On Fri, 26 Nov 2010 15:24:57 -0500 Randy Bush <randy@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