Ibm describes websphere as a software platform for _____ environments

System Costs - Discussion

Part 1:

System Costs

Please respond to the following in not more than 200 words:

When analyzing cost/benefit and total cost of ownership (TCO), should systems analysts concentrate most on payback analysis, net present value (NPV), or return on investment (ROI)?
Provide an example that supports your position. Do not use one from the textbook or that has been posted by another student.
Professor Notes:

"There's a famous saying, "pay me now or pay me later." This week, I'd like you to apply it to the costs of an information system.

Usually, you can put more effort up front in development and expect lower operating and maintenance costs later on. Or, you could build the minimum viable product and plan for more extensive revisions throughout the lifetime of the system. Real systems are often somewhere in between, but I'd like you to explain which strategy you prefer, and why. Please address the analysis for product development. "

Part 2:

Then, in a separate post, follow up in a substantive post of up to 150 words to one of your fellow students who took a different position. What considerations might they have overlooked?

Support your positions with explanations and/or sources, as appropriate, but do not quote. (choose one reply with a different position than the one you took)

a.

Large cost can be quite a enormous entity if the purchases are large as well. I own a smoke shop right outside of Los Angeles, CA. called Lynwood Smokes and Snacks. I purchase all goods and materials at whole sale and turns profit by selling half the products for the total cost of what I paid. A sI come to understand the TCO system it's simply uncovering lifetime cost on products that have a great value. The TCO system is utilizing networks like IT communities and large cooperations around the world. For example IBM server can be pruchased for three years and all set for different prices. year 1=500, year 2=250, year 3=150 this depicts the lifetime cycle of cost.

R/S

AUGUST

b.

I personally like Net present value (NPV) since I believe in the concept that the money you have in hand now is more valuable than the money you collect later. Perhaps I am attracted to this concept since you can use the money to make more money by investing it in a business or put it in a bank to earn interest. Meanwhile, ROI measures the efficiency of an investment and calculates the return that the investment produces over time. But it is reportedly less accurate and can be easily manipulated. So, I would advise a network analyst to focus on NPV since It is a good indicator whether to proceed with a project or investment.

For example, when deciding to purchase a new laptop or a computer system. The purchase price would be the cost and plus additional cost of the computer system such as software and installations. One could buy a used/refurbished laptop to lower the cost, but the lap top might need more repairs (maintenance) or may need to be upgraded to keep up with changing technology. So, the used laptop might be cheaper, but the overall cost of ownership would be much higher than purchasing a new system.

c.

After reading about NPV and ROI both are ways of measuring the good or bad outcome of designing a system. Both ways use an equation that can be manipulated in certain ways to achieve goals good or bad. It seems best to pick an option that is going to be stable and reliable in any environment. Everyone knows for the most part you get what you pay for, spending more money upfront goes along way in the future. The best example i can use at my work the managers look at ROI for everything. Sometimes spending more money causes less headaches even if ROI suffers. In our shop they bought cheap access points to connect the front and back shop, over time they where constantly going down. We flash all new cars on this network causing the flashes to fail. Replacing those controllers toke time and made customers mad. Eventually they hire a firm to replace those access points and secure the network for future use.

CHAPTER 10 System Architecture

Chapter 10 is the final chapter in the systems design phase of the SDLC. This chapter describes system architecture, which translates the logical design of an information system into a physical blueprint. As you plan the system architecture, you will learn about servers, clients, processing methods, networks, and related issues.

OBJECTIVES

When you finish this chapter, you will be able to:

· Provide a checklist of issues to consider when selecting a system architecture

· Trace the evolution of system architecture from mainframes to current designs

· Explain client/server architecture, including tiers, cost-benefit issues, and performance

· Compare in-house e-commerce development with packaged solutions and service providers

· Discuss the impact of cloud computing and Web 2.0

· Define network topology, including hierarchical, bus, ring, star, and mesh models

· Describe wireless networking, including wireless standards, topologies, and trends

· Describe the system design specification

INTRODUCTION

At this point in the SDLC, your objective is to determine an overall architecture to implement the information system. You learned in Chapter 1 that an information system requires hardware, software, data, procedures, and people to accomplish a specific set of functions. An effective system combines those elements into an architecture, or design, that is flexible, cost-effective, technically sound, and able to support the information needs of the business. This chapter covers a wide range of topics that support the overall system design, just as a plan for a new home would include a foundation plan, building methods, wiring and plumbing diagrams, traffic flows, and costs.

System architecture translates the logical design of an information system into a physical structure that includes hardware, software, network support, processing methods, and security. The end product of the systems design phase is the system design specification. If this document is approved, the next step is systems implementation.

PREVIEW CASE: Mountain View College Bookstore

Background: Wendy Lee, manager of college services at Mountain View College, wants a new information system that will improve efficiency and customer service at the three college bookstores.

In this part of the case, Tina Allen (systems analyst) and David Conroe (student intern) are talking about system architecture issues.

Participants:

Tina and David

Location:

Mountain View College cafeteria, Thursday afternoon, January 9, 2014

Project status:

The team completed user interface and data design work. The last step in the systems design phase is to consider a system architecture for the bookstore system.

Discussion topics:

System architecture checklist, client/server architecture, processing methods, and network issues

Tina:

Hi, David. Did you enjoy the holiday break?

David:

I sure did. Now I’m ready to get back to work.

Tina:

Good. As the last step in the systems design phase of the SDLC, we need to study the physical structure, or architecture, of the bookstore system. Our checklist includes our college’s organization and culture, enterprise resource planning, total cost of ownership, scalability, Web integration, legacy systems, processing methods, security issues, and portals that could affect the system design.

David:

So, where do we start?

Tina:

Well, the bookstore interfaces with many publishers and vendors, so we’ll consider supply chain management, which is part of enterprise resource planning, or ERP for short.

David:

What happens after we finish the checklist?

Tina:

Then we’ll define a client/server architecture. As I see it, the bookstore client workstations will share the processing with a server in the IT department. Also, we may need to look at middleware software to connect the new system with existing legacy systems, such as the college accounting system.

David:

Anything else?

Tina:

Yes. We need to select a network plan, or topology, so we’ll know how to plan the physical cabling and connections — or possibly use wireless technology. When we’re done, we’ll submit a system design specification for approval.

David:

Sounds good to me.

Tina:

Good. Here’s a task list to get us started:

FIGURE 10-1 Typical system architecture tasks.

© Cengage Learning 2014

ARCHITECTURE CHECKLIST

Just as an architect begins a project with a list of the owner’s requirements, a systems analyst must approach system architecture with an overall checklist. Before making a decision, the analyst must consider several issues that will affect the architecture choice:

· Corporate organization and culture

· Enterprise resource planning (ERP)

· Initial and total cost of ownership (TCO)

· Scalability

· Web integration

· Legacy system interface requirements

· Processing options

· Security issues

· Corporate portals

Corporate Organization and Culture

To be successful, an information system must perform well in a company’s organization and culture. For example, consider two large bicycle brands, Green Bikes and Blue Bikes. Each firm has three operating divisions: an Asian subsidiary that manufactures the bicycles, a factory in Los Angeles that produces bike accessories and clothing, and a plant in Canada that makes bike carriers, racks, and custom trailers.

