Lucent Technologies 555-661-150 manual Routing for Outside Calls

MERLIN LEGEND Communications System Release 6.1	Issue 1
Network Reference 555-661-150	August 1998
2 Call-Handling Scenarios
Network Configuration Scenarios	Page 2-26

Routing for Outside Calls

This topic examines routing for hypothetical outside calls, to show how the system managers in Scenario 1 work together to maximize cost benefits from the private network. As you study the call route examples in Table 2–4, page 2-27, review the general setup as described in Table 2–2, page 2-24 and the ARS routing summary in Table 2–3, page 2-25.

The first example call shows a user at the System A New York location dialing an ARS call beginning with the digits ￿￿￿￿￿, for a call in the same area code as the System B location in Holmdel, NJ. System A’s ARS feature, invoked by the dialed ￿, allows the call, because the Route 1 (and 2) FRL is 0, equal to the extension FRL. System A prepends the System B ARS access code, 9, and directs the call to Route 1, tandem PRI trunks connected to System B. The call is accepted by System B, because the FRL for the default COR assigned to all non-tie trunks takes the place of an extension FRL. Its value is 3.

If Route 1 is busy, System A’s ARS directs the call to Route 2, which consists of pools of local PSTN trunks. However, the FRL of 1 for the second route is higher than the extension FRL of 0, so the call is denied. The user hears the fast busy tone and could turn on Selective Callback to wait for an available Route 1 tandem PRI trunk.

In this example and the others, the local ARS first allows or disallows the call based on the Allowed/Disallowed list and a comparison of the extension FRL and the FRL for the available route. If the extension FRL is equal to or higher than the route FRL, the call is permitted. If the call is routed to the other system, that system’s ARS feature compares its route FRL to the default COR FRL assigned to all non-tie (tandem PRI) trunks before routing the call to the PSTN. Both systems use a default COR FRL of 3. The COR FRL must be equal to or higher than the route FRL in order for the call to go out. In your own system, you may need to assign a lower remote access COR FRL, depending upon whether you want to reserve local ARS routes.

The COR settings also include an option for barrier code requirement. This option is ignored for ARS-routed and intersystem extension calls that arrive on tandem trunks; no barrier code is required for these calls. However, if a remote access DID or PRI dial-plan routed call arrives at the local system from the PSTN, a barrier code is required; this requirement is important because the default COR settings does not outward restrict such remote access calls. In addition, a barrier code is required when a user dials a Remote Access code that is included in the non-local dial plan. The system managers apply FRL restrictions, outward restrictions, and Disallowed Lists to each barrier code.

Both systems assign Disallowed List 7 to the default, non-tie COR. This list prevents calls across the private network to 900 and 976 numbers, as well as to other numbers that organizations often want to prohibit. See “Facility Restriction Levels and Remote Access” on page 5 for more information.