Layers 1 and 2 — topology and data link protocols

Networks require physical connections between computers or nodes, and there are several options when it comes to network topology. Early networks often employed a bus topology, in which nodes are connected to a single cable which acts as a backbone. A terminating resistor at either end of the cable prevented signal reflection. This topology had many advantages. It was simple to implement, and could function even if one or more nodes went down. There were several disadvantages, however. A break at any point in the cable, or a missing terminating resistor, could bring down the whole network.

Another problem stemmed from the protocol used on these early bus networks. Most of these networks used ...

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