Quoting "Chris Samuel" <chris@csamuel.org>

On Tue, 26 Nov 2013 03:15:33 PM Petros wrote:

...

I don't understand it.. Why do the port 80 packets loop forever?

I think that's a problem with traceroute, I see the same behaviour from it but can successfully connect to that port on that host.

Thanks. I guess the router before was discarding port 80 packets because they were not proper HTTP packets. A F5 or so will do that when doing content inspection (one theory at least) In the meantime I found the problem. An error in the configuration down the line to the ISP limited the MTU to much less than 1492 or 1500 bytes (1458 if I remember correctly). Everything bigger was "eaten" by the provider network. And because most requests were small it only showed up in a few requests - and quite random so I had problems to see the issue. Well, the ISP could not connect to the ADSL modem/router for a week. So they never checked the configuration of the device they own and manage. I needed to point at the MTU problem repeatedly until they finally sent a technician - first to regain remote access to their own device. It took them 4 weekdays to do so. Before it was always "someone else's" problem.. Well, I refreshed my TCP debugging skills;-) Thanks all Peter