Now that I know where to look.. PMTU has caused me a
lot of headache
lately. I believe it could be the problem. Sending large packets to
44.135.179.28 yields no reply. tracepath does send back need to frag,
but when TTL expires at
amprgw.ucsd.edu. I believe
amprgw.ucsd.edu
should send back need-to-frag for higher TTLs as well.
That is always a bit tricky, often those packets *are* sent back but they
are blocked somewhere closer to the client, and/or the TCP stack of the
system does not process them in a reasonable way.
It is possible to work around that by adjusting the MSS of a TCP SYN
passing the point where outgoing MTU is smaller than incoming MTU
(incidentally something that I invented and implemented in NET in 1995,
but later almost any router and routing software started to support it)
so as a result the TCP segments sent by the endpoints will be smaller and
won't need to be fragmented.
Roger can do that on his own server, e.g. like this:
iptables -t mangle -A INPUT -p tcp --syn -j TCPMSS --set-mss 1400
iptables -t mangle -A OUTPUT -p tcp --syn -j TCPMSS --set-mss 1400
Or on a router/gateway along the path (using FORWARD instead of INPUT/OUTPUT).
However, I'm not convinced that this is the problem as the site works OK
for me over internet. Why wouldn't it work for Google then?
Rob