On the surface, the two firms are similar, but they have very different organizations and corporate cultures. Green Bikes is highly centralized, and oversees day-to-day operations from its Los Angeles office. Blue Bikes also has a Los Angeles executive office, but allows its three business units to operate separately, with minimal corporate oversight. Both firms are successful, and it is unlikely that their managerial styles will change anytime soon.

Suppose you were a consultant, and both firms asked you to suggest an IT architecture that would boost productivity and reduce costs. How would corporate organization and culture issues affect your recommendation? There is no easy answer to that question. The best approach probably would be to study day-to-day business functions, talk to users at all levels, and focus on operational feasibility issues, just as you did earlier in the development process.

Enterprise Resource Planning (ERP)

Many companies use enterprise resource planning (ERP) software, which was described in Chapter 1. The objective of ERP is to establish a company-wide strategy for using IT that includes a specific architecture, standards for data, processing, network, and user interface design. A main advantage of ERP is that it describes a specific hardware and software environment, also called a platform , that ensures connectivity and easy integration of future systems, including in-house software and commercial packages.

Even though ERP has been very popular, some argue that it is outdated because of major advances in technology. For example, in her CIO Magazine article shown in Figure 10-2, author Karen Goulart calls ERP an “old workhorse.” She suggests that ERP’s future success depends on integrating new technologies such as mobility and cloud computing, among others. In other words, an ERP designer might have to bring enterprise data, anytime, anywhere, to a smart phone in a sales rep’s pocket.

Many companies are extending internal ERP systems to their suppliers and customers, using a concept called supply chain management (SCM) . For example, in a totally integrated supply chain system, a customer order could cause a manufacturing system to schedule a work order, which in turn triggers a call for more parts from one or more suppliers. In a dynamic, highly competitive economy, SCM can help companies achieve faster response, better customer service, and lower operating costs.

FIGURE 10-2 Is ERP outdated, or will it still be around? Author Karen Goulart says that ERP’s future success depends on integrating new technology, such as mobility and cloud computing.

© 2007–2012, TechTarget

Microsoft offers an enterprise solution called Microsoft Dynamics, as shown in Figure 10-3 on the next page. The interesting “test drive” video provides a scenario-based preview of how the software can integrate financial management, customer relationship management (CRM), supply chain management (SCM), and business metrics.

CASE IN POINT 10.1: ABC SYSTEMS

You are a systems analyst at ABC Systems, a fast-growing IT consulting firm that provides a wide range of services to companies that want to establish e-commerce operations. During the last 18 months, ABC acquired two smaller firms and set up a new division that specializes in supply chain management. Aligning ABC’s internal systems was quite a challenge, and top management was not especially happy with the integration cost or the timetable. To avoid future problems, you have decided to suggest an ERP strategy, and you plan to present your views at the staff meeting tomorrow. ABC’s management team is very informal and prefers a loose, flexible style of management. How will you persuade them that ERP is the way to go?

Initial Cost and TCO

You learned earlier about the importance of considering economic feasibility and TCO during systems planning and analysis. TCO includes tangible purchases, fees, and contracts called hard costs. However, additional soft costs of management, support, training, and downtime are just as important, but more difficult to measure.

Firms such as Micromation, which is shown in Figure 10-4 on page 409, offer specialized TCO analysis, benchmarks, and consulting. As the Micromation chart shows, user-related costs represent a very large slice of the total pie.

A TCO analysis should include the the following questions.

· If in-house development was selected as the best alternative initially, is it still the best choice? Is the necessary technical expertise available, and does the original cost estimate appear realistic?

· If a specific package was chosen initially, is it still the best choice? Are newer versions or competitive products available? Have any changes occurred in pricing or support?

· Have any new types of outsourcing become available?

FIGURE 10-3 Microsoft invites you to watch or take a scenario-based test drive of its Microsoft Dynamics product.

Screenshots used with permission from Microsoft.

· Have any economic, governmental, or regulatory events occurred that could affect the proposed project?

· Have any significant technical developments occurred that could affect the proposed project?

· Have any major assumptions changed since the company made the build versus buy decision?

· Are there any merger or acquisition issues to consider, whereby the company might require compatibility with a specific environment?

· Have any new trends occurred in the marketplace? Are new products or technologies on the verge of being introduced?

· Have you updated the original TCO estimate? If so, are there any significant differences?

FIGURE 10-4 The Micromation site suggests that soft costs are very significant, but are more difficult to measure.

© 2012 Micromation

The answers to these questions might affect the initial cost and TCO for the proposed system. You should review system requirements and alternatives now, before proceeding to design the system architecture.

Scalability

A network is composed of individual nodes. A node represents a physical device, wired or wireless, that can send, receive, or manage network data. For example, nodes can be servers, workstations, shared printers, mass storage devices, wireless access points, or mobile computers.

Scalability , also called extensibility , refers to a system’s ability to expand, change, or downsize easily to meet the changing needs of a business enterprise. Scalability is especially important in implementing systems that are volume-related, such as transaction processing systems. A scalable system is necessary to support a dynamic, growing business. For example, a scalable network could handle anywhere from a few dozen nodes to thousands of nodes, and a scalable DBMS could support the acquisition of an entire new sales division. When investing large amounts of money in a project, management is especially concerned about scalability issues that could affect the system’s life expectancy.

Web Integration

An information system includes applications , which are programs that handle the input, manage the processing logic, and provide the required output. The systems analyst must know if a new application will be part of an e-commerce strategy and the degree of integration with other Web-based components. As you learned earlier, a Web-centric architecture follows Internet design protocols and enables a company to integrate the new application into its e-commerce strategy. Even where e-commerce is not involved, a Web-centric application can run on the Internet or a company intranet or extranet. A Web-based application avoids many of the connectivity and compatibility problems that typically arise when different hardware environments are involved. In a Web-based environment, a firm’s external business partners can use standard Web browsers to import and export data.

Legacy Systems

A new system might have to interface with one or more legacy systems , which are older systems that use outdated technology, but still are functional. For example, a new marketing information system might need to report sales data to a server-based accounting system and obtain product cost data from a legacy manufacturing system.

Interfacing a new system with a legacy system involves analysis of data formats and compatibility. In some cases, a company will need to convert legacy file data, which can be an expensive and time-consuming process. Middleware, which is discussed later in this chapter, might be needed to pass data between new systems and legacy systems. Finally, to select the best architecture, the analyst must know if the new application eventually will replace the legacy system.

Processing Options

In planning the architecture, designers also must consider how the system will process data — online or in batches. For example, a high-capacity transaction processing system, such as an order entry system, requires more network, processing, and data storage resources than a monthly billing system that handles data in batches. Also, if the system must operate online, 24 hours a day and seven days a week (24/7), provision must be made for backup and speedy recovery in the event of system failure.

