Subject: RE: [Enum] Standard DNS Delegation or CNAME/DNAME Redirection

From: Christian Huitema <[email-masked]>
Date: Thu, 2 Nov 2000 08:28:51 -0800

I support the use of DNAME in ENUM. I believe ENUM faces a major deployment
problem, that of finding the authoritative publisher of an information.
There are basically two solutions to this problem, bureaucratic management
and competition. DNAME enables competition.

If we have a single tree, we will end up with a set of regional monopolies
deciding what goes in the mapping. At the top, we will indeed find the ITU,
then the various local authorities, then the various phone providers. At
each level, there will be confusion and power struggles. For example, look
at "1.e164.arpa." Who has authority? The area is actually shared between
several North American countries; even within the US, the delegation to the
ITU is managed by the State Department while the regulation of telephony is
managed by the FCC. If you go down to the area code level, the matter is not
any clearer. Who has authority over "2.1.2.1.e164.arpa"? Is this the New
York State public utilities commission, Bell Atlantic, or a third party? The
matter only becomes kind of clearer at the lower level of the hierarchy,
where "x.x.x.2.1.2.1.e164.arpa" corresponds to a bloc of addresses, the
current unit of management for assignment of numbers to local competitive
carriers, and also for LNP. (The most likely result is that each PUC will
hire a contractor that manages the listing.) But then, a potential use of
ENUM is to bypass the local carrier, for example to send documents as e-mail
instead of faxes; this means, potentially, a loss of revenues. So, while the
users of phone numbers have an interest in listing their numbers, the phone
companies are conflicted. Expect some interesting developments.

IMHO, the only way out is to allow a competition, have a forest instead of a
tree, so that we could get alternative services such as
"2.1.2.1.joe-s-listings.com." The clients that decide to use Joe's listings
know what they get: Joe's idea of who owns what number; they can trade
bureaucratic certainty and pace for rapid updates and potential mistakes.
DNAME allows us to build forests instead of tree; Joe's listing may use the
DNAME technology to point at branches managed by other servers, maybe even
to point back to the main tree for some countries.

Another interesting case is that of enterprises, who manage a local dial
plan. If an enterprise uses 4 digits extensions, then it is much more
natural to resolve "x1234" through "4.3.2.1.local-plan.example.com" than to
go back all the way to the e164.arpa root. But then, it is also useful to
store any piece of data only once, so there is no point in replicating the
records of the local plan under "4.3.2.1.a.b.c.d.e.f.g.e164.arpa." This is a
case where DNAME are very interesting. By the way, this works both ways. If
the enterprise's dial plan has an escape code for international codes, say
"00", and if it contracts with Joe's Listing company for the ENUM service,
then it can enter a DNAME pointing "0.0.local-plan.example.com" to
"joe-s-listings.com."

In short, DNAME allow for a forest instead of a tree. A forest looks scary
for bureaucrats, but it enables competition. And it also enables local
management of resources without replication of records, smooth transitions
between local dial plans and global registries. In any case, the tool is in
the box, so the debate is a little bit futile...

-- Christian Huitema

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From: "Robert H. Walter" <[email-masked]>
Date: Fri, 3 Nov 2000 16:25:25 -0500

Hi Christian,

Thank you for your insights... I'd like to follow-up with you.

> and competition. DNAME enables competition.

I totally agree with your first statement about two solutions, but fail
to see how CNAME/DNAME enables competition.

> companies are conflicted. Expect some interesting developments.

Again, I agree with you that exclusive distribution the authority of
the first tier across multiple, potentially conflicting operating authorities
restricts competition and is wrought with all sorts of complexities.

> to point back to the main tree for some countries.

As I understand it, DNAME enables an entire subdomain to be mapped to a
different subdomain. This is very similar to what CNAME provides for a
single domain name. I see how CNAME/DNAME can be leveraged in the first
tier to facilitate dialing plan changes during the transition period, but
this does not address the issue of delegation to the second tier or
competition.  This is a well understood DNS administrative trick of the
trade.  Are you proposing that a single E.164 domain name entry be
provisioned in the first tier with multiple CNAME/DNAME records? For
example:

2.1.2.1.5.5.5.0.0.8.1.e164.arpa. IN CNAME 2.1.2.1.5.5.5.0.0.8.1.joes.com.
                                 IN CNAME 2.1.2.1.5.5.5.0.0.8.1.anns.com.
                                 IN CNAME 2.1.2.1.5.5.5.0.0.8.1.ikes.com.

I'm going out on a limb and assuming an ENUM resolver would query
directly for the CNAME records and then re-write/re-issue the query
using the canonical name.  DNAME could be used similarly for blocks
of numbers registered in the first tier.  How would the resolver choose
which service registrar to re-issue the query too?  Would it simply use
DNS rotation? Please help me out here and further elaborate on how
CNAME/DNAME can be leveraged to increase competition.

> then it can enter a DNAME pointing "0.0.local-plan.example.com" to

I must be missing the point.  This appears to be a second tier issue, hence
the delegation from the first tier to the second has already been performed.
It is reasonable that an enterprise would run it's DNS in a split configuration
where CNAME/DNAME is used internally to map to a publically operated
e164.arpa zone.  IMHO, if an enterprise chooses to privately provision it's
DNS servers with CNAME/DNAME it's completely up to them.

> the box, so the debate is a little bit futile...

More power to eliminating duplication of records and smoothing transitions
between local plans and global registries!  Long live CNAME/DNAME, but
how does CNAME/DNAME support competition at the first and/or second tiers?

Thanks,

Bob