Extension dialing via the PNP (Private Numbering Plan) and extension to the GNP (Global Numbering Plan) tables allows extension based dialing to be routed to a globally usable set of entries for all BG (Business Groups) and PNPs, to include globally defined gateways/endpoints.
While it uses the PAC (Prefix Access Code) prefix type of Extension Dialing to mark this call type as extension-to-extension calling, it does not leverage the home extension tables or optional location code defined within a PNP. Instead, it sends the digits to the GNP PAC with an NoA (Nature of Access) of Unknown and E.164 destination selected, so that it can be processed and routed via global tables.The selection of the Extension Dialing PAC prefix type, rather than On-Net Access, does the following:
Permits the potential support of external application and routing scenarios that require this information type
Future-proofs the calling in the event that on-net access later takes on properties that conflict with the proper operation of extension-based dialing that leverages global tables versus private table entries within a PNP.
This method requires the definition of a PNP PAC that is used to send digits to a GNP PAC that can further provide translations, but most specifically to change the NOA to the required type that allows a match to the home DN (Directory Number) tables. From the GNP PAC, the digits are processed by the Global E.164 Code table, and sent to the proper home DN table required to match to a subscriber's record and access the EP (Endpoint) profile for the dialed SIP device/EP. If properly configured, these entries can potentially be used to process incoming gateway/EP calls that also wish to reach subscribers via global routing tables when the gateway is defined in the GNP or even if they are defined in a BGs PNP.
Parent topic: Routing and Translation