The Magic Behind TMT – The Global Numbering Plan

A brief introduction to TMT ID’s global numbering plan

Being a mobile-centric identity and intelligence company, the data that resides at the base layer of most of the things we do is the global number range layer that contains all numbering resources allocated to all network operators by regulators around the globe.

When we started building our services, we began by researching and building our number range data for the countries we initially serviced. As we added more and more datasets globally, we realised we needed a very accurate global number range to provide the best possible service to the market.

For those who do not know, a global numbering plan contains all the number ranges that have been allocated to network operators around the world. Those numbering resources are assigned by telecommunication regulators to the networks in their countries and from those ranges, phone numbers are assigned to customers.

A very important lesson learned in those early days was when one of our MNP query customers stopped sending queries for a country. When asked why, they told us they had access to the MNP database directly. However, two weeks later the queries returned — they couldn’t figure out the correct numbering plan for the country, resulting in higher SMS termination costs than using our query solution.

Initially, the plan was not to build a global solution, however as demand increased, we decided to set about building a truly worldwide one.

Where does the data come from?

We have a dedicated team that researches the correct sources, scripts automatic updates where possible and verifies the accuracy. So, where do they get the data?

• International Telecommunication Union Telecommunication Standardization Sector (ITU-T): the ITU-T receives updates from regulators on numbering resources. Most regulators only publish to ITU-T the structure of the numbering plan — for example, what prefixes are landlines, what prefixes are mobile, what the dialling rules are, and what the possible lengths of the numbers are. This is a good source of data, but not granular or updated regularly enough to use by itself.
• National regulators: as the telecom industry is regulated, number ranges are assigned by national regulators. Some publish the data regularly and in a structured format, others make it available only to network operators, others publish PDF decisions on range assignments, and others don’t publish it at all.
• IR.21 documents: being a member of the GSMA, TMT ID has access to the IR.21 documents where mobile operators publish data relevant to international roaming, including information about their numbering ranges. Of course, some do this more regularly than others.
• HLR data: as we found out the hard way, sometimes the data from ITU-T, regulators and IR.21 may differ, so we turn to our own Live HLR solution for querying the networks directly to find where some numbers are, validating the source of truth in many cases.

There is no single source of truth, unfortunately. There are cases where regulators publish incorrect data or operators publish incorrect data in their IR.21 documents. In countries with a high level of merger and acquisition activity between network operators, numbering resources are either fully or partially transferred when networks are acquired. We have to get all the layers working smoothly to resolve conflicting data — and this is why our number plans team are worth their weight in gold.

How often is it updated?

It depends on the complexity and dynamism of the number range allocations and the merger and acquisition activity of each country. To make sure we have the most accurate and up-to-date global number range allocations, we created an internal SLA for our numbering plans team. Following that SLA, some countries are updated:

• Daily — where we can trust the regulators and IR.21 documents and can automate the process.
• Weekly — where the dynamic is relatively high and manual intervention is needed.
• Bi-weekly — for countries with lower dynamic and manual intervention.
• Monthly — where the dynamic is really low.

There are also two more important dynamics of the global numbering plan:

We receive alerts from regulators, operators or when a new IR.21 is published indicating that a new range is about to be allocated or a range owner has changed. We act immediately.

And as there is no such thing as perfection — although we aim for it — if we get anything wrong our customers will alert us if we miss a range or if the range holder has changed. We investigate through the normal support process and bring forward the particular country update to resolve the ticket.

How and where is it used?

Being the base layer of our data stack, the numbering plan is used in most of our products. We offer the numbering plan by itself in what we call TeleShield. Our customers use the data either by downloading it or by real-time querying it (ENUM, HTTP, SIP redirect) for:

• Routing and screening of voice calls and SMS
• Preventing fraud
• Preventing bypass such as flash calling
• Inside signalling firewalls
• Origin-based rating and routing (OBR)
• Validating online sign-ups
• Customer data cleansing
• Verifying identity

Technically, most companies doing voice use prefix-based allocation, some use prefix plus length and others prefix plus min/max length. Even with our strong background in voice, we use the data internally as ranges (start, stop) because numeric searches — for example, number in (start, stop) — are much faster computationally. We can deliver a very high number of TPS (transactions per second) at sub-millisecond latency using our own in-memory database optimised for phone numbers and attributes.

At the time of writing, there are 3.1 million ranges assigned to 18,000 networks globally (landline, mobile, virtual, VoIP, and more).

How to get it?

We serve the global numbering plan through several channels:

• Download — we can export the data in a few formats (ranges, prefixes, prefixes plus length, prefixes plus min/max length).
• Single number queries — via our TeleShield product. The standard query interfaces are ENUM and REST API.
• Batch number queries — through our portal or by uploading files to our SFTP.
• SIP redirect service — a custom solution for delivering the data either as redirects or SIP error codes.

The data contains:

• Range or prefix
• Country code
• Number type (landline/mobile)
• Extended number type (toll-free, VoIP, etc.)
• Network ID
• MCC
• MNC
• Network name
• Full operator name