Re: Wierd metro WiFi problem

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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