Specifications

2-30
Reference Guide
Model No.
Running Head
ISDN Primary Rate Interface (PRI) Server Applications
When an incoming call is received by the system, it first scans all of the primary HSU or FXS
phone numbers to attempt a match. If no match is found, the system then searches the list of
hunt group numbers to find a match. If a match is not found, the system will begin searching
the D channel routing tables, for routing of the call to a PRI line. If no matches are found, the
call is rejected.
2.6.7.2 Local Routing
From an integrated access system perspective, devices such as video codecs or PBXs that are
directly attached to the system, (i.e. do not pass through a carrier network to connect to the
system) are considered “local” devices. All HSU ports are local devices. Any PRI device, such
as a PBX, that is connected to an system D channel configured for “Network” side is a local
device. Local routing is defined as call routing between any two devices. Calls can be locally
routed from a PRI to a PRI (for example, from a local PBX to another local PBX), or from an
HSU to a PRI. HSU to HSU call routing is not supported.
Incoming calls are routed based on the called phone number, not on call profiles. Because the
system does not provide billing information, users may want to prohibit local routing of
D-channels. For example, a carrier may require that all calls are routed through the CO based
switch for billing purposes. To provide for this, local routing can be disabled.
If local routing is disabled, any call coming into the system on a network side (i.e. local) D
channel will be routed only to a user side D channel based on the called number. Even if the
called number matches, such a call will never be routed to an HSU port or a network side D
channel when local routing is disabled.
When local routing is enabled, then any call coming in on a D channel will be routed to the
first matching phone number, regardless of whether or not the match is for a local device.
2.6.7.3 Bi-directional Default Routing
Bi-directional Default Routing is provided for automatic routing when a node is configured
with two Primary Rate D channels as shown in Figure 2-19. In two channel systems, the user
does not have to configure any routing information, as all calls received on one D channel are
automatically routed to the second D channel. The user only needs to enter routing
information for those calls destined to a local HSU or FXS ports.