Types of Switching in Computer Network
A computer network consists of many switching devices. There are mainly three types of Switching in Computer Network:
1. Circuit Switching
2. Packet Switching
3. Message Switching
Circuit Switching is a dedicated path is established between two communicating nodes before actual data transfer begins. The path means that connected sequence of physical links in which logical channel is dedicated to the connection.
Example: Telephonic Communication.
Phase of Circuit Switching:
There are three phases of circuit switching.
1. Circuit Establishment
2. Data Transfer
3. Circuit Disconnect
In circuit switching, data transfer can’t start automatically, before data transfer, a dedicated link is to established end-to-end. At first, the sender sends a request for connection to its attached switch. The switch depending on the destination address and the condition of traffic routes the connection request to the next switch. The second switch also does the same work. This process goes on until a switch is reached with which the destination node is connected directly. The last switch sends the connection request then it sends an acknowledgement signal to the sender. The time required for circuit establishment is 2-10 seconds depending on the network and distance between the endpoints.
Once the connection is established, the data can be transferred from one sender to receiver. Generally, the connection is full-duplex. In that case, the data can be exchanged both ways simultaneously. Data may be digital or analogue depending on the network architecture. Data are exchanged in a block and sent continuously. No routing or other controlling mechanisms are required during data transfer.
The circuit may be disconnected by either end and the disconnection information is transferred from one end to another following the dedicated path. The intermediate switches after passing the disconnection information release the path. In this way, the dedicated path becomes free and it can be used for a new connection.
Features of Circuit Switching:
In Packet Switching, the sender breaks the whole message into a number of packets of suitable length and consisting sequential packet numbers. No dedicated path is established between the two end parties prior to data communication. The sender sends packets to the next node sequentially. Each node after receiving a packet decides the next route for the packet, the routing decision is done by a node in the path before sending every packet. All the packets are independent in nature and it may traverse different paths to reach the destination. So, the packet may reach the destination in a jumbled fashion. It is the responsibility of the receiver to rearrange the packets according to their sequence number.
Message Switching is a combination of circuit switching and packet switching. Like circuit switching, the message is not broken into packets rather it is sent to the next node as a whole. Like packet switching, no dedicated path is established between the two end parties prior to data communication. The routing decision is done at each and every node for the whole message.