A network consists of two or more computers that are linked in order to share resources (such as printers and CD-ROMs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.
In summary, all networks must have the following:
- Something to share (data)
- A physical pathway (transmission media)
- Rules of communication (Protocol)
The goal of computer networking is to provide services and to reduce equipment costs. Networks enable computers to share their resource by offering services to other computers. Some of the primary reasons for networking PCs are as follows:
- Share files
- Share printers and other devices
- Enable common administration and security.
- Supporting network applications such as electronic mail and database service.
To have a network you typically have four things (besides the computers themselves):
- Network Interface Cards (NICs) – cards that plugs into the back (or side) of your computers and lets them send and receive messages from other computers
- Network Media – the medium to connect all of the computers together
- Hub/Switch – hardware to perform traffic control
- Protocol – a set of communication rules to make sure that everyone speaks the same language
- How Does a Network Work?
How does one computer send information to another? It is actually rather simple. The diagram below shows a simple network:
If Computer A wants to send a file to Computer B, the following would take place:
- Based on a protocol that both computers use, the NIC in Computer A translates the file (which consists of binary data — 1’s and 0’s) into pulses of electricity.
- The pulses of electricity pass through the cable with a minimum (hopefully) of resistance.
- The hub takes in the electric pulses and shoots them out to all of the other cables.
- Computer B’s NIC interprets the pulses and decides if the message is for it or not. In this case, it is, so, Computer B’s NIC translates the pulses back into the 1’s and 0’s that make up the file.
- Sounds easy, however, if anything untoward happen, along the way, you have a problem, not a network. So, if Computer A sends the message to the network using NetBEUI, a Microsoft protocol, but Computer B only understands the TCP/IP protocol, it will not understand the message, no matter how many times Computer A sends it. Computer B also won’t get theMessage if the cable is getting interference from the fluorescent lights . . . or if the network card has decided not to turn on today . . . etc. etc. etc.