# About Voice Networks

A voice network is a group of elements that are interconnected via IP trunks and/or DPNSS over T1 trunks.

To place a call to an extension on another element, a user must dial Automatic Route Selection (ARS) digits in addition to the extension number. When a user calls an extension on another element these ARS digits appear in the phone display of the called phone. In addition, certain features, such as Message Waiting Indication and Group Paging, are not supported across the network.

A large network can consist of standalone network elements and cluster elements.

## Primary Node Identifier

A Primary Node Identifier (PNI) is used to route calls between standalone network elements, between standalone network elements and a cluster, or between multiple clusters. If all the elements are members of a single cluster, you do not need to assign the elements with PNIs. If you have a large network consisting of more than one cluster, you must assign each cluster or standalone network element its own PNI. In this case, each element in the cluster shares the same PNI.

## About Resilient Networks

The Resiliency feature allows a network to maintain calls in progress, handle new incoming and outgoing calls, and continue to provide voice mail service in the event of a MiVoice Business failure or a network-level failure.

Resiliency is achieved through setting up a network of MiVoice Business systems in a resilient cluster, which is a specially configured network of MiVoice Business systems that can direct IP phones and route and maintain calls.

See the MiVoice Business Resiliency Guide for information about designing and implementing a resilient MiVoice Business network.

Related Topics

- About Clusters

- How Calls are Routed in a Cluster

- Managing the Telephone Directory