VoIP and ENUM

The ENUM update session on Thursday was moderated by Wilhelm Wimmreuter (Siemens) and featured three presentations:

• ENUM and Interconnect by myself
• ENUM, VoIP and "Gangsta Rap" - How they all come together by Tom Kershaw (Versign) and
• ENUM and XConnect by Baruch Sterman (Kayote)

The order was naturally given by the content, because I was talking about "User" ENUM" only, Tom about - in his words: Private (Carrier) vs. Public (User) ENUM - and Baruch about a specific implementation of Carrier (Infrastructure) ENUM within XConnect.

So I will also start with my presentation:

What was the basic idea of ENUM?

To allow end-users to opt-in with their EXISTING phone-numbers on the PSTN into e164.arpa to provide OTHER end-users with the capability to look up contact URIs on the Internet the first user wants to link to this number.

This approach has some draw-backs because most VoIP providers do not provide end-users with SIP URIs to be reached on the Internet without termination fees.
(Note: I will come back to this issue in my comments to the last presentation)

What is the basic requirement for ENUM?

A public SIP URI on the Internet. Any „IP Telephony or VOIP service“ not providing a SIP URI cannot be reached via the public Internet and cannot be used in ENUM, therefore Vonage and Skype cannot be considered as VoIP. Vonage is POTSoIP and Skype is an NGN.

In addition there is the problem of Metcalfe’s Law.
(or the critical mass or networking problem as Tom also mentions)

And last but not least: nobody understands ENUM.

What is needed today to implement ENUM?

• A virtual VoIP provider on the Internet providing you with a SIP URI
• A SIP Softclient, Terminal Adapter or an IP-phone
• You need to configure it properly
• If you want to use your own domain name, you need a DNS-hosting service providing you with the possibility to host SRV records.
• You need your national regulator to opt-in to ENUM
• Your regulator has not done this yet? - Then there is no-way to use ENUM with your national number
• You need to find a Registrar in this country
• You have to put all these pieces together by yourself
• Now you have to sit and wait, hoping that somebody will call you with an ENUM enabled device, or using a provider supporting ENUM look-ups
• BTW, is your provider from above doing ENUM look-ups?
• Calls from the PSTN will still terminate on your primary line
• Only calls from the Internet terminate on your IP device

Nobody is able to do this, except some freaks.

You cannot sell ENUM as is, because nobody understands it.

You can only sell a service or a product a customer understands.

What you can sell is:

• a product to an enterprise (or a freak)
• a service to moms and dads ah.. residential users

You have to bundle ENUM into a product or a service e.g. a VoIP (IP Communications) product or service

So new approaches are needed:

• ENUM for IP-based private networks ("PBX“ and “IP-Centrex”) with direct-dial-in (DDI) (a product)
• ENUM-enabled number ranges for nomadic users (teleworkers and road-warriors, using laptops, PDAs, WiSIP phones and dual-mode devices)
  
• mobile numbers with validation via the SIM-Card, to be potentially used with dual-mode devices -> both bullets enabling Fixed Mobile Convergence
• Geographic numbers (genuine or ported) for virtual VoIP providers
• residential users with terminal adapters and FXO ports (product for freaks)

In all these cases the calls are terminated on the same device

I then presented an real example for the usage of ENUM within enterprise PBX linking VoIP-islands together, featuring the following advantages (see animated slides)

• the enterprise PBX can be reached from PSTN and from Internet
• calls to other ENUM-enabled numbers are routed via VoIP and the Internet
• improved functionality (IM, Video, Conferencing, presence, …)
• better quality for native VoIP calls

A second real example showed the usage of the ENUM-enabled number range in operation in Austria since May 17th:

• The format of the number range is: +43 780 abcdef (ghi)
• the registration of the ENUM domain IS the number assignment
• a cancellation of the ENUM domain will relinquish the number
• easy, cheap, one-step process
• end-user is in control of the ENUM entries
• decoupling of number range allocation and gateway operator
• any gateway may route the whole number range,ust needs to be able to query ENUM
• any gateway may route similar number ranges (e.g. +87810, +42360, +260510, …)
• these gateways are called generic gateways

The ENUM-enabled number range provides for the first global IN-service.

So ENUM is on its way, but as Tom also pointed out in the next presentation, there a many problems left to be resolved (if ever):

• Opt-in of more countries (especially the US)
• Metcalfe's Law
• More applications and implementations
• VoIP providers providing SIP URIs
• etc, etc.

I will report on Toms presentation in my next post.