Date: Tue, 28 Jan 1997 19:45:36 +0200 (EET) From: Petri Helenius <pete@sms.fi> To: hal@vailsys.com Cc: hackers@freebsd.org Subject: best mtu for lo0? Message-ID: <199701281745.TAA25913@silver.sms.fi> In-Reply-To: <32EE370F.7CDD@vailsys.com> References: <32EE370F.7CDD@vailsys.com>
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Hal Snyder writes: > While searching FreeBSD archived mail items, I found that > > Petri Helenius <pete@sms.fi> wrote: > > > What's your lo0 MTU? If it's the 16384 that some > > non-tcp-knowledgeable person put in sometime in the past > > I think what you are seeing is called "TCP deadlock" which appears when > > window size is equal or smaller than the MTU. This makes TCP to be > > stop-and-go protocol (remember XMODEM? or non-windowing kermit) and thus > > the troughput of the protocol is pretty horrible. This happens on ATM also > > if you are running with 4096 or 8192 window sizes and the RFC1577 default > > MTU of 9180. > > Fortunately not too many applications use the 127.0.0.1 address but use > > the loopback provided by the ethernet-interface. (and thus get the MTU of > > 1500) > > Is this correct? I notice 2.1.6-R sets MTU for lo0 to 16384. Should > this be reduced to 1500? Will it affect performance of aliased IP > addresses, for which a static route through lo0 is usually specified? Want me to comment on this (I'm not on the hackers list any longer though)? The above still stands true that if you set your TCPWIN < MTU you'll experience TCP 'deadlock' which ends up being of horrible performance. Pete
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