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Re: [HSSG] Jumbo frames

I agree with you about jumbo frames.  I am glad that Joel mentioned it though because it is a good discussion to get out of the way.  I had a couple of other thoughts about the issues with jumbo frames and I'd appreciate your feedback (as the P802.3as chair) and that of others with more MAC standards expertise (Shimon, Larry, etc.):
1) 802.3as is expanding the Ethernet frame, but this was done in conjunction with 802.1.  Therefore, I would assume that any jumbo frame project would require the same effort.
2) The 802.3 MAC specification doesn't "buffer" information; therefore, a change in the MAC would be required to perform this operation to be compliant with the 802.3 MAC service interface.
3) Would this have impact on other 802 dots (.11, .17, etc.) if something was done in conjunction with 802.1?
I know that jumbo frames have been brought up in the past.  Most previous projects have rejected doing it, and in my humble opinion, the primary reason has been that the change is more complex than just altering the 802.3 MAC frame size.

From: Kevin Daines [mailto:Kevin.Daines@xxxxxxx]
Sent: Thursday, August 10, 2006 2:16 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: [HSSG] Jumbo frames

Joel's statement below can be grossly misinterpreted. He states that all system and silicon vendor supports jumbo frames. That may be true but I highly doubt it. However, what is not true is that all or the even the majority of the installed base of Ethernet gear supports jumbo frames. In addition, many products on the market today do not support jumbo frames (by products I mean both equipment and silicon). During the P802.3as Frame Expansion project (soon to complete), UNH IOL kindly tested hundreds of pieces of gear and combed through hundreds of reports to determine the maximum frame size supported by Ethernet gear (that had been submitted to UNH). While not exhaustive, the data indicated a wide range of maximums from 1515 (not a typo) through 2K, 4K, 5K, and 9K and beyond.
Within P802.3as, we discussed jumbo frames at various times. The following constitutes my recollection of the reasons against "standardizing jumbo frames" (not ordered):
1) Interoperability with legacy gear
2) Increasing frame size is a slippery slope. Why 9KB? Why not something larger, like 16KB or 64KB?
3) The network performance bottlenecks change over time. Each major component of the network/system goes through improvements and upgrades, which changes the requirements on other parts of the network/system.
4) QoS (frame delay, frame delay variation, etc.) impacts
Kevin Daines
Chair, P802.3as TF
Note from archive attached below:


If I go to any search engine and input "
jumbo ethernet frames chips", I will see that every system and silicon vendor supports jumbo ethernet frames.

My question is not wether to support jumbos, because we all already do ... my question is should we finally spec it out?  I think we should, at a minimum, provision for it.