Slow Transfer Speeds from WHS Fixed with Jumbo Frames

I have been playing with my home server for more than a year now and I have always just dealt with the slow transfer speeds to and from my server, until now.  I have a gigabit switch (Linksys EG005W) and I am running Cat6 to all my machines that host gigabit adapters. With that said, I would consistently only get 20-30 % throughput on my network.  Now I get 40-50% throughput and sustain transfer speeds of around 60+MB/s by simply enabling Jumbo Frames!

The problem and answer lie in your network adapter configuration (provided you have a gigabit adapter in your WHS). Even though you may be auto negotiating at 1Gb/s you are still limiting your frame size to 1518 bytes . In order to get faster throughput and consume less resources you can enable Jumbo frames on your gigabit network adapters.

A bit about Jumbo Frames

The original 1,518-byte MTU for Ethernet was used because of the high error rates and low speed of communications. Thus, if one receives a corrupted packet, only 1,518 bytes must be re-sent to correct the error. However, each frame requires that the network hardware and software process it. If the frame size is increased, the same amount of data can be transferred with less effort. This reduces CPU utilization (mostly due to interrupt reduction) and increases throughput by allowing the system to concentrate on the data in the frames, instead of the frames around the data. At the sender, a similar reduction in CPU utilization can be achieved by usingTCP segmentation offloading , although this does not reduce the receiver CPU load. Interrupt-combining Ethernet chipsets, however, do provide most of the same gain for the receiver, and work without special consideration without requiring all stations to support jumbo frames.Zero-copy NICs and device drivers, when combined with interrupt combining, can provide effectively all the gains of jumbo frames without the re-send costs, and without requiring any changes to other stations on the network. – Wikipedia

Prerequisites

• Gigabit Router/Switch that supports Jumbo Frames
• Gigabit Adapter in your WHS
• Gigabit Adapter in another workstation

Enabling Jumbo frames on your network adapter is simple. As usual, all work will need to be completed from your WHS. Initiate a Remote Desktop connection to your home server.  This will allow you to work on your Home Server as if there were a monitor, keyboard, and mouse attached to it.  This article will also assume that you have some computer knowledge and are able to use RDC or the Add-in Asoft AutoExit, but I will try to be as thorough as possible regardless.

1. Right Click on “My Computer” and choose “Properties”
   • If you don’t have “My Computer” on your desktop, you may go to the Control Panel and double click “System”
2. Choose the “Hardware” Tab.
3. Click “Device Manager”
4. Expand “Network Adapters”
5. Right click on your network adapter and select “Properties”
6. Select the option for “Jumbo Frame” and choose the largest size possible.
7. You will lose your desktop connection when you press OK, don’t be alarmed.

Now, for this to work; you have to do this on all the machines that have a gigabit adapter on your network as Jumbo Frames are not enabled by default on Vista, 2000, or XP.