[c-nsp] Performance issue on link

Laurent Geyer geyer.laurent at gmail.com
Mon Apr 1 19:04:37 EDT 2013

Bandwidth delay product (BDP).

You'll find a bunch of articles out there searching for those terms. Adjusting the TCP windows size to compensate for the delay should help you achieve close to CIR.

You mention a Linux server (most distributions have TCP window scaling enabled), but I'll venture to say you're testing from a Windows client.

Windows systems are notoriously poor at dealing with BDP without some fine tuning.

BDP would certainly explain the discrepancy between UDP and TCP throughput.

On Mon, Apr 1, 2013 at 6:56 PM, CiscoNSP List <cisconsp_list at hotmail.com>

> Hi,
> We have a 40Mb link between 2 POPs - Latency ~65m/sec (No packet-loss)
> POP A Is a 7301 and 2960POP B is a 7200 and 4948
> 40Mb link is connected to the two switches (L2), and then a trunk link to both routers for all L3.
> Have a Linux server connected to both switches, and achieve the following performance:
> POP A -> POP B - 38.5Mb/secPOP B -> POP A - 38.5Mb/sec
> POP A -> POP B - ~20Mb/secPOP B -> POP A - ~12Mb/sec
> POP A -> POP B - ~38Mb/secPOP B -> POP A - ~16Mb/sec
> POP A -> POP B - ~30Mb/sec POP B -> POP A - ~16Mb/sec
> Any suggestions on why I am seeing poor performance with TCP transfers? (Especially POP B -> POP A direction) - I've tried adjusting the window size in IPERF but it actually made the results worse?
> Thanks in advance.
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