Whether they are corporate intranets, wireline carrier networks, or wireless networks, networks are comprised basically of nodes and transmission channels. Nodes, also known as network elements (NEs), support a variety of communication functions. Several dozen different NEs exist for the aforementioned networks. Many of these NEs reside at a particular layer of the Open Systems Interconnection Reference Model (OSIRM); others support several layers of the protocol model. (Generally, it is more cost-effective to have an NE cover multiple layers than discrete devices; this way, there is no need for multiple chassis, multiple power supplies, multiple racks with interconnecting cables, multiple network monitoring systems, and so on.) Regardless of the functional bundling, NEs are critical to proper functioning of any network.
In this chapter we look at some of the basic NEs that are commonly used to construct communication networks. Specifically, the purpose of this chapter is to review basic networking functions and contrast switching to grooming and ...