Re: what about 48 bits?

[Bill Bogstad <bogstad () pobox com>]

On Mon, Apr 5, 2010 at 12:05 AM, joel jaeggli <joelja () 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