Subject: RE: Identification

From: "Tony Li" <[email-masked]>
Date: Sun, 16 Mar 2003 23:56:50 -0800

I agree with most of what David said, except for this.  I interpret
Jim's comment as asking
if the identifier is local to a particular location.  In other words, it
acts as the low order bits
of the 'address'.  The issue with this is that it makes absolute
identification a bit more
challenging.  For example, suppose that A, B, C, ... are locators and we
have identifier Z.
 
A.Z and B.Z just happen to be the same host because it's multihomed, but
then C.Z is another
host entirely.  What happens?  It means that hosts can no longer key on
'Z', and then have to
have other mechanisms so that they can determine that A.Z and B.Z are
the same host, both
at an insecure and secure level.
 
If Z is instead global, then I believe that the identification problem
is a bit simpler.  Consider the
role of looking up the TCB in your TCP implementation.  You just index
by Z and ports and you're
done.  No futzing around trying to figure out if A.Z and B.Z are the
right thing.
 
For this reason, I would tend to favor making identifiers global.  I
think it's just simpler.
However, the other way probably CAN be made to work with enough effort.
In my mind, this
is one of the microarchitectural pieces that we don't need to argue
about now.
 
Tony

	 Can identifiers be within the context of Location? 

	Not sure what this means. Reachability to a given identifier
depends on its locator, so perhaps I'd say yes.