Subject: RE: TRIP

From: "John Mainwaring" <[email-masked]>
Date: Tue, 7 Dec 1999 16:02:16 -0500

|From: Jonathan Rosenberg [mailto:[email-masked]]

|I'm less sure about deferring the LNP query to N-1. In the SIP
|architecture,
|at least, each proxy is responsible for doing a translation function
|(called the
|location service), which is similar in concept to an LNP 
|database query.

I understand that SIP is different from the tandem network of circuit
switches.  I think SIP will require the originator to know LNP information,
but I'm not sure that existing collection of SCPs accessed by the TCAP/SS7
signaling system is the place to get it.

|I'll also
|note that I have been told that the LNP dip being done at the N-1
|carrier is
|only a north american thing, and that in Europe, its done differently.

Of course.

Actually, last I heard the Europeans were still considering Release to
Pivot, which might be a plausible model for SIP.  Initiate to the default
code owner first, and allow for a "refuse with redirection" or something.
It's got its weaknesses, which include putting a burden on the donor of the
ported number and relying on an uninvolved third party to set up a call, but
it does keep the supporting infrastructure simple.

Another interesting working model is wireless roaming.  It is capable of
dynamically redirecting you anywhere (at least within a continent or so) and
it works at the level of individual telephone numbers.  Of course a single
wireless operating company owns all the numbers in an NPA NXX, which avoids
the major problem LNP was designed to create.  (No, that's not a typo, it's
editorial comment.)

Probably it's more of an administrative problem than a technical one.  It's
so easy to fall into the trap of thinking there are technical solutions to
administrative problems, although technical solutions can certainly help
perpetuate administrative problems.

John Mainwaring 
Nortel Networks 
[email-masked]