System Architecture Chapter 10
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Transcript of System Architecture Chapter 10
Systems Analysis and Design 9th Edition
Chapter 10System Architecture
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
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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
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Chapter Objectives
• Explain network protocols and licensing issues• Describe wireless networking, including
wireless standards, topologies, and trends• Describe the system design specification
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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
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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
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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
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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
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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
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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
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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
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Planning the Architecture
• Servers– Server– Clients– Mainframe architecture– Server-based processing
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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
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Planning the Architecture
• Clients– Stand-Alone Computing– Local and wide area
networks– Client-based processing
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Client/Server Architecture
• Overview
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Client/Server Architecture
• Client/Server Design Styles
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Client/Server Architecture
• Fat and Thin Clients
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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
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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
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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
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Internet-Based Architecture
• Developing E-Commerce Solutions In-House
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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
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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
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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
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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
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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
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Processing Methods
• Combined Online and Batch Processing
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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
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Network Models
• Network Protocols– In all cases, the network must use a protocol– Transmission Control Protocol/Internet Protocol
(TCP/IP)– File Transfer Protocol (FTP)
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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
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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
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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)
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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
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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
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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
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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
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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)
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Wireless Networks
• Wireless Network Standards– 802.11g– 802.11n– Multiple input/multiple output (MIMO)– Multipath design– 802.11y
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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
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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
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Systems Design Completion
• System Design Specification– A typical system design specification uses a
structure similar to the following:1. Management summary2. System components3. System environment4. Implementation requirements5. Time and cost estimates6. Additional material
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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
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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
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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
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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
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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
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