System Architecture Design Chapter 10 Slide 1 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Key Definitions The system architecture design consists of plans for the hardware, software, communications, security , and global support for the new application The designers must decide if processing will occur in the server (server-based), at the personal computer (client-based), or in some combination of these (clientserver based). Slide 2 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Key Definitions The network model shows major components of the system, where they are located and how they will be connected to one another. The hardware and software specifications describe these components in detail and aid those responsible for purchase and acquisition of these products. Slide 3 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. COMPUTING ARCHITECTURES Slide 4 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Functions of the Application System Data storage Data access logic Application logic Presentation logic Slide 5 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Architectures Server based Client based Client-server based Slide 6 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Alternative Servers In server based architectures, the servers do the work and present the results Mainframe Minicomputer Microcomputer (personal computer) Slide 7 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Server-Based Computing Slide 8 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Alternative Clients In client based architectures, clients do most of the work (except data storage) and present the results Terminals Microcomputer (personal computer) Special purpose terminals (ATMs, kiosks, Palm Pilots, and many others) Slide 9 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Client-Based Computing Slide 10 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Client-Server-Based Computing (2 Tiers) Slide 11 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Client-Server Attributes Typical Pros Compatible with web-based system design Scaleable Work with multiple vendors/products No central point of failure Slide 12 Typical Cons/Limits Complexity New programming languages and techniques (stress for personnel) More complex to update PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Client-Server -- Three Tiers Slide 13 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Client-Server -- Four Tiers Slide 14 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. N-Tiered Client-Server Attributes Typical Pros Separates processing to better balance load More scaleable Slide 15 Typical Cons/Limits Greater load on the network More difficult to program and test PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Distributed Objects Computing Middleware between clients and servers Update middleware when changing client code May reduce efficiency of the application CORBA DCOM Slide 16 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Realities of Infrastructure Design Most often the infrastructure will be in place Coordination of infrastructure components is very complex The application developer will need to coordinate with infrastructure specialists Slide 17 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Selecting a Computing Architecture Server-Based Client-based Client-server Cost of infrastructure Very high Medium Low Cost of development Medium Low High Ease of development Low High Low-medium Interface capabilities Low High High Control and security High Low Medium Scalability Low Medium High Slide 18 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Your Turn Consider the course registration system at your university: What computing architecture does it use? What computing architecture would you use if you were replacing it today? Slide 19 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. INFRASTUCTURE DESIGN Slide 20 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. The Network Model No standard format Conveys complexity of the system and how components fit together Components are Clients Equipment Connection to external systems or networks Slide 21 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Top-Level Network Model Slide 22 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Hardware and Software Specification Used if new hardware or software must be purchased Actual acquisition of hardware and software usually left to a purchasing department -especially in larger firms Slide 23 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Steps in Hardware and Software Specification Note hardware in low-level network model to create list of needed hardware Describe equipment in as much detail as possible Consider whether increased processing and traffic will absorb unused hardware capacity Note all software running on each hardware component Slide 24 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. GLOBAL ISSUES Slide 25 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Global Requirements Multilingual requirements Concurrent multilingual systems Discrete multilingual systems Local versus centralized control Unstated norms (e.g. dates, currency) 24-7 Support Communications infrastructure Slide 26 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. SECURITY Slide 27 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Identifying Threats to the System A threat is any potential adverse occurrence that can do harm to the application or its data Threats come from internal as well as external sources Categories of threats Disruptions, destruction and disaster Unauthorized access Slide 28 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Most Common Threats Slide 29 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Assessing the Risk of Each Threat Slide 30 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Creating Controls A control is something that mitigates or stops a threat Controls include redundancy fault tolerant servers disaster recovery plans anti-virus software Slide 31 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Additional Controls Include A security policy Passwords and encryption Firewalls Slide 32 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. What sort of computer architecture would you recommend for CD Solutions? Explain your preference. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Summary The three fundamental computing architectures are server-based, client-based, and client-server based. The network model shows technical components of the system and their geographic location throughout the organization. Hardware and software must be specified for acquisition in the project The systems analyst needs to also account for global issues and security measures. Slide 34 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Expanding the Domain To contrast the approaches of CORBA and DCOM/COM from Microsoft, check the following websites: http://www.corba.org http://www.microsoft.com/com Slide 35 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.