Re: Wierd metro WiFi problem

Agreed, unfortunately this does not appear to be the case.  We can use the 
same interfaces and make the download speed change simply by increasing the 
latency between.  We look at the switches, routers, etc and there are no 
errors on the ports.

a hypothesis of the problem is that maybe with an upload, the latency and 
wireless hops are at the beginning of the link, causing any retransmissions 
to be immediate.  with a download, the latency and hops are at the end, 
potentially causing retransmissions.  We dont however, detect any 
retransmissions.

ty



----- Original Message ----- 
From: "Jack Unger" <[email protected]>
To: "SeattleWireless Talk List" <[email protected]>
Sent: Thursday, January 26, 2006 12:50 PM
Subject: Re: Wierd metro WiFi problem


> Could be a router Ethernet port speed-mismatch issue.
>                                                        jack
>
> 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 <http://www.azulstar.com>
>>
>>
>> ------------------------------------------------------------------------
>
> -- 
> Jack Unger - President, Ask-Wi.Com, Inc.
> Serving the License-Free Wireless Industry Since 1993
> Author of the WISP Handbook - "Deploying License-Free Wireless WANs"
> True Vendor-Neutral WISP Consulting-Training-Troubleshooting
> [email protected]  (818) 227-4220  http://www.ask-wi.com
>
>
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