[c-nsp] Effect of simultaneous TCP sessions on bandwidth

[Youssef Bengelloun-Zahr]

Hello John,

Yes, sorry but I forgot to mention that we have activated every possible
TCP extension on servers in order to support latency effects over long WAN
distances.

Plus, latency is garantied end-to-end : 5 ms.

Best regards.



2013/11/10 John Osmon <josmon at rigozsaurus.com>

> You don't mention latency for TCP windowing in your note.
>
> If you haven't thought about it already, look up "bandwidth-delay
> product" and see if that helps you in your troubleshooting.
>
>
> On Sun, Nov 10, 2013 at 06:42:53AM +0100, Youssef Bengelloun-Zahr wrote:
> > Hello community,
> >
> > Need your help and hands on experience to shed some light on some problem
> > I'm facing.
> >
> > We have contracted a Layer 2 ethernet connection hand-off between our DC
> > (Frankfurt) and a customer site (Hamburg) with a carrier.
> >
> > Carrier provides us with an ethernet MPLS pipe up to a DC in hamburg and
> > relies on a third party local loop provider to extend it up to customer
> > site. Nothing new under the sun here.
> >
> > We have been testing this connection because we think we are facing
> > bandwidth issues. Let me summarize our results :
> >
> >    - Carrier claims E2E Ethernet RFC2544 passed : we have been to check
> the
> > results and they seem OK,
> >
> >    - UDP traffic reaches up to 95 Mbits/s for one way streams (both ways)
> > and simaltaneous bi-directionnal streams,
> >
> >    - TCP traffic reaches up to 90 Mbits/s for one way streams (both
> ways),
> >
> >    - TCP traffic hits some kind of limit and isn't able to achieve more
> > than 40-60 Mbits/s in average      <=== That's the problem we are facing.
> >
> > One bit of information I think is relevant :
> >
> >     - FRA Handoff between our provider and our PE is using a GigE port,
> >
> >     - HBG Handoff between our provider and local-loop provider is using a
> > Fast ethernet ports between their facing equipments,
> >
> >     - CE in Hamburg is a Fast Ethernet port and is forced with 100 Full
> > duplex,
> >
> >
> > We have carried tests with multiple devices directly connected behind our
> > PE in FRA and carrier's CE in HBG, results are always the same.
> >
> > In the end, we connected servers directly in order to suppress any
> uneeded
> > equipments on the path, tests we're carried using iPerf and some other
> > tools.
> >
> > We have been debugging this, no improvement. We have tried everything,
> > disabling all policiers, etc.... nothing nails it !
> >
> > Our provider claims this is normal behavior for TCP. Does this sound
> normal
> > to you ?
> >
> > Thanks for your help.
> >
> > Best regards.
> > _______________________________________________
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>



-- 
Youssef BENGELLOUN-ZAHR