System Architecture Chapter 10


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Systems Analysis and Design

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System Architecture Chapter 10

  1. 1. Systems Analysis and Design9th EditionChapter 10System Architecture
  2. 2. Chapter Objectives• Provide a checklist of issues to consider when selecting a system architecture• Describe servers, server-based processing, clients, and client-based processing• Explain client/server architecture, including tiers, cost-benefit issues, and performance• Compare in-house e-commerce development with packaged solutions 2
  3. 3. Chapter Objectives• Discuss the potential impact of cloud computing and Web 2.0• Explain the difference between online and batch processing• Define network topology, including hierarchical, bus, ring, and star models 3
  4. 4. Chapter Objectives• Explain network protocols and licensing issues• Describe wireless networking, including wireless standards, topologies, and trends• Describe the system design specification 4
  5. 5. Introduction• An effective system combines elements into an architecture, or design, that is flexible, cost-effective, technically sound, and able to support the information needs of the business• System architecture translates the logical design of an information system into a physical structure that includes hardware, software, network support, and processing methods 5
  6. 6. System Architecture Checklist• Enterprise Resource Planning (ERP) – The objective of ERP is to establish a company- wide strategy for using IT resources – Supply chain management (SCM)• Initial Cost and TCO – During the final design stage, you make decisions that will have a major impact on the initial costs and TCO for the new system – You should review all previous cost estimates 6
  7. 7. System Architecture Checklist• Scalability – Scalability, also called extensibility, refers to a system’s ability to expand, change or downsize easily to meet the changing need of a business enterprise – Especially important in implementing systems that are volume-rated, such as transaction processing systems 7
  8. 8. System Architecture Checklist• Web Integration – An information system includes applications – Web-centric architecture – Avoids many of the connectivity and compatibility problems that typically arise – E-marketplaces 8
  9. 9. System Architecture Checklist• Legacy System Interface Requirements – The new system might have to interface with one or more legacy systems – Interfacing a new system with a legacy system involves analysis of data formats and compatibility – The analyst must know if the new application eventually will replace the legacy system 9
  10. 10. System Architecture Checklist• Processing Options – In planning the architecture, designers also must consider how the system will process data - online or in batches – Provision must be made for backup and speedy recovery in the event of system failure 10
  11. 11. System Architecture Checklist • Security Issues – Security threats and defenses are a major concern to a systems analyst – The analyst must consider security issues that relate to system design specifications – Web-based systems introduce additional security concerns 11
  12. 12. Planning the Architecture• Servers – Server – Clients – Mainframe architecture – Server-based processing 12
  13. 13. Planning the Architecture• Clients – As PC technology exploded in the mid-1980s and 1990s, powerful microcomputers quickly appeared on corporate desktops – Users found that they could run their own word processing, spreadsheet, and database applications – Companies linked the stand-alone computers into networks 13
  14. 14. Planning the Architecture • Clients – Stand-Alone Computing – Local and wide area networks – Client-based processing 14
  15. 15. Client/Server Architecture• Overview 15
  16. 16. Client/Server Architecture• Client/Server Design Styles 16
  17. 17. Client/Server Architecture• Fat and Thin Clients 17
  18. 18. Client/Server Architecture• Client/Server Tiers – Two-tier design – Three-tier design• Middleware – Enables the tiers to communicate and pass data back and forth – Provides a transparent interface – Can integrate legacy systems and Web-based applications 18
  19. 19. Client/Server Architecture• Cost-Benefit Issues – Client/server systems enable the firm to scale the system in a rapidly changing environment – Client/server computing also allows companies to transfer applications from expensive mainframes to less expensive client platforms – Client/server systems reduce network load and improve response times 19
  20. 20. Client/Server Architecture• Client/Server Performance Issues – In contrast to the centralized system, a client/server design separates applications and data – Distributed database management system (DDBMS) – The system is scalable, so new data sites can be added without reworking the system design – The system is less likely to experience catastrophic failure 20
  21. 21. Internet-Based Architecture• Developing E-Commerce Solutions In-House 21
  22. 22. Internet-Based Architecture• Packaged Solutions and E-commerce Service Providers – Many vendors offer turnkey systems for companies – Another alternative is to use an application service provider (ASP) – Another option is managed hosting – Consider the experience of other companies in the same industry 22
  23. 23. Internet-Based Architecture• Corporate Portals – A corporate portal can provide access for customers, employees, suppliers, and the public• Cloud Computing – Effectively eliminates compatibility issues – Scaling on demand – Requires significantly more bandwidth 23
  24. 24. Internet-Based Architecture • Web 2.0 – Envisions a second generation of the web that will enable people to collaborate, interact, and share information more dynamically – Wiki – Internet operating system 24
