Network speed varies from PC to PC--why?
March 14, 2006 4:30 PM 
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I work in an office with several not-for-profits share a high speed internet connection. My internet connection on my Mac Book seemed slow, so I tried the online test at
Speakeasy. (I disabled the Airport connection so that I could test Ethernet) I ran the test several times and always found I had around a 400 K connection. Wireless, same test, circa 150 K. So I asked my collegue to run the same test from his Dell desktop---he got almost 1200K across several tests. I thought maybe it was the jack in my office, so I tried yanking out the plug and trying it in my collegue's office with another Dell desktop--she got 1200k--I got 400. I thought it might have been the MBP, so I dug out a Dell laptop--guess what--the most it would get in any office location was 400K. Same for a Mac mini that's on the same network. Now here's the thing--if I take that same MBP laptop home I get 3000K over my cable modem.
Why would some computers get higher throughputs than others?
They have an outside vendor administer the network and they seem to have disabled ping and traceroute.
I started to wonder if maybe they limit bandwidth to the IP address, but all I really do during the day is work in Basecamp and reply to emails with an occassional look at Bloglines. Any ideas for the MeFi community about why this might happen and how I can intelligently describe the problem to the network admin so it doesn't sound like I'm nuts?
posted by teddyb109 to computers & internet (4 comments total)
As an experiment, on your Mac Book Pro (and assuming the Mac is connected via Ethernet), try the following:
- From the Apple menu, choose System Preferences.
- Select the Network pane.
- From the Show pop-up menu, choose Built-in Ethernet.
- Click the Ethernet tab.
- From the Configure pop-up menu, choose Manually (Advanced).
- For Maximum Packet Size (MTU) select the radio button labeled Custom.
- In the field to the right of Custom, enter a new value lower than 1500 - I'd try 1492, 1484, or perhaps 1480.
If this fixes the problem, you can either talk to your provider or network administrator to get the ICMP filtering fixed (ask them to let ICMP can't fragment (type 3, code 4) messages through the filter) or leave the MTU lower on your machine. If you leave the MTU lower it will slightly degrade your performance when communicating with other machines in your local network.posted by RichardP at 5:28 PM on March 14, 2006