The characteristics of online and batch processing methods are described later in this chapter, with examples of each type.

Security Issues

From the password protection shown in Figure 10-5 to complex intrusion detection systems, security threats and defenses are a major concern to a systems analyst. As the physical design is translated into specific hardware and software, the analyst must consider security issues and determine how the company will address them. Security is especially important when data or processing is performed at remote locations, rather than at a centralized facility. In mission-critical systems, security issues will have a major impact on system architecture and design.

Web-based systems introduce additional security concerns, as critical data must be protected in the Internet environment. Also, firms that use e-commerce applications must assure customers that their personal data is safe and secure. System security concepts and strategies are discussed in detail in Chapter 12, Managing Systems Support and Security.

FIGURE 10-5 User IDs and passwords are important elements of system security.

© JMiks / Shutterstock.com

Corporate Portals

Depending on the system, the planned architecture might include a corporate portal. A portal is an entrance to a multifunction Web site. After entering a portal, a user can navigate to a destination using various tools and features provided by the portal designer. A corporate portal can provide access for customers, employees, suppliers, and the public. A well-designed portal can integrate with various other systems and provide a consistent look and feel.

SYSTEM ARCHITECTURE: THEN AND NOW

Every business information system must carry out three main functions:

· Manage applications that perform the processing logic.

· Handle data storage and access.

· Provide an interface that allows users to interact with the system.

Depending on the architecture, the three functions are performed on a server, on a client, or are divided between the server and the client. As you plan the design, you must determine where the functions will be carried out and the advantages and disadvantages of each design approach.

Mainframe Architecture

A server is a computer that supplies data, processing services, or other support to one or more computers, called clients . The earliest servers were mainframe computers, and a system design where the server performs all the processing sometimes is described as mainframe architecture . Although the actual server does not have to be a mainframe, the term mainframe architecture typically describes a multiuser environment where the server is significantly more powerful than the clients. A systems analyst should know the history of mainframe architecture to understand the server’s role in modern system design.

In the 1960s, mainframe architecture was the only choice. In addition to centralized data processing, the earliest systems performed all data input and output at a central location, often called a data processing center. Physical data was delivered or transmitted in some manner to the data processing center, where it was entered into the system. Users in the organization had no input or output capability, except for printed reports that were distributed by a corporate IT department.

As network technology advanced, companies installed terminals at remote locations, so that users could enter and access data from anywhere in the organization, regardless of where the centralized computer was located. A terminal included a keyboard and display screen to handle input and output, but lacked independent processing capability. In a centralized design, as shown in Figure 10-6, the remote user’s keystrokes are transmitted from his or her terminal to the mainframe, which responds by sending screen output back to the user’s screen.

Today, mainframe architecture still is used in industries that require large amounts of processing that can be done at a central location. For example, a bank might use mainframe servers to update customer balances each night. In a blend of old and new technology, an Internet-based retail operation might use mainframe architecture at a customer service center that fulfills its online sales as shown in Figure 10-7 on the next page.

FIGURE 10-6 In a centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back to the user’s screen.

© Cengage Learning 2014

Impact of the Personal Computer

When PC technology exploded in the 1990s, powerful microcomputers quickly appeared on corporate desktops. Users found that they could run their own word processing, spreadsheet, and database applications, without assistance from the IT group, in a mode called stand-alone computing. Before long, companies linked the stand-alone computers into networks that enabled the user clients to exchange data and perform local processing.

When an individual user works in stand-alone mode, the workstation performs all the functions of a server by storing, accessing, and processing data, as well as providing a user interface. Although stand-alone PCs improved employee productivity and allowed users to perform tasks that previously required IT department assistance, stand-alone computing was inefficient and expensive. Even worse, maintaining data on individual workstations raised major concerns about data security, integrity, and consistency. Without a central storage location, it was impossible to protect and back up valuable business data, and companies were exposed to enormous risks. In some cases, users who were frustrated by a lack of support and services from the IT department created and managed their own databases. In addition to security concerns, this led to data inconsistency and unreliability.

FIGURE 10-7 Internet-based retail operations such as Amazon.com use customer service centers to fulfill online sales.

© Bloomberg via Getty Images

Network Evolution

As technology became available, companies resolved the problems of stand-alone computing by joining clients into a local area network (LAN) that allows sharing of data and hardware resources, as shown in Figure 10-8. One or more LANs, in turn, can connect to a centralized server. Further advances in technology made it possible to create powerful networks that could use satellite links, high-speed fiber-optic lines, or the Internet to share data.

A wide area network (WAN) spans long distances and can connect LANs that are continents apart, as shown in Figure 10-9. When a user accesses data on a LAN or WAN, the network is transparent because a user sees the data as if it were stored on his or her own workstation. Company-wide systems that connect one or more LANs or WANs are called distributed systems . The capabilities of a distributed system depend on the power and capacity of the underlying data communication network. Compared to mainframe architecture, distributed systems increase concerns about data security and integrity because many individual clients require access to perform processing.

FIGURE 10-8 A LAN allows sharing of data and hardware, such as printers and scanners.

© Cengage Learning 2014

CLIENT/SERVER DESIGNS

Today’s interconnected world requires an information architecture that spans the entire enterprise. Whether you are dealing with a departmental network or a multinational corporation, as a systems analyst you will work with a distributed computing strategy called client/server architecture.

FIGURE 10-9 A WAN can connect many LANs and link users who are continents apart.

© Cengage Learning 2014

Overview

Although no standard definition exists, the term client/server architecture generally refers to systems that divide processing between one or more networked clients and a central server. In a typical client/server system, the client handles the entire user interface, including data entry, data query, and screen presentation logic. The server stores the data and provides data access and database management functions. Application logic is divided in some manner between the server and the clients. In a client/server interaction, the client submits a request for information from the server, which carries out the operation and responds to the client. As shown in Figure 10-10 the data file is not transferred from the server to the client — only the request and the result are transmitted across the network. To fulfill a request from a client, the server might contact other servers for data or processing support, but that process is transparent to the client. The analogy can be made to a restaurant where the customer gives an order to a server, who relays the request to a cook, who actually prepares the meal.

Figure 10-11 on the next page lists some major differences between client/server and traditional mainframe systems. Many early client/server systems did not produce expected savings because few clear standards existed, and development costs often were higher than anticipated. Implementation was expensive because clients needed powerful hardware and software to handle shared processing tasks. In addition, many companies had an installed base of data, called legacy data , which was difficult to access and transport to a client/server environment.

FIGURE 10-10 In a client/server design, data is stored and usually processed on the server.

© Cengage Learning 2014

As large-scale networks grew more powerful, client/server systems became more cost-effective. Many companies invested in client/server systems to achieve a unique combination of computing power, flexibility, and support for changing business operations. Today, client/server architecture is the dominant form of systems design, using Internet protocols and network models such as the ones described on pages 426–430. As businesses form new alliances with customers and suppliers, the client/server concept continues to expand to include clients and servers outside the organization.

