What is Packet Switching

Packet Switching is a technique employed widely these days in many communication systems that involves the transmission of data in the form of packets from the source to the destination with the help of various routing mechanisms and protocols.

Here is a brief summary of how the whole mechanism takes place:-

The data to be transmitted is first of all broken in to smaller data packets. Each of these packets is then associated with a source address and a destination address. On the internet, currently these addresses follow the IP-v4 protocol. These packets are also associated with individual numbers that determine their order. Each of these packets is then transmitted on the network. Every node in the network uses the IP addresses associated with the packet to derive the physical address of the possible nodes in the network to which the packets can be transmitted. This process is known as routing. As there are always multiple options for the routing of a packet, each packet therefore follows an independent path to reach the destination address after hopping a large number of nodes in the network. On reaching the destination address, the packets are de-capsulated and then are recombined together according to their order to form the original data stream. This recombination is carried out by the TCP protocol in the transport layer of the network. It is possible that many a packets can be lost or corrupted in the network and never reach the destination address. The TCP protocol on the destination end can reorder these lost packets from the source TCP, or the source TCP can automatically retransmit these packets on not receiving an acknowledgement signal about them from the destination TCP after a given period of time.

The biggest advantage of a packet switched network is the large amount of traffic it can handle as the resources are dynamically allocated according to the transmission needs of the users. This is starkly opposite to the traditional circuit switched networks in which a network path is allocated between the source and the destination in a static manner, thereby making the path unavailable to the rest of the network until it is freed up by one of the communication parties, even if no data transmission is taking place on the path.

A drawback of the packet switched networks is its inability in supporting real time applications. This is because of the delay that takes place in routing of the packets at each node. Though this problem can be somewhat solved by providing a high priority to the desired packets during framing them in the Network layer.

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