Date: Sun, 9 Feb 1997 12:57:05 PST From: Bill Fenner <fenner@parc.xerox.com> To: Jim Shankland <jas@flyingfox.com> Cc: bugs@freebsd.org, freebsd-isp@freebsd.org, bvt@mp.aha.ru, freebsd-questions@freebsd.org, robert@nanguo.chalmers.com.au Subject: Re: I give up! no ideas left. Message-ID: <97Feb9.125709pst.177476@crevenia.parc.xerox.com> In-Reply-To: Your message of "Sat, 08 Feb 97 22:52:01 PST." <199702090652.WAA07862@saguaro.flyingfox.com>
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In message <199702090652.WAA07862@saguaro.flyingfox.com> you write: >I receive the *second* data packet from you (covering bytes >1440:2049, or something like that), but I never get the first >(bytes 1:1440). Of course, my end immediately does an ACK 1 >to signal that it got an out-of-sequence packet; but to no >avail. That packet simply never arrives. So it looks like there's a router in the middle that drops big packets but doesn't return ICMP packet-too-big errors. This router is in violation of RFC1812 (but that never stops anyone). This is a problem with Path MTU Discovery as specified; it doesn't allow for a hop that simply discards packets with no notification. You can probably find this hop by using traceroute; "traceroute <host> 1500" will just start timing out at the hop that is not returning ICMP errors; then "traceroute <host>" and see what router that hop is. Contact the owner of the router and get them to configure it (or upgrade it) so that it replies properly when dropping a packet with DF set. Bill
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