NGN Number Challenge

According to Matt Townend, Managing Director of networking consultancy illume, one of the key challenges faced by carriers transitioning to Next Generation Networks (NGN) was identified as numbering.

“Our recent research that in the all new world of IP telephony, carriers need to translate the worlds existing telephone numbering scheme into IP addresses, a mechanism known as ENUM (Electronic Numbering or Electronic Number Mapping).
In essence, ENUM is a mapping and look-up service which can translate an E.164 number (the global PSTN numbering scheme), into a domain name (i.e. an IP address). The structure is similarly based on DNS looks ups and is an IETF standard defined within RFC 3761.”
The challenge, according to illume is that the task of ‘number translation’ is not easily scalable; meaning that larger service providers already committed to NGN will have a proportionally larger problem to solve.

If the system is to compare favourably with the call setup times experienced within the PSTN, (i.e. less than 200 milliseconds), then the latency required with ENUM lookup must be within a few milliseconds. Such a system will be expected to cope with (for example) 20-30,000 queries/second and hold millions of records. The DNS ‘style’ servers must exhibit consistently high levels of performances even under high load conditions; the failure of which would otherwise render the whole NGN unusable.

The other challenge facing NGN operators concerns the peering of their networks with other NGN operators and the associated requirement to share ENUM.

“Handing off calls across a networking boundary is not such much a technical issue as one concerning customer ownership and control. The contents of an ENUM registry can contain sensitive information which needs to be ‘managed’ within a competitive environment. As a consequence, the market has seen the creation of a number of third party Peering providers who offer to independently ‘manage’ a common ENUM on behalf of their members; ensuring security and ownership remain intact.

How BT 21CN will cope with both the technical challenge of ENUM and the commercial arrangements surrounding peering is a matter of conjecture, what is not in doubt however is the challenge faced.”

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