AT&T DS1/DMi/ISDN-PRI Generic 1 Implementation, Networking Restrictions and ISDN-PRI Limitations

INTRODUCTION 1-29

one trunk type is needed, only one trunk group is available, and conventional routing digits are inadequate for the current application (for example, when using the same trunk group to provide DID, SDN, and DOD). A single trunk type, other than ISDN-dynamic, cannot provide all services since some calls use CO or tie trunk types.

4.Each AT&T ISDN-PRI nodal service (MEGACOM 800, SDN, ACCUNET switched digital service) may be provisioned to deliver from 0 to 7 digits.

Generic 1 — Implementation

The following describes details of CBC on Generic 1:

1.

2.

The SID-ANI number can be received either per trunk group or per call

When receiving calls over a CBC trunk group, define the usage-allocation plans. These plans prevent a particular nodal service from monopolizing a trunk group or being deprived of the minimum number of trunks.

3.On Generic 1, the “service type” field on the trunk group form permits entries such as CBC, access, tie, and tandem. When CBC is administered, the call-processing software analyzes the

NSF (for incoming calls) for called party number or length. The other entries do not analyze the NSF but permit CBC Service Selection.

Networking Restrictions and ISDN-PRI Limitations

ISDN-PRI has the following limitations:

1.ISDN-PRI facilities cannot be used to connect a main and a satellite (such as a main/satellite trunk). ISDN-PRI trunks provide more feature capabilities than conventional main/satellite trunks. Therefore, it is recommended that AAR be used with ISDN-PRI trunks to provide private network facilities.

Even though main/satellite trunks cannot be used over ISDN-PRI facilities, the main/satellite feature may still exist on a switch that uses ISDN. For example, ISDN-PRI facilities may be used to access the public network using the ARS software while non-ISDN-PRI trunks (such as main/satellite trunks) may be used to connect subtending switches to the main switch. Calls may originate and terminate on the satellite or on the tandem through the main, and route onto the ISDN public network via ISDN-PRI trunks.

2.Centralized Attendant Service (CAS) uses an ISDN-PRI unsupported trunk type. Therefore, CAS is unavailable with ISDN-PRI facilities.

3.Distributed communications system (DCS) network configurations are supported over ISDN- PRI facilities. However, a separate DCIU signaling link is required. This separate signaling link may be a B-channel that is used as a DSC or an analog facility.

4.ISDN-PRI and DCS are two separate networking services. If DCS is used over an ISDN-PRI trunk, in most cases the DCS display appears instead of the ISDN-PRI messages.

With ISDN-PRI, the calling party information is sent to the called party and the called party information is returned to the calling party.