  25. 25. Processing Methods• Online Processing – Because it is interactive, online processing avoids delays and allows a constant dialog between the user and the system – Online processing also can be used with file- oriented systems 25
  26. 26. Processing Methods• Batch Processing – The IT operations group can run batch programs on a predetermined schedule, without user involvement, during regular business hours, at night, or on weekends – Require significantly fewer network resources than online systems 26
  27. 27. Processing Methods• Combined Online and Batch Processing 27
  28. 28. Network Models• The OSI Reference Model – The OSI model consists of seven layers – Each layer performs a specific function – Offers a set of design standards 28
  29. 29. Network Models• Network Protocols – In all cases, the network must use a protocol – Transmission Control Protocol/Internet Protocol (TCP/IP) – File Transfer Protocol (FTP) 29
  30. 30. Network Models• Network Topology – Hierarchical network • it mirrors the actual operational flow in the organization • One disadvantage of a hierarchical network is that if a business adds additional processing levels, the network becomes more complex and expensive to operate and maintain 30
  31. 31. Network Models • Network Topology – Bus network • Devices can be attached or detached from the network at any point without disturbing the rest of the network • Overall performance declines as more users and devices are added • Today, the bus design is much less popular 31
  32. 32. Network Models• Network Topology – Ring network • One disadvantage of a ring network is that if a network device fails (such as a PC or a server), the devices downstream from the failed device cannot communicate with the network • Multistation Access Unit (MAU) 32
  33. 33. Network Models • Network Topology – Star network • Disadvantage of the star design is that the entire network is dependent on the switch • However, in most large star networks, backup switches are available immediately in case of hardware failure 33
  34. 34. Network Models• Network Topology – Mesh network • While this design is extremely reliable, it also is very expensive to install and maintain • Originally developed for military applications 34
  35. 35. Network Models• Routers – Routers differ from switches in that they work at a higher OSI level – Can connect to a larger, dissimilar network, such as the Internet – Gateway – Proxy server 35
  36. 36. Network Models • Network Modeling Tools – As you translate the OSI logical model into a physical model of the networked system, you can use software tools • Network Licensing Issues – Software licensing restrictions 36
  37. 37. Wireless Networks• A wireless local area network, or WLAN• Wireless Network Standards – 802.11 – Institute of Electrical and Electronics Engineers (IEEE) – Amendments – Mbps (megabits per second) 37
  38. 38. Wireless Networks• Wireless Network Standards – 802.11g – 802.11n – Multiple input/multiple output (MIMO) – Multipath design – 802.11y 38
  39. 39. Wireless Networks• Wireless Network Topologies – Basic Service Set (BSS) – infrastructure mode – Access point – Extended Service Set (ESS) – Roaming – Independence Service Set (ISS) – peer-to-peer mode 39
  40. 40. Wireless Networks• Wireless Trends – Wi-Fi Alliance – Wi-Fi (wireless fidelity) – BlueTooth – On addition to 802.11 protocols for LANs, IEEE is working on 802.16 standards – MANs (metropolitan area networks) – WiMAX 40
  41. 41. Systems Design Completion• System Design Specification – A typical system design specification uses a structure similar to the following: 1. Management summary 2. System components 3. System environment 4. Implementation requirements 5. Time and cost estimates 6. Additional material 41
  42. 42. Systems Design Completion• User Approval – Users must review and approve the interface design, report and menu designs, data entry screens, source documents, and other areas of the system that affect them – Other IT department members also need to review the system design specification – When the system design specification is complete, you distribute the document to a target group of users, IT department personnel, and company management 42
  43. 43. Systems Design Completion• Presentations – The first presentation is to the systems analysts, programmers, and technical support staff members – Your next presentation is to department managers and users from departments affected by the system – The final presentation is for company management – Management might reach one of three decisions: proceed with systems development, perform additional work on the systems design phase, or terminate the project 43
  44. 44. Chapter Summary• An information system combines hardware, software, data, procedures, and people into a system architecture• The analyst must consider enterprise resource planning, initial cost and TCO, scalability, Web integration, legacy interface requirements, processing options, and security issues• An architecture requires servers and clients 44
  45. 45. Chapter Summary• Compared to file server designs, client/server systems are more scalable and flexible• In implementing a design, an analyst should consider e-commerce strategies, the availability of packaged solutions, and corporate portals, which are entrances to a multifunction Web site• The primary processing methods are online and batch processing 45
  46. 46. Chapter Summary• Networks allow the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users• The way a network is configured is called the network topology• The system design specification presents the complete systems design for an information system• Chapter 10 complete 46