packetloss only on TCP

Whats thoughts on this.

Someone's connection (they on BT retail), has packetloss on TCP traffic to certian destinations, but not on udp or icmp. Which to me I can only think of one rationale explanation which would be some kind of traffic management dropping the packets. Of course BT retail no longer has traffic management on their unlimited packages (at least officially) so I am trying to find another reason. Of course also not ruling out shaping on the other isp's involved in the transit.

The packet loss seems to occur on all eu destinations that go over third party transit but any over direct peering are fine.

Today, or ongoing over a considerable period? All the time or at certain times?

Edited by RobertoS (Sun 14-Feb-16 23:58:15)

Why would a transit provider manage traffic?

capacity management? otherwise dont know.

But rather then asking me why would they do that do you have an idea why this pattern would be occurring?

not today only.

Seems to mostly be at what can be considered peak time, but is not limited to that time period, it has been observed occasionally e.g. early morning or early afternoon but 80% of the time its observed evenings or late afternoons.

Some scripted tests have been setup to see if its only on specific ports, as mainstream ports like port 80 have yet to be tested.

Edited by Chrysalis (Mon 15-Feb-16 01:00:49)

Are you sure there is no UDP packetloss?

UDP would not tell you if there was...

Could this be congestion management? By something that knows to focus on big TCP transfers for effective management, and not UDP?

Stuff like fq_codel would fit the bill.

Only needs to be implemented in the router at the congested link, down that third party transit.

Traffic management != Congestion management

In reply to a post by WWWombat:

Could this be congestion management? By something that knows to focus on big TCP transfers for effective management, and not UDP?

Stuff like fq_codel would fit the bill.

Only needs to be implemented in the router at the congested link, down that third party transit.

Traffic management != Congestion management

That would be a big no-no as a general rule. Running transit that hot is frowned upon and probably breaches the terms and conditions of the transit provider.

yeah I have tried various tests, and not seeing any dropped udp packets.

found the cause, tcp checksum offloading on the network card was causing the issues. So was nothing to do with any isp's.