Ch.10 - System Architecture
wireless local area network (WLAN)
A wireless network that is relatively inexpensive to install and is well-suited to workgroups and users who are not anchored to a specific desk or location.
server
a computer that supplies data, processing services, or other support to one or more computers, called clients - earliest ones were mainframe computers
IEEE 802.11
a family of standards developed by the Institute of Electrical and Electronics Engineers (IEEE) for wireless LANs - most popular wireless network standard
advantages of the batch processing method
- 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.
4 typical characteristics of online processing systems
- The system processes transactions completely when and where they occur. - Users interact directly with the information system. - Users can access data randomly. - The information system must be available whenever necessary to support business functions.
Every business information system must carry out three main functions:
1. Manage applications that perform the processing logic 2. Handle data storage and access 3. 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
Gbps (gigabits per second)
A bandwidth or throughput measurement indicating billions of bits per second.
Mbps (megabits per second)
A bandwidth or throughput measurement indicating millions of bits per second.
wireless access point (WAP)
A central wireless device that provides network services to wireless clients. Also called an access point.
bus network
A computer network where a single communication path connects the mainframe computer, server, workstations, and peripheral devices. - Information is transmitted in either direction between networked devices, and all messages travel over the same central bus - 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. - major disadvantage is that if the central bus becomes damaged or defective, the entire network shuts down - disadvantage is that overall performance declines as more users and devices are added, because all message traffic must flow along the central bus. - one of the oldest LAN topologies, and is a simple way to connect multiple workstations.
router
A device that connects network segments, determines the most efficient data path, and guides the flow of data. - Networks such as LANs or WANs can be interconnected using these - can be used to create gateways between different network topologies and large, dissimilar networks such as the Internet.
hierarchical network
A network design where one computer (typically a mainframe) controls the entire network. - Satellite computers or servers control lower levels of processing and network devices. - Departmental servers control lower levels of processing and network devices
system design specification
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 - typically includes the following sections: 1. management summary: A brief overview of the project for company managers and executives 2. system components: Contains the complete design for the new system, including the user interface, outputs, inputs, files, databases, and network specifications. 3. system environment: Describes the constraints, or conditions, affecting the system 4. implementation requirements: start-up processing, initial data entry or acquisition, user training requirements, etc. 5. time and cost estimates: includes staffing 6. additional material: ex. = documents from previous phases
mesh network
A network design in which each node connects to every other node. - While this design is very reliable, it is also expensive to install and maintain. - resembles the Internet in that a message can travel on more than one path. - primary advantage is redundancy, because multiple paths provide backup if communication problems arise or some nodes become inoperable. - used in situations where a high degree of redundancy is needed, such as military applications
Local Area Network (LAN)
A network design that allows the sharing of data and hardware, such as printers and scanners. - Advances in data communication technology have made it possible to create powerful networks that use satellite links, high-speed fiber-optic lines, or the Internet to share data.
fat client
A network design that locates all or most of the application processing logic at the client. - handles more of the processing and must access and update the data more often, which can slow it down - higher network traffic (more server queries) - slower performance (more net traffic usage) - higher initial cost (powerful hardware) - higher maintenance cost - easier development (centralized processing) - Also called a thick client design.
two-tier client/server design
A network design where 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
star network
A network design with a central device and one or more workstations connected to it in a way that forms a star pattern. - By far the most popular LAN topology today - Has a central networking device called a switch, which manages the network and acts as a communications conduit for all network traffic - Because of its speed and versatility, the star network is a popular LAN topology - provides a high degree of network control, because all traffic flows into and out of the switch. - inherent disadvantage of the star design is that the entire network is dependent on the switch.
ring network
A network resembling a circle of computers that communicate with each other. - often is used when processing is performed at local sites rather than at a central location. - Still exist but somewhat outdated - Resembles a circle where the data flows IN ONLY ONE DIRECTION from one device to the next - disadvantage 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.
Wide Area Network (WAN)
A network spanning long distances that can link users who are continents apart. - ex. Internet itself
legacy systems (architecture checklist)
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 - 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 may be needed to pass data btw new and legacy systems
knee of the curve
A performance characteristic of a client/server computing environment. - Client/server response times tend to increase gradually, and then rise dramatically as the system nears its capacity. The point where response times increase dramaticall
node
A physical device, wired or wireless, that can send, receive, or manage network data.
web-centric
A strategy or approach that emphasizes a high degree of integration with other web-based components. - this architecture follows Internet design protocols and enables a company to integrate the new application into its ecommerce strategy
thin client
A system design that locates most or all of the processing logic at the server - these designs provide better performance because program code resides on the server, near the data - lower net traffic - faster performance (not limited to workstation) - lower initial cost - lower maintenance cost (code on server) - more difficult to develop (divide processing) - also called net-centric computing
mainframe architecture
A system design where the server performs all the processing - typically describes a multiuser environment, where the server is significantly more powerful than the clients
system architecture
A translation of the logical design of an information system into a physical structure that includes hardware, software, network support, and processing methods.