Cloud computing, which is discussed later in this chapter, is seen by some observers as an entirely new concept. Others see it as the ultimate form of client/server architecture, where Internet-based computing becomes the server part of client/server and handles processing tasks, while the Internet itself becomes the platform that replaces traditional networks. The bottom line is that it doesn’t matter whether cloud computing is part of a client/server evolution, or a whole new way of thinking about computing. Either way, successful systems must support business requirements, and system architecture is an important step in the systems development process.

FIGURE 10-11 Comparison of the characteristics of client/server and mainframe systems.

© Cengage Learning 2014

The Client’s Role

The client/server relationship must specify how the processing will be divided between the client and the server. A fat client , also called a thick client , design locates all or most of the application processing logic at the client. A thin client design locates all or most of the processing logic at the server. What are the advantages and disadvantages of each design? Most IT experts agree that thin client designs provide better performance, because program code resides on the server, near the data. In contrast, a fat client handles more of the processing and must access and update the data more often. Compared with maintaining a central server, fat client TCO also is higher, because of initial hardware and software requirements and the ongoing expense of supporting and updating remote client computers. A fat client design, however, is simpler and less expensive to develop, because the architecture resembles traditional file server designs where all processing is performed at the client. Figure 10-12 compares the characteristics of fat and thin clients.

Client/Server Tiers

Early client/server designs were called two-tier designs. In a two-tier design, the user interface resides on the client, all data resides on the server, and the application logic can run either on the server or on the client, or be divided between the client and the server.

More recently, another form of client/server design, called a three-tier design, has become popular. In a three-tier design, the user interface runs on the client and the data is stored on the server, just as with a two-tier design. A three-tier design also has a middle layer between the client and server that processes the client requests and translates them into data access commands that can be understood and carried out by the server, as shown in Figure 10-13. You can think of the middle layer as an application server , because it provides the application logic , or business logic , required by the system. Three-tier designs also are called n-tier designs, to indicate that some designs use more than one intermediate layer.

FIGURE 10-12 Characteristics of fat and thin clients.

© Cengage Learning 2014

The advantage of the application logic layer is that a three-tier design enhances overall performance by reducing the data server’s workload. The separate application logic layer also relieves clients of complex processing tasks. Because it can run on a minicomputer that is much more powerful than the typical client workstations, the middle layer is more efficient and cost-effective in large-scale systems. Figure 10-14 on the next page shows where the data, the application logic, and the user interface are located on various architectures. In a client/server system, the tiers communicate using software called middleware, which is described in the following section.

FIGURE 10-13 Characteristics of two-tier versus three-tier client/server design.

© Cengage Learning 2014

Middleware

A recent Internet search for the phrase “What is Middleware” returned 80,500 sites. Unfortunately, the term middleware means different things to different people. So, what is middleware?

FIGURE 10-14 The location of the data, the application logic, and the user interface depend on the type of architecture.

© Cengage Learning 2014

In a multi-tier system, special software called middleware enables the tiers to communicate and pass data back and forth. Here are some other definitions you might encounter:

· Middleware offers an interface to connect software and hardware.

· Middleware can integrate legacy systems and Web-based applications. For example, when a user enters a customer number on a Web form, middleware can update a legacy accounting system.

· Middleware is like glue that holds different applications together.

· Middleware represents the slash in the term client/server.

· Middleware resembles the plumbing system in your home: it connects important objects in a way that requires little or attention.

The bottom line is that a hard and fast definition isn’t all that important. If you grasp the concept of middleware, you’ll be able to handle the development tools and learn the techniques required in your IT environment.

Cost-Benefit Issues

To support business requirements, information systems need to be scalable, powerful, and flexible. For most companies, client/server systems offer the best combination of features to meet those needs. Whether a business is expanding or downsizing, client/server systems enable the firm to scale the system in a rapidly changing environment. As the size of the business changes, it is easier to adjust the number of clients and the processing functions they perform than it is to alter the capability of a large-scale central server.

Client/server computing also allows companies to transfer applications from expensive mainframes to less-expensive client platforms. In addition, using common languages such as SQL, clients and servers can communicate across multiple platforms. That difference is important because many businesses have substantial investments in a variety of hardware and software environments.

Finally, client/server systems reduce network load and improve response times. For example, consider a user at a company headquarters who wants information about total sales figures. In a client/server system, the server locates the data, performs the necessary processing, and responds immediately to the client’s request. The data retrieval and processing functions are transparent to the client because they are done on the server, not the client.

Performance Issues

While it provides many advantages, client/server architecture does involve performance issues that relate to the separation of server-based data and networked clients that must access the data.

Consider the difference between client/server design and a centralized environment, where a server-based program issues a command that is executed by the server’s own CPU. Processing speed is enhanced because program instructions and data both travel on an internal system bus, which moves data more efficiently than an external network.

In contrast to the centralized system, a client/server design separates applications and data. Networked clients submit data requests to the server, which responds by sending data back to the clients. When the number of clients and the demand for services increases beyond a certain level, network capacity becomes a constraint, and system performance declines dramatically.

In the article shown in Figure 10-15, IBM states that the performance characteristics of a client/server system are not the same as a centralized processing environment. Client/server response times increase gradually as more requests are made, but then rise dramatically when the system nears its capacity. This point is called the knee of the curve , because it marks a sharp decline in the system’s speed and efficiency. To deliver and maintain acceptable performance, system developers must anticipate the number of users, network traffic, server size and location, and design a client/server architecture that can support current and future business needs.

What is the answer to enhancing client/server performance? According to IBM, client/server systems must be designed so the client contacts the server only when necessary and makes as few trips as possible.

Another issue that affects client/server performance is data storage. Just as processing can be done at various places, data can be stored in more than one location using a distributed database management system (DDBMS) .

Using a DDBMS offers several advantages: Data stored closer to users can reduce network traffic; the system is scalable, so new data sites can be added without reworking the system design; and with data stored in various locations, the system is less likely to experience a catastrophic failure. A potential disadvantage of distributed data storage involves data security. It can be more difficult to maintain controls and standards when data is stored in various locations. In addition, the architecture of a DDBMS is more complex and difficult to manage. From a system design standpoint, the challenge is that companies often want it both ways — they want the control that comes with centralization and the flexibility associated with decentralization.

FIGURE 10-15 According to IBM, client/server response times increase gradually, and then rise dramatically when the system nears its capacity. That point is referred to as the knee of the curve.

© Copyright IBM Corporation 1994, 2012.

THE IMPACT OF THE INTERNET

The Internet has had an enormous impact on system architecture. The Internet has become more than a communication channel — many IT observers see it as a fundamentally different environment for system development.

