[3422] in linux-net channel archive
Re: MTU problems
daemon@ATHENA.MIT.EDU (really kuznet@ms2.inr.ac.ru)
Sun Jun 23 14:21:40 1996
From: inr-linux-net@ms2.inr.ac.ru (really kuznet@ms2.inr.ac.ru)
To: linux-net@vger.rutgers.edu
Date: 23 Jun 1996 21:59:54 +0400
Michael Lausch (mla@gams.co.AT) wrote:
: 16:46:19.305143 ppp-dialin2.gams.co.at.1022 > loki.gams.co.at.22: S
: 1298278750:1298278750(0) win 512 <mss 1460>
: 16:46:19.305143 loki.gams.co.at.22 > ppp-dialin2.gams.co.at.1022: S
: 1034541773:1034541773(0) ack 1298278751 win 31744 <mss 236>
How loki guessed that mss=236 ?
Besides that, this value is wrong, should be 196.
: 16:46:22.295810 loki.gams.co.at.22 > ppp-dialin2.gams.co.at.1022: S
: 1034541773:1034541773(0) ack 1298278751 win 31744 <mss 236>
: 16:46:22.335819 ppp-dialin2.gams.co.at.1022 > loki.gams.co.at.22: . ack 1
: win 31744 [tos 0x10]
: 16:46:22.335819 loki.gams.co.at.22 > ppp-dialin2.gams.co.at.1022: P
: 1:16(15) ack 1 win 31744 (DF) [tos 0x10]
: 16:46:22.375828 ppp-dialin2.gams.co.at.1022 > loki.gams.co.at.22: P
: 1:16(15) ack 16 win 31744 (DF) [tos 0x10]
: 16:46:22.375828 loki.gams.co.at.22 > ppp-dialin2.gams.co.at.1022: P
: 252:292(40) ack 16 win 31744 (DF) [tos 0x10]
: 16:46:22.415836 ppp-dialin2.gams.co.at.1022 > loki.gams.co.at.22: . ack 16
: win 31744 [tos 0x10]
Until now we did not see any packet with size > ppp mtu on ethernet.
PMTU discovery has not been yet started.
: 16:46:22.575872 truncated-ip - 44 bytes missing!193.46.122.142 >
: ppp-dialin2.gams.co.at: (frag 10725:256@1824) [tos 0x10]
: ......
loki sends truncated&garbled datagrams, loki believes that mtu=276
---> loki is broken or strongly misconfigured.
BTW loki is the only host on your picture that needs PMTU discovery.
Alexey Kuznetsov.
