Date: Mon, 11 Feb 2013 12:18:13 +0100 From: Andre Oppermann <andre@freebsd.org> To: Andrey Zonov <zont@FreeBSD.org> Cc: net@freebsd.org, Alfred Perlstein <bright@mu.org>, Randall Stewart <rrs@lakerest.net>, Kevin Oberman <kob6558@gmail.com>, John Baldwin <jhb@freebsd.org> Subject: Re: [PATCH] Add a new TCP_IGNOREIDLE socket option Message-ID: <5118D375.5000501@freebsd.org> In-Reply-To: <51177818.2090900@FreeBSD.org> References: <201301221511.02496.jhb@freebsd.org> <50FF06AD.402@networx.ch> <061B4EA5-6A93-48A0-A269-C2C3A3C7E77C@lakerest.net> <201302060746.43736.jhb@freebsd.org> <511292C9.4040307@mu.org> <E6BF2B74-175F-49D9-B480-8941294D2E19@neville-neil.com> <51166019.9040104@mu.org> <CAN6yY1uX__JDEk9dLdJr3pdE1u848jaF_jTn%2B_mrP05bXqm_Pw@mail.gmail.com> <51177818.2090900@FreeBSD.org>
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On 10.02.2013 11:36, Andrey Zonov wrote: > On 2/10/13 9:05 AM, Kevin Oberman wrote: >> >> This is a subject rather near to my heart, having fought battles with >> congestion back in the dark days of Windows when it essentially >> defaulted to TCPIGNOREIDLE. It was a huge pain, but it was the only >> way Windows did TCP in the early days. It simply did not implement >> slow-start. This was really evil, but in the days when lots of links >> were 56K and T-1 was mostly used for network core links, the Internet, >> small as it was back then, did not melt, though it glowed a >> frightening shade of red fairly often. Today too many systems running >> like this would melt thins very quickly. >> > > Google made many many TCP tweaks. Increased initial window, small RTO, > enabled ignore after idle and others. They published that, other people > just blindly applied these tunings and the Internet still works. In general Google does provide quite a bit of data with their experiments showing that it isn't harmful and that it helps the case. Smaller RTO (1s) has become a RFC so there was very broad consensus in TCPM that is a good thing. We don't have it yet because we were not fully compliant in one case (loss of first segment). I've fixed that a while back and will bring 1s RTO soon to HEAD. I'm pretty sure that Google doesn't ignore idle on their Internet facing servers. They may have proposed a decay mechanism in the past. I'd have to check the TCPM archives for that. -- Andre
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