Local Area Networks - Unit 1 Summary

Unit 1

Summary

This unit reviewed the basic concepts that underlie all networks.

Networks fall into one of four broad classifications, according to their size and the distance between their nodes:

	LANs link computers within one building or floor.
	Campus networks link several LANs in adjacent buildings.
	MANs link LANs across a city-wide area.
	WANs link LANs across a region, nation, or the world.

Networks can also be described in terms of the physical arrangement of their internal connections. Five main types of topologies are common in networks:

	Bus networks link nodes to a single shared electrical cable. This approach has largely been replaced by star networks.
	Star networks link nodes to a shared wiring device, such as a hub or switch. This arrangement is flexible and easy to manage.
	Ring networks link each node to two others, forming a physical ring. If one station fails, the ring is broken. Thus, some ring networks (such as FDDI) use two parallel rings.
	Star ring networks are physically wired in a star topology, but data moves from node to node in a logical ring pattern.
	Mesh networks link each node to every other. These are more common in MANs and WANs, and become expensive and hard to manage when the network grows to more than a few nodes.
	Cloud networks are privately owned systems that provide transmission services for a fee. The actual structure of the cloud may use any of the topologies above, but those details are invisible to the user of the network's services. The telephone system and the Internet are two widely used network clouds.

We also looked at the difference between programs, processes, and protocols. A network uses many specialized programs and processes to move data, rather than a few complex components. Because these elements interact in a hierarchical pattern, we call a set of cooperating processes a protocol stack. The OSI reference model describes an idealized protocol stack, in which each layer provides a service to the layer above, and uses the services of the layer below.

Each layer of the stack uses its own protocol to communicate, and each protocol uses its own type of address. Thus, several types of addresses, both physical and logical, are needed to transmit a data message between applications on different nodes.

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