Re: Wierd metro WiFi problem

On 1/26/06, Tyler van Houwelingen <[email protected]> wrote:
>
> I am contacting the best wireless minds I know to help with a bizarre
> issue that has us stumped.
>
> Situation:
> - We have 4 bonded T1 lines currently for our backbone, running a large
> (400 AP) metro WiFi network.
> - When connecting directly into the backbone router, we get 6M down, 6M up
> as expected.
> - However, when we begin to add a little latency between a testing PC and
> the backbone connection, the upload speed stays the same, but the download
> gets hammered.  With 10ms of average latency from the metro WiFi network
> side, the speed drops to 2M down and 5M up.  At 40ms, it is around 800k/5M.
> - The wireless communications are more than fine as we get 8M/8M back to
> our headquarters from anywhere in the metro WiFi network.  The problems only
> come from testing into the Internet.  We get the same goofy results when we
> disconnect the city network completely and just add latency in the lab.
> - We have run all the DrTCP (MTU, RWIN) like tricks which provides some
> improvement, but not much.
>
> Why would this additional latency kill the downloads so much?  I suspect
> the problem is with our backbone provider (Expedius) or some limitation
> of metro WiFi that worries me.  In our other metro WiFi network, we do not
> see this, but they all use a different backbone provider (AT&T).
>
> Any suggestions to debug/fix this would be very much appreciated.
>

Couple of thoughts:

Have you done packet captures of the speed tests from the various locations?


Possibly setup an NTOP box on span port at each of the various switches to
analyze traffic?

Is the provider doing any sort of rate limiting on their end? Is it possible
that something funky with the traffic coming from the wireless is causing
their rate limiting to freak out?

Are the wireless hops bridging at layer 2 or are they routing? If the first
can you configure the hops to route at layer 3 and see if the problem
persists or vice versa?

Usually traffic captures can explain what is causing weird behavior.

-Ken




tyler
>
>
>
> Tyler van Houwelingen
> Founder and CEO
> Azulstar Networks, Inc.
> 1051 Jackson, Grand Haven, MI 49417
> 1117 Rio Rancho Blvd 13, Rio Rancho, NM 87124
> 1-877-AZULSTAR
> www.azulstar.com
>
> _______________________________________________
> Talk mailing list
> [email protected]
> http://seattlewireless.net/mailman/listinfo/talk
>
>
>


--
Ken Caruso
[email protected]

_______________________________________________
Talk mailing list
[email protected]
http://seattlewireless.net/mailman/listinfo/talk