Understanding the Internet

Overview
The Internet is a WAN linking millions of computers in LANs worldwide. Special protocols are used for the Internet which enable it to work across any kind of network, and browsers to access the Web have made it user-friendly.

The software used to access the Internet includes clients which request information and servers which deliver it.  Services on the Internet include email, the Web, FTP, chat, and Internet telephony.  Much of the content on the Internet is freely available, but some is provided by online services which charge for access to their proprietary network content.

Computers directly connected to the Internet have a unique IP address and an equivalent domain name which is easier to remember.  Companies have begun to use Internet tools such as email and Web browsers to access their own internal communication and information systems, because these tools are so widely known.  Access to the Internet also allows companies to use it as a medium to distribute information both within the company and to outside clients.

The increasing traffic on the Internet will require more addresses and higher bandwidth.

Lecture Notes
Introducing the Internet:  The Network of Networks
The services provided by the Internet are another example of convergence, as discussed in earlier modules.

The Internet network of networks structure is similar to the telephone system in which local subscribers are linked by a local company, but long distance lines link the local companies.

A "Galactic" Network
The "IP" in "IP address" stands for Internet protocol.

Many computers which use the Internet are not "fully connected" with their own IP address.  Instead, they access a computer which is fully connected.  Thus, the Internet is a network of fully connected machines which in turn have their own networks of machines which use them to access the Internet - a "network of networks."

Interoperability
The ability for one computer to ask another to display information, download a file, accept and store a mail message, etc. is the basic principle of the Internet.  However, the control that one machine has over another on the Internet must, of course, be limited to the functions that the owner of the controlled machine is willing to allow.  Not just any files can be downloaded, for example, but only those which are specifically made available for this purpose.

Leave the Lower Layers to the LANs and WANs
The concept of a protocol stack, as covered in earlier modules, isolates the mechanics of the physical transmission of data from the way data is presented to the computers and applications at either end of an Internet connection.

The Internet vs. Online Services
Even some users who have other Internet access, such as through their employer or an independent service provider, may choose to use an online service, too.  An online service usually offers local phone numbers to connect to the service, and the Web, from many cities and countries, which makes Net access available away from home without a long-distance change to access your regular provider.

AOL's customer base was built largely by giving away millions of free disks or CDs which installed AOL access software and provided a free trial period for the service.  This proved to be an appealing, cheap, and easy way for novices to "see what the Internet was all about" and many became regular AOL customers.

Portals, which are Internet sites that provide services and content similar to that of online services, are supported not by users' fees but by advertising on their sites.

The Internet's History
Using the ARPANET formerly required a user to register with a central authority. Today, anyone can use the Internet without registering. However, the company or organization granting you access typically is responsible for your behavior, and so usually some local registration or application is required (possibly in electronic form).

The Internet was designed with no central office or computer because the Internet designer's were told to think of the possible consequences of a nuclear attack. If an enemy attack were to take out a node of the Internet, it is designed to route around the destroyed node and not be crippled.

Internet Software:  Clients and Servers
The client/server concept is rapidly becoming the dominant form of network organization.  Make sure that students understand the differing roles of the server, which provides information, and the client, which requests it.  The client can only request the types of information that a given server is set up to provide and can only make requests follow the appropriate protocols.  Most of the processing needed to provide information is done by the server, not the client.

Exploring Internet Services
Electronic Mail (Email):  Staying in Touch
Email is popular in part because it is both faster and cheaper than conventional mail, but it provides a hard copy if needed, unlike the telephone.  Many people also like to send email messages instead of using the telephone because they can compose the message carefully and send it to multiple recipients at once.  Some people prefer to get email message instead of phone calls because they are less interruptive;  emails can be opened and read at the receiver's convenience.
Although you will receive notification if an email message cannot be delivered, you cannot know for sure if or when the addressee will open and read the message.

The World Wide Web (WWW): Accessing Information
The Web is probably the best-known and most widely-used Internet service.
The hypermedia of Web documents is created using HyperText Markup Language (HTML). Another module explains in greater detail how to use HTML.

