Re: IPv6 w.g. Last Call on "Unique Local IPv6 Unicast Addresses"

[Erik Nordmark <Erik.Nordmark@sun.com>]

> This is a IPv6 working group last call for comments on advancing the
> following document as an Proposed Standard:
> 
> 	Title		: Unique Local IPv6 Unicast Addresses
> 	Author(s)	: R. Hinden, B. Haberman
> 	Filename	: draft-ietf-ipv6-unique-local-01.txt

I assume the last call is on the draft named
draft-ietf-ipv6-unique-local-addr-01.txt


>          - In practice, applications may treat these address like global
>         scoped addresses.

I don't see how this can be true in general.
Here is an example using referrals; the three nodes involved are A, B, C.
Node A and B are in the same site, have both local and global addresses,
and C is in a different site.

Node A and B are communicating using these local addresses.
In particular, B contacted A using FQDN(A) and the naming system somehow
so that they ended up communcating with local addresses. (My understanding
is that part of the benefit of these local addresses is that local
communication prefer using local addresses over global addresses.)
As a result the only thing A knows about B is its local address AL(B).

C contacts A using A's global address.
Node A needs to refer C to communicate with B; it sends B's address (AL(B))
to see. But C can't reach that address since it is not in the same site.

This type of problem doesn't appear when using global addresses even
if each node has multiple global addresses.
Thus I don't think the above statement and section 8 in the document are 
incorrect.

The fundamental difference between unique local addresses and global
addresses is that the former are permentently unreachable by design
(except from the local domain) whereas the latter might be temporarily 
unreachable due to some failure.
I believe this means that applications need to be aware of the difference
between the two types. 
Hence not ready for proposed standard IMHO.

BTW: what is the expected interaction between this and mobile IPv6?
Is it different for mobile nodes that move within their home site, and
mobile nodes which move outside their home site?

   Erik


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