Packet Switching

                   Packet Switching
  
              In packet switching, messages are broken downinto smaller pieces called packets. Each packet is assigned source,destination, and intermediate node addresses. Packets are required to have thisinformation because they do not always use the same path or route to get totheir intended destination. Referred to as independent routing, this is one ofthe advantages of packet switching. Independent routing allows for a better useof available bandwidth by letting packets travel different routes to avoidhigh-traffic areas. Independent routing also allows packets to take analternate route if a particular route is unavailable for some reason.
            Ina packet-switching system, when packets are sent onto the network, the sendingdevice is responsible for choosing the best path for the packet. This pathmight change in transit, and it is possible for the receiving device to receivethe packets in a random or no sequential order. When this happens, thereceiving device waits until all the data packets are received, and then itreconstructs them according to their built-in sequence numbers.
            Twotypes of packet-switching methods are used on networks:
                        1.virtual-circuit packet switching and
                        2.Datagram packet switching.
·     Virtual-Circuit Packet Switching When virtual-circuitswitching is used, a logical connection is established between the source andthe destination device. This logical connection is established when the sendingdevice initiates a conversation with the receiving device. The logicalcommunication path between the two devices can remain active for as long as thetwo devices are available or can be used to send packets once. After thesending process has completed, the line can be closed.
·     Datagram Packet Switching Unlike virtual-circuit packetswitching, datagram packet switching does not establish a logical connectionbetween the sending and transmitting devices. The packets in datagram packetswitching are independently sent, meaning that they can take different pathsthrough the network to reach their intended destination. To do this, eachpacket must be individually addressed to determine where its source anddestination are. This method ensures that packets take the easiest possibleroutes to their destination and avoid high-traffic areas.
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