Packet switching is a method of transferring the data to a network in form of packets. In order to transfer the file fast and efficiently manner over the network and minimize the transmission latency, the data is broken into small pieces of variable length, called Packet. At the destination, all these small parts (packets) have to be reassembled, belonging to the same file. A packet composes of payload and various control information. No pre-setup or reservation of resources is needed. Packet Switching uses Store and Forward technique while switching the packets; while forwarding the packet each hop first stores that packet then forward. This technique is very beneficial because packets may get discarded at any hop due to some reason. More than one path is possible between a pair of sources and destinations. Each packet contains Source and destination address using which they independently travel through the network. In other words, packets belonging to the same file may or may not travel through the same path. If there is congestion at some path, packets are allowed to choose different paths possible over an existing network. Packet-Switched networks were designed to overcome the weaknesses of Circuit-Switched networks since circuit-switched networks were not very effective for small messages. Advantage of Packet Switching over Circuit Switching :
The disadvantage of Packet Switching over Circuit Switching :
Modes of Packet Switching : 1. Connection-oriented Packet Switching (Virtual Circuit) : All address information is only transferred during the setup phase. Once the route to a
destination is discovered, entry is added to the switching table of each intermediate node. During data transfer, packet header (local header) may contain information such as length, timestamp, sequence number, etc. 2. Connectionless Packet Switching (Datagram)
: A---R1---R2---B A is the sender (start) R1, R2 are two routers that store and forward data B is receiver(destination) To send a packet from A to B there are delays since this is a Store and Forward network. Delays in Packet switching :
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