Subject: [SIP] Re: TRIP

From: S_S_Dinesh/India/[email-masked]
Date: Mon, 8 May 2000 14:10:31 +0530

James Yu wrote:
>
> For overlap signaling, a GW or LS that receives a call with partial
address
> information may not know that the address info. is complete.  If it
launches
> a query (DNS or NPDB), the entity that has the "number portability" info.
> won't be able to find the info. because the address info. is incomplete.
It
> seems that either this LS or GW may wait a little while to see whether
there
> are subsequent address info. before launching the query, or it can launch
a
> query (DNS or NPDB-like), receives an error (hope that it is specific
such
> as incomplete address instead of something ambiguous), and then wait for
> additional address info. before timing out.

I think Dean had sent out some pseudo-code some time back on how trip
and enum and overlap interact, and this was more or less what the code
suggested. I believe he thought it was a bad thing, and so do I.

Overlap dialing seems fundamentally in conflict with LNP or enum queries
at the local outbound proxy.

To do LNP, the local outbound proxy needs to have the entire string of
digits before it can perform the query. But, overlap seems to imply that
it won't ever know the entire string of digits, as it doesn't have
knowledge of those numbering plans. It just forwards the request to some
other proxy or gateway that does.

Sooo, it would seem that a proxy should only use enum or LNP for numbers
it knows to be complete. This means that for overlap dialing, the LNP
query will happen close to the destination (possibly even in the PSTN),
not unlike the N-1 case we've been discussing. However, for en-bloc, it
can happen anywhere. This does seem to imply that a proxy needs to know
whether the number in the request URI of an incoming request is en-bloc
or overlap. It could make this determination if it knew the structure of
the numbering plans, but thats unlikely. Might we need a parameter
somewhere (ugh)? I really hate to crowd SIP with things to support old
legacy technologies like overlap, so if we can avoid this, I'd be very
happy.

-Jonathan R.
--
Jonathan D. Rosenberg                       200 Executive Drive
Chief Scientist                             Suite 120
dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

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