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  • 1. INF4/MSc Computer NetworkingLecture 1: Introduction & Overview D K Arvind dka AT IF 2.18

2. We will look at: Network architecture principles From signals and wires to protocols Architecture of the Internet Wireless networks LANs, personal area, wide/metropolitan area 2 3. Recommended Reading Much of the course is based on the textbook: Computer Networking: A top-down approach featuring the Internet, (3/e) J. Kurose & K. Ross, Addison-Wesley, 2005 Many other good books: 1.Communication Networks (2e), Leon-Garcia & Widjaja. McGraw Hill, 2004 Last years book. Still OK, if you got it second hand, or from thelibrary 2.Computer Networks (4e), Andrew S. Tanenbaum. Prentice Hall, 2003 3.Data and Computer Communications (7e), William Stallings. Prentice Hall, 2003 News on developments on comp. networking3 4. Learning Outcomes Knowledge of key concepts, protocols and algorithms in networking An understanding of the complexity of networks, their structure and utility The ability to apply knowledge to networking applications, to network infrastructure and to network management The ability to write and present clear and concise description of complex issues An insight into likely future developments in the field of networking 4 5. Assessment 75% of course mark Final exam Past papers available from the School archive 25% of course mark Two coursework assignments, equally weighted Coursework (look web page for dates, etc)1.Essay on convergence in telecommunication networks2.Technical report based on a survey of papers Plagiarism: dont do it! Read the relevant informatics and university web pages 5 6. Course admin Lecturers: DK Arvind & Mahesh Marina Two lectures / week 10am Mon, WRB G.04 10am Thu, WRB G.04 Course web page: Newsgroup:eduni.inf.ug4Contact: dka AT the usual address6 7. Networked Critical Infrastructure A modern state has a network of control systems for the measurement and change of the infrastructure state for safe, uninterrupted, and efficient delivery of utilities (electricity, water), of services (telecommunication, health, transportation, banking), and of essential commodity (gas, oil) A network of distributed sensors for collecting data and software for extracting and interpreting information to raise the security of the critical infrastructure7 8. Interdependencies, Interdependencies,FASB; IRC e-commerce, Trading,transfersITBanking & FinanceRegulations & enforcementCurrency (US Treasury;FERC; DOEFederal Reserve ) Communications Communications Communications Communications Communications Communications Ee-government, LITGovernment Detection, 1st responders, Personnel/Equipment Erepair(Military)TMedical CequipmentFEMA; DOTEFinancing, regulations, & enforcementFinancing, regulations, & enforcementFinancing, regulations, & enforcementFinancing, regulations, & enforcementFinancing, regulations, & enforcementFinancing, regulations, & enforcementEmergency Response TFire Location, EMLsuppressioncontact RSignalization,Eswitches, DOT Icontrol systems TransportationC Communications Communications Communications Communications Communications SCADA COStorage, Ipumps, DOE; DOTMcontrol systems,Oil & Natural Gas TcompressorsWater for production, cooling, SCADAYWater for cooling,emissions controlemissions control EPAPotable & Waste WaterSCADAPumps, lifts,control systems Cooling Switches, control systems8Source: Miriam Heller 9. The Plant: A Complex EnvironmentPlant Other Servers Computing DeviceshoursBusiness Management min Personal Computer Network Manager ArchiveReplay Module Area ServersPlantControl Stations secs NetworkApplicationHistory AdditionalCN ModulesModules ModuleModule Fiber Optics1 secProcess Management Network NetworkPLC Gateway msecGateway Subnetwork GatewayNetwork InterfaceGatewayControl Networ Other Data ModulePLC Other Extenders Hiway BoxesSubsystemsMultifunction CON k Logic Manager orController Process etw secExtended ManagerTRO bn ControllerSu L NEBasic AdvancedControllerProcessTWOAdvancedField ManagementManagerMultifunction RKLocalProcessorsControllerTransmittersSmartine Source: TRUST Transmitters9 10. Service-oriented view of computer networks A computer network provides a communication service, i.e. enables the exchange of information between computers (and their users) that are located at various geographical locations Communication service is ubiquitous and an essential infrastructure of modern society Comparable in value with transportation, water, electricity, Because there are no limits to information, networking enables further services For example the telephone network enables fax, voicemail, electronicbanking, , Computer networks enable email, information search, electronic commerce, Value of the network depends on its size: the larger, the better Whats the use of email if only a few people use it?10 11. Characteristics of the communicated information Non-interactive: Text, pictures, music, video Two sub-categories: streaming or not jitter is most important for streaming multimedia Interactive: Teleconferencing, videoconferencing, instant msg/chatingSize is an important factor Compression (lossy/lossless) can help, opens up a computation vscommunication trade-offWorst case: Musicians playing instruments together through the network Requires low latency, high-throughput (for quality sound), low jitter11 12. Characteristics of the communication services Connection-oriented (think telephone) Receiver is active while information is transmitted Must establish connection, before any data is transmitted Connectionless (think [e]mail) Data transmission can start earlier Other service characteristics: Confirmed unconfirmed delivery Quality of service characteristics: Performance (delay, throughput, delay-variation) Error rate, security,12 13. Approaches to Network Design Networks provide connectivity between users at the network edge through a transmission system, the network core Using various types of physical media (wires, radio, optical fibre, etc.)and devices (switches, routers, multiplexers, etc.) Network core equipment is fundamentally different to equipment atthe network edget0 t1Network Cost-effective design necessary to meet user requirements Networks usually designed to carry specific types of information Voice, TV, bits, characters etc. 13 14. The N2 Problem Pairwise interconnections would require N*(N-1) links or a central switching access network, and just N access links Networks consist of point-to-point links interconnected by switches for a multi-hop path, routing decides which path to take at a switch forwarding actually moves the data in the direction decided14 15. Larger Networks Connections between local communities use trunks between local switches Multiplexers concentrate the traffic over the more expensive line Demultiplexers separate out the individual parts of the traffic for distribution Networks are hierarchical: Metropolitan networks interconnect access networks Regional networks connect metropolitan networks National networks, international networks etc. using backbone networks a Ab A cdMetropolitan National15 16. Internetworksnet 3 G = gateway Gnet 1G G Gnet 5 net 2 G net 4G Networks of networks The Internet Protocol (IP) was developed to provide connectionless transfer ofpackets across an internet The component networks are interconnected by packets switches calledgateways or routers, which direct the transfer of packets IP provides a best-effort service i.e. it does its best to deliver a packet, but itdoes not guarantee successful delivery 16 17. AddressingAddressing required to identify source and destination end- points Hierarchical addressing uses common prefixes for end-points in thesame geographical areas Facilitates routing As in a postal address: country, county, town, district, street, number;the Post Office batches mail for countries and for towns, districts,streets etc. Hierarchical addressing in Wide Area Networks e.g. the Internet Also facilitates routing Flat addressing in Local Area Networks e.g. ethernets Adequate for the typically small number of local area end-points17 18. Switching Circuit-switching In early communication networks, switching was performed at the electrical signal level, creating a real circuit end to end In modern digital transmission media, circuit-switching means allocation of dedicated resources (e.g. a share of a links transmission capacity) end to end Switches forward information one bit at a time (in theory) Packet/message switching Switches store whole packet and then forward it using the full link transmission capacity Connectionless or datagram Each packet/message routed independently of all other packets Virtual circuit A route set up through switches and links in the network All subsequent packets forwarded along the same path18 19. Factors in Communication Network EvolutionTechnology, Regulation, Markets, Standards Can it be built? Will it inter-operate?Technology Standards Will it sell?Is it allowed?Regulation Market Availability of a technology does not mean it will sell Never very clear beforehand whether a market exists for a product or service The move away from monopoly telecomms suppliers makes standards essential 19 20. Computer network uses Resource sharing Printers, disks, specialised hardware, Information sharing Database access Human communication Email, Voice-over-IP, file-sharing (pictures, music,) Commerce Shopping on-line, banking, Entertainment Movies, games Remote access/monitoring/workingUsers of the network Computers Humans: experts, general public 20 21. Technology Limited by fundamental physical laws In most cases substantial opportunities for improvement remain Key technologies Transmission systems Computer processing capacity (Moores Law) Cumula