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Time for frame expansion?

Jul 20, 20042 mins

* IEEE begins to weigh prospect of changing maximum Ethernet frame size

In a meeting last week, an ad hoc group in the IEEE decided to request a study group be formed to look into expanding the size of Ethernet frames.

This is not something the IEEE undertakes lightly. The maximum size of Ethernet frames, at 1,518 bytes, is one of those fundamental things that you just don’t mess with unless you absolutely have to. The standards prospects of jumbo frames died because of this fact, despite the technique’s potential benefits.

So what’s driving the new effort? Not the payload, this time. Work from the IEEE 802.1 group requires more information be included in frames. Don Pannell, 802.1’s liaison to 802.3 (the group that oversees basic standards for Ethernet), requested in a letter that 802.3 “increase 802.3’s frame size to support 802.1ad, Provider Bridges, and 802.1AE, MACSec.”

The letter continues:

“Currently an additional 64 to 128 octets are required to support the above 802.1 standards, but future work in these standards could expose the need for a few more octets.

“802.1 is requesting 802.3 to start a project to define a larger 802.3 maximum frame size with the new size being in the range of 1650 to 2048 octets. 802.1 further requests 802.3 to investigate and define what the largest feasible maximum frame size increase should be with minimal impact to existing networks and standards.”

The 802.3 ad hoc committee met, created a list of questions for 802.1, agreed that a study group should be formed and decided to meet again in September.

Next time: More on the issues raised by the possibility of changing the maximum standard frame size.