Lispp42 - Programming Project#4 Network/Trees Fall 2011 CMSC 420 Hanan Samet The use of computer networks has seen a dramatic rise in recent years

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Fall 2011 Programming Project #4 — Network/Trees CMSC 420 Hanan Samet The use of computer networks has seen a dramatic rise in recent years. Historically, it is based on the use of the telephone as a communications medium between different computers. The network concept is a solution to the interconnection problem. In greater detail, suppose that 7 people at different locations wish to be able to talk to each other. One solution is to establish a separate direct line from each person to the other. This requires 21 different lines (e.g., Figure 1). Clearly, the more people, the greater the cost. The number of lines (and their length) can also be decreased by insisting that at any instance of time each person can only talk to one other person. In fact, this is how your home telephone works with respect to phone numbers having the same prefix — i.e., if your number is 345-xxxx, then your phone is connected by a line to the 345 switching office as is everyone else with that prefix (e.g., Figure 2). If you have a two-party line, then you and another person share that line to the switching office and thus at any instance of time only one of the two of you can have a conversation with someone else. Notice, that with a single party line we require only 7 lines — one per person going from that person to the switching office. B A C D F O E Figure 1: Full network 345 F A B C D E O Figure 2: Switched network In order to be able to talk to people having phone numbers with a different prefix than yours, the phone company dedicates some lines from your switching office to the switching office of the other prefix. This is based on the premise that not everyone with prefix A will want to simultaneously speak to someone with prefix B. For example, see Figure 3 where there are 7 people with prefix
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This note was uploaded on 01/13/2012 for the course CMSC 420 taught by Professor Staff during the Fall '08 term at Maryland.

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Lispp42 - Programming Project#4 Network/Trees Fall 2011 CMSC 420 Hanan Samet The use of computer networks has seen a dramatic rise in recent years

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