So I recently built a RAID 5 system to be used primarily as a media file server. I transfer large home video files over my network to this machine on a continual basis. Since both my server and personal machine have gigabit nic cards in them I thought it might be a good idea to get a gigabit switch now that they’ve come down to reasonable price points.

So today I saw my local Fry’s ad and saw an Airlink Gigabit switch on sale for $29.99. I started to do a little research on the switch and came to find out about “jumbo frames” which is a feature that some switches had to increase speed that this router lacked. The network cards also need to support this as well as the switch for it to work.

I tapped on my friend Will’s shoulder to glean more info on “jumbo frame” and here’s an excerpt from his email reply:

“Jumbo frames allows a larger chunk of data to go through each frame so there’s not so much start-and-stop, CRC checking, packet unwrapping, etc and you get more throughput- like when running Xmodem with it’s 128byte frames vs. Ymodem’s 1K frames back in the old days.”

This was a great analogy and helped me understand the benefits quite easily.

So I started to try to determine if both my machines (Dell 400sc server & Dell Dimension 8400 personal machine) supported “jumbo frame”. Well both systems have integrated nic’s on the motherboard. I quickly found out that the 400sc did support it. But trying to determine if the 8400 did was another story.

I started by googling for the info which was very difficult to find but ultimately found this posting which was the closest I could get but still no answer. So I had to dig further.

I wondered onto the dell support site which led me to the driver download page. From here I downloaded the html manual which once I opened it in a browser I searched various pages for the word “jumbo”. Upon reaching the introduction page I saw that under features the following line was listed:

“Jumbo frames (up to 9 KB) (only for the BCM5702 device)”

Ahh…getting warmer. So I try to see if I can determine the device number from wandering into the device manager in windows. Unfortunately I couldn’t find the info in there. So I also read in the html manual about the Broadcom Advanced Control Suite 2. So I ran that little utility and voila, under the hardware tab I see that my device is the “BCM5751”. So based on this I’m pretty sure that my nic doesn’t support jumbo frames.

Ok, that took a while and was a bit of a pain but I got my answer. Now think I’ll hold off and buy a gigabit switch that supports jumbo frames. It looks like a good candidate that’s been on sale for ~$35 in the past is the SMC 8505T. Of course now I will have to buy another nic for my Dell 8400 to support it, but oh well.


It’s funny, I haven’t even weighed or tested the benefits of moving to gigabit in the first place (although from what i’ve read the performance gains appear to be good for my situation). Yet I find a way to further complicate things with this jumbo frame functionality. This is a case where trying to keep up with cutting edge technology can be a curse and ignorance can be blissful…oh well.

7/29/05 Update
I found this great article that explains Jumbo Frames

NIC’s with Jumbo Frame Support
D-Link DGE-530T

Netgear KB Article on Jumbo Frame Support

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