Computer Science and Technology

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TMC1254 Communication and Computer Network Semester 2 2013/2014 Switching 1 Learning Unit Objectives • Understand the concept of switching. • Understand and able to differentiate between different types of switching. 2 • How many connection per device? 3 Introduction • A network is a set of connected devices • How to connect them for communication? – Using mesh topology but wasteful – Used switching • Switched network consists of a series of interlinked nodes, called switches (temporary connection btw 2 or > devices) 4 Switched network 3 Simple Switching Network 6 Taxonomy of switched networks 7 Circuit Switched Networks Three Phases Efficiency Delay 8 9 CIRCUIT-SWITCHED…show more content…
• In a packet-switched network, there is no resource reservation; resources are allocated on demand. 22 A datagram network with four switches (routers) 23 Example: Routers 24 Characteristics of Datagram Network • • • • • No scheduled processing time for each packet Resources are allocated on demand Each packet is treated independently of all others Done at the network layer Referred as connectionless network (packet switch does not keep information about the connection state) • No setup and teardown phases • Each switch has routing table (for forwarding packet to correct destination) 25 Routing table in a datagram Network • A switch in a datagram network uses a routing table that is based on the destination address. • The destination address in the header of a packet in a datagram network remains the same during the entire journey of the packet. 26 Issues in datagram networks • Efficiency – better than circuit-switched network – Resources are allocated only when there are packets to be transferred • Delay – Greater delay – Each packet experience a wait at a switch before it is forwarded – Not all packets in a message necessarily travel through the same switches, the delay is not uniform for the packets of a message 27 Delay in a datagram network 28 Virtual-circuit networks Addressing Three Phases Efficiency Delay 29 VIRTUAL-CIRCUIT NETWORKS • A virtual-circuit network is
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