Web navigators include Internet Explorer, Netscape, MacWeb, and Lynx. Lynx is unique in that it follows a text-based interface to WWW; the interface doesn't require a mouse and will run on any dumb terminal (or PC emulating a dumb terminal); however, you can't view graphics or listen to sound with it.

FTP:  Transferring Files
FTP client programs enable you to connect to FTP server programs running on computers on the Internet. Both Macintosh and PC-compatible machines can be servers.

Public file archives get around the user-password problem by providing the special user "anonymous," and they request you to enter your e-mail address for the password so that they have an idea about how many users from other sites are accessing their server.

Companies that produce software use FTP servers to provide updates and bug fixes to their customers. Although anyone can download the updates, they are not the entire program, rather just something that will update the program a customer already owns.  Like Internet Explorer 5.0, Netscape Communicator can upload files.

Sidebar:  A Taxing Question
There are two aspects to taxation of the Internet:  taxing the provision of Internet services in general, and applying sales tax to the goods and services purchased on the Net.

Taxing services is a long-established policy in some jurisdictions, although specific laws vary from state to state, so there is no reason in principle why it should not apply to Internet services.  There remain practical problems, such as the understandable tendency of Internet suppliers to leave high-tax states or areas for lower-tax areas, but these problems have arisen in other taxed industries as well, and states and municipalities have learned to balance the need for revenue with the need to encourage business.

Collecting sales tax on goods and services bought over the telephone or by mail order presents  many of the same issues as Internet purchase taxes.  States' experiences with these taxes can be used as a guide on how to proceed with Internet sales.

Usenet:  Joining Online Discussions
Usenet originally was based on systems that periodically telephoned one another and exchanged articles that hadn't been received yet via modem. Some systems were connected directly and exchanged information more frequently. Today, most large-volume systems are directly connected.

Newsgroups can be created or destroyed; creation involves a "vote" by electronic mail after a period of discussion. Some special types of newsgroups can be created by anyone for any reason, but these aren't always taken as seriously as ones created through the formal process. Articles are also called posts or postings.

Computer programs, images, and sounds can be specially encoded using standard letters and numbers and sent through electronic mail or through the Usenet system.

Some newsreaders present all articles on a given thread at one time, but others present articles in the order in which they arrive at your system. Remember that articles are submitted from all over the world, so this order will be different for each system.

IRC:  Text Chatting in Real Time
Chat services similar to IRC are available at various Web sites.  These may be accessed using standard Web browsers and mouse interfaces with which users are already familiar, while IRC channels require a special client.  IRC clients can be downloaded from the Internet.

Some of the Web-based chat is not text-based only but uses visual depictions of the chatters called avatars which move around and interact on screen in scenes called "virtual worlds."  The avatars are not actual likenesses of the people chatting, but may be animals, robots, fantasy creatures, or caricatures.

Internet Telephony:  Real-Time Voice and Video
While these services are relatively primitive today, there is every reason to believe that quality will improve as PCs become faster and more powerful, and higher bandwidth connections more readily available.

At the same time, new protocols and network designs will help deliver voice and video. Some new protocols already available compress data for faster transmittal and then decompress it at the receiving computer.

The combination of these various developments may lead to Internet telephony becoming a new standard communication device.

More Internet Services
MUDs are similar to IRC channels or Web chat rooms, but were designed for players of "Dungeons and Dragons" type fantasy games.  Accessing MUDS requires Telnet.  Telnet is an Internet service that enables you to access libraries, databases, and other public services all over the world. Hytelnet is a tool that helps you access the various sites through Telnet.

How the Internet Works:  A Geography of Cyberspace
Configuring Your Computer for Internet Access
In general, any computer purchased today will have full Internet support built in for at least regular dial-up service.  If you are building your own computer, or trying to upgrade an older model, you will need expert advice.

Accessing the Internet
Dialup access usually means that you use a terminal emulator or communications package on the personal computer. The clients for FTP, e-mail, and the like, all run on the computer your personal computer has dialed.

Direct Internet access allows the client software to access various resources on the computer in front of you.

