AT&T 7100 series, 7500 series, 2500 series, 7200 series, 7400 series manual Definity PBX ⎜ Feature

DISTRIBUTED COMMUNICATIONS SYSTEM (DCS) 6-21

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∙Leave Word Calling — Leave Word Calling messages can be stored on AUDIX for users on remote switches. Leave Word Calling activation can be from any switch.

ENGINEERING CONSIDERATIONS

The design of a DCS cluster is the process of determining the size, quantity, and configuration of the switching nodes, internode (intracluster trunks), main PBX access lines, data links, and off-net facilities. A design objective is to provide, at minimum cost, the traffic and transmission grades of service that are acceptable to the customer. Very small DCS configurations may be designed manually, but most will be designed with the aid of a mechanized design system, like E-INOS.

The limitations of the number of nodes and other cluster criteria are listed below:

Table 6-5.DCS Cluster Limits

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⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ DIMENSION

⎜

SYSTEM 85

⎜

SYSTEM 75

⎜

DEFINITY

⎜

⎜

⎜

PBX

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ FEATURE

⎜

FP8

⎜ R1

R2

⎜

R1

⎜

G1

G2

⎜

⎜

⎜

Iss 3

⎜

-

⎜

V1

⎜

V2

⎜

V3

⎜

V4

⎜

V1

⎜

V2

⎜

V3

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

_

⎜

⎜

⎜

⎜

⎜

⎜ Nodes/Cluster

⎜

12

⎜ N/A

⎜

12

⎜

20

⎜

20

⎜

63

⎜ N/A

⎜

64

⎜

64

⎜

64

⎜

63

⎜

⎜ Ext/Cluster

⎜

81K

⎜ N/A

⎜

81K

⎜

81K

⎜ 100K

⎜ 100K

⎜ N/A

⎜ 100K

⎜

100K

⎜ 100K

⎜

100K

⎜

⎜

⎜

*

⎜

⎜

2500

⎜ 5000

⎜

5000

⎜

6000

⎜

⎜

200

⎜

200

⎜

400

⎜

6000

⎜

⎜ Trks/Switch

⎜

⎜ N/A

⎜

⎜ N/A

⎜

⎜

⎜

Dependent on memory size: 256 for DIMENSION 600; and 250, 475, and 1100 for DIMENSION 2000 with memory sizes C, D, and F, respectively.

Cluster limits are determined by the switch with the least functionality. For example, if a System 85, R2V1 is in the cluster, the maximum number of nodes that can be in the cluster is 12. Note that the maximum number of switches supported by AUDIX in a DCS network is 20.

Since a message is associated with a particular trunk and trunk group, the message must originate and terminate on the same two systems connected by that trunk group. Terminating a message means that it comes in on a link and channel and is routed to a processor channel and then into the system where it interacts with call processing and administration software. If the call is routed on to another node, the message is regenerated with new trunk group and trunk number information and sent on. This message must, in turn, terminate on the system connected to the other end of the trunk the call is routed to.

In a hop, however, the message does not terminate at the hopped system, but passes into and out of the DCIU or PI without interacting with the system — it goes into the DCIU or PI on one link and channel and comes out on a different link and channel, the message unchanged. This is done because the terminating system might not have any available channels to the originating system, but some other system might have some unused channels on a link to the destination system. The message can do this multiple times to eventually get to the destination. Thus, by using these available channels on other systems, it is possible to interconnect DCS nodes with more channels. The following figure illustrates a hop: