Computer network - A collection of computing devices that are connected in various ways in order to communicate and share resources.
Types of networks:
· Local-area network (LAN) A network that connects a relatively small number of machines in a relatively close geographical area.
· Wide-area network (WAN) A network that connects two or more local-area networks over a potentially large geographic distance.
· Metropolitan-area network (MAN) The communication infrastructures that have been developed in and around large cities.
Various configurations, called topologies, have been used to administer LANs
- Ring topology A configuration that connects all nodes in a closed loop on which messages travel in one direction
- Star topology A configuration that centers around one node to which all others are connected and through which all messages are sent
- Bus topology All nodes are connected to a single communication line that carries messages in both directions.
Twisted-Pair Cables: If the pair of wires are not twisted, electromagnetic noises from, e.G., motors, will affect the closer wire more than the further one, thereby causing errors.
Unshielded Twisted-Pair (UTP) : Typically wrapped inside a plastic cover (for mechanical protection). A sample UTP cable with 5 unshielded twisted pairs of wires.
Shielded Twisted-Pair (STP): STP cables are similar to UTP cables, except there is a metal foil or braided-metal- mesh cover that encases each pair of insulated wires.
- In general, coaxial cables, or coax, carry signals of higher freq (100KHz–500MHz) than UTP cables
- Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit.