Curtis/Cobham © Pearson Education Limited 2008 Slide 4.1 Chapter 4 Distributed Systems, Networks and the Organization Lecture 1 Distributed systems

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.2 A Hierarchical Distributed System Figure 4.1 An example of functions in a hierarchical distributed system

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.3 A Centralized System Figure 4.2 An example of functions in a centralized system

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.4 Distributed Systems Location of processing –distributed vs. cooperative processing Location of data storage –distributed databases Communications links –WANs and LANs Standards –OSI

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.5 Network Topologies Figure 4.3 Various network topologies: (a) hierarchical; (b) star; (c) ring; (d) bus; (e) hybrid

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.6 Organizational Benefits of Distributed Systems User satisfaction Flexibility Reduced telecommunications costs Failsoft Transborder data flow Reduced response times

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.7 Organizational Drawbacks of Distributed Systems Loss of centralized control Complex networking issues (including software) Replicated common data Changing career paths

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.8 The Extent of Distribution Corporate culture and employee behaviour Location of decision making Interdependent activities Homogeneous activities Client–server computing –system performance –consistency –bandwidth –volume of data/size of application

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.9 Client–Server Computing Figure 4.5 Models of client–server computing: (a) two-tier with thick client; (b) three-tier model with thin clients

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.10 Chapter 4 Distributed Systems, Networks and the Organization Lecture 2 Networks and Communications

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.11 Networks and Communications Type of communication –simplex, half duplex, full duplex Transmission signals –frequency modulation, amplitude modulation Modem Bandwidth –broadband, baseband

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.12 Figure 4.7 A modem link Networks and Communications (Continued)

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.13 Multiplexing –frequency division, time division Parallel and serial transmission Synchronous and asynchronous Networks and Communications (Continued)

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.14 Transmission Media Twisted-pair Coaxial Fibre optic Microwave Satellite link

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.15 Transmission Media (Continued) Figure 4.8 Alternative forms of cabling: (a) twisted pair; (b) coaxial cable; (c) optical fibre

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.16 Public Transmission Links Leasing Public switched telephone network Packet-switched network ISDN

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.17 Packet Switching Figure 4.10 Packet-switched telecommunications network

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.18 Local Area Network (LAN) CSMA/CD Token passing Figure 4.12 LAN topologies

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.19 Standards Open Systems Interconnection Model Figure 4.13 The seven-layer OSI model

Curtis/Cobham © Pearson Education Limited 2008 Slide 4.20 Electronic Data Interchange Benefits –speed of transaction –reduction in paperwork –reduced transaction costs –reduced errors Effects of the internet on business