For more notes and topics visit: www.eITnotes.com eITnotes.com A Switched Network consists interlinked nodes called Switches. of Switches are hardware and software that are capable of creating temporary connections between two or more devices linked to the switch. In a Switched network, some of nodes are connected to the end system or communication devices like computer or telephone. eITnotes.com A,B,C,D,E and so on are end systems or communication devices. eITnotes.com Switches are labeled as I,II,III,IV,V and so on. eITnotes.com Dedicated physical connection or path is established between the sending and receiving device. Dedicated path made of one or more links. Routing is made when the path or link is set up across the network. After the has been set between the sender and receiver, the information is forwarded continuously over the link. eITnotes.com eITnotes.com eITnotes.com eITnotes.com Dedicated path establish guaranteed data rate. provides Data a is transmitted without any delay, as there is no waiting time at each switch. Suitable for long continuous transmission. eITnotes.com It cannot be used to transmit any other data even if the channel is free. Inefficient resources. Long in time is physical link. terms of required utilization to establish eITnotes.com of a eITnotes.com Packet node. are sent over network node to At each node, packet is stored briefly and then routed according to information in its header. These types of networks are called store and forward networks. Individual packets may follow different routes to reach destination. Two types of Packet Switching:-Datagram Packet Switching -Virtual Packet Switching eITnotes.com eITnotes.com Datagram Packet Switching eITnotes.com Datagram approach is used to deliver four packets from station A to X. All the four packets belong to same message but they travel via different paths to reach the destination. It can cause the datagram to arrive out of order at their destination with different delays between the packets. Packets may also be lost because of lack of resources. eITnotes.com Circuit connection called virtual circuit is set up between sender and receive before any data transfer takes place. Virtual circuit approach has a set up, data transfer and tear down phase. Resources can be allocated during set up phase or on demand. eITnotes.com All the packets of a message follow the same path establish during the connection. It is implemented in the data link layer. eITnotes.com eITnotes.com Packets may be lost on their route, so sequence numbers are required to identify the missing packets. Large amount RAM is required to handle the large quantities of packets. eITnotes.com eITnotes.com eITnotes.com When message reaches a node, the channel on which it came is released for use by another message. Message M1 is transmitted from A to D and M2 is transmitted from C to B. Message M1 follows route A->I->II->D and M2 follows route C->IV->II->B depending upon availability of free path at that particular moment. eITnotes.com eITnotes.com No physical connection is required between source and destination. Reduces traffic congestion on network because of store and forward facility. Support message length of unlimited size. eITnotes.com eITnotes.com Parameter Circuit Switching Packet Switching Message Switching Path or Route Path is created Virtual circuit is No need to between two points created between create a link or by setting switches. two points. path. Dedicated or sharing Links that make a path are dedicated and cannot be used other connections. In virtual circuit , links that make a route can be shared by other connections. Message reaches a node the channel on which it came is released by another message. Store and forward transmission No use Each node may store incoming packet temporarily & forward them later. Store and forward transmission is used. eITnotes.com Parameter Circuit Switching Packet Switching Message Switching Path followed by packets It is always same. May or may not May or may not be different be same. Call setup It is required. Not required. Application Real time transfer Internet for Telegraph network of voice signal. datagram and for transmission of reliable stream telegrams. service between computers. Layer used for implementation It is implemented Virtual circuit at physical layer. network is implemented at data link layer and datagram network at network layer. Not required. eITnotes.com eITnotes.com