Numbering plan
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A numbering plan is a type of numbering scheme used in telecommunications. This is a set of rules used for making numbers. For example, most telephone numbers belong to the E.164 numbering plan, though that won't include internal extensions in some PABXs.
The E.164 numbering plan for telephone numbers, includes:
- Country calling codes
- Regional numbering plans, such as:
- Various national numbering plans, such as:
- The UK National Numbering Scheme
Apart from the use of numbering plans for telephone numbers, they are also used in routing of SS7 signalling messages as part of the Global Title. In Public Land Mobile Networks, the E.212 numbering plan is used for subscriber identities (e.g. stored in the GSM SIM) whilst E.214 is used for routing database queries across PSTN netwprks.
Numbering Plan Indicator
The Numbering Plan Indicator (NPI) is a number which is defined in the ITU standard Q.713, paragraph 3.4.2.3.3. The NPI is used primarily in SCCP messages. As of 2004 the following numbering plans and their respective Numbering Plan Indicator values have been defined:
| NPI | Description | Standard |
|---|---|---|
| 0 | unknown | |
| 1 | ISDN Telephony | E.164 |
| 2 | generic | |
| 3 | data | X.121 |
| 4 | telex | F.69 |
| 5 | maritime mobile | E.210 and E.211 |
| 6 | land mobile | E.212 |
| 7 | ISDN/mobile | E.214 |