Subject: Encoding of multiple levels

From: Radia Perlman - Boston Center for Networking <[email-masked]>
Date: Fri, 30 Apr 1999 22:32:46 -0400 (EDT)

Rather than having a zillion packet types (level 7 CSNP, level5 Hello, etc),
perhaps the packet type field should be divided into level/type.
So then you can just put in "level" in 3 bits, and the type into 3 bits
(pt-to-pt Hello, LAN Hello, CSNP, PSNP, LSP). Right now that octet has
3 reserved bits and 5 bits for PDU type.

Personally, I don't think you need to explicitly state what level you're
at. Really the only important thing is to know whether you're going up,
down, or across in the hierarchy.

**********
Also, does anyone remember why version is there twice in the fixed part
of the header? I got to make a joke about it in the book, which is nice,
but how did it happen? Was one field intended as a major version number and
the other a minor version number? That would have been useful. I think
it was that way in DECnet Phase V (major/minor version
number, where minor was bumped for compatible changes). Doesn't matter, but I'm 
just curious.

Radia