Dialup IP access is not faster than dialup access; in fact dialup IP is usually slower due to the overhead incurred by the TCP/IP protocols. Dialup IP access also requires a special dialup server that can "attach" your remote personal computer to the network after you dial in.

A local area network connection offers much higher data rates, as does a connection via ISDN.
Internet Service Providers (ISPs)

ISPs are found in most communities-check your local phone directory.  Small communities may not have a local ISP.  In this case, dial-up access to the ISP will require a long distance call, which can make access prohibitively expensive.  Cable and satellite access may be alternatives in these cases.

If you have access through your employer or college, you may not need an ISP because you may be able to dial in to the employer's or college's network for access.

Backbones
Backbone networks enable messages traveling long, common routes (such as New York to Los Angeles) to take an "express line." Backbone networks may have multiple lines between the same two points to provide redundancy in case of failure, as well as providing more capacity.

The Internet Protocols (TCP/IP)
Internet protocols are the standards that enable computer users to exchange data through the Internet. Protocols determine how data packets are layered or packaged into small packets for transmission. Most hardware and software developers subscribe to a standard set of protocols called OSI (Open Systems Interconnection) that consists of seven layers of protocols for worldwide computer communications.

Low-level Internet protocols are formal ways for computers to exchange information reliably. (At a still lower level are the physical signals between the computers.) At a higher level are protocols for sending electronic mail (Simple Mail Transfer Protocol-SMTP) and for exchanging other forms of information.

The Domain Name System
Domain names are meant to make it easier to refer to or locate Internet sites, but some domain names do not access the site that you might expect.  That is because domain names can be registered by anyone, not necessarily by the organization that might have that name or trademark.  For example, http://www.alamo.com does not take you to the Web site of the famous building in San Antonio Texas, nor to Alamo Car Rental, but to another firm in Texas with a completely different name.

If you type a domain name into your browser and get an error message, there may be several reasons, including a typographical error on your part, an error in accessing the domain name server, trying to access a server which is protected by a firewall, or a temporary (or permanent) problem on the server you are trying to access.

Intranets:  Using TCP/IP Inside the Enterprise
Internal intranets which operate behind secure firewalls are the fastest-growing part of the Internet today.  They are favored by businesses and organizations for their internal use because they are cheaper to set up and to run than networks based on proprietary protocols. In addition, users can navigate intranets using browsers and tools they are already familiar with from the World Wide Web.

The Future of the Internet
More Internet Addresses
In "IPv6," the "v6" stands for version 6 (the current version is 4) and it is also known as "Ipng," where the "ng" stands for "new generation".

It is anticipated that the two versions will coexist for some time, with the new protocol gradually taking over as more users convert to equipment which can handle it.

More Bandwidth
The federal government, which financed the development of the original ARPANET from which the present Internet grew, is now financing development of improved networks; however, the availability of more bandwidth may also create more demand for services and permit the development of new clients which require more and faster data transfer.  The development and expansion of Internet technology to meet demand may be a never-ending task.

Overview
Computer information systems include not only computers and software, but also the data they process, the people who use the system, and procedures which govern use of the system.  These elements work together to collect, process, store, and disseminate data to help the organization accomplish its purposes.

Organizations have both functional divisions and hierarchical divisions.  Functional divisions include finance, marketing/sales, human resources, operations as well as information systems.  The hierarchical divisions of a company include various levels of management: (1) senior management who plan and lead the entire organization, (2) middle managers who plan and organize to implement the goals of senior management, and (3) operational managers who lead and control on a day-to-day basis.

The various divisions of an organization need different types of information from the information system.  Tailoring information for the receiver includes routing, summarizing, selecting, and excluding.  Jointly, these are known as techniques of information reduction.

Some common types of information systems include transaction processing systems, management information systems, decision support systems, executive information systems, knowledge management systems, groupware, workflow routing, business processing reengineering, and data warehousing, which provides data that can be accessed by all of these systems.

