Why do data networks use packet-switching?
Economics can explain most of the preference for packet-switching over circuit-switching in the Internet and other public networks. Circuit networks use lots of lines in order to economize on switching and routing. That is, once a call is set up, a line is dedicated to its use regardless of its rate of data flow, and no further routing calculations are needed. This network design makes sense when lines are cheap relative to switches. The costs of both communications lines and computers have been declining exponentially for decades. However, since about 1970, switches (computers) have become relatively cheaper than lines. At that point packet switching became economic: lines are shared by multiple connections at the cost of many more routing calculations by the switches. This preference for using many relatively cheap routers to manage few expensive lines is evident in the topology of the backbone networks. For example, in the NSFNET any packet coming on to the backbone had to pass thro
Economics can explain most of the preference for packet-switching over circuit-switching in the Internet and other public networks. Circuit net works use lots of lines in order to economize on switching and routing. That is, once a call is set up, a line is dedicated to its use regardless of its rate of data flow, and no further routing calculations are needed. This network design makes sense when lines are cheap relative to switches. The costs of both communications lines and computers have been de clining exponentially for decades. However, since about 1970, switches (computers) have become relatively cheaper than lines. At that point packet switching became economic: lines are shared by multiple con nections at the cost of many more routing calculations by the switches. This preference for using many relatively cheap routers to manage few expensive lives is evident in the topology of the backbone networks. For example, in the NSFNET any packet coming on to the backbone has to pass t
