Computer Networks - Lecture 10

Switching
The Concept of switching is:
- Passage of massage from source to destination involves many decisions.
- When a message reaches a connecting device, a decision needs to be made to select one of the output ports through which the packet needs to be sent out.
- The connecting device acts as a switch that connects one port to another port.
Switching techniques are:


Circuit Switching

Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.
The defining example of a circuit-switched network is the early analog telephone network. When a call is made from one telephone to another, switches within the telephone exchanges create a continuous wire circuit between the two telephones, for as long as the call lasts.
Packet Switching
Packet switching features delivery of variable bit rate data streams (sequences of packets) over a computer network which allocates transmission resources as needed using statistical multiplexing or dynamic bandwidth allocation techniques. When traversing network adapters, switches, routers, and other network nodes, packets are buffered and queued, resulting in variable delay and throughput depending on the network s capacity and the traffic load on the network.
Packet switching is used to optimize the use of the channel capacity available in digital telecommunication networks such as computer networks