1 IK1500 Communication Systems IK1330 Lecture 3: Networking Anders Västberg

HT08/P1IK15002 Content Elements of networking –Multiplexing –Switching –Routing –Network management (not discussed in this course). Problem solving

HT08/P1IK15003 Distributed information applications source/sink Distributed information applications

HT08/P1IK15004 Examples of Sources/Sinks Sources –Telephone –Video cameras –Files on a disk Sinks –Telephone receivers –Television monitors –Computer storage devices

HT08/P1IK15005 Layered Model

HT08/P1IK15006 Layered Model Information Services –e.g. Packet telephony, electronic mail, www Networking –Quality of Service requirements –Resource sharing Communication Links –Regarded in this course as imperfect bit-pipes: They can delay, lose or modify the information they carry

HT08/P1IK15007 Quality of Service Certain Quality of Service (QoS) e.g. in terms of: –Guaranteed bounds of service denial –Statistical bounds of service denial –Information loss –Throughput –Delay

HT08/P1IK15008 Design Perspectives Communication Link –Highest possible bit transmission rate (given the resources used) –Acceptable bit rate Networking –QoS requirements for the flows may be different for different applications: Short delay but can tolerate higher bit error rates Reliable transfer and high throughput

HT08/P1IK15009 Comparison: Networking – OS Protocols

HT08/P1IK Functional Elements Multiplexing Switching Routing Network management

HT08/P1IK Multiplexing Circuit Multiplexing –Link transmission rate is divided into channels –Each conversation gets one channel and holds that channel for the duration of the connection –Rate is fixed at connection setup time –If there are no available channels then the new communication reqeust is blocked Main performance objectives: –Probability of blocking –Handling of different classes of flows

HT08/P1IK Circuit multiplexing

HT08/P1IK Traffic Flow

HT08/P1IK Multiplexing Packet Multiplexing –Average rate must be less than the bit rate of the link –Peak rate can exceed the link’s bit rate Excess data must be queued  delay If the buffer is to small  data loss –Overhead Header (and in certain cases a Trailer) Main performance objectives: –Low probability of loss –Bounded delay

HT08/P1IK Packet Multiplexing

HT08/P1IK Multiplexing Taxonomy multiplexing circuit multiplexedpacket multiplexed centralizeddistributed random access polled access reservation access token passingmaster-slave

HT08/P1IK Centralized Packet Multiplexing Terminal Host Multiplexer multiplexer ports full-duplex link

HT08/P1IK Distributed Packet Multiplexing link Nodes Random Access

HT08/P1IK Polling Based Distributed Packet Multiplexing

HT08/P1IK Reservation Based Distributed Packet Multiplexing

HT08/P1IK Hybrid Link Multiplexing

HT08/P1IK Six-Node Network linksN links

HT08/P1IK Switch

HT08/P1IK Switch Functionality Demultiplexing each flow Determine the output link for the flow Forward (switch) the element of each flow to the right output link

HT08/P1IK Packet Switch Store-and-forward –Receive the entire packet first, then forward it Cut-through –Start forwarding the packet as soon as it arrives

HT08/P1IK Packet Switch O/p Queue scheduling, processing O/p queue scheduling, processing Control and signaling functions Switch fabric Queueing and scheduling Queueing and scheduling Input processing and forwarding Input processing and forwarding Line interface Line interface Line interface Line interface

HT08/P1IK Call Setup Procedure for a Circuit Multiplexed Network

HT08/P1IK Operation of a Circuit Switch

HT08/P1IK Routing Establish paths through the network between sources and sinks Difference between routing and forwarding Two types: –Centralized Routing –Distributed Routing

HT08/P1IK Routing Routing Algorithms –Find end-to-end path through the networks –While: Fulfilling QoS constraints Utilize network resources efficiently Two main types: –Hop-by-Hop routing –Source routing

HT08/P1IK Packet Multiplexed Network Virtual circuit-based –Routes are determined at the connection setup time –Sufficient to know the label of the connection and not the complete source and destination address Datagram-based –Each packet is routed separately –Each packet must know the source and destination address