Subject: [Enum] ENUM interworking

From: Kevin McCandless <[email-masked]>
Date: Wed, 31 Oct 2001 07:30:43 -0800

After having my ENUM in box full of religious debate I began to wonder if
this is the technical department?
 
Enum by RFC 2916 is rooted in .arpa.
 
Enum is also a way to resolve a E.164 numbers, in DNS, to a given set of
NAPTR records.  Therefore, resolving E.164 numbers to a set of NAPTR records
could exist in any top level domain.  The important point is how could these
different systems interoperate.  Now that is a good technical question to
focus on.  The ENUM Forum that just recently met in Kansas discussed this
issue.  We first discussed the use of CNAME records at Tier 1 under RFC2916.
Representatives from both VeriSign and Registrar.com said that this is very
burdensome on a database because it would require a double look up every
time.  The easiest approach would be to have a resolver for the client.
This resolver would be capable of searching multiple domains for the E.164
number.  If one is merely trying to obtain NAPTR records for anything but
call setup the resolver approach should work fine.  An issue we should be
aware of is if ENUM is used for call setup and the resolution of multiple
domains takes a large amount of time then this would not be an acceptable
delay for the call completion.  Circuit switched calls are considered toll
grade if they are set up under 250ms.  That is a target we should keep in
mind if we expect ENUM to be an enabler of call setup and be rooted in
multiple domains.
 
Sincerely,

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

---

From: Rob Freilich <[email-masked]>
Date: Wed, 31 Oct 2001 09:55:13 -0600

All,

I have to agree with Kevin, the religious debates are really just a waste of
time.  There is nothing stopping any company from using the ENUM
“technologies and methodologies” and anchoring their “private” tree in some
other area of the DNS.  I believe only ICANN could stop a company from doing
that, but more than likely will not.  Regardless, the ENUM Forum recognizes
that these independent trees, not routed in e164.arpa, are possible and has
provided a medium (a specific Task Group) to debate the technical means to
interoperate with the Golden Tree.

So far there have been 3 ways speculated to interoperate with the Public
Golden Tree but no one has come forth with a concrete technical proposal on
how it should be done.

Summary of the 3 proposals:

1.	Interconnected Registries with a new URI (If I remember correctly) that
“refers:” to the correct registry the ENUM is listed.
2.	Use of existing DNS constructions to jump to other areas – such as CNAME
records in the e164.arpa domain to correct domain
3.	Provisioning the ENUM Resolver to look in multiple domains.

From a carrier’s perspective we would like to minimize the time for call set
up as Kevin mentioned.  But it should be noted that the 250ms. Kevin quoted
that ENUM is but a portion of that.  There are a number of other “typical”
elements that contribute to the call delay.   ENUM must be accounted as part
of the Call Set–Up Time Budget.  Also remember that ENUM actually will lead
to atleast 2 DNS dips, regardless on interworking, one for the NAPTR RR
(URI) and then another to resolve the URI into and IP Address.  All these
need to be factored into that Call-Setup Budget and determine its impacts,
if any.

Just my 2 cents…

Rob Freilich
WorldCom
972-729-5139
[email-masked]

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Kevin
McCandless
Sent: Wednesday, October 31, 2001 9:31 AM
To: [email-masked]'
Cc: [email-masked]'; Bob Wienski
Subject: [Enum] ENUM interworking

Sincerely,

Kevin McCandless
Senior Network Planner
Illuminet
913-814-6397