From owner-freebsd-current Fri Jun 4 6:32:17 1999 Delivered-To: freebsd-current@freebsd.org Received: from enst.enst.fr (enst.enst.fr [137.194.2.16]) by hub.freebsd.org (Postfix) with ESMTP id E891214D4F; Fri, 4 Jun 1999 06:32:10 -0700 (PDT) (envelope-from beyssac@enst.fr) Received: from bofh.enst.fr (bofh-2.enst.fr [137.194.2.37]) by enst.enst.fr (8.9.1a/8.9.1) with ESMTP id PAA15589; Fri, 4 Jun 1999 15:32:03 +0200 (MET DST) Received: by bofh.enst.fr (Postfix, from userid 12426) id D3A9AD21A; Fri, 4 Jun 1999 15:32:02 +0200 (CEST) Message-ID: <19990604153202.A17563@enst.fr> Date: Fri, 4 Jun 1999 15:32:02 +0200 From: Pierre Beyssac To: Matthew Dillon , Poul-Henning Kamp Cc: current@FreeBSD.ORG Subject: Re: net.inet.tcp.always_keepalive on as default ? References: <20883.928262460@critter.freebsd.dk> <199906012202.PAA84865@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93.2i In-Reply-To: <199906012202.PAA84865@apollo.backplane.com>; from Matthew Dillon on Tue, Jun 01, 1999 at 03:02:47PM -0700 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tue, Jun 01, 1999 at 03:02:47PM -0700, Matthew Dillon wrote: > I think keepalive's could easily be turned on by default. At BEST, one > of the first things I did 5 years ago was to turn them on permanently > on all of our machines. I'd like to disagree on the "by default" part, on the following assumptions: 1. If you turn on keepalive by default, you will have to increase the keepalive timeout value well over the current 2 hours (at least that's what most people suggest to alleviate the concerns about having keepalives on) 2. Changing this default value of 2 hours will affect ALL applications. Many of them (and their users) are more or less expecting a 2 hours value. For example that's the case for Telnet: probably you don't want to wait for ONE WEEK before a connection dies if you are currently using keepalives! I don't see what this fuss is all about. If for _some_ big servers there are many dead connections around after a while (*), why don't THEY use a sysctl at boot-time to change the default state, rather than impose on the rest of us a change that might not be as innocuous as it looks? (*) In theory, for a FTP server, most such connections will be when the user does a PUT, not a GET. In a GET, the server has data to push and will timeout anyway. In the case of the control connection, there's a application timeout in most ftpds who close the connection after some configurable amount of time. > This used to be a HUGE argument in the days where networks were less > reliable and dialup lines were scarse. It is not an argument now, > however. Go explain that to my cable provider :-). Keeping a long-lived connection through them is a real challenge; keepalives on would make my life even more difficult. > Whatever we do, we should not start messing around with the internals > of the kernel trying to 'fix' a non-problem. Keepalives work just dandy > as they are currently implemented, we do not have to mess with it beyond > possibly changing the default in rc.conf. "possibly", but *only* as a last resort if there are good reasons for it, IMHO. But I haven't seen any such reason yet. I also think that having at least a kernel-wide (or better, having it configurable on a per-socket basis), dynamically configurable keepalive would be a good thing. -- Pierre Beyssac pb@enst.fr To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message