Subject: RE: [ITU+IETF] RE: [Enum] Re: Structure of DNS entry for ENUM

From: "Vaudreuil, Greg M (Greg)" <[email-masked]>
Date: Fri, 18 Feb 2000 10:15:53 -0600

I recognise this work is out of scope for the current ENUM project, but it
is important contextwe need to be aware of.

Private numbering is used both in public virtual private networks or
centrex, and inter-PBX numbering plans with leased or virtual tie lines.

From the public network side, the virtual private numbering plans is reached
by entering an access code prior to the virtual telephone number.  This
access code may itself be a PSTN number, or simply a magic sequence caught
by the serving switch.  The ingress switch either 1) uses the access code to
translate the dialed VPN number into a valid E.164 number, in effect
resolving the alias, or 2) uses the access code to determine the context of
the number and treats the number as a routeable number within a separate
private network.   

The access code is not always explicitly dialed by the user.  Digit analysis
or a short-code coupled with the senders class-of-service information may
note that a single digit prefix (for instance 8) should really translate
into an access code for the subscriber VPN.  In this case, what results if I
dial 8-1212 will be different than if you dial 8-1212 if we are served by
separate VPN numbers.  The mapping the dialed numbers into a context and
number is frequently called a "dial plan".

In enum space, it would be up to the client to determine that the dialed
number was other than E.164 and determine which numbering plan (DNS suffix)
it belonged to.  Standards and auxillary directory services to make a
network-based dialed digit analysis function to map access codes to domain
names may be a future project.  However, it seems that the result of any
local or standard approach will take the initial digits, number length, and
local configuration to determine the domain name suffix to append to the
dotted digits.  From that point the mechanics and protocol are identical for
E.164 and private spaces.  Assuming the domain name suffix was part of the
public DNS space, the private numbering plan would be world-accessable,
i.e., my phone could be reached at 2.2.7.2.dallas-dev.lucent.com.
Interestingly, there is no national numbering authority involved, so a
multi-national corporation can easily use a single, unified, short-digit
numbering plan.

Closed networks are another tier to the problem, and one which the DNS-based
proposals are not naturally suitable.  That is, the caller outside a given
community may not be authorized to send to a given address in a private
address plan.   I also believe this functionality is best addressed by other
directory services (LDAP, TCAP) or using trial-and-error, enforced at
service establishment time.

Greg V.

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Friday, February 18, 2000 8:38 AM
To: 'David P. Peek'
Cc: IETF Enum
Subject: RE: [ITU+IETF] RE: [Enum] Re: Structure of DNS entry for ENUM

David P. Peek wrote:

> For example, I believe the private numbering solution
> should be
> capable of support down to the user  level.  This will require the
> identification of the source
> making a query and DNS isn't really good for that.   A method 
> discussed
> with memebers of the VMA Technical Working Group is one that 
> addresses the
> private numbering solution at the second tier or ADS (Authoritative
> Directory Server) by
> making an LDAP query.  This internal private query made by a 
> communication's
> platform will retrieve the E164 number associated with the 
> private number
> dialed
> and then perform a DNS query as described in this "One 
> Global" solution.

This makes perfect sense to me. And one clean way to support the "second
tier" numbering solution might also be to use domains that are unique to the
country where that numbering plan is in effect. For example,
<localtelephonenumber>.telnumbers.fr would accept numbers in the French
plan. So even if you move your appliance around the world, you can continue
to use the numbering plan that appliance is set up to use?

Bert
[email-masked]

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From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 18 Feb 2000 11:57:44 -0500

"Vaudreuil, Greg M (Greg)" wrote:
> E.164 and private spaces.

Exactly. Another way to look at it is that the system enum is defining
takes two things as input: a phone number AND a domain suffix, and then
returns a list of URIs. 

-Jonathan R.

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