Routing Outbound Calls through the PSTN
Calls destined to be routed through the PSTN usually require only one route
pattern. In some offices, you may find it necessary to create an access code to
access the PSTN, such as dialing a 9 before the number. In North America, the
dialing convention is divided into sections.There is an area code (510), the
exchange number (536), and the station ID number (XXXX). In order to make a
long distance call (a call outside your calling area), you may also need to dial a 1
at the beginning of the string. In some cities the convention for ten-digit dialing
is always necessary to complete calls. In these circumstances it is necessary to dial
the area code, but not the preceding 1.
With Cisco CallManager, you are able to create route patterns allowing you
to route calls that differentiate between a local call that requires ten-digit dialing
and a call that only requires seven-digit dialing. If the rule is not set, then Cisco
CallManager will wait ten seconds without dialed digit detection, and will
assume if there are no other digits dialed, then the user has completed dialing.
Creation of a local PSTN gateway dial plan is easy (and mostly painless).
Gateways that are based on Skinny Gateway Protocol and MGCP will have their
dial plan information configured within Cisco CallManager itself, whereas H.323
gateways will require only a small set of dial peers.The dial peers are then used
by the gateway to direct calls destined for the PSTN through the Cisco
CallManager.
If you are located outside North America, the numbers of digits that must be
dialed for call completion differ. In this case, you will need to create multiple
length dial-plans.The problem is, with the current version of Cisco CallManager,
the system doesn’t know when the dialing is complete, so you need to create
specific route patterns.