Subject: RE: [Enum] Tier I database

From: "Pfautz, Penn L, NNAD" <[email-masked]>
Date: Mon, 22 Jan 2001 15:30:23 -0500

Kevin:
As the term Tier 1 has been used in most of the I-Ds, it refers to the level
at which at which invidual numbers or block of numbers *within* country
code, say 1 for North America, are mapped to the authoritative Tier 2 (or
Service Registrar) that contains the actual NAPTR records for the number.
Some more details of possible implementations are in 
draft-pfautz-na-enum-01 and draft-pfaytz-yu-enum-adm-00

 Tier I would have the NS, and perhaps A information for the name server.

An ENUM request has to come from some IP-enabled device, but that device
could be a gateway or something else. Recall that use of ENUM is optional
for both the end user to which the number belongs and to the carrier, if
any, that is handling the call for the user. A PSTN originated call *could*
be routed to a gateway and information from ENUM *could* be used to route
the call, but the presumption, at least for now and at least for the US, is
that there is a PSTN point of interface for all numbers.

Penn Pfautz

-----Original Message-----
From: Kevin McCandless [mailto:[email-masked]]
Sent: Monday, January 22, 2001 1:03 PM
To: [email-masked]
Subject: [Enum] Tier I database

Hello Everyone:

I hope you can help with this question.  I just finished updating our
executives at my company on ENUM.  During my presentation on the Tier I
database  a question came up on why do we need a Tier I database?  I know
that the documents say the Tier I is for county code routing.  But if this
service is very similar to domain names then why the Tier I database.  Also
I had in my presentation the following " Tier I database directs the request
to the controlling country.  Then the DNS service translates a domain name
representation of an E.164 number into the NS and A record for the Tier II
database."    Does the Tier I database give the NS and A record information
or just translates the E.164 number into a NS and A record?

Any clarification or more detailed explanation on why the Tier I database
was envisioned and input on my last sentence on the first paragraph.  Are we
assuming that an ENUM service request would come from an IP device such as a
computer, only?  If I dialed an ENUM enabled number from the PSTN, would my
call be routed just as it is today through the PSTN?

Regards,

Kevin McCandless
Senior Network Planner
Illuminet
913-814-6397
[email-masked]

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From: "Conley, Pat" <[email-masked]>
Date: Mon, 22 Jan 2001 17:26:08 -0500

Kevin,

My simple way of thinking about the e164.arpa model
of ENUM is as follows.

There is a "root layer" that points to the .arpa.

There is a "enum layer" that points to e164.arpa.

There is some "international layer" that points to
the implementation for each country.  

Within that country there is a layer that contains
potentially many physical servers that together implement
a "tier 1".  Tier 1 by definition contains info that
goes all the way to a fully qualified E.164 number.

Within tier 1 there are 3 options.  1.) Store URIs directly
the NAPTR records of the Tier 1.  2a) Use NS records to point
out to a DNS implementation of Tier 2.  2b) Use NAPTR records
with LDAP URIs to point out to an LDAP Tier 2 implementation.

pat

-----Original Message-----
From: Robert H. Walter [mailto:[email-masked]]
Sent: Monday, January 22, 2001 3:58 PM
To: Kevin McCandless; [email-masked]
Subject: RE: [Enum] Tier I database

Hi Kevin,

> service is very similar to domain names then why the Tier I database.

Both Tier-1 and Tier-2 ENUM DNS represent LOGICAL rather than PHYSICAL
control tiers.  Tier-1 is the logical abstraction of all physical name
servers performing delegation upto but not including the Tier-2 name
servers where NAPTR records are stored.  Tier-1 intrinsically
exists because of the assumption that their will be multiple Tier-2
ENUM providers and/or operators.

> Does the Tier I database give the NS and A record information

Typically the handling of delegation in DNS resolution is implicitly
performed by client resolvers.  A resolver will query an ENUM system
for the NAPTR records associated with an E.164 name.  Because ENUM has
the potential for many physical DNS tiers, the resolver will
reissue the query for NAPTR records to one or more of the physical
name servers that respond with NS and A records.  The resolution
process terminates when a name server responds with the NAPTR records
or there are no more name servers to query.

Regards,

Bob