Recall that in a traditional client/server system, the client handles the user interface, as shown in Figure 10-14 on the previous page, and the server (or servers in a multi-tier system) handles the data and application logic. In a sense, part of the system runs on the client, part on the server. In contrast, in an Internet-based architecture, in addition to data and application logic, the entire user interface is provided by the Web server in the form of HTML documents that are displayed by the client’s browser. Shifting the responsibility for the interface from the client to the server simplifies data transmission and results in lower hardware cost and complexity.

The advantages of Internet-based architecture have changed fundamental ideas about how computer systems should be designed, and we are moving rapidly to a total online environment. At the same time, millions of people are using Web-based collaboration and social networking applications to accomplish tasks that used to be done in person, over the phone, or by more traditional Internet channels. The following sections examine cloud computing and Web 2.0. It is important to understand these trends, which are shaping the IT industry’s future.

Cloud Computing

Cloud computing refers to the cloud symbol that often is used to represent the Internet. The cloud computing concept envisions a cloud of remote computers that provide a total online software and data environment that is hosted by third parties. For example, a user’s computer does not perform processing or computing tasks — the cloud does. This concept is in contrast to today’s computing model, which is based on networks that strategically distribute processing and data across the enterprise. In a sense, the cloud of computers acts as one giant computer that performs tasks for users.

Figure 10-16 shows users connected to the cloud, which performs the computing work. Instead of requiring specific hardware and software on the user’s computer, cloud computing spreads the workload to powerful remote systems that are part of the cloud. The user appears to be working on a local system, but all computing is actually performed in the cloud. No updates or maintenance are required of the user, and there are no compatibility issues.

Cloud computing effectively eliminates compatibility issues, because the Internet itself is the platform. This architecture also provides scaling on demand , which matches resources to needs at any given time. For example, during peak loads, additional cloud servers might come on line automatically to support the workload.

FIGURE 10-16 The explosive growth of cloud computing has attracted many firms that fight hard for market share.

© Cengage Learning 2014

Cloud computing is an ideal platform for powerful Software as a Service (SaaS) applications. As you learned in Chapter 7, SaaS is a popular deployment method where software is not purchased but is paid for as a service, much like one pays for electricity or cable TV each month. In this architecture, updates and changes to services can be easily made by service providers without involving the users.

Even though cloud computing has tremendous advantages, some concerns exist. First, cloud computing requires significantly more bandwidth (the amount of data that can be transferred in a fixed time period) than traditional client/server networks. Second, because cloud computing is Internet-based, if a user’s Internet connection becomes unavailable, he or she will be unable to access any cloud-based services. In addition, there are security concerns associated with sending large amounts of data over the Internet, as well as concerns about storing it securely. Finally, there is the issue of control. Because a service provider hosts the resources and manages data storage and access, the provider has complete control of the system. Many firms are wary of handing over control of mission-critical data and systems to a third-party provider.

Future technology advances will make cloud computing even more feasible, desirable, and secure. As the IT industry moves toward a Web-based architecture, cloud computing will be marketed aggressively and growth will be rapid. Figure 10-16 lists some of the major players in the cloud market. Although the list will change from month to month, or week to week, one thing will not change: cloud computing will be a cornerstone of IT growth in the coming decade.

Web 2.0

The shift to Internet-based collaboration has been so powerful and compelling that it has been named Web 2.0 . Web 2.0 is not a reference to a more technically advanced version of the current Web. Rather, Web 2.0 envisions a second generation of the Web that will enable people to collaborate, interact, and share information more dynamically.

Leading Web 2.0 author Tim O’Reilly has suggested that the strong interest in Web 2.0 is driven by the concept of the Internet as a platform. O’Reilly sees future Web 2.0 applications delivering software as a continuous service with no limitations on the number of users that can connect or how users can consume, modify, and exchange data.

Social networking sites, such as Facebook, Twitter, and LinkedIn are seeing explosive growth in the Web 2.0 environment. Another form of social collaboration is called a wiki. A wiki is a Web-based repository of information that anyone can access, contribute to, or modify. In a sense, a wiki represents the collective knowledge of a group of people. One of the best-known wikis is Wikipedia.org, but smaller-scale wikis are growing rapidly at businesses, schools, and other organizations that want to compile and share information.

One of the goals of Web 2.0 is to enhance creativity, interaction, and shared ideas. In this regard, the Web 2.0 concept resembles the agile development process and the open-source software movement. Web 2.0 communities and services are based on a body of data created by users. As users collaborate, new layers of information are added in an overall environment known as the Internet operating system . These layers can contain text, sound bytes, images, and video clips that are shared with the user community.

E-COMMERCE ARCHITECTURE

The huge expansion of Web-based commerce is reshaping the IT landscape. Internet business solutions must be efficient, reliable, and cost-effective. When planning an e-commerce architecture, analysts can examine in-house development, packaged solutions, and service providers. The following sections discuss these options.

In-House Solutions

In Chapter 7, you learned how to analyze advantages and disadvantages of in-house development versus purchasing a software package. The same basic principles apply to system design.

If you decide to proceed with an in-house solution, you must have an overall plan to help achieve your goals. How should you begin? Figure 10-17 offers guidelines for companies developing e-commerce strategies. An in-house solution usually requires a greater initial investment, but provides more flexibility for a company that must adapt quickly in a dynamic e-commerce environment. By working in-house, a company has more freedom to integrate with customers and suppliers and is less dependent on vendor-specific solutions.

FIGURE 10-17 Guidelines for companies developing e-commerce strategies.

© Cengage Learning 2014

For smaller companies, the decision about in-house Web development is even more critical, because this approach will require financial resources and management attention that many small companies might be unable or unwilling to commit. An in-house strategy, however, can provide valuable benefits, including the following:

· A unique Web site, with a look and feel consistent with the company’s other marketing efforts

· Complete control over the organization of the site, the number of pages, and the size of the files

· A scalable structure to handle increases in sales and product offerings in the future

· More flexibility to modify and manage the site as the company changes

· The opportunity to integrate the firm’s Web-based business systems with its other information systems, creating the potential for more savings and better customer service

Whether a firm uses an in-house or a packaged design, the decision about Web hosting is a separate issue. Although internal hosting has some advantages, such as greater control and security, the expense would be much greater, especially for a small- to medium-sized firm.

CASE IN POINT 10.2: SMALL POTATOES, INC.

Small Potatoes is a family-operated seed business that has grown rapidly. Small Potatoes specializes in supplying home gardeners with the finest seeds and gardening supplies. Until now, the firm has done all its business by placing ads in gardening and health magazines, and taking orders using a toll-free telephone number.

Now, the family has decided to establish a Web site and sell online, but there is some disagreement about the best way to proceed. Some say it would be better to develop the site on their own, and Betty Lou Jones, a recent computer science graduate, believes she can handle the task. Others, including Sam Jones, Betty’s grandfather, feel it would be better to outsource the site and focus on the business itself. Suppose the family asked for your opinion. What would you say? What additional questions would you ask?

