Data Communications Networking Devices - 4th Ed.pdf

838 _____________________________________________ MULTIDROP LINE ROUTING ANALYSISbetter understand the procedure used in applying the minimum-spanning-treetechnique, let us examine an example of its use.Figure D.1 illustrates the location of a mainframe computer with respect to fourremote locations that require a data communications connection to the computer.Assuming that remote terminal usage requires a dedicated connection to the computer,such as busy travel agency of®ces might require to their corporate computer,an initial network con®guration might require the direct connection of each locationto the computer by separate leased lines. Figure D.2 illustrates this networkapproach.Figure D.1Terminal locations to be servicesFigure D.2Using separate leased linesWhen separate leased lines are used to connect each terminal location to themainframe, a portion of many line segments can be seen to run in parallel. Thus,from a visual perspective, it is apparent that the overall distance of one circuitlinking all locations to the computer will be less than the total distance of individualcircuits. Other factors that can reduce the cost of a composite multidrop circuit incomparison to separate leased lines include differences in the number of computerports and modems required between the use of a multidrop line and individualleased lines.