4/11/40 page 1 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Switching network

4/11/40 page 2 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Simple switching network Communication Network Communication Network Node Network Station end node (source &destination) provide switching facility (routing) Commuincations is achieve by transmitting data from source to destination through a network of switching nodes

4/11/40 page 3 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Switching technology Circuit switching need a connection establishment between end nodes connection is maintained until one of end nodes terminates Connection is dedicated to the communication between two nodes Example : Public Switch Telephone Network (PSTN) Packet switching data are transmitted in short message called packet a connection between the two end-nodes is not maintained a node-to-node link can be dynamically shared by may packets Example : Public Data Network (PDN) likes X.25, Frame Relay

4/11/40 page 4 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Keys different Keys Circuit switching Public switching data dedicated single route different routes message by pass temporary store at each node node status both must be ready sender ready to send is enough connection dedicated shared utilization poor good data rate fixed vary Prioritisation not support support

4/11/40 page 5 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Routing in circuit switch Alternate routing need a connection establishment between end nodes connection is maintained until one of end nodes terminates Connection is dedicated to the communication between two nodes Example : Public Switch Telephone Network (PSTN) Adaptive routing data are transmitted in short message called packet a connection between the two end-nodes is not maintained a node-to-node link can be dynamically shared by may packets Example : Public Data Network (PDN) likes X.25, Frame Relay

4/11/40 page 6 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Public Switching Telephone Network end offic Long-distance office connecting trunk subscriber loop Intercity trunk subscriber loop (local loop) link between subscriber and network connecting trunk (exchanges) switching center; localized support subscriber Intercity trunk (trunks) branches between exchanges; carry multiple voice circuits

4/11/40 page 7 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL PSDN PSDN= Public Switched Data Network = LAN PSDN PSDN is designed specifically for the transmission of data rather than voice Comunication is shared

4/11/40 page 8 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Packets header data packet Messages is broken up into a series of packets Header is used to route the packet through the network header data data packet

4/11/40 page 9 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Packet size header data packet Messages is broken up into a series of packets Header is used to route the packet through the network header data data packet

4/11/40 page 10 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL PSDN switching approach Virtual Circuit network protocol establish a logical route called virtual circuit packets use the same route; data arrive in the order similar to circuit switching ! but the route is not dedicated need call setup Datagram each packet is transmitted independently network protocols route each packet as though it were a separate message packet may not arrive in the order; need protocol to ensure ordering call setup is not required

4/11/40 page 11 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Virtual circuit A B C A B C virtual circuit #1 virtual circuit #2 A logical connection known as virtual circuit (VC) is set up between two stations. Packets are labled with a virtual circuit number and a sequence number

4/11/40 page 12 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Datagram B.3 B.2 B.1 C.3 C.2 C.1 C.3 C.2 C.1 B.3 B.2 B.1 A B C A B C B.3 B.2 B.1 C.3 C.2 C.1 Aeach packet is transmitted independently. Packets are labled with a destination address and may arrive out of sequence

4/11/40 page 13 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Routing in packet switch Fixed routing each packet is transmitted independently Flooding network protocol establish a logical route called virtual circuit packets use the same route; data arrive in the order Random routing the route taken is a random Adaptive routing the route reacts to changing conditions within the network