Re: Wierd metro WiFi problem

Hi Tyler,

Here is a link for UDP Bandwidth Test Utility

http://dast.nlanr.net/Projects/Iperf/

The error count seems quite small to have such drastic effect. Btw, what is
the time frame for the error count?

Also try changing your patch/cross cables.

Faisal


On 1/27/06, Tyler van Houwelingen <[email protected]> wrote:
>
> My netstat -s is below.  This is across 2 5GHz wireless hops (1 mile
> each),
> one of which has about 2Mbps of constant metro WiFi traffic.   I have
> about
> 10ms of latency back to the Main Internet router from my test.  Links
> quality is exceptional on both.
>
> Recieved packets discarded:  234
> Recieved packets delivered:   4180
> TCP Segments recieved:  2583
> TCP Segments Sent:  2271
> TCP Segments retransmitted:  15
>
> Can anyone recomend a nice tool or utility to watch the receive errors?
> They seem to be getting out of order or some other issue.
>
> Tyler
>
>
> ----- Original Message -----
> From: "Alberto Escudero-Pascual" <[email protected]>
> To: "Tyler van Houwelingen" <[email protected]>
> Cc: "Claude" <[email protected]>; "Alberto Escudero-Pascual"
> <[email protected]>; "SeattleWireless Talk List" <[email protected]>;
> "Juan Rivero" <[email protected]>; "Dave Tapscott" <[email protected]
> >;
> "Paul Stark" <[email protected]>; "Greg Vert"
> <[email protected]>; "Marc Van Houwelingen" <[email protected]
> >;
> "Jose Manuel Gonzalez Saez" <[email protected]>;
> <[email protected]>
> Sent: Thursday, January 26, 2006 1:09 PM
> Subject: Re: Wierd metro WiFi problem
>
>
> > Hi Tyler,
> >
> > What do you mean by "you add a little latency" to the download. Do you
> > artificially add delay into one of the hops? How is your testing PC
> > connected to the backbone?
> >
> > The best way to ensure that it is not a TCP implementation related
> > behavior is to run some kind of UDP stateless tests.
> >
> > Check the following link (Section 2.1), might give you some hints!
> >
> > http://www.29west.com/docs/THPM/tcp-latency.html
> >
> > Alberto
> >
> >
> >
> > On Thu, 2006-01-26 at 12:05 -0700, Tyler van Houwelingen 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.
> >>
> >> 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
> >
> >
>
>
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