Date: Tue, 4 Jul 2000 21:47:19 -0400 (EDT) From: David Gilbert <dgilbert@velocet.ca> To: "Kevin Oberman" <oberman@es.net> Cc: "Louis A. Mamakos" <louie@TransSys.COM>, David Gilbert <dgilbert@velocet.ca>, Joerg Micheel <joerg@cs.waikato.ac.nz>, freebsd-stable@FreeBSD.ORG Subject: Re: Ethernet MTUs > 1500? Message-ID: <14690.37799.546582.824877@trooper.velocet.net> In-Reply-To: <200007042325.e64NPCn20451@ptavv.es.net> References: <200007040508.BAA59763@whizzo.transsys.com> <200007042325.e64NPCn20451@ptavv.es.net>
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>>>>> "Kevin" == Kevin Oberman <oberman@es.net> 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
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