Different geographical locations, but the computer will function with a plurality of independent computer systems, connected by a communication apparatus and a communication line, sharing of resources under the coordination of fully functional network software (network protocols, network operating systems, network application software, etc.) of collection system, a collection of computer systems to share resources for the purpose of self-interconnected. Four elements: a set of independent computer systems; connecting to a computer over a communication medium; must abide by a rule or protocol; resource sharing and data communications for the purpose.
Classified according to the network transmission technology
Transmission technology employed in the network there are two types: broadcast and point to point
In the broadcast network, more than a networked computers share a common channel, when a computer using the shared channel to send messages packets to all other computers are "listening" to the packet. Since the packet is transmitted with a destination address and the source address, if the first few to a computer the packet's address and the same destination address of the packet, it accepts the packet, whether by the packet is discarded, thus transmitting the broadcast network destination address in the message packet may have a class 2 : unicast address, multicast, and broadcast addresses
In the point to point network, no physical lines is connected to a computer, if there is no direct connection between the source node and the destination node line, the packet transmitted by the source node name should accepted by the intermediate node, it is stored in the forward, to the transmission from the hair Oh destination node, so there are multiple paths from the source node to the destination node may decide the communication packet from the source node subnet route to the destination node needs to have the routing algorithm, using the quasi-fat storage mechanisms is a point and routing network one of the important distinction between the broadcast networks