Linux Router: TCP slow, UDP fast

[fw at deneb.enyo.de (Florian Weimer)]

> I'm losing the will to live with this networking headache ! Please feel free
> to point me at a Linux list if NANOG isn't suitable. I'm at a loss where
> else to ask.

The linux-net might be more appropriate indeed.

> With and without shaping and over different bandwidth providers using the
> e1000 driver for an Intel PRO/1000 MT Dual Port Gbps NIC (82546EB) I can
> replicate full, expected throughput with UDP but consistently only get
> 300kbps - 600kbps throughput _per connection_ for outbound TCP

I've seen this behavior as the result of duplex mismatches.

(The tcp settings are end system matters and do not affect how the
router forwards traffic.)