what is packet switched network?

what is packet switched network?

            PACKED SWITCHED NETWORK in packet switched network, two communication subscribers can operate at different data rates, since th... 22:28

            PACKED SWITCHED NETWORK
in packet switched network, two communication subscribers can operate at different data rates, since the rate at which data is passed at two interfaces to the network is separately regulated by each subscriber's equipment. also, no physical connections are established through the network with a packet switched network. instead, all data to be transmitted is first assembled into one or message units,called packets.these packets include both the source and destination network addresses. they are passed by the source computer to its local packet switching exchange (ESP). on receipt of each packet, the exchange first stores the packet and then inspects the destination address it contain. each ESP contains a routing directory specifying the outgoing links' transmission paths to be used for each networks address. the ESP forwards the packed on the appropriate link at the maximum available bit rate. this mode often  referred to as packet store-and-forward.

a number of packets may arrive simultaneously at a ESP of different incoming links a each may require forwarding on the same outgoing links. if a number of particular long packets are waiting to be transmitted on the same link, other packets may experience unpredictable long delays.to prevent this and to ensure that the network has a reliably fast transit time, a maximum length is allowed for each packet.these packets are reassembled into a single message by the corresponding transport protocol at the destination.

X.25 protocol describes a method of encapsulating and handling packets with high reliability. several companies manage networks of special computerized switches spread across the nation and across the world that connect together with high-speed data communication lines and use X.25. these companies sell their network' data handling and transmission capabilities to subscribers under several pricing schemes. national telephone companies in many countries offer X.25 service, sometimes at lower rates then leased line or dial-up lines.