Date: Sun, 6 Dec 1998 12:01:05 +1300 From: Joe Abley <jabley@clear.co.nz> To: Nate Williams <nate@mt.sri.com>, Ruslan Ermilov <ru@ucb.crimea.ua> Cc: Thomas David Rivers <rivers@dignus.com>, eischen@vigrid.com, dillon@apollo.backplane.com, hackers@FreeBSD.ORG, luigi@labinfo.iet.unipi.it, jabley@clear.co.nz Subject: Re: TCP bug Message-ID: <19981206120105.A9111@clear.co.nz> In-Reply-To: <199812021720.KAA06413@mt.sri.com>; from Nate Williams on Wed, Dec 02, 1998 at 10:20:54AM -0700 References: <199812021636.JAA06068@mt.sri.com> <199812021647.LAA09094@lakes.dignus.com> <19981202185808.A4604@ucb.crimea.ua> <199812021720.KAA06413@mt.sri.com>
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On Wed, Dec 02, 1998 at 10:20:54AM -0700, Nate Williams wrote: > > Some sites block ICMP and thus break PMTU discovery. > > Umm, if this is the case, why would we be having a problem with a > network segment with a smaller MTU not being able to send packets to a > network with a bigger MTU? You don't. You have a problem with inbound packets larger than your local MTU with the DF (do-not-fragment) bit sent. You should find you are sending packets out just fine; however your router is dropping inbound packets sized larger than the MTU. This is what it should do. Nothing broken at your end. However, to make the problem go away you either have to (a) fix all the sites on the intenet which presume an MTU of 1500 or greater, or (b) install a workaround. Changing your local MTU to 1500 is probably the easiest workaround. > It would seem to me that the small MTU > network connection would be the one having the problems, not the larger > MTU network connection. You're right. You're just not thinking four-dimensionally :) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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