Re: comments on the architecture document

[Noel Chiappa <[e-mail]>]

	I have requested copies of these papers from him on several occasions
(since I found some of his quoted results quite amazing), and have yet to
receive a copy. Can you send me a copy? Actually, if they are online, I
suspect lots of us would find them interesting.

	I'm not sure I understand your terminology about 'new atom'
completely, but I'll take a crack at answering. My apologies if I'm out of it.
	I'll deal only with how someone who doesn't understand a new attribute
uses map elements which are marked with them; actually allocating the new
attribute number from the number czar, defining its syntax and semantics,
etc, are clearly trivial.
	In the simplest algorithm, you simply ignore any links or nodes in
your topology map which have attributes you do not understand. You then
construct a route using the other links. Of course, this may result in a
non-optimal route, or no route at all, when one is possible.
	In the next version, all attributes are divided into two classes,
informative and restrictive. The former say something about the link, but
will not result in any traffic being dropped or refused. You can safely
use any link which has informative attributes you do not understand;
you may not get great service, but TANSTAAFL. You can't use links which
have restrictive attributes you don't understand; your traffic may croak.
	In the last version I can think up quickly, links with restrictive
attributes have to fail at set-up time if someone who is not allowed to use
them mistakenly tries to set-up across them. (You pretty much have to do this
policy enforcement anyway, since if you trusted people not to use your links
if you simply advertised they couldn't use them, they'd probably discover they
could ignore the advertisement and use you anyway. It's also obviously more
efficient to do the policy enforcement at set-up time, rather then per-packet;
an argument for the set-up version of source routing.) If you do this, you
can try using links whose restrictive attributes you don't understand; if
you really can't use it, you get bonked. Not very efficient, but...
	This also allows you to have have attributes on links which are
deliberately *not* globally understood. You may not want everyone to
understand your policy markings...


	Noel