AT&T 7400 series Distributed Communications System Clusters, Main-Satellite/Tributary Networks

5-14ELECTRONIC TANDEM NETWORK (ETN) THROUGH THE ETN AND PNA PACKAGES

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Distributed Communications System Clusters

The distributed communications system (DCS) is a information system that provides a messaging overlay for main-satellite/tributary (MS/T) networks, electronic tandem networks (ETNs), or ETN-MS/T complexes that are designed for DCS implementations. This overlay provides communication among the network nodes so that the operation of a limited number of features is transparent across the network. That is, the operation of certain features is the same (or nearly the same) on each network node.

DCS networks are installed in clusters of switches. Although DCS clusters can include ETN network nodes, the clusters cannot extend through the Software-Defined network (SDN) to include remote ETN nodes.

See chapter 6 for a detailed explanation of DCS.

Main-Satellite/Tributary Networks

Main-satellite/tributary (MS/T) networks are linked to ETN tandems via access tie trunks. It is through ETN tandems that MS/T calls enter and exit the wide-area private network.

Within the MS/T network, calls may be routed via extension number steering, while the ETN demands extension number portability or UDP routing (RNX steering). Between the ETN and the MS/T, this difference is bridged by subnet trunking (see chapter 2) at the ETN tandem; and subnet trunking, internal dial plan extension-to-RNX matching, or direct dial access of the tandem from the MS/T side of the connection (see chapter 4).

ENGINEERING CONSIDERATIONS

The chapter on Designing Alternate Routing Networks in the DEFINITY Communications System and System 75 and System 85 Traffic Theory manual (555-104-504) explains how to design a small ETN. To design larger ETNs, use the Enhanced Interactive Network Optimization System (E-INOS).