AT&T 7500 series, 7100 series, 2500 series manual DCS Clusters, Switch Node Capacity, DCS Links

6-2DISTRIBUTED COMMUNICATIONS SYSTEM (DCS)

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DCS CLUSTERS

DCS is installed on groups of switches, called "DCS clusters." Nodes in DCS clusters can be DIMENSION, System 75, System 85, Generic 1, or Generic 2 communications system. Each node must share the cluster’s uniform numbering plan. That is, each extension in the network must be identified by the same number of digits, and DCS users must reach each other by 4- or 5-digit extension-number dialing.

The number of nodes a DCS cluster can contain is dependent upon the type of switches in the cluster and the version of switch software they are running. In addition, the number of nodes in a DCS cluster is limited by the number of switches that can be connected to the node with lowest signaling link capacity and the number of signaling links that are already used for other connections (such as connections with adjunct processors). Shown below is a table giving the maximum number of DCS node connections each type of switch can support.

	Table 6-1.DCS Node Capacity
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⎜	Switch	⎜	Node Capacity	⎜
⎜		⎜		⎜
______________________________________				⎜
⎜		⎜
⎜		⎜	12	⎜
⎜ DIMENSION		⎜		⎜
⎜ System 85, R2V1		⎜	12	⎜
⎜ System 85, R2V2 and V3		⎜	20	⎜
⎜ System 85, R2V4		⎜	63	⎜
⎜ Generic 2		⎜	63	⎜
⎜		⎜		⎜
⎜ System 75		⎜	64	⎜
⎜ Generic 1		⎜	64	⎜
⎜		⎜		⎜

Figure 6-1shows a DCS cluster. In the figure, a System 75 is connected to a System 85 DCS node through both a tie trunk and a signaling link (PI/DCIU). While both System 85s are connected to a DIMENSION DCS node by tie trunks and signaling links (DCIUs).

Note that a DCS network node can function as a DCS endpoint, or DCS tandem, or both. Network endpoints are nodes that can initiate or terminate DCS calls; DCS tandem nodes relay interswitch DCS calls. (See Engineering Considerations at the end of this chapter for a discussion of the number of hops for which a DCS cluster should be engineered.) Note that the System 75 R1V2 and System 75 XE R1V2 can function only as DCS endpoints.

DCS LINKS

As stated, DCS nodes communicate with each over two types of links: tie trunks and signaling links. The tie trunks carry the actual voice communications, while the signaling links carry call information that the destination switch uses to provide feature transparency.