Network Communications

This lesson introduces the basic building blocks of network communications and some of the structures used to construct data networks. There are many different kinds of data networks- from enterprise networks used by large corporations to a simple two- node local area network (LAN) used in a private home. However , many of the same of the same principles apply to all networks, regardless of size or complexity.

After this lesson , you will be able to

·          List the services provided by network protocols.

·          Describe how protocols enable networked computers to communicate

·          Distinguish a LAN from a wide area network (WAN)

·          Understand the difference between baseband and broadband networks

·          Identify and distinguish the characteristics of a packet- switched network and a circuit- switched network

·          Understand full- duplex and half- duplex communications

·          Describe the basic segment and backbone design of an enterprise network

·          Distinguish a server- based network from a peer- to- peer network

Estimated lesson time: 30 minutes

When you connect two or more computers so they can communicate with each other, you create a date network. This is true whether you connect the computers using a cable , a wireless technology such as infrared or radio waves , or even modems and telephone line. The technology that connects the computers together , no matter what form it tacks, is called the network medium , and for this reason the term network cable is often used to refer to any kind of network medium.

Signals and Protocols

Computers can communicate over a network in many ways and for many reasons , but a great deal that goes on in the networking process is unconcerned with the nature of the data passing over the network medium. By the time the data generated by the transmitting computer reaches the cable or other medium, it has been reduced to signals that are native to that medium. These might be electrical voltages for a copper cable network, pulses of light for fiber optic , or infrared or radio waves. These signals form a code that the network interface in each receiving computer converts back into the binary data understood by the software running on that computer. The computer then interprets the binary code into information it can use in a variety of ways. Of course there is a great deal more to this process than this description indicates , and there is a lot going on to make it possible for the e- mail you just sent to your mother to get reduced to electrical voltages , transmitted halfway across the country , and then reconstituted into text on her computer.

In some cases , a network consists of identical computers running the same version of the same operating system and using all the same applications , whereas other networks consist of many different computing platforms running entirely different software. It might seem that it would be easier for the identical computers to communicate than it would be easier for the different ones, and in some ways it is. But no matter what kind of computers the network uses and what software the computers are running , they most have a common language to understand each other. These common languages are called protocols, and computers use many of them during even the simplest exchanges of network data. Just as two people must speak a common language to communicate , two computers must have one or more protocols in common to exchange data.

A network protocol can be relatively simple or highly complex. In some cases , a protocol is simply a code  - such as a pattern of electrical voltage - that defines the binary value of a bit of data: 0 or 1. The concept is the same as that of Morse code, in which a pattern of dots and dashes represents a latter of the alphabet.

More complicated networking protocols can provide a variety of services , including the following: