Numbering Scheme
The VoIP network has to resolve the dialed destination number to an IP host address by
using a dial-plan mapper, which takes inputs from the ITU-T numbering scheme.
The standard PSTN uses a specific numbering scheme, which complies with the ITU-T
international public telecommunications numbering plan (E.164) recommendations. For
example, in
consists of an area code, an office code, and a station code. Area codes are assigned
geographically, office codes are assigned to specific switches, and station codes identify a
specific port on that switch. The format in
through 9 and x = digits 0 through 9. Internationally, each country is assigned a one- to
three-digit country code; the country's dialing plan follows the country code.