Subject: [PEPPERMINT] Public Identity, TNRange and LRN Objects Amoungts other things...

From: "Robert H. Walter" <[email-masked]>
Date: Wed, 12 Mar 2008 15:02:08 -0400

I have many questions/comments regarding the ESPP draft documents,
consequently, I will start with just a few of the simple ones and spread
them topically over a series of threads.  The first line of
questions/comments will deal with Public Identity, TNRange and LRN Objects

The introduction of draft-mule-peppermint-espp-protocol-01.txt states that: 

   An ENUM-SIP addressing server is a session routing server which
   resolves telephone numbers or any type of public user addresses into
   routable Uniform Resource Identifiers (URIs) based on various rules
   and routing logic. [Page 2]

The phrase "any type of public user addresses" feels ambiguous.  I see the
correlation to Public Identity in that its description states:

   A Public Identity may be a telephone number, an email address, or
   other identity as deemed appropriate.

There is no correlation for TNRange or LRN.  It's not clear how an ENUM-SIP
addressing server will resolve an email address or other arbitrary identity
that is not a telephone number to a set of URI's.  What is the intent here?
Is it acceptable for the ESPP server to simply refuse to process a public
identity if it contains an identity that is not deemed appropriate by the
ENUM-SIP addressing server?  If so, what is the appropriate protocol
response?

Interestingly enough, the logical structure diagram appears to have been
updated from an earlier PacketCable version to constrain the public identity
to an LRN, though the XML object structure defines a "PubId" attribute as an
arbitrary string of unspecified length.  Am I interpreting this correctly?
In the context of ESPP, I recommend that a public identity be constrained to
a telephone number, not over-constrained to a 10-digit LRN or
under-constrained to an ambiguous public user address of unspecified length.
For example:

   A Public Identity is uniquely identified by a telephone number
   consisting of 1-31 hexadecimal (0-9, A-F) digits.

What happens when two public identities have different eid/oid, but the same
pubId value?  Doesn't the  pubId (i.e. telephone number) attribute need to
be unique?

Is the intent of the TNRange object to allow for arbitrary number ranges?
For example 9788482830 - 9788482832 represent a range of three national
telephone numbers.  I ask this question because it places a potentially
significant burden on the ESPP server implementation to expand the number
ranges into individual telephone numbers.  I recommend ESPP define number
blocks instead of arbitrary ranges.  Use of wildcard (best match) algorithms
within the ENUM-SIP Addressing server eliminate the requirement to expand
the blocks.

Finally, the draft defines an LRN as the following:

   A 10-digit number that identifies the switching port for a local
   telephone exchange.  LRN is used to support Local Number
   Portability in North America.  An LRN is associated with a Service
   Area.  [Page 12]

This object is specifically associated with the US and Canadian national
number portability implementation.  I believe ESPP would be better served by
defining a Routing Number (prefix)?  In North America, the routing number
would represent an NPA-NXX office code.  There is little or no need to bring
North American implementation semantics into the specification.

If ESPP uses conventional number blocks verses arbitrary number ranges, I
would argue, that the TNRange and LRN objects may be subsumed into a single
RN object.

This brings up the issue of national verses international numbering plans.
The specification appears to intermix national verses international
numbering without providing any context of when a public identity or TNRange
is national or international.  It feels like the specification is missing an
important contextual element with regards to national verses international
numbering.  Please advise on how I should be thinking about this issue.

Regards,

Bob Walter
NetNumber, Inc.
+1-978-848-2831

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