Re: Reopening jumbo frames in IS-IS

[Curtis Villamizar <curtis at faster-light.net>]

In message <026601c58978$13564970$6501a8c0 at dax>
"Stephen Sprunk" writes:
>  
> Thus spake "Bob Hinden" <bob.hinden at nokia.com>
> > Radia,
> >
> >>What are the technical reasons that IEEE does not like large packets?
> >
> > I can't speak for IEEE, but I have always thought that one of there
> > reasons that Ethernet has been so successful is that that IEEE tried
> > very hard to insure backward compatibility between the different
> > versions.  It made it easier to bridge between 10M/100M/1G/10G/etc.
> > versions, new versions didn't break any protocols that ran over Ethernet,
> > and it is easier to build NICs that supported a range of variants.
> >
> > It also avoided having to build things like a FDDI/Ethernet bridge I once 
> > heard about that supported IP fragmentation.  I bet you remember that :-)
>  
> Wait a minute...  If Ethernet supported jumbo frames, the FDDI-Ethernet 
> bridge wouldn't have needed to support fragmentation -- just set the 
> Ethernet side's MTU to 4470 and all would be well.
>  
> I dealt with this many times when bridging Token Ring and Ethernet, and the 
> only solution that worked in every case was to drop the Token Ring's MTU 
> (network-wide, since TR implies SRB) down to 1500 -- a horrible kludge. 
> Sometimes other tactics worked, including dropping oversized frames with no 
> fragmentation, but some SNA apps were really touchy about that.  IP handled 
> things a bit better, but still not as well as jumbos would have.
>  
> S
>  
> Stephen Sprunk      "Those people who think they know everything
> CCIE #3723         are a great annoyance to those of us who do."
> K5SSS                                             --Isaac Asimov 


Maybe the problem is that bridging dissimilar interfaces is itself a
horrible hack.  That's what routing is for.  Yes, some protocols don't
support routing but they are now dinosaurs, SNA included.  I thought
the days of building networks around the needs of netbios, netware 3,
and sna were over.

Curtis