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Jumbo Frames

In the past few days we have been doing some tests for Ethernet MTU “The never ending story” in our MPLS backbone.  Playing with MTU for long may have bad effects on your health on the long run :) but is still a must to have an operational network.

We have tested a lot of things about packet fragmentation in the MPLS backbone, the appropriate MTU size when running ATOM and other MPLS services. We may share these tests when we write up a good documentation.

One of the interesting topics I would like to share with you is Jumbo frames; its a really promising improvement and I am just pointing to the door..!

What are Jumbo Frames?

The normal Ethernet frame size can not exceed the 1522 bytes boundary; any packet that is more than this value will be fragmented into smaller datagrams. Jumbo frames extend this maximum frame size of the Ethernet from 1522 and upto 9022 bytes (including Ethernet headers).

Why Jumbo frames or why do you need bigger frames?

The more the frames that the network device has to handle the less the TCP througthput and the more the CPU overhead. By allowing the frame to extened in size from 1522 to 9k jumbo frames network devices will handle lower number of frames or datagrams (6×1.5k Frames = 1x9k Frame). Jumbo frames improve network throughput by 50% while decreasing the CPU overhead by 50%.

I will list here some qeustions and will leave it for whom is intrested to use jumbo frames in his network to find out the answers…

  • Where to use Jumbo Frames in your network?
  • How to measure network performance after using Jumbo frames ?
  • How to choose the right frame size for you network applications?
  • How Jumbo frames affect your delay sensitive applications?
  • How to use Jumbo frames in mixed networks?

these were some of the qeustions you need to answer before deciding to use jumbo frames in your network, go on find out the answers and keep yourself busy.

A man is not idle because he is absorbed in thought. There is a visible labor and there is an invisible labor.  Victor Hugo (1802 – 1885)

5 comments

  1. nice write up wael

  2. Wael it seems like an exam to me :) is it?

  3. 1. I have used Jumbo frames on SAN.
    2. Performace improvment is great from multiserver access to SAN.

  4. Does enabling larger frame sizes create a problem if their servers do not use it all the time.

  5. @Carl

    to avoid communication problems all devices in your network must support the same frame size else you may encounter packet losses.

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