Long-haul 100Mbps EPL circuit throughput issue

Bob Evans bob at FiberInternetCenter.com
Thu Nov 5 23:31:39 UTC 2015


I have seen that happen.

1st double check that the gear is truly full duplex....seems like it may
claim it is and you just discovered it is not. That's always been an issue
with manufactures claiming they are full duplex and on short distances
it's not so noticeable.

Try to perf in both directions at the same time and it become obvious.

Thank You
Bob Evans

> Hello NANOG,
> We've been dealing with an interesting throughput issue with one of our
> carrier. Specs and topology:
> 100Mbps EPL, fiber from a national carrier. We do MPLS to the CPE
> providing
> a VRF circuit to our customer back to our data center through our MPLS
> network. Circuit has 75 ms of latency since it's around 5000km.
> Linux test machine in customer's VRF <-> SRX100 <-> Carrier CPE (Cisco
> 2960G) <-> Carrier's MPLS network <-> NNI - MX80 <-> Our MPLS network <->
> Terminating edge - MX80 <-> Distribution switch - EX3300 <-> Linux test
> machine in customer's VRF
> We can full the link in UDP traffic with iperf but with TCP, we can reach
> 80-90% and then the traffic drops to 50% and slowly increase up to 90%.
> Any one have dealt with this kind of problem in the past? We've tested by
> forcing ports to 100-FD at both ends, policing the circuit on our side,
> called the carrier and escalated to L2/L3 support. They tried to also
> police the circuit but as far as I know, they didn't modify anything else.
> I've told our support to make them look for underrun errors on their Cisco
> switch and they can see some. They're pretty much in the same boat as us
> and they're not sure where to look at.
> Thanks
> Eric

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