Packet switching is a connectionless network switching technique. Here, the message is divided and grouped into a number of units called packets that are individually routed from the source to the destination. There is no need to establish a dedicated circuit for communication.
Each packet in a packet switching technique has two parts: a header and a payload. The header contains the addressing information of the packet and is used by the intermediate routers to direct it towards its destination. The payload carries the actual data.
A packet is transmitted as soon as it is available in a node, based upon its header information. The packets of a message are not routed via the same path. So, the packets in the message arrives in the destination out of order. It is the responsibility of the destination to reorder the packets in order to retrieve the original message.
The process is diagrammatically represented in the following figure. Here the message comprises of four packets, A, B, C and D, which may follow different routes from the sender to the receiver.
Delay in delivery of packets is less, since packets are sent as soon as they are available.
Switching devices don’t require massive storage, since they don’t have to store the entire messages before forwarding them to the next node.
Data delivery can continue even if some parts of the network faces link failure. Packets can be routed via other paths.
It allows simultaneous usage of the same channel by multiple users.
It ensures better bandwidth usage as a number of packets from multiple sources can be transferred via the same link.
They are unsuitable for applications that cannot afford delays in communication like high quality voice calls.
Packet switching high installation costs.
They require complex protocols for delivery.
Network problems may introduce errors in packets, delay in delivery of packets or loss of packets. If not properly handled, this may lead to loss of critical information.