FIGURE 10-18 Intershop offers software solutions for smaller companies that want to get an e-business up and running quickly.

© 2009–2012 Intershop Communications AG

Packaged Solutions

If a small company is reluctant to take on the challenge and complexity of developing an Internet commerce site in-house, an alternative can be a packaged solution. This is true even for medium- to large-sized firms. Many vendors, including Microsoft and Intershop, offer turnkey systems for companies that want to get an e-business up and running quickly, as shown in Figure 10-18.

For large-scale systems that must integrate with existing applications, packaged solutions might be less attractive.

Service Providers

Another alternative is to use an application service provider (ASP). As explained in Chapter 7, an ASP provides applications, or access to applications, by charging a usage or subscription fee. Today, many ASPs offer full-scale Internet business services for companies that decide to outsource those functions.

managed hosting, which also was discussed in Chapter 7. As shown in Figure 10-19 on the next page,

Another service provider option is managed hosting, which also was discussed in Chapter 7. As shown in Figure 10-19 on the next page, a solution provider such as Rackspace can host and maintain a corporate Web site. Rackspace states that its customers will “never have to implement, update, troubleshoot, patch, monitor, administer, backup data, or worry again.”

A systems analyst confronts a bewildering array of products and strategies when implementing Internet-based systems. A good starting point might be to consider the experience of other companies in the same industry. Many firms offer the names of clients and customers, along with their success stories. Although this information might or might not be reliable, it can provide valuable knowledge regarding a vendor’s products and services.

PROCESSING METHODS

In selecting an architecture, the systems analyst must determine which transactions will be handled online, and what functions, if any, can be carried out using a batch processing method.

FIGURE 10-19 Rackspace offers managed hosting and a variety of cloud-based services.

© 2012 Rackspace, US Inc.

Online Processing

Early computer systems were designed to handle data records as a group, or batch. Few, if any systems use that model today. However, even the most advanced online systems must perform maintenance, post large quantities of data during off-hours when network traffic is low, and carry out housekeeping tasks just as their legacy computer ancestors did. This section will discuss the online processing capability that is at the core of powerful, modern systems, and the following section will describe the evolution of batch processing.

An online system handles transactions when and where they occur and provides output directly to users. Because it is interactive, online processing avoids delays and allows a constant dialog between the user and the system.

An airline reservations system is a familiar example of online processing. When an online customer visits the airline’s Web site, he or she can enter the origin, destination, travel dates, and travel times. The system searches a database and responds by displaying available flights, times, and prices. The customer can make a reservation, enter a name, address, credit card information, and other required data and the system creates the reservation, assigns a seat, and updates the flight database immediately.

Online processing also can be used with file-oriented systems. Figure 10-20 shows what happens when a customer uses an ATM to inquire about an account balance. After the ATM verifies the customer’s card and password, the customer enters the request (Step 1). Then, the system accesses the account master file using the account number as the primary key and retrieves the customer’s record (Step 2). The system verifies the account number and displays the balance (Step 3). Data is retrieved and the system transmits the current balance to the ATM, which prints it for the customer. Online processing systems have four typical characteristics:

1. The system processes transactions completely when and where they occur.

2. Users interact directly with the information system.

3. Users can access data randomly.

4. The information system must be available whenever necessary to support business functions.

Batch Processing: Still With Us After All These Years

Batch processing means that data is managed in groups, or batches. That was an acceptable choice in the 1960s, and for most firms, it was the only choice. Today, all businesses need realtime information to operate, and batch processing is not practical. However, batch methods can be efficient and convenient in some situations.

For example, batch processing can be used for large amounts of data that must be processed on a routine schedule, such as weekly paychecks, daily credit card transaction updates, or closing stock data that must be calculated and published in the following day’s news media. The main advantages of batch methods are:

FIGURE 10-20 When a customer requests a balance, the ATM system verifies the account number, submits the query, retrieves the current balance, and displays the balance on the ATM screen.

© Cengage learning 2014

· Tasks can be planned and run on a predetermined schedule, without user involvement.

· Batch programs that require major network resources can run at times when costs, and impact on other traffic, will be lowest.

· A batch method is well-suited to address security, audit, and privacy concerns, because it runs in a relatively controlled environment.

Real-World Examples

Figure 10-21 shows a familiar point-of-sale (POS) terminal in a supermarket chain. The diagram in Figure 10-22 on the next page shows how that POS terminal might trigger a series of online and batch processing events. Notice that the system uses online processing to handle data entry and inventory updates, while reports and accounting entries are performed in a batch. Why would any company choose a mix of online and batch processing? The answer is that it makes good business sense. Consider the following scenario in a typical retail store:

FIGURE 10-21 Retail point-of-sale terminals provide customer sales support and transaction processing capability.

© Karlheinz Schindler/dpa/Landov

· During business hours, a salesperson enters a sale on a POS terminal, which is part of an online system that handles daily sales transactions and maintains an up-to-date inventory file.

· When the salesperson enters the transaction, online processing occurs. The system performs calculations, updates the inventory file, and produces output on the POS terminal in the form of a screen display and a printed receipt. At the same time, each sales transaction creates input data for day-end batch processing.

· When the store closes, the system uses the sales transactions to produce the daily sales report, perform the related accounting entries, and analyze the data to identify slow or fast-moving items, sales trends, and related issues — such as store discounts for the next day.

FIGURE 10-22 Many retailers use a combination of online and batch processing. When a salesperson enters the sale on the POS terminal, the online system retrieves data from the item file, updates the quantity in stock, and produces a sales transaction record. At the end of the day, a batch processing program produces a daily sales report and updates the accounting system.

© Cengage Learning 2014

Which method is better, online or batch processing? The answer is neither — they are totally different, but can work well together. In this scenario, an online system handles point-of-sale processing, which must be done as it occurs, while a batch method provides routine, overnight processing and marketing analysis. Online processing allows the data to be entered and validated immediately, so the information always is up to date. However, a heavy volume of online transactions can be expensive for smaller firms, and data backup and recovery also adds to IT costs. In contrast, when used properly, batch processing can be cost-effective and less vulnerable to system disruption.

CASE IN POINT 10.3: R/WAY TRUCKING COMPANY

You are the new IT manager at R/Way, a small but rapidly growing trucking company headquartered in Cleveland, Ohio. The company slogan is “Ship It R/Way — State-of-the-Art in Trucking and Customer Service.” R/Way’s information system currently consists of a file server and three workstations where freight clerks enter data, track shipments, and prepare freight bills. To perform their work, the clerks obtain data from the server and use database and spreadsheet programs stored on their PCs to process the data.

Unfortunately, your predecessor did not design a relational database. Instead, data is stored in several files, including one for shippers, one for customers, and one for shipments. The system worked well for several years, but cannot handle current volume or support online links for R/Way shippers and customers. The company president is willing to make changes, but he is reluctant to spend money on major IT improvements unless you can convince him that they are necessary.

What would you recommend and why?

