Date: Tue, 1 Jun 1999 18:47:57 +0000 (GMT) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: phk@FreeBSD.ORG (Poul-Henning Kamp) Cc: current@FreeBSD.ORG Subject: Re: net.inet.tcp.always_keepalive on as default ? Message-ID: <199906011847.LAA13583@gndrsh.aac.dev.com> In-Reply-To: <20883.928262460@critter.freebsd.dk> from Poul-Henning Kamp at "Jun 1, 1999 08:41:00 pm"
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> > Considering the number of hosts on the net today, which come and > go with no warning and with dynamic IP assignments, I would propose > that we disregard what the "old farts" felt about TCP keepalives, > and enable the sysctl net.inet.tcp.always_keepalive as default. > > Setting this will make all TCP connections send a probing ACK every > couple of hours if no other activity were present on the connection, > this enables the TCP stack to figure out if the other end has gone > or is still there. > > The typical symptom that you need this is that netstat shows many > connections which have been standing there for any amount of time > up to your uptime, simply because your machine is waiting to receive > something from the other end, and for all practical purposes, "the > other end" doesn't exist anymore. I have no problem with this, though the traffic load created by the aggregate base of installed FreeBSD boxes over the global internet might even be measurable :-). > > The argument against is that this will increas trafic and keep > dynamic lines up when they should otherwise have been allowed to > fall down. > > The former argument doesn't hold water, since we're talking about > a TCP segment per hour (or less) per connection. > > The second argument falls on the same reasoning in my book, I don't > know of any on-demand lines with a timeout longer than 10 minutes > anyway. Well, we run many at 1 to 3 hours, but then they have ``activity filters'' that could be tweaked to not consider these packets as real traffic so they would still timeout. I would rather save the connection table for things that are useful than save a few port/hours of connect time :-). This may have more drastic effects for others though. -- Rod Grimes - KD7CAX - (RWG25) rgrimes@gndrsh.aac.dev.com Accurate Automation, Inc. Reliable computers for FreeBSD http://www.aai.dnsmgr.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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