[j-nsp] TCP

[Payam Chychi]

John,

Given you made this sound like a controlled test as you are 
troubleshooting a problem, normally its assumed that the tests are being 
done in a controlled state with replicated like for like as close as 
possible, specially with tcp tuning and non of the below would be 
applicable.

if you re randomly running a test and emailing a list asking for help, 
then yes, you are correct... it is very possible



On 2014-11-21, 12:49 PM, John Neiberger wrote:
> Actually, it's quite possible to have 400 in one direction and 60 in 
> the other. As an example, if you assume a 1 Gbps link with 20ms RTT, a 
> receiver using a 1 MB receive window might see between 300-400 Mbps, 
> whereas a receiver stuck with a 64 KB receive window on the same link 
> might see only 20 Mbps. It's pretty common, especially if one side is 
> an older OS.
>
> John
>
> On Fri, Nov 21, 2014 at 10:46 AM, Payam Chychi <pchychi at gmail.com 
> <mailto:pchychi at gmail.com>> wrote:
>
>     Hi Johan,
>
>     This sounds like a network issue, i'm actually dealing with the
>     same thing with one of my off-net providers.
>
>     Latency does of course play a factor however, latency has a
>     bidirectional influence and not asymmetric (as in 200ms rtr both
>     ways).
>     No reason as to why you should be getting 400 one way and 60 the
>     other.
>
>     Only thing comes to mind is different paths the packets may
>     travel, hitting a congestion/problem point.
>
>     You should grant your provider a maintenance window to take down
>     your circuit and do an end to end throughput test and make sure
>     they provide you with the results.
>     If they can get 1:1 capacity then look at your optics, interfaces,
>     any bundled links, and switch/routing fabric at both ends.
>
>     Cheers
>     Payam
>
>
>
>
>     On 2014-11-19, 1:18 PM, Johan Borch wrote:
>
>         Hi!
>
>
>         I'm doing some performance troubleshooting between two linux
>         systems, the
>         servers are located in each end of an L3VPN, with a bunch of
>         routers
>         between them.
>
>         Using Iperf and UDP I get ~1Gbps in both directions
>         Using iperf and TCP i get ~400Mbps in one direction and
>         ~60Mbps in the
>         other direction
>
>         Could this still be a network problem or should I dig on the
>         linux side?
>
>         Johan
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