- Table of contents
- Type Of Number and Numbering Plan Indicator
Type Of Number and Numbering Plan Indicator¶
In PSTN networks, calling and called party numbers are relatively simple: they just consist of a linear row of decimal digits.In ISDN (and its cousin, the SS7 signaling network), party identifiers are a tuple consisting of three components:
- the numbering plan indicator (NPI)
- the type of number (TON)
- a series of digits
When sending addresses (numbers) in an ISDN or SS7 network such as OCTOI, you have to make sure that the entire tuple of (NPI, TON, digits) is given in a meaningful way. You cannot use an international number with trailing zeroes, or a national number with international prefix!
Numbering Plan Indicator¶
E.164 is the normal numbering plan in telephony. It is specified in ITU-T Recommendation E.164, and it is what people normalyl consider a phone number. It also is the specification for the familiar international prefixes like
49 for Germany,
1 for North America, etc.
This Unknown type of number indicator is used if the type is unknonw to the sender. This basically makes the interpretation of the dialled digits dependent on the context/location/position in the network.
Type Of Number¶
The National type of number indicator is used to specify that the digits are in fully-qualified national format, including any national area code but excluding any prefix (such as e.g. the
0 used by the end-user in Germany when dialling a number like
30 is the Berlin Area code. The correct representation of a German national number with Berlin prefix is
3012343038, without the trailing zero)
The International type of number indicator is used to specify that the digits are in fully-qualified international format, including any international prefix such as
49 for Germany. The above-mentioned national number hence would be
493012343038 in international type.
The Subscriber number
This Unknown type of number indicator is used if the type is unknonw to the sender. This basically makes the interpretation of the dialled digits dependent on the context/location/position in the network