Subject: Unable to fetch http://www.netbsd.org - MSS problem?
To: None <current-users@netbsd.org>
From: Andreas Priebe <andreas.priebe@promos-consult.de>
List: current-users
Date: 11/11/2003 20:01:10
Hi,

I seem to be unable to access the NetBSD web pages due to some
MSS ignorance (?)

Here is a piece of tcpdump (originating from an access try):

# /usr/sbin/tcpdump -v -n -i ex3 host 204.152.184.116
tcpdump: listening on ex3
19:51:17.206995 62.80.20.1.53248 > 204.152.184.116.80: S [tcp sum ok] 3677457737:3677457737(0) win 16384 <mss 1452,nop,wscale 0,nop,nop,timestamp 0 0> (ttl 64, id 8021, len 60)
19:51:17.414917 204.152.184.116.80 > 62.80.20.1.53248: S [tcp sum ok] 416106623:416106623(0) ack 3677457738 win 32768 <mss 1460,nop,wscale 0,nop,nop,timestamp 3162155 0> (ttl 48, id 52432, len 60)
19:51:17.415014 62.80.20.1.53248 > 204.152.184.116.80: . [tcp sum ok] ack 1 win 17424 <nop,nop,timestamp 0 3162155> (ttl 64, id 8023, len 52)
19:51:20.366538 62.80.20.1.53248 > 204.152.184.116.80: P [tcp sum ok] 1:8(7) ack 1 win 17424 <nop,nop,timestamp 6 3162155> (ttl 64, id 8052, len 59)
19:51:20.589451 204.152.184.116.80 > 62.80.20.1.53248: . 1:1449(1448) ack 8 win 33580 <nop,nop,timestamp 3162162 6> (ttl 48, id 52532, len 1500)
19:51:20.614159 204.152.184.116.80 > 62.80.20.1.53248: . 1449:2897(1448) ack 8 win 33580 <nop,nop,timestamp 3162162 6> (ttl 48, id 52533, len 1500)
[and so on until timeout]

As you see my side announces MSS 1452 and if I understand Stevens correctly,
the other side (www.NetBSD.org) should not send segments greater than
this, but as you can see it send me 1500 Bytes packets, i.e. MSS=1460 -
right?

Is it me, who is wrong here? Anybody can enlighten me?

TIA,

Andreas

PS
I am almost sure, this is the wrong list, but I am unable at the moment
to find out a better one from www.netbsd.org :-(