But at the same time one might want to have different sessions (where
there isn't a need to present the same identifier to the peer)
explicitly use different identifiers for privacy reasons.
One can definitely create APIs by which the applications can express
both
the privacy requirements for communication, and the set of
communication
that must use the same identifier for the host.
But if we do that then the question is what the default settings should
be for (unmodified) applications which do not express anything using
those
APIs.
Should we err on the side of privacy? Should we err on the side of
making as many unmodified applications as possible work by using the
same identifier all the time by default?
Now, just to mix things a bit more, how would a solution like NOID
support the privacy requirements? Are the DNS times compatible with
this requirement?
draft-nordmark-multi6-noid-02 (which I submitted on Wed so it should be
in the I-D directory any day now) talks a bit more about this.
Briefly:
For a host to take advantage of itself (or its site) being multihomed
for rehoming, the host needs to have a FQDN and consistent forward and
reverse
information for itself in the DNS.
For such a host to have multiple pseudonyms, this implies having
multiple
FQDNs. (Such as host-2002-8192-56bb-9258-0-0-8192-5882.example.com i.e.
the FQDN doesn't have to provide any mnemonic meaning to a user.)