International Numbering and SMS - Type of Numbering, TON, Numbering Plan Indicator, NPI
In daily life, people talk about national and international numbers they use for dialing. Such numbers contain an international trunk prefix or the '+' sign, and for many countries a national trunk prefix.
In most European countries the '00' indicates the international trunk prefix whereas the '0' is in many countries the national trunk prefix. In the telecommunications world where numbers are digitally transmitted through multiple networks, the Type of Number (TON) values of National and International are an easy means of indicating mobile numbers without dialing prefixes (international trunk prefix, national trunk prefix). The value Unknown is used when number analysis is to be performed for destination routing purposes An international TON means that the number starts with the country code followed by the national destination code and the subscriber number. The national destination code is also known as the operator code, operator prefix, and is similar to the fixed-line network area codes. It is common for numbering plans to have multiple national destination codes.In some countries, the wireless and fixed-line network numbering plans are fully integrated. On the mobile terminal the '+' is used as a visible cue to indicate an international number. The '+' itself is not encoded in the address, it simply translates to TON International.
Example:
a mobile sending a message to +4467811223344 is in fact using a TON=1 and dest_addr = 4467811223344
A national TON means that the number starts with the national destination code followed by the subscriber number. Effectively, it is the international number format with the country code stripped off. When a mobile sends a message, unlike the '+' for international number format, there is no visual cue to indicate a national number. It is purely an address encoding value.
Message Centers typically operate with international numbers as the mobile network interface usually requires this. So ESMEs sending message to the MS should expect that a national number will be expanded into international format. ESMEs should expect the source_addr TON of a mobile originated message to be set to international or national, and that the TON can vary from one message to another, even if they are from the same mobile device. This is especially important for application-based database lookups using the mobile number.