Subject: Re: Strange networking problem on i386
To: George Coulouris <glc5@cornell.edu>
From: Manuel Bouyer <bouyer@antioche.lip6.fr>
List: tech-net
Date: 11/10/1998 12:28:08
On Nov 9, George Coulouris wrote
> I've been having some strange networking problems under i386.
> I have a 486 running ipnat with 2 ne2000 clones. ne1 goes to the outside
> (a RoadRunner cable modem), ne0 goes to the inside hosts.
> 
> Symptom:
> I get bad performance on outbound tcp connections to certain
> machines, but not to others. The problem is consistent; ie, all connections
> to machine foo are slow, while all connections to machine bar are fast. It's
> not a routing problem, as I've tried the case where foo and bar are in the
> same domain and the same route is taken to both machines. Nor is it a
> congestion problem; an ftp to machine foo could go at 160k/s when I have an
> all-but-unsable telnet connection to machine bar, where again foo and bar
> are in the same domain.
> [...]

Did you make any stats at which OS are good, and which OS are bad for the
remote machine ?
There's known problems with, for example, path MTU discovery, because
ICMP messages are blocked by a firewall. Some OS ships with PMTU disc
enabled by default. Some also have window size negotiation problems ...

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
--