Editing Circuit switching (section)

==Alternatives==
In circuit switching, a route and its associated bandwidth is reserved from source to destination, making circuit switching relatively inefficient since capacity is reserved whether or not the connection is in continuous use. Circuit switching contrasts with [[message switching]] and [[packet switching]].<ref name=":4">{{Cite book|last=Davies|first=Donald Watts|url=http://archive.org/details/computernetworks00davi|title=Computer networks and their protocols|date=1979|publisher=Chichester, [Eng.]; New York : Wiley|others=Internet Archive|pages=456–477|isbn=9780471997504}}</ref> Both of these methods can make better use of available network bandwidth between multiple communication sessions under typical conditions in [[data communication]] networks.

Message switching routes messages in their entirety, one hop at a time, that is, [[store and forward]] of the entire message. Packet switching divides the data to be transmitted into packets transmitted through the network independently. Instead of being dedicated to one communication session at a time, network links are shared by packets from multiple competing communication sessions, resulting in the loss of the quality of service guarantees that are provided by circuit switching.

Packet switching can be based on [[connection-oriented communication]] or [[connectionless communication]]. That is, based on virtual circuits or datagrams.

[[Virtual circuit]]s use packet switching technology that emulates circuit switching, in the sense that the connection is established before any packets are transferred, and packets are delivered in order.

Connection-less packet switching divides the data to be transmitted into packets, called [[datagram]]s, transmitted through the network independently. Each datagram is labelled with its destination and a sequence number for ordering related packets, precluding the need for a dedicated path to help the packet find its way to its destination.  Each datagram is dispatched independently and each may be routed via a different path.  At the destination, the original message is reordered based on the packet number to reproduce the original message.  As a result, datagram packet switching networks do not require a circuit to be established and allow many pairs of nodes to communicate concurrently over the same channel.

[[Multiplexing]] multiple telecommunications connections over the same physical conductor has been possible for a long time, but each channel on the multiplexed link was either dedicated to one call at a time or it was idle between calls.