well, if the connection on the server's side is going-down you should see lines that look kinda like this in it's /var/log/messages
Dec 20 19:46:22 darkstar kernel: eth0: link down
Dec 20 19:46:24 darkstar kernel: eth0: link up, 100Mbps, full-duplex, lpa 0x41E1
Dec 20 19:46:58 darkstar kernel: eth0: link down
Dec 20 19:46:59 darkstar kernel: eth0: link up, 100Mbps, full-duplex, lpa 0x41E1
also, maybe post these parameters just to make sure they are sane:
there's others you could look at but i can't remember them right now, so this is just my $0.02...