On Mon, Apr 5, 2010 at 12:05 AM, joel jaeggli <joe...@bogus.com> wrote: > On 4/4/2010 7:57 PM, Richard A Steenbergen wrote: >> >> On Mon, Apr 05, 2010 at 10:57:46AM +0930, Mark Smith wrote: >>> >>> Has anybody considered lobbying the IEEE to do a point to point version >>> of Ethernet to gets rid of addressing fields? Assuming an average 1024 >>> byte packet size, on a 10Gbps link they're wasting 100+ Mbps. 100GE / >>> 1TE starts to make it even more worth doing. >> >> If you're lobbying to have the IEEE do something intelligent to Ethernet >> why don't you start with a freaking standardization of jumbo frames. The >> lack of a real standard and any type of negotiation protocol for two >> devices under different administrative control are all but guaranteeing >> end to end jumbo frame support will never be practical. > > Not that I disagree, given that we use them rather a lot but 7.2usec (at > 10Gbe) is sort of a long time to wait before a store and forward arch switch > gets down to the task of figuring out what to do with the packet. The > problem gets worse if mtu sizes bigger than 9k ever become popular, kind of > like being stuck behind an elephant while boarding an elevator.
I didn't run the numbers, but my guesstimate is that would be roughly half the latency that a max sized standard packet would have taken on a 1Gbe switch. It sound reasonable to me that at some point during the march from 10->100->1000->10000 mbit/sec a decision could have been made that one of those upgrades would only decrease max. per hop packet latency by a factor of 2 rather then 10. Particularly since when first introduced, each speed increment was typically used for aggregating a bunch of slower speed links which meant that the actual minimum total latency was already being constrained by the latency on those slower links anyway. OTOH, I totally buy the argument on the difficulty of frame size negotiation and backward compatibility. I think that one of the reasons for the continuing success of "Ethernet" technologies has been implementation simplicity and 100% compatibility above the level of the NIC. Bill Bogstad