Lecture Notes
Computerized Information Systems (CIS):  Serving an Organization's Needs
System as a general term refers to any organized group of elements that work together for a purpose.  Information systems is a system that provides information, and all businesses-indeed all human activities-have some sort of information system, even if it is only the system of our humans senses working together to provide us with information on the physical world around us.
In any of these cases, collecting and storing the information itself is not a goal, but a means to achieve another end.  Similarly, computerized information systems collect, process, and store information for the use of other areas of the organization to achieve their goals.

Understanding Complex Organizations:  The Power Pyramid
People in different functional areas of the organization will needs different types of information.  Often it is not even appropriate for people in one area to have information given to workers in another area. For example, most companies do not allow people outside of the human resources and payroll departments to have information about various employees' salaries.

Therefore, one of the functions of a CIS, besides making information available to employees who need it, is to keep information away from employees who should not have it.  Sometimes this second function is harder to manage than the first.

Chain of Command
This may be a good point to discuss the move toward flatter organizational structures, with fewer layers of management between upper management and workers. The flat organizational structure is, in turn, dictating the way information is used.  Information is no longer kept in the hands of the top few, but is seen as a way to empower employees at every level so they can perform more intelligently and productively.

Information:  The Good Kind and the Other Kind
The techniques discussed here not only reduce information to control information overload, but they are also the basic techniques of sorting, filtering, and routing information so that people receive what they need and only what they need.

Sidebar:  Dealing with Techno-Stress
Much of the information we receive each day is not information that we really need.  Filtering and selecting from it the data that we choose to accept and work with is an essential skill, and one that we all possess.  Psychologists tell us that at every waking moment, human beings receive much more data from our senses than we can process, so the human brain has a built-in filter that allows us to focus our conscious attention on only that data which is needed at any given moment.  Thus you aren't consciously aware of everything in your physical field of sight, only of the object on which you are focusing.

As an employee, or simply as a member of modern society, trying to process all the data you receive is like trying to focus on seeing and hearing everything going on around us all at once.

Information Systems in Organizations:  A Survey
This section describes several types of information systems which perform different functions, some of which are closely related or overlap.  Students probably don't need to memorize the name and function of each system, especially since different terms may be used for the same system, but they should know basic terms and processes that are in widespread use, such as workgroup, batch and online processing, MIS, expert systems, workflow automation, reengineering, data warehousing, and data mining.

Overview
Programming is both a part of the systems development life cycle and also has a life cycle of its own with similar stages: defining the program, designing the program, coding the program, testing and debugging the program, formalizing the solution, and implementing and maintaining the program.

Early programming was error-prone and difficult to debug or maintain.  New techniques in programming include modularization, top-down, and structured programming which uses only three basic structures.  Use of these techniques improves program quality and maintainability, and reduces both syntax and logic errors.

Lecture Notes
The Need for PDLC:  Better Software, Please
The pattern of development followed by software is similar to that followed in the manufacturing of hard goods.  For example, the first cars were hand-assembled.  For all their charm and often impressive craftsmanship, it became clear over time that standardizing the manufacture of cars provided more predictable performance and easier repair, all at less expense.  Although software is an intellectual product rather than a tangible good, it has become clear that it, too, will provide more predictable performance and be easier to maintain and cheaper if it is "manufactured" according to standards.

Phase 1:  Defining the Problem
Program specifications can be highly detailed or rather general.  Although they may change during the course of developing the program, it is best to avoid such changes because changing even one element of a program may have ramifications for the entire program and cause extensive re-writing.   The use of self-contained program modules (described in Phase 2) has reduced, but not entirely eliminated, this problem.

Phase 2:  Designing the Program
The distinction between DO..WHILE and DO..UNTIL loops may not be clear to students.  Point out that in order for the repetition condition to be tested at the entry point to a loop, the control word WHILE + the condition is placed at the beginning of a loop.  Likewise, a DO..UNTIL structure tests the condition at the bottom of the loop because that is where the control word UNTIL + the condition is placed.

That is, it is not the use of the word WHILE or UNTIL that controls whether a condition is tested at the beginning or end of a loop and thus whether the loop will be performed at least once.  It is the placement of the condition itself, following the word WHILE or UNTIL at either the beginning or end of a loop.  Language rules vary, but the word WHILE can usually be placed at either the beginning or end of a loop with DO to mark the beginning.  UNTIL, which does not exist in all languages, is usually found only at the end of a loop with DO at the beginning.

