From owner-freebsd-stable Tue Jul 4 18:47:34 2000 Delivered-To: freebsd-stable@freebsd.org Received: from sabre.velocet.net (sabre.velocet.net [198.96.118.66]) by hub.freebsd.org (Postfix) with ESMTP id 400FE37B952 for ; Tue, 4 Jul 2000 18:47:23 -0700 (PDT) (envelope-from dgilbert@office.tor.velocet.net) Received: from office.tor.velocet.net (trooper.velocet.net [216.126.82.226]) by sabre.velocet.net (Postfix) with ESMTP id 6A67A137F08; Tue, 4 Jul 2000 21:47:20 -0400 (EDT) Received: (from dgilbert@localhost) by office.tor.velocet.net (8.9.3/8.9.3) id VAA62207; Tue, 4 Jul 2000 21:47:19 -0400 (EDT) (envelope-from dgilbert) From: David Gilbert MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <14690.37799.546582.824877@trooper.velocet.net> Date: Tue, 4 Jul 2000 21:47:19 -0400 (EDT) To: "Kevin Oberman" Cc: "Louis A. Mamakos" , David Gilbert , Joerg Micheel , freebsd-stable@FreeBSD.ORG Subject: Re: Ethernet MTUs > 1500? In-Reply-To: <200007042325.e64NPCn20451@ptavv.es.net> References: <200007040508.BAA59763@whizzo.transsys.com> <200007042325.e64NPCn20451@ptavv.es.net> X-Mailer: VM 6.75 under 20.4 "Emerald" XEmacs Lucid Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >>>>> "Kevin" == Kevin Oberman writes: Kevin> Louis has it exactly right. 802.3 was modified a couple of Kevin> years ago to allow for a maximum frame size of 1522 octets, up Kevin> from the original 1518. This was to allow the VLAN information Kevin> to fit in the frame. Kevin> Since the terminating switch/router should be removing this Kevin> information, the end system (and MTU) should be unaffected, but Kevin> many nets seem to not fully support the longer frames in their Kevin> infrastructure and probably lots of Internet routers don't Kevin> either. This is often a hardware issue, so the only fixes Kevin> available are to upgrade all hardware to support the added Kevin> octets or to reduce the MTU so that the frame size does not Kevin> exceed 1518. Kevin> In an enterprise, the upgrade is feasible, but in the Internet Kevin> backbone, if you are not extremely lucky to have all VLAN Kevin> supporting equipment along the path, the packet is fragmented Kevin> or dropped. And there is a LOT of equipment out there that does Kevin> not support VLANs. In this case, the BSD box is meant to be the terminator of the VLAN trunks. In this case, Linux (to use the awful L word) forwards 1500 byte packets into the VLANs. I just want my FreeBSD router to do the same. Dave. -- ============================================================================ |David Gilbert, Velocet Communications. | Two things can only be | |Mail: dgilbert@velocet.net | equal if and only if they | |http://www.velocet.net/~dgilbert | are precisely opposite. | =========================================================GLO================ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message