Inconsistent bandwidth


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Hello Neowin Community,

This is the story. Small business in domain enviroment with about 10 PCs connected through brand new cisco switch and Verizon FIOS. Users complain about slow website loadings. Different users at different times of a day, never all at the same time. Whenever someone complained I went and performed speedcheck and results were not what there were supppose to be but after maybe 15 minutes the results were perfect. So i went and scanned all PCs for possible malware etc. that could of possibly cause this but found nothing special. Decided to upgrade the switch and still no change. Called verizon about this issue and they assure me that everything is allright on their side. They even send out a tech to make sure.

It's happening to everyone so it's not a workstation issue. Maybe network card configuration? Brand new switch, Cisco SF100-24. Maybe it has to be configured? but same problem was on old switch. To me it looks like a bad distribution of bandwdith to the workstations. Collisions? This is beyond of my knowledge. What else should i be looking for and what more tests should i perform?

Thanks,

Darek

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I would say if you can do a test when those systems are running slow that would help you narrow it down. Just setup a file share with a large file on the server then once internet is slow then copy that file locally and see if there's any issues locally. If not then it's a Verizon thing or just maybe a routing issue. If there is a problem locally then that could be due to cabling or heat maybe?

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I dont assume you are because you didnt mention it, Are you using a proxy server? Has all your network hardware got the latest firmware? It might be a redherring but run a speedtest.net on Speed Test see what speed you are getting from each PC and check that against what speed was advertised to you on FIOS.

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Like I said, the results on speedtest.net are lower than advertised by FIOS but thats only when user complain about slow speed. It doesnt happen all the time. When everything works, speeds match. No proxy server involved. What about MTU size packets? Changing or configuring those would make any difference?

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Generally not! I would get something like Solarwinds and set up a CPU/Bandwidth graph on the switch see what is happening at times of the day, Are users transfering large files around, Are you doing backups at some point during the day. You might need to implement some sort of QoS. I suspect that users of Neowin are going to shoot me for suggesting this but have you thought of looking at something like TCPOptimizer. Run that on one of the PC's and see. Do you use any kind of wireless?

Actually that switch is only 10/100, Are the clients all connecting at 100MB? Try getting a Gig Switch.

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