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:
  • the European Telephony Numbering Space
  • the North American Numbering Plan
• Various national numbering plans, such as:
  • Telephone numbers in the United Kingdom

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) while E.214 is used for routing database queries across PSTN networks.

[edit] 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, indicating the numbering plan of the attached telephone number. NPIs can be found in SCCP and SMS messages. As of 2004^[update] 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

[edit] See also

• Telephone numbering plan