Subject: RE: e2e & global view

From: "Christian Huitema" <[email-masked]>
Date: Thu, 3 Apr 2003 14:50:12 -0800

> % Let me try an rephrase my question.  I would like to know if there
is
> % consensus on the architectural view that IPv6 should have addresses
with
> % different scopes? 

No, there is definitely not consensus on that point. There are three big
classes of arguments.

The first class of argument is more against "ambiguous addresses" than
scoped addresses: using ambiguity as a surrogate for unreachability is
unnecessary (firewall can do that on any address) and inconvenient
(ambiguity of addresses makes several error scenarios undecipherable).

The second class of argument relates to routing and network management.
Maintaining scoped addresses makes routing hard, especially if a node
has to support multiple instantiations of a given scope. Margaret also
developed an argument about the need to maintain a site convex, and the
interaction of that requirement with shortest path routing.

The third class of argument considers the use of addresses by
applications. Using scoped addresses forces applications to understand
scopes, which is much more complex and error prone than just considering
that all addresses are equal. 

> % Again, I fail to see how deprecating site-local addresses
(specifically
> the
> % FEC0::/10 prefix) solves the underlying problem (e2e communications
> failing
> % with some src/dst address pairs).

Everybody should know that, and Bill is perfectly correct: just because
an address is globally unique does not mean it is reachable. However, if
it is unique, you eliminate a number of the error cases caused by
ambiguity.

-- Christian Huitema

--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------