Routing refers to the process that a router receives a packet from one interface, orients and forwards it to another interface according to the destination address of the packet. Routes are often compared to bridges, which seem to accomplish the same thing to a careless person. The main difference between them is that the bridging takes place in the second layer (data link layer) of the OSI reference model, while the routing takes place in the third layer (network layer). This difference enables them to use different information in the process of information transmission, so as to complete their tasks in different ways.
The topic of routing has long appeared in the computer industry, but it was not until the mid-1980s that it achieved commercial success. The main reason is that in the 1970s, the network was very simple, and later large-scale network was more common.