NETWORK MODELS

A network allows the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users. When planning a network design, you must consider network terms and concepts, including the OSI model, network modeling tools, network topology, network protocols, and wireless networks, which are covered in this section. Other important issues, such as network performance and security, are covered in Chapter 12, Managing Systems Support and Security.

The OSI Model

Based on the discussion of system architecture earlier in this chapter, you already understand basic network terms such as client, server, LAN, WAN, client/server architecture, tiers, middleware, and cloud computing.

Before you study network topology, you should be aware of the OSI (Open Systems Interconnection) model , which describes how data moves from an application on one computer to an application on another networked computer. The OSI model consists of seven layers, and each layer performs a specific function.

The OSI model provides physical design standards that assure seamless network connectivity, regardless of the specific hardware environment. If you took a networking course, you probably studied the OSI model in detail. As an IT professional, if your tasks include network installation, configuration, and maintenance, you will need additional resources and information about the OSI model.

Network Topology

The way a network is configured is called the network topology . Topology can refer to a physical or a logical view of the network. For example, physical topology describes the actual network cabling and connections, while logical topology describes the way the components interact. It is important to understand the distinction, because a specific physical topology might be able to support more than one logical topology. For example, it is not uncommon to run cabling in a certain pattern because of physical installation and cost issues, but to use a different pattern for the logical topology.

The workstations in Figure 10-23 are arranged in a circular shape, but that might or might not reflect the network topology. The examples shown in Figures 10-24 to 10-28 on pages 426 to 428 represent a logical topology, as seen by network users, who do not know or care about the physical cabling pattern.

LAN and WAN networks typically are arranged in four patterns: hierarchical, bus, ring, and star. The concepts are the same regardless of the size of the network, but the physical implementation is different for a large-scale WAN that spans an entire business enterprise compared with a small LAN in a single department. The four topologies are described in the following sections.

FIGURE 10-23 Although these workstations form a circle physically, the layout has no bearing on the network topology, which might be a bus, ring, star, or other logical design.

© Patrick Seeger/dpa /Landov

HIERARCHICAL NETWORK In a hierarchical network , as shown in Figure 10-24 on the next page, one or more powerful servers control the entire network. Departmental servers control lower levels of processing and network devices. An example of a hierarchical network might be a retail clothing chain, with a central computer that stores data about sales activity and inventory levels and local computers that handle store-level operations. The stores transmit data to the central computer, which analyzes sales trends, determines optimum stock levels, and coordinates a supply chain management system. In this situation, a hierarchical network might be used, because it mirrors the actual operational flow in the organization.

FIGURE 10-24 A hierarchical network with a single server that controls the network.

© Cengage Learning 2014

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. Hierarchical networks were often used in traditional mainframe-based systems, but are much less common today.

BUS NETWORK In a bus network , as shown in Figure 10-25, a single communication path connects the central server, departmental servers, workstations, and peripheral devices. Information is transmitted in either direction between networked devices, and all messages travel over the same central bus. Bus networks require less cabling than other topologies, because only a single cable is used. Devices can also be attached or detached from the network at any point without disturbing the rest of the network. In addition, a failure in one workstation on the network does not necessarily affect other workstations on the network.

One major disadvantage of a bus network is that if the central bus becomes damaged or defective, the entire network shuts down. Another disadvantage is that overall performance declines as more users and devices are added, because all message traffic must flow along the central bus. This does not occur in the treelike structure of a hierarchical network or the hub-and-spoke design of a star network, where network paths are more isolated and independent.

The bus network is one of the oldest LAN topologies, and is a simple way to connect multiple workstations. Before the proliferation of star networks, bus networks were very common. Today, the bus design is much less popular, but some firms have retained bus networks to avoid the expense of new wiring and hardware.

RING NETWORK Although ring networks are still around, they are somewhat outdated. IBM was a leader in ring network technology, and large companies who use IBM mainframe equipment still deploy the ring network design. A ring network , as shown in Figure 10-26, resembles a circle where the data flows in only one direction from one device to the next. In function, a ring network can be thought of as a bus network with the ends connected. One disadvantage of a ring network is that if a network device (such as a PC or a server) fails, the devices downstream from the failed device cannot communicate with the network.

FIGURE 10-25 A bus network with all devices connected to a single communication path.

© Cengage Learning 2014

STAR NETWORK Because of its speed and versatility, the star network is by far the most popular LAN topology today. A star network has a central networking device called a switch , which manages the network and acts as a communications conduit for all network traffic. In the past, a device known as a hub was used to connect star networks, but a switch offers advanced technology and much better performance. A hub or switch functions like a familiar multi-socket power strip, but with network devices such as servers, workstations, and printers plugged in rather than electrical appliances. The hub broadcasts network traffic, called data frames , to all connected devices. In contrast, a switch enhances network performance by sending traffic only to specific network devices that need to receive the data.

A star configuration, as shown in Figure 10-27 on the next page, provides a high degree of network control, because all traffic flows into and out of the switch. An inherent 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.

FIGURE 10-26 A ring network with a set of computers that send and receive data flowing in one direction.

© Cengage Learning 2014

MESH NETWORK In the mesh network shown in Figure 10-28 on the next page, each node connects to every other node. While this design is extremely reliable, it also is very expensive to install and maintain. A mesh network resembles the Internet in that a message can travel on more than one path. Originally developed for military applications, the primary advantage of a mesh network is redundancy, because multiple paths provide backup if communication problems arise or some nodes become inoperable.

FIGURE 10-27 A typical star network with a switch, departmental server, and connected workstations.

© Cengage Learning 2014

FIGURE 10-28 Mesh networks are used in situations where a high degree of redundancy is needed, such as military applications. The redundant design provides alternate data paths, but is expensive to install and maintain.

© Cengage Learning 2014

Network Devices

Networks such as LANs or WANs can be interconnected using devices called routers. A router is a device that connects network segments, determines the most efficient data path, and guides the flow of data.

FIGURE 10-29 Routers can be used to connect LANs and WANs to other networks, such as the Internet.

© Cengage Learning 2014

Using a router, any network topology can connect to a larger, dissimilar network, such as the Internet. This connection is called a gateway . The example in Figure 10-29 shows a star topology, where a switch connects nodes in the LAN and the router links the network to the Internet. A device called a proxy server provides Internet connectivity for internal LAN users. The vast majority of business networks use routers to integrate the overall network architecture.

Modeling Tools

As you translate a network model into a physical version of the system, you can use software tools, such as Microsoft Visio, which is a multipurpose drawing tool, to represent the physical structure and network components. Visio offers a wide variety of drawing types, styles, and downloadable templates, as shown in Figure 10-30.

TOOLKIT TIME

The CASE Tools in Part B of the Systems Analyst’s Toolkit can help you document business functions and processes, develop graphical models, and provide an overall framework for information system development. To learn more about these tools, turn to Part B of the four-part Toolkit that follows Chapter 12.

FIGURE 10-30 Visio offers many network templates that users can download free.

