Yo,
I am trying to figure out why the Macs in a cutomer's office have slow upload speeds to external sites, but Windows based computers do not have this issue. I will have to explain everything first to make sure I give you as much information as possible.
I work in a serviced office building, and so does the company I'm helping here (one of our customers). There is a (roughly) 10Mbps leased line coming into the building's comms room, where it is split using managed Cisco equipment. This Cisco kit is configured so that the ports each company connects their router to has limited upload speeds from 64Kbps up to 512Kbps and the more you pay the building's owners, the higher they set your upload speed to. Thankfully, the download speed is not limited!
The customers are an image design team with management who all use Mac Pros and iMacs, with an Xserve for data storage and group permissions, etc. They have recently upgraded their upload speed from 64Kbps to 256Kbps because they need to upload their work to their clients and 64Kbps really wasn't good enough!
The problem is that even though they now have 256Kbps upload, their Macs can only seem to get a maximum upload speed of about 80Kbps. Even more strange is that if I unplug the ethernet cable from any of their Macs and plug it into my Dell XPS M1330 laptop, I get over 200Kbps upload speeds. I have been using
http://www.speedtest.net for this testing so far.
They were using a normal DSL router for DNS and DHCP with an unmanaged gigabit ethernet switch for all the Macs in the comms room. I thought that there could be a duplex conflict somewhere so I moved an iMac and a Mac Pro over to a 3Com Baseline 2924-SFP layer 2 managed gigabit switch and spent a long time testing various duplex settings in the Mac ethernet config and in the switch. I also changed other things in the switch such as turning off the spanning tree protocol to stop loopbacks but none of this helped.
Next, I connected one of the Macs directly into the router's 4 port switch and it still couldn't get above 100Kbps upload. At this point I started to think that the problem could have something to do with OS X or the drivers for the ethernet cards, but I can't be sure.
Does anyone have any suggestions?
Thanks for any help!
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