Nortel VoIP Gateway, Configuration Manual, Page: 149 / 220

Numbering Plans in H.323 149
Norstar VoIP Gateway Configuration Guide
Numbering Plans in H.323
The Norstar VoIP Gateway uses the H.323 protocol for its call control. To setup a dialing plan, you
therefore need to understand a bit about how H.323 represents numbers.
In H.323, numbers are classified by their Numbering Plan Indication (NPI) and their Type of
Number (TON). The Norstar VoIP Gateway supports all NPI/TON classifications used in the
standard. A short list of the most important NPI/TON values are as follows:
H.323 protocol also can use a “H323-ID” for identification of an endpoint. This H323-ID is a text
string that can be used to descriptively identify an endpoint within the H323 protocol. An example
might be “Head Office” or “Branch 4332”. This should not be confused with the Caller ID name.
H323-ID is not used for caller ID.
Planning Your Numbering Plan
This is the most important step. For all VoIP endpoints in your network, you need to know what
numbering plan is used for each location and ensure that they are coordinated with all other
endpoints.
Private numbers can be handled in one of two ways. In a Coordinated Dialing Plan (CDP)
extension numbers are unique across the system. In other words, if there is an extension DN of
4332 in Site A, there will not be an extension of 4332 anywhere else in the system. In a Universal
Dialing Plan, many different sites could have local DN of 4332. Each site, though, would also have
a location number. For example, site A may use 393, site B may use 394 and so on.
Table 24 NPI/TON values
NPI TON Description
Unknown
Unknown A valid classification, but one that has no information about the
numbering plan.
E164 Public
Unknown A public number in E.164 format, but no information on what
kind of E.164 number.
International A public number in complete international E.164 format.
For example: 16135551234
National A public number in complete national E.164 format.
For example: 6135551234
Subscriber A public number in complete E.164 format representing a local
subscriber. For example: 5551234
Private
Unknown A private number, but with no further information about the
numbering plan
Level 1 Regional A private number with a location. Sometimes called “UDP” or
universal dialing plan. For example: 3932200
Level 0 Regional A private local extension number. Sometimes called “CDP” or
coordinated dialing plan. For example: 2200