Screenshots used with permission from Microsoft.

WIRELESS NETWORKS

Although a wired LAN provides enormous flexibility, the cabling cost can be substantial, as well as the inevitable wiring changes that occur in a dynamic organization. Many companies find wireless technology to be an attractive alternative. A wireless local area network , or WLAN , is relatively inexpensive to install and is well-suited to workgroups and users who are not anchored to a specific desk or location. Most notebook computers are equipped with built-in wireless capability, and it is relatively simple to add this feature to existing desktop computers and workstations in order to set up a wireless network.

Like their wired counterparts, wireless networks have certain standards and topologies, which are discussed in the following sections.

Wireless Network Standards

Wireless networks are based on various standards and protocols that still are evolving. The most popular of these is called IEEE 802.11 , which is a family of standards developed by the Institute of Electrical and Electronics Engineers (IEEE) for wireless LANs.

Current wireless networks are based on variations of the original 802.11 standard. Several versions, or amendments, were intended to improve bandwidth, range, and security. The table in Figure 10-31 contains a brief comparison of the IEEE 802.11 amendments. Note that speed is measured in Mbps (megabits per second) or Gbps (gigabits per second) .

Early IEEE 802.11 standards had limited transmission capacity and were not popular. Later versions, such as 802.11g , offered increased bandwidth and were widely accepted by the IT industry. The more recent 802.11n uses multiple input/multiple output (MIMO) technology to boost performance. MIMO relies on multiple data paths, also called multipath design , to increase bandwidth and range. The latest proposed standards, 802.11ac and 802.11ad, are currently being tested. If wireless capacity continues to expand and security issues can be overcome, WLANs could replace wired networks in many situations. Wireless security is discussed in detail in Chapter 12, Managing Systems Support and Security.

Wireless Network Topologies

Like wired networks, wireless networks also can be arranged in different topologies. The two most common network topologies available for IEEE 802.11 WLANs are the Basic Service Set and the Extended Service Set Figure 10-32 shows simplified models of these topologies.

FIGURE 10-31 IEEE Wi-Fi standards and characteristics.

© Cengage Learning 2014

The Basic Service Set (BSS) , also called the infrastructure mode , is shown at the top of Figure 10-32. In this configuration, a central wireless device called an access point or wireless access point (WAP) , is used to serve all wireless clients. The access point is similar to a hub in the LAN star topology, except it provides network services to wireless clients instead of wired clients. Because access points use a single communications medium, the air, they broadcast all traffic to all clients, just as a hub would do in a wired network. Typically, the access point itself is connected to a wired network, so wireless clients can access the wired network.

The second wireless topology is the Extended Service Set (ESS) , as shown at the bottom of Figure 10-32. An Extended Service Set is made up of two or more Basic Service Set networks. Thus, using an ESS topology, wireless access can be expanded over a larger area. Each access point provides wireless services over a limited range. As a client moves away from one access point and closer to another, a process called roaming automatically allows the client to associate with the stronger access point, allowing for undisrupted service.

FIGURE 10-32 Notice that the user in the upper screen has moved out of the BSS coverage area, and cannot communicate. In the lower screen, the user roams into another ESS coverage area, and the transition is seamless.

© Cengage Learning 2014

Wireless Trends

Wireless technology has brought explosive change to the IT industry, and will continue to affect businesses, individuals, and society. Even in the ever-changing world of IT, it would be difficult to find a more dynamic area than wireless technology.

With the growing popularity of 802.11, many firms offer networking products, services, and information. One of the most significant groups is the Wi-Fi Alliance , which maintains a Web site at www.wi-fi.org . According to the site, the Alliance is a nonprofit international association formed in 1999 to certify interoperability of wireless network products based on IEEE 802.11 specifications. Products that meet the requirements are certified as Wi-Fi (wireless fidelity) compatible. Currently the Wi-Fi Alliance has over 500 member companies from around the world, and over 9,000 products have received Wi-Fi certification. The stated goal of the Wi-Fi Alliance is to enhance the user experience through product interoperability.

Even though they have many advantages, wireless networks also have limitations and disadvantages. For example, devices that use the 2.4 GHz band can pick up interference from appliances such as microwave ovens and cordless telephones that use the same band. More important, wireless networks pose major security concerns because wireless transmissions are much more susceptible to interception and intrusion than wired networks. These issues are discussed in detail in Chapter 12, Managing Systems Support and Security.

In addition to Wi-Fi, another form of wireless transmission called Bluetooth is very popular for short-distance wireless communication that does not require high power. Examples of Bluetooth devices include wireless keyboards, mice, printers, cell phone headsets, and digital cameras, among others. People with Bluetooth-equipped phones or PDAs can even beam information to each other and exchange digital notes.

Although the expansion of Wi-Fi has been dramatic, future technology promises even greater wireless speed, range, and compatibility. For example, in addition to 802.11 protocols for LANs, IEEE is working on 802.16 standards, sometimes called WiMAX , which are broadband wireless communications protocols for MANs (metropolitan area networks) .

CASE IN POINT 10.4: SPIDER IT SERVICES

Spider IT Services specializes in custom network design and installation. Firms hire Spider to do an overall analysis of their network needs, including a detailed cost-benefit study. Recently, a problem arose. One of Spider’s clients complained that the relatively new network was too slow and lacked sufficient capacity. Reviewing the case, Spider’s top management realized that the rapidly growing client had simply outgrown the network much earlier than anticipated.

Could this problem have been avoided? Note that IBM, in the article shown in Figure 10-15 on page 417, commented that performance can “degrade exponentially” in certain kinds of network situations. Consider the IBM article and other material in this chapter, and offer your views.

SYSTEMS DESIGN COMPLETION

System architecture marks the end of the systems design phase of the SDLC. Recall that back in the systems analysis phase, all functional primitives were identified and documented with process descriptions. The objective then was to identify the system’s functions and determine what each logical module would do, without attempting to determine how that function would be carried out. Moving from analysis to design tasks, the development process continued with consideration of output and user interface design, data design, and system architecture issues. Now, based on a clear definition of system requirements and design, software applications can be developed, documented, and tested as part of the systems implementation phase of the SDLC, which is described in Chapter 11, Managing System Implementation.

Developers must also consider system management and support tools that can monitor system performance, deal with fault management, handle backup, and provide for disaster recovery. These topics are covered in detail in Chapter 12, Managing Systems Support and Security.

The final activities in the systems design phase are preparing a system design specification, obtaining user approval, and delivering a presentation to management.

System Design Specification

The system design specification is a document that presents the complete design for the new information system, along with detailed costs, staffing, and scheduling for completing the next SDLC phase — systems implementation.

The system design specification is the baseline against which the operational system will be measured. Unlike the system requirements document, which is written for users to understand, the system design specification is oriented toward the programmers who will use it to create the necessary programs. Some sections of the system requirements document are repeated in the system design specification, such as process descriptions, data dictionary entries, and data flow diagrams.