E.164 is an international standard for telephone numbers, formally known as "The international public telecommunication numbering plan." Published and maintained by the International Telecommunication Union (ITU), it defines the format and characteristics of telephone numbers used in public switched telephone networks (PSTN) and some other data networks. Essentially, E.164 provides a globally unique numbering system that allows any telephone subscriber in the world to be reached by any other subscriber, regardless of their location or network.
Key Characteristics of E.164 Numbers:
Variable Length: E.164 numbers can have a total length of up to 15 digits (excluding the international prefix, like '+' or '00'). This flexibility accommodates the varying numbering plans of different countries.
Structure: An E.164 number typically consists of:
Country Code (CC): A one to three-digit code that uniquely identifies a country or a specific geographic area (like a group of smaller nations sharing a numbering plan).
National Destination Code (NDC): A code that identifies armenia mobile phone number list a specific geographic area (like a city or region) or a network operator within a country. The length and structure of the NDC are determined by the national numbering plan.
Subscriber Number (SN): The number that uniquely identifies the subscriber's terminal within the NDC. Its length is also determined nationally.
Leading Digit Restrictions: The first digit following the country code often has specific meanings, depending on the national numbering plan. For instance, in some countries, it might indicate a mobile number or a specific type of service.
Global Uniqueness: The combination of the country code, NDC, and subscriber number ensures that each E.164 number is globally unique. This is crucial for proper call routing across international networks.
Why is E.164 Important?
The E.164 standard is fundamental to the operation of the global telecommunications network for several key reasons:
International Interoperability: By providing a standardized format for telephone numbers, E.164 enables seamless interconnection and communication between different national networks. Without this standard, it would be virtually impossible to reliably dial and connect to phone numbers in other countries. The network wouldn't know how to interpret the digits or where to route the call.
Global Addressing System: E.164 acts as a universal addressing system for telephony. Just like IP addresses for the internet or postal codes for mail, E.164 numbers provide a globally recognized identifier for each telephone endpoint. This consistent structure allows for efficient routing of calls from any point in the world to any other point.
Facilitates Roaming: For mobile subscribers, E.164 numbers are essential for international roaming. When a user travels to another country, their E.164 number remains their unique identifier, allowing them to receive calls and make calls using the visited network, which can correctly route the traffic back to their home network or the intended destination based on the E.164 number.
Foundation for Billing and Accounting: The standardized format of E.164 numbers is crucial for international call billing and accounting between different network operators. It provides a consistent way to identify the originating and terminating numbers, enabling accurate charging for international calls.
Supports Value-Added Services: E.164 numbering underpins various value-added services, such as international toll-free numbers, premium-rate services, and shortcodes that might have international extensions. The consistent structure allows these services to be offered and billed across different countries.
Stability and Longevity: The E.164 standard has been in place for a long time and continues to be maintained and updated by the ITU to accommodate the evolving telecommunications landscape. This stability ensures that the global numbering system remains robust and adaptable to new technologies and services.
In essence, E.164 is the bedrock of international telephony. It provides the necessary framework for global connectivity, ensuring that telephone numbers are structured in a way that allows for unique identification and efficient routing of calls across the complex web of international telecommunications networks. Without this standard, the simple act of dialing a phone number in another country would be a far more complicated and unreliable process.
