PACKET SWITCHING

Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay. This contrasts with the other principal paradigm, circuit switching, which sets up a limited number of constant bit rate and constant delay connections between the nodes for their exclusive use for the duration of the communication. Packet mode or packet oriented communication may be utilized with or without a packet switch or router. Examples of the latter case are point-to-point data links, digital video and audio broadcasting or a shared physical medium, such as a bus network, ring network, or hub network.
Packet mode communication is a statistical multiplexing technique, also known as a dynamic bandwidth allocation method, where a physical communication channel is divided into an arbitrary number of logical variable bit-rate channels or data streams. Each stream is divided into packets that normally are forwarded by a network node asynchronously in a first-come first-serve fashion. Alternatively, the packets may be forwarded according to some scheduling discipline for fair queuing or differentiated and/or guaranteed Quality of service. In case of a shared physical media, the packets may be delivered according to some packet-mode multiple access scheme.
Networks using packet switching can use datagrams or connectionless messages and/or virtual circuit switching (also known as connection oriented). Some connectionless protocols include Ethernet, UDP, IP. Some connection oriented protocols include TCP, Multiprotocol Label Switching (MPLS), Asynchronous Transfer Mode (ATM), X.25 and Frame relay.