[c-nsp] Performance issue on link

[Laurent Geyer]

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.
—
Laurent

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

> 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:
> IPERF (UDP)
> POP A -> POP B - 38.5Mb/secPOP B -> POP A - 38.5Mb/sec
> IPERF (TCP)
> POP A -> POP B - ~20Mb/secPOP B -> POP A - ~12Mb/sec
> FTP
> POP A -> POP B - ~38Mb/secPOP B -> POP A - ~16Mb/sec
> WGET
> 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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