Sunday, April 30, 2006

User vs. Infrastructure vs. Private ENUM 

I posted on Monday about the newly submitted draft-ietf-enum-infrastructure-00 and Martin Geddes commented:

Richard -- given that the separation of connectivity from service means anyone can be a carrier, doesn't "carrier ENUM" kind of smell of a cartel that will stitch-up the public? Isn't the problem that the issuance of phone numbers to telcos who act as trustees for the users one of misaligned interests, where the users always come off worse? At least public DNS comes closer to a proper ownership model. Does my phone number really need to be managed by a single entity who happens to be providing one of my many services (voice)? Or am I missing something and being paranoid, and not reading the consumer-friendly small print?

Martin made a very good point here, and I promised an answer. The problem is that Martin is raising here a lot of issues at once and I have troubles where to start.

First of all, User ENUM is still there (at least in countries where it is implemented). Any end-user can enter the phone number he has the right to use into User ENUM and point to any service on the Internet he wants to, e.g. to his VoIP service. This is a perfect separation of transport and services (applications). Anybody may provide VoIP services on the Internet, an end-user may even provide his own VoIP services.

This does not imply that anybody can be a "Carrier". The E.164 numbering scheme is the naming and addressing scheme of the PSTN, and assignement of E.164 numbers is happening acoording to defined international and national rules. A "Carrier" or "Carrier-of-Record" is defined in draft-ietf-enum-infrastructure-enum-reqs-02 as:
  • The Service Provider to which the E.164 number was allocated for end user assignment, whether by the National Regulatory Authority (NRA) or the International Telecommunication Union (ITU), for instance a code under "International Networks" (+882) or "Universal Personal Telecommunications (UPT)" (+878) or,
  • if the number is ported, the service provider to which the number was ported, or
  • where numbers are assigned directly to end users, the service provider that the end user number assignee has chosen to provide a Public Switched Telephone Network/Public Land Mobile Network (PSTN/PLMN) point-of-interconnect for the number.
So even if numbers are assigned directly to end-users, they need a "carrier" on the PSTN to get their E.164 number into operation, as the last bullet states.

Side remark: we are talking here about VoIP using E.164 numbers, not about VoIP using SIP URIs in the first place.

Now let's step back a moment and look at "Carriers" providing voice services. These "Carriers" may use any technology within their networks they deem convenient. More and more are migrating fully or partially to IP technology. This causes more and more VoIP islands to come into existence. The only way to interconnect these VoIP islands currently is the PSTN. This has many draw-backs: cost, QoS and most important: loss of features. The PSTN may only carry voice calls.

So the "Carriers" operating VoIP islands are looking for ways to interconnect these islands with IP-technology. There are different possibilities to interconnect (peer) VoIP islands with IP technology (and I will not go down this road here, this is SPEERMINT territory), but if the VoIP islands are using E.164 numbers as their prime identifier, they first need to find out which other VoIP island (destination netwrk) is hosting an E.164 number an end-user has requested to be connected to.

The VoIP island have already a solution to this and some of them have already implemented it or are planning to do so:

Private ENUM.

Mobile Operators in the US are already peering their MMS traffic via ENUM, the US cable operators are planning to peer their voice traffic via ENUM, the Dutch cable operators have already decided to use a private ENUM tree provided by XConnect, the GSM operators are planning to use an extension of the GRX network (IPX) and ENUM to peer their traffic.

The "Carriers" are completely free to do so, minding their own business, and may create such "clubs" on a national and /or international level, without needing to ask anybody, particularly not any national regulatory authority (NRA). It is up to the club to decide where the Private ENUM datebase is implemented, it may be in the public DNS namespace or in a private one.

This will happen and happens already.

This solution has only one "minor" drawback: even if the club is large, it will never contain all E.164 numbers in operation worldwide. Of course a given "Carrier" may participate in more then one of these clubs, but never in all of them. And if he is participating in many clubs, the question comes up in which club a given number is hosted. Querying one club after the other may not be efficient.

So some kind of a "superclub" or umbrella club is required.

This could be the Infrastructure ENUM we are talking about.

"Carriers" now have the choice to opt-in into the public Infrastructure ENUM tree. Any "Carrier" hosting E.164 numbers should have the right to opt-in here. The draw-back of this approach is that again the NRAs are involved, which may not allow all countries to participate immediately. But this is then up to the "carriers" to pester their national NRAs to opt-in.

The entries in Infrastructure ENUM are controlled only by the "Carrier", no opt-in of the end-user is required, and a "Carrier" may enter all of numbers he is hosting.

It is also the decision of the "Carrier" what information is entered (as long as he is not disclosing any privacy information about the end-user), e.g.

Some "Carriers", particularly VoIP providers on the Internet may enter data directly pointing to their proxy server or at least to the ingress element of their network (not to mention the SBC word).

Others may decide to enter a "hint" only to which club(s) they belong, without disclosing their identity, or providing in addition some kind of service provider ID.

So Infrastructure ENUM is used only by "Carriers" and it will co-exist with User ENUM. User ENUM will be user still by end-users to point to their Internet services and we see currently many ideas popping up with recent contributions to the ENUM WG.

Does my phone number really need to be managed by a single entity who happens to be providing one of my many services (voice)?

As long as the PSTN exists, for providing services there, yes. On the Internet is is already your business, in User ENUM.

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