Re: iperf / ftp / http TCP poor performance in one direction (UDP good)
Hi
>Provider of the link is stating it is a tcp window issue
I think that would be a bit weird, TCP is a very robust protocol
capable to adapt pretty much any bandwidth / latency situations.
What are the specifications on the hosts? Maybe POPA has too little
RAM and can't allocate a big enough TCP window?
Can you use wireshark or some other tool to capture the TCP segments
and look at the advertised window?
Greetings, Guido.
On Fri, Apr 12, 2013 at 12:37 AM, John Elliot <johnelliot67@hotmail.com> wrote:
> Hi Guys,
>
>
> I have a 40Mb connection between 2 POPs, and 2 Debian servers connected at
> each end(L2, same broadcast domain) - I am seeing consistent poor
> performance with TCP in only one direction.
>
>
> Latency between the POP's is ~67m/sec
>
>
> POPA->POPB UDP(IPERF) - consistent 38.5Mb/sec
>
> POPA->POPB TCP(IPERF) - fluctuates ~30Mb/sec -> 32Mb/sec
>
> POPA->POPB TCP(FTP) - fluctuates ~30Mb/sec -> 32Mb/sec
>
> POPA->POPB TCP(WGET) - fluctuates ~30Mb/sec -> 32Mb/sec
>
> POPB->POPA UDP(IPERF) - consistent 38.5Mb/sec
>
> POPB->POPA TCP(IPERF) - fluctuates ~10Mb/sec -> 15Mb/sec
>
> POPB->POPA TCP(FTP) - fluctuates ~10Mb/sec -> 15Mb/sec
>
> POPB->POPA TCP(WGET) - fluctuates ~10Mb/sec -> 15Mb/sec
>
>
> Both Deb boxes are running the same kernel (2.6.32-5), and I have tried
> adjusting tcp window without seeing any improvements...all ports are running
> full duplex, and Im not seeing any errors/drops, nor packet-loss on the
> link.
>
>
> Any suggestions are greatly appreciated (Provider of the link is stating it
> is a tcp window issue) -If that is the case, if someone can provide some
> suggested tweaks/changes to the Deb servers, It would be fantastic!
>
> Cheers.
>
>
>
>
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