corporate portals (architecture checklist)
A website that provides various tools and features for an organization's customers, employees, suppliers, and the public. - 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 - portal = entrance to multifunction website
basic service set (BSS)
A wireless network configuration in which a central wireless device called an access point is used to serve all wireless clients; also called infrastructure mode. - 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
Extended Service Set (ESS)
A wireless network configuration made up of two or more Basic Service Set (BSS) networks, which allows wireless clients to roam from BSS to BSS. - wireless access can be expanded over a larger area - 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.
802.11n
An IEEE wireless network specification adopted in 2009 that uses multiple-input/multiple output (MIMO) technology to achieve speeds of 200+ Mbps while increasing the wireless range, and is backward-compatible with 802.11 a, b, and g. - MIMO relies on multiple data paths, also called multipath design, to increase and width and range
802.11b
An IEEE wireless network specification introduced in 1999, based on a frequency of 2.4 GHz, and maximum bandwidth of 11 Mbps. Replaced by 802.11g.
802.11g
An IEEE wireless network specification introduced in 2003 based on a frequency of 2.4 GHz and maximum bandwidth of 54 Mbps; compatible with and replaced 802.11b, and has been superseded by the 802.11n standard. - offered increased bandwidth and was widely accepted by the IT industry
802.11ac
An IEEE wireless network specification, approved in 2014, that uses expanded multiple-input/multiple output (MIMO) technology to achieve theoretical speeds of nearly 7 Gbps while increasing the wireless range, and is backward-compatible with 802.11 a, b, g, and n.
distributed systems
Company-wide systems that are connected by one or more LANs or WANs. - The capabilities of a distributed system depend on the power and capacity of the underlying data communication network.
OSI (Open Systems Interconnection) model
Describes how data actually moves from an application on one computer to an application on another networked computer. The OSI consists of seven layers, and each layer performs a specific function. - Provides physical design standards that assure seamless network connectivity, regardless of the specific hardware environment
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. - data is stored and usually processed on the server. - the data file is not transferred from the server to the client — only the request and the result are transmitted across the network. - also allows companies to transfer applications from expensive mainframes to less-expensive client platforms, sometimes moving heavyweight processing needs to the cloud
online processing method (online system)
Handling transactions when and where they occur and providing output directly to users. - Because it is interactive, it avoids delays and allows a constant dialog between the user and the system. - ex. airline reservations system, ATM balance query process - good for POS (point of sale) processing - allows the data to be entered and validated immediately, so the information always is up to date
centralized design
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
packaged solutions (e-commerce architecture)
Many vendors, including IBM and Microsoft, offer turnkey systems for companies that want to get an e-business up and running quickly - may be less attractive for large-scale systems that must integrate with existing applications
network modeling tools
Microsoft Visio, which is a multipurpose drawing tool, is used to represent the physical structure and network components - Visio offers a wide variety of drawing types, styles, and downloadable templates - Newer applications, such as Creatly.com, offer network diagram drawing capabilities that are completely web-based
applications
Part of the information system, an application handles the input, manages the processing logic, and provides the required output.
security issues (architecture checklist)
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 - Web-based systems introduce additional security concerns, as critical data must be protected in the Internet environment. - Also, firms that use ecommerce applications must assure customers that their personal data is safe and secure. - other concerns like finger print logon (finger print scanners and other biometric devices)
middleware
Several different types of software that sit between and provide connectivity for two or more software applications - enables tiers to communicate and pass data - sometimes called glueware because it is used to connect 2 or more software component - offers an interface to connect software and hardware - can integrate legacy systems and Web-based applications - represents the slash in the term client/server. - resembles the plumbing system in your home: it connects important objects in a way that requires little or attention
Cloud computing is an ideal platform for:
Software as a Service (SaaS) applications - a popular deployment method where software is not purchased but is paid for as a service
Initial Cost and TCO (architecture checklist)
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.
supply chain management (SCM)
The coordination, integration, and management of materials, information, and finances as they move from suppliers to customers, both within and between companies. - In a totally integrated supply chain, a customer order could cause a production planning system to schedule a work order, which in turn could trigger a call for certain parts from one or more suppliers.
difference between a hub and a switch
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.
