Jumbo frame Question

John Kristoff jtk at cymru.com
Mon Nov 29 13:10:27 CST 2010


On Fri, 26 Nov 2010 15:24:57 -0500
Randy Bush <randy at psg.com> wrote:

> the reason ieee has not allowed upping of the frame size is that the
> crc is at the prudent limits at 1500.  yes, we do another check above
> the frame (uh, well, udp4 may not), but the ether spec can not count
> on that.

I wasn't there, but I paid some attention to the discussion of
jumbos when it would frequently pop up on comp.dcom.lans.ethernet.
Rich Seifert, who was involved, would jeer jumbos and point out the
potential problems.  A search in that group with his name and jumbo
frames should bring up some useful background.

In a nutshell, as I recall, one of the prime motivating factors for not
standardizing jumbos was interoperability issues with the installed
base, which penalizes other parts of the network (e.g. routers having
to perform fragmentation) for the benefit of a select few (e.g. modern
server to server comms).

I also seem to recall Rich had also once said something to the effect
that it might have been nice if larger frames were supported at the
onset of Ethernet's initial development, but alas, such is life and
it's simply too late now.  The "installed base defeats us".

John




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