Data Communications Networking Devices: Operation, Utilization and Lan and Wan Internetworking, 4th Edition

APPENDIX D

MULTIDROP LINE ROUTING ANALYSIS

One of the most frequent problems encountered by organizations is to determine an economical route for the path of a multidrop circuit. This type of circuit is used to interconnect two or more locations that must be serviced by a common mainframe computer port. Although there are several commercial services that the reader can subscribe to as well as a free service offered by AT&T to obtain a routing analysis, in many situations this analysis can be conducted internally within the organization. Doing so not only saves time but may also eliminate some potential problems that can occur if one relies upon programs that do not consider whether the resulting number of drops on a circuit can support the data traffic while providing a desired level of performance.

In this appendix, the use of a simple algorithm that can be employed to minimize the routing distance and resulting cost of a multidrop circuit will be discussed. Since there is a finite limit to the number of drops a multidrop circuit can support, we will also investigate a method that will enable users to estimate the worst case and average terminal response times as the number of drops increase. Then if the response time exceeds the design goal of the organization, the networks manager can consider removing one or more drops and placing them on a different multidrop circuit.

The minimum-spanning-tree technique

When the total number of drops to be serviced does not exceed the capacity ...