Enterprise resource planning (ERP) (architecture checklist)
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 , which ensures connectivity and easy integration of future systems - ERP's future success depends on integrating new technology, such as mobility and cloud computing (flexibility) - Many companies are extending internal ERP systems to their suppliers and customers, using a concept called supply chain management (SCM) .
web integration (architecture checklist)
The systems analyst must know if a new application will be part of an ecommerce strategy and the degree of integration with other web-based components. - a web-centric architecture follows Internet design protocols and enables a company to integrate the new application into its ecommerce strategy - Will the application be part of an e-commerce strategy and what is the degree of integration with other Web-based components?
network topology
The way a network is configured. - LAN and WAN networks typically are arranged in one of four common patterns: hierarchical, bus, star, and ring. - can refer to a physical or a logical view of the network
stand-alone computing
Using a PC (personal computer), users can run their own word processing, spreadsheet, and database applications without assistance from the IT group - Companies then linked the stand-alone computers into networks that enabled the user clients to exchange data and perform local processing - the workstation performs all the functions of a server by storing, accessing, and processing data, as well as providing a user interface.
The main issue in choosing a processing method:
Whether to use online processing or batch processing
client
Workstation that users interact with in a client/server design. - these computers are supplied data, processing services, or other support from other computers, called servers
three-tier client/server design
a network design where the user interface runs on the client and the data is stored on the server, just as in a two-tier design. - however, 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 (application server) - also are called n-tier designs , to indicate that some designs use more than one intermediate layer. - may enhance overall performance by reducing the data server's workload (application server). - The separate application logic layer also relieves clients of complex processing tasks - Because it can run on a server that is much more powerful than the typical client workstations, the middle layer is more efficient and cost-effective in large-scale systems.
web 2.0
a second generation of the web that will enable people to collaborate, interact, and share information more dynamically - exs. Social networking sites, such as Facebook, Twitter, and LinkedIn - major goal is to enhance creativity, interaction, and shared ideas
batch processing method
data/transactions are managed in groups, or batches - An acceptable choice in the 1960s, and for most firms, it was the only choice - 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 - is well-suited to address security, audit, and privacy concerns, because it runs in a relatively controlled environment - very old data processing method but still used today - 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 - good for routine, overnight processing and marketing analysis
physical network topology
describes the actual network cabling and connections as well as physical hardware
logical network topology
describes the way the components interact in a network
processing options (architecture checklist)
designers must also consider how the system will process data — online or in batches. - some systems require more network, processing, and data storage resources - 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.
when considering system architecture, the objective at this point is to
determine an overall architecture to implement the information system - 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
In a multi-tier system, special software called______
enables the tiers to communicate and pass data back and forth.
Application Service Provider (ASP)
offer full-scale Internet business services for companies that decide to outsource those functions - provides applications, or access to applications, by charging a usage or subscription fee -
To support business requirements, information systems need to be:
scalable, powerful, and flexible
what activity marks the end of the systems design phase of the SDLC?
system architecture
The two most common network topologies available for IEEE 802.11 WLANs
the Basic Service Set and the Extended Service Set
the end product of the systems design phase of the SDLC is:
the system design specification - If this document is approved, the next step is systems implementation.
Architecture Checklist (what could affect your decision of architecture design?)
}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
features of in-house solutions (e-commerce architecture)
•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 - 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.
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 •Cloud computing requires significantly more bandwidth (the amount of data that can be transferred in a fixed time period) than traditional client/server networks - effectively eliminates compatibility issues, because the Internet itself is the platform. - provides scaling on demand , which matches resources to needs at any given time
internet based architecture
•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
scalability (architecture checklist)
◦A system's ability to expand, change, or downsize easily to meet the changing needs of a business enterprise - sometimes also called extensibility - especially important in implementing systems that are volume-related, such as transaction processing systems. - is necessary to support a dynamic, growing business. - management is especially concerned about scalability issues that could affect the system's life expectancy.
corporate organizational structure (architecture checklist)
◦An information system must perform well in a company's organization and culture - study day-to-day business functions, talk to users at all levels, and focus on operational feasibility issues
presentation to management
◦Give you an opportunity to explain the system, answer questions, consider comments, and secure final approval ◦The first presentation is technically oriented - to the systems analysts, programmers, and technical support staff members who will be involved in future project phases or operational support for the system ◦Next presentation is to department managers and users from departments affected by the system ◦Final presentation is delivered to management - By the time this presentation is delivered, all necessary approvals should have been obtained from prior presentations, and the users and IT department should be onboard - management might reach one of three decisions: proceed with systems development, perform additional work on the systems design phase, or terminate the project.
the three final activities in the systems design phase of SDLC
◦Preparing a system design specification ◦Obtaining user approval ◦Delivering a presentation to management
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 ◦Ensures that you do not have a major task of obtaining approvals at the end ◦Keeps the users involved with the system's development ◦Gives you feedback about whether or not you are on target
