7080307@wemm.org> <52C85EED.801@wemm.org> Date: Sat, 4 Jan 2014 12:41:00 -0800 Message-ID: Subject: Re: Long-haul problems - connections stuck in slow start From: Peter Wemm To: "freebsd-net@freebsd.org" Content-Type: text/plain; charset=ISO-8859-1 Cc: Gavin Atkinson , Andre Oppermann , Peter Wemm X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 04 Jan 2014 20:41:01 -0000 On Sat, Jan 4, 2014 at 11:20 AM, Peter Wemm wrote: > On 1/4/14, 10:38 AM, Peter Wemm wrote: >> We're seeing some unfortunate misbehavior with tcp over an intercontinental >> link. > > I forgot to mention, the socket buffers have been generously tuned for these > endpoints. They don't seem to be being used while the sender is in some sort > of limited transmit mode. > > When reading the tcpdumps, keep in mind the window scaling factor is 11 and > that's wasn't captured in the session. You'll have to manually compensate > when reading the mid-session dumps. > > XXX footnote: It seems turning SACK off makes a huge difference for this > connection. The server must have been running with sack disabled when it > was working and hadn't been saved in sysctl.conf. Turning sack off on the > server again has raised the throughput from 8K/sec to 32MB/sec. That's a > nice 400x speedup. > > I'm investigating. > It's still not solved. We just had a lucky break and the session ran fast for a while. SACK doesn't seem to be the variable. I'm looking at the duplicate acks in this trace from each end.. any clues where they're coming from? http://people.freebsd.org/~peter/acks.txt -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV Yes, I know, gmail sucks now. If you see this then I forgot. Habits are hard to break.