Systems Analysis and Design 9th Edition Chapter 10 System 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

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

Chapter Objectives Explain network protocols and licensing issues Describe wireless networking, including wireless standards, topologies, and trends Describe the system design specification

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

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

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

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

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

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

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

Planning the Architecture Servers Server Clients Mainframe architecture Server-based processing

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

Planning the Architecture Clients Stand-Alone Computing Local and wide area networks Client-based processing

Client/Server Architecture Overview

Client/Server Architecture Client/Server Design Styles

Client/Server Architecture Fat and Thin Clients

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

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

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

Internet-Based Architecture Developing E-Commerce Solutions In-House

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

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

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

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

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

Processing Methods Combined Online and Batch Processing

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

Network Models Network Protocols In all cases, the network must use a protocol Transmission Control Protocol/Internet Protocol (TCP/IP) File Transfer Protocol (FTP)

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

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

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)

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

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

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

Network Models Network Modeling Tools Network Licensing Issues 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

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)

Wireless Networks Wireless Network Standards 802.11g 802.11n Multiple input/multiple output (MIMO) Multipath design 802.11y

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

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

Systems Design Completion System Design Specification A typical system design specification uses a structure similar to the following: Management summary System components System environment Implementation requirements Time and cost estimates Additional material

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

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

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

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

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