[Dime] Need to know the location of a roaming peer?

[Sebastien Decugis <[e-mail]>]

Hello all,

During the last meeting (thanks Hannes and Jouni for the minutes) there
was a discussion about the need (or absence of need) to notify the home
domain when a peer changes its authenticator in a visited domain. During
the discussion on ERP, my understanding of the conclusion was that we
should do the re-authentication locally when possible in the visited
domain, without going back to home domain. Then, in case new
authorization attributes are needed, we have a separate exchange with
the home realm to fetch these fresh authorization attributes, after the
authentication is performed.

Later during the session, a remark on emergency services (related to
Diameter Parameter Query draft if I am not mistaken) sent the question
back on the table, highlighting that in some contexts we may want to
query the home server for the current location of the user. I am
wondering, if the peer can move without the home server being notified
(we assume server-initiated messages are routed transparently to the
correct recipient) then the design of such query mechanism will be
affected and complexity added.

I would like to ask the list if there is strong concerns with "hiding"
the current authenticator of a roaming user to the home server, the
result being that the home realm only knows the current location with a
granularity of the realm (inter-realm handovers should still have to go
to the home realm, AFAIU).

PS: I am wondering, in the context of emergency services, if we are
really interested by the authenticator or by the point of attachment for
the given peer, as I understand there is a difference in some deployment
schemes...

Thank you for any comment,

Best regards,
Sebastien.

-- 
Sebastien Decugis
Research fellow
Network Architecture Group
NICT (nict.go.jp)