Circuit
Switching
Circuit
Switching allows temporary connections to be established, maintained,
and terminated between message sources and message destinations. For
example in the case of the voice- based phone network with which most
people are familiar, a call is routed through a central office piece
of equipment known as a switch, which creates a temporary circuit
between the source phone and the phone of the party to whom one
wishes to talk. This connection or circuit only lasts for the
duration of the call. This switching technique is known as circuit
switching and is one of two primary switching techniques employed
to deliver messages from here to there. In a circuit switched
network, a switched dedicated circuit is created to connect the two
or more parties, eliminating the need for source and destination
address information such as that provided by picketing techniques.
The
switched dedicated circuit established on circuit switched
networks makes it appear to the user of the circuit as if a wire has
been run directly between the phones of the calling parties. The
physical resources required to create this temporary connection are
dedicated to that particular circuit for the duration of the
connection. If system usage should increase to the point where
insufficient resources are available to create additional
connections, users would not get connected.
Packet
Switching
The
other primary switching technique employed to deliver messages from
here to there is known as packet
switching.
Packet switching differs from circuit switching in several key areas.
First, packets travel one at a time from the message source through a
packet
switched network, otherwise
known as a public
data network, to
the message destination.The physical path which any packet takes may
be different than other packets and in any case, is unknown to the
end users.
Remember that packets are specially structured groups of
data, which include control,
sequence,
source
address,
destination
address
information in addition to the data itself. These packets must be
assembled (control and address information added to data) somewhere
before entry into the packet switched network and must be
subsequently dis-assembled before delivery of the data to the message
destination.
