Role of ENUM in NGN Interconnect

I have blogged about ENUM here and here and its been quite a while. In these last couple of years ENUM has evolved a bit and now GSMA has its own Number translation service called Pathfinder.

The following is a presentation by GSMA in the recently concluded The 3GPP release 8 IMS Implementation, Deployment & Testing workshop.

The Role of ENUM in NGN Interconnect

View more presentations from Zahid Ghadialy.

NRS, ENUM and NGN

The way most of mobile savvy people work is that they have bundles of free minutes on their mobile which they use for calling people locally/nationally and then they have VoIP based clients like Skype they use for calling people on similar services locally/nationally/internationally. There is a constant juggle between Mobile numbers and VoIP numbers. What if we were able to use our number with VoIP client so regardless of whom you are calling, if they have a similar VoIP service on their side, you get free call and if they dont have this VoIP client then you use your inclusive minutes or get charged. ENUM will be able to solve this.

According to a Yankee Group report titled "ENUM Will Be Reinvented as a Strategic NGN Element", In spite of its early struggles, ENUM, short for Electronic Numbering or Telephone Number Mapping, is well positioned to provide a fundamental underpinning of the Anywhere Network™ as it relates to the efficient routing of any IP-based service across operator domains. It is in this new role that ENUM evolves from its rather meager beginnings to a strategic role in the transition to IP.

I wrote about ENUM sometime back as that was mentioned as magical entity in one of the conferences. Since then I have managed to find the Nominet presentation which was discussed in the conference. Infact there was a conference in London on ENUM organised by Nominet. If you are not clear about ENUM from my earlier Blog then please check Technology Inside Blog here.

We can discuss again here, why ENUM is important:

Imagine the NHS has 500 telephone numbers that it operates as 0800 freephone numbers to allow customer (patients) to contact various local departments. The cost of each minute of every call is borne by the NHS so ultimately by the British taxpayer. Now the NHS also has VoIP connectivity and decides to advertise their 0800 numbers through DNS using ENUM. Subsequently, every time someone using VoIP decides to call any of those 0800 numbers their VoIP provider will find the 0800 number in the ENUM DNS listings for the NHS and will connect the caller to the medical department using VoIP alone - at no cost to either party (usually).

Siemens have a very good presentation that shows different uses of ENUM.

Clearly with this approach there is scope for financial savings. That said, there remains considerable work needed to achieve even this small goal, let alone the potential options further down the road.

In case you were wondering, ENUM is an international standard being implemented by individual countries separately through their respective Governments. The UK Government, through regulator OFCOM, has assigned the design, implementation and ongoing administration of the project to UKEC who, in turn, have contracted much of the work to Nominet. Nominet administer and maintain the .uk gTLD - when you buy any domain ending .uk it is ultimately sold by Nominet although almost always through a reseller (”registrar”) like GoDaddy.

GSMA and NeuStar have been working with leading operators to provide a standards-based solution to this problem. This solution is the Number Resolution Service, or NRS.

NRS is a GSMA Managed Service operated by NeuStar. The service facilitates IP interoperability by translating telephone numbers to IP-based addresses. Interoperability is particularly important in facilitating the uptake of emerging services such as MMS, IMS and Packet Voice.

Based on Carrier ENUM, NRS is available to mobile operators, fixed network operators, and related service providers. The service is currently being piloted with a number of operators, with commercial availability scheduled for the autumn of 2008.

As next generation IP-based services proliferate, operators can utilise NRS to position new services behind the telephone number already used by subscribers. Whenever a telephone number is used to identify an end user, the NRS service will facilitate the discovery of URI containing information specific to the service being provided.

NRS is provided as an off the shelf managed service, interoperable on a global basis, providing all the facilities and features necessary to implement an operator’s interconnect policies. Pricing is based on a cost effective “pay as you go” model with no up front capital investment required. NRS thus helps lower the entry barrier for new services and promotes innovation by simplifying the product development and implementation process.

ENUM is going to be hated by the CPs because it will lower their per minute revenue which they are getting at the moment but they it is definitely going to provide new opportunities (and competetion). At the same time the customers will love it because they will get loads of free calls and dont have to worry too much about installing different VoIP clients on their phones. At present it is still in the initial stages with everyone waiting for others to adopt it first but ENUM is here to stay.

Abbreviations:

• ENUM - tElephone NUmber Mapping (I have also seen Electronic NUMbering)
• CP - Communications Provider
• SBC - Session Border Controller
• NHS - National Health Service (in UK)
• NRS - Number Resolution Service
• GSMA - GSM Association

Whats this ENUM business

In the recently concluded Unified Communications 08, one of the presentations was titled "The Magic of ENUM". I didnt get a chance to attend that but tried to dig out what this magical thing called ENUM is.

The following is from The IP Multimedia Subsystem by Travis Russel:

In the SIP domain, subscription addresses use the form of a Universal Resource Identifier (URI). This is analogous with the Universal Resource Locators (URLs) we use to reach Web sites on the Internet, but they are assigned to subscriptions for reaching individual subscribers. It is the concept of the URI that makes communications models in the IMS unique. The ability to reach a subscriber based on these very personal identities rather than numbers, and to apply these addresses to all forms of communications, is the purposeof the SIP protocol within the IMS.

A URI can take two forms. A SIP URI uses the same form as an e-mail address, consisting of username@domain. The first part of the address is typically the username of the subscriber, while the last part is the domain name of the network provider where the subscription resides. The last part of the domain name (.com, .org, etc.) defines the type of organization according to Internet rules. SIP also supports addresses in the form of telephone numbers, referred to as TEL URIs. A TEL URI uses the same form as a SIP URI, substituting the telephone number for the user name. These are used most commonly when a call is originated in a non-SIP domain, or when a call is being placed to a non-SIP network (such as a call from the IMS to a wireline subscriber in the PSTN). The TEL URI is a good example of interoperability between legacy PSTN and IMS.Since legacy networks will continue to support the use of telephone numbers for some time to come, there remains a need to translate these telephone numbers into public identities for use within the IMS.

The actual conversion process is provided through a function known as ENUM. This function translates an E.164 telephone number into a SIP or TEL URI. The ENUM function does not translate the identity into an IP address, however. This remains the function of the Domain Name Server (DNS). We will talk more about these functions later. Eventually, TEL URIs may disappear completely as we become more and more accustomed to using SIP URIs for all communications. This is still a long way off, however, and something we may not see for decades.



For more information see the following book:

You may also be interested in the following presentations:

• ENUM Variants by Jim McEachern, Nortel
• ENUM will it pay? by Richard Shockey