[rbridge] Making fields in TRILL's IS-IS bigger?

[Radia Perlman]

There were some fields in IS-IS that, 40 years ago or whatever, we made 
too small. We actually
can change the size of fields for TRILL, right? How badly would that 
make it to adapt an implementation
of IS-IS to TRILL if we changed the size of:

a) fragment number (to 2 bytes presumable)
b) pseudonode extra byte (to 2 bytes?)

Actually, I don't think b) needs to be done, because all that matters is 
that the pseudonode have
a unique ID, not that the first 6 bytes have to be the same as the 
system ID of the DR. So the
DR could assign the pseudonode address to be its MAC address *on that 
link*, with
a final byte of 1. And so a single byte, as it is currently, shouldn't 
be a problem.

So the only example I can think of in this (insomniacal) moment is the 
fragment number.
Are there any other examples?

Radia