[j-nsp] TCP

[John Neiberger]

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> 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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