Date: Thu, 15 Jun 2000 18:23:36 -0400 From: "Patrick Bihan-Faou" <patrick@mindstep.com> To: "David Gilbert" <dgilbert@velocet.ca> Cc: <freebsd-net@freebsd.org> Subject: Re: "frag-anyways" knob. Message-ID: <010701bfd718$5917c460$040aa8c0@local.mindstep.com> References: <14664.60992.300592.147710@trooper.velocet.net>
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Hi, Is your problem related to the PPPoE bug that some people face where windows machine behind a NAT FreeBSD box seem to not be able to reach some web sites but do fine with others ? I have a friend who has that exact problem, all the packets get out no problem, but some don't come back because they are too big and the telco silently drops them. The easy fix is to set the MTU for windows to be something smaller than the MTU of the PPPoE link (somewhere around 1400). This has the effect of setting the MSS option in outbound TCP packets to something that the PPPoE link can handle. The server then honors that value and no fragmentation occurs. I am working on a patch for natd/libalias that modifies the MSS option for outbound TCP packets and sets that to a value acceptable for the PPPoE link. This means that you don't have to temper with the configuration of the machines on the local network and that the remote sites know what MTU you can handle (at the telco end). This is a hack in as much as the behaviour of some routers that you can't control is broken (not sending back the need frag indication or filtering them), but I believe that it should work. I am currently testing the hack at my friends place, once I get it working I'll submit the patch. Let me know if you want to use it. Patrick. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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