From owner-freebsd-hackers Thu Mar 26 15:33:54 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA11332 for freebsd-hackers-outgoing; Thu, 26 Mar 1998 15:33:54 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from implode.root.com (implode.root.com [198.145.90.17]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA11327 for ; Thu, 26 Mar 1998 15:33:46 -0800 (PST) (envelope-from root@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.5/8.8.5) with ESMTP id PAA27477; Thu, 26 Mar 1998 15:33:25 -0800 (PST) Message-Id: <199803262333.PAA27477@implode.root.com> To: Open Systems Networking cc: freebsd-hackers@FreeBSD.ORG Subject: Re: mssdflt size 512? or 536? In-reply-to: Your message of "Thu, 26 Mar 1998 14:54:36 EST." From: David Greenman Reply-To: dg@root.com Date: Thu, 26 Mar 1998 15:33:24 -0800 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >I was just thumbinb through the sysctl's of my freebsd -current box and a >bsdi 3.1 box, and comparing the set sizes and options inboth sysctl trees >on the OS's to the figures in vol. I of TCP/IP illustrated. > >What is the actual correct dflt MSS size? 512? or 536? >Im asking for purely academic reasons. >stevens says most BSD imlementations need to be multiples of 512 which >ours is (512), but he also says if no mss option is found on the other end >it defaults to 536. Whic is not a multiple of 512. I prefer ours of 512 >sticking to the fact it has to be a multiple of 512, but on the other hand >whats the point of setting our mssdflt to 512 if by default it goes to 536 >if no mss option is found on the connection? The official non-local network mss default for implementations that don't support Path MTU Discovery is 512. FreeBSD has PMTU Discovery, however, so the default starts at the interface MTU and goes down from there depending on what it learns from the network. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message