Date: Mon, 10 Feb 1997 10:04:38 +1100 (EST) From: "Daniel O'Callaghan" <danny@panda.hilink.com.au> To: Bill Fenner <fenner@parc.xerox.com> Cc: Jim Shankland <jas@flyingfox.com>, 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: <Pine.BSF.3.91.970210093512.427V-100000@panda.hilink.com.au> In-Reply-To: <97Feb9.125709pst.177476@crevenia.parc.xerox.com>
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On Sun, 9 Feb 1997, Bill Fenner wrote: > 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. Well, that really sounded like it would be solve the problem, but as the traces below show, it did not quite work. Is there any way to set Don't Fragment in traceroute? Danny cuckoo# traceroute www.chalmers.com.au. 1500 traceroute to nanguo.chalmers.com.au (203.1.96.5), 30 hops max, 1540 byte packets 1 border-ed3.aus.net (203.2.135.254) 5.677 ms 5.537 ms 5.497 ms 2 gw-eth0.aus.net (203.8.15.9) 8.101 ms 8.889 ms 8.439 ms 3 ml2.Melbourne.aone.net.au (203.12.177.216) 642.739 ms 421.222 ms 331.150 ms 4 mc3-reg2-5.Melbourne.aone.net.au (203.12.177.222) 293.630 ms 565.735 ms 430.286 ms 5 sc1-f10-ms2-8.Sydney.aone.net.au (203.102.128.245) 565.205 ms 396.279 ms 353.259 ms 6 bc1-f10-s1-2.Brisbane.aone.net.au (203.102.128.197) 447.261 ms 299.660 ms 279.950 ms [ there was a 30 second pause here, may not be relevant - my own router has been funny this morning.] 7 max1.Mackay.aone.net.au (203.61.61.129) 394.066 ms 399.916 ms 500.645 ms 8 eros.chalmers.com.au (203.1.96.4) 1944.422 ms 1539.953 ms 992.830 ms 9 nanguo.chalmers.com.au (203.1.96.5) 1532.759 ms 1483.978 ms 1640.986 ms cuckoo# traceroute www.chalmers.com.au. 1460 traceroute to nanguo.chalmers.com.au (203.1.96.5), 30 hops max, 1500 byte packets 1 border-ed3.aus.net (203.2.135.254) 12.436 ms 8.688 ms 12.119 ms 2 gw-eth0.aus.net (203.8.15.9) 58.326 ms 9.817 ms 13.526 ms 3 ml2.Melbourne.aone.net.au (203.12.177.216) 734.838 ms 712.851 ms 892.871 ms 4 mc3-reg2-5.Melbourne.aone.net.au (203.12.177.222) 709.052 ms 516.863 ms 336.940 ms 5 sc1-f10-ms2-8.Sydney.aone.net.au (203.102.128.245) 438.273 ms 392.142 ms 561.540 ms 6 bc1-f10-s1-2.Brisbane.aone.net.au (203.102.128.197) 708.056 ms 846.406 ms 758.388 ms 7 * max1.Mackay.aone.net.au (203.61.61.129) 433.632 ms 552.244 ms 8 eros.chalmers.com.au (203.1.96.4) 1054.622 ms 911.240 ms 947.772 ms 9 nanguo.chalmers.com.au (203.1.96.5) 1117.149 ms 1146.223 ms 1073.057 ms cuckoo#
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