Sidebar:  An Issue of Timing
The messy Y2K problem could have been prevented if programmers had originally allocated enough space in their programs to write all 4 digits of the year instead of allowing for only 2.  However, programmers did not take this approach due to laziness, lack of foresight, or stupidity.  Until relatively recently, memory was quite expensive and programmers were under pressure to conserve it as much as possible.  It was considered good programming practice to take such "sensible" shortcuts as eliminating a couple of digits wherever possible.

Phase 3:  Coding the Program
Coding the program is the heart of the programming process, but it is not necessarily the most difficult or the most time-consuming.  Debugging and maintenance are more likely to take these "honors."

Phase 4:  Testing and Debugging the Program
There are two types of testing.  Alpha testing involves entering various kinds of data to see how the program handles it;  Beta testing means the users test the system under actual working conditions, not only to find additional bugs, but also because a concern of users, along with accuracy, is the friendliness of the system.  User acceptance means that users feel it is ready for use and the system can be put into production.

Phase 5:  Formalizing the Solution
Documentation includes both software documentation for programmers as well as user and reference documentation for the users of the system.

Phase 6:  Implementing and Maintaining the Program
All software must be maintained throughout its lifetime. No matter how carefully designed and error-free, software must be changed from time to time to reflect external changes that affect the performance needs of users.  For example, a retail business may begin to accept credit cards or to carry new items, a service business may expand into new states which have new tax rates; or a change in the law may require keeping new data, etc.

In general, maintenance requires a larger amount of time than the original development of a program.

Overview
Computer networks, which link computer to exchange data or share research, achieve a synergy that gives the two computers working together the ability to do more than the sum of what each of the two computers acting alone can do.  Networks achieve this extra productivity by reducing hardware costs, sharing data and applications, and facilitating new kinds of collaborations between workers.

Computer networks may be LANs, MANs, or WANs.  Any of these require both physical connections and protocols that regulate the messages sent between each machine.  Protocols are organized as a stack:  a series of hierarchical layers which pass messages down for processing before they are sent out over the network, then back up in the receiving machine.  Ethernet is the mostly widely used LAN protocol, usually implemented in star topology using twisted-pair wiring and hubs.

Two kinds of transmission can occur over a network:
· circuit switching-messages are sent over a permanent, continuous, and therefore fast, pathway
· packet switching.-messages follow any of a variety of links to reach their destination

Types of LANs include:
· Peer-to-peer, in which no machine directs the total network
· Client/server, in which a server machine holds shared applications and data

WANs connect LANs, and can be used for transaction acquisition or to implement electronic data interchange (EDI).

Lecture Notes
Introducing Computer Networks:  Synergy at Work
What Is a Computer Network?
Networks are similar to mainframe systems with multiple user terminals in that many people can be working simultaneously.  However, the processing power of a network is "distributed" among various computers, instead of being located in a single machine.

Hooking separate computers up through networks is also similar to hooking them up through data communications telephone lines; however, networks are usually connected with greater bandwidth than regular telephone lines can provide.

Types of Computer Networks:  LANs and WANs
The distinction between these various types of networks is not clear-cut; the definitions may fade into each other.

Corporate networks may involve a number of LANs connected together into a WAN. LANs can also be connected directly to the Internet via a server or a corporate Intranet, thus turning the Internet into the WAN.

Networking Synergies in a Nutshell
The first two advantages mentioned result in savings of money or time or both.  The last two have to do with providing greater access to resources of information or people.

Network Fundamentals
Physical Media
A communications channel is a physical means of connecting the communicating computers so they can exchange the programs or data.  This means of connection, or transmission, is commonly wires of one sort or another but may also take just about any form, from satellite and radio signals to infrared beams.

Switching and Routing Techniques
As packet-switched networks use new technologies to increase their speed, they may supplant circuit-switched networks.  One of these techniques, Asynchronous Transfer Mode, or ATM, may become the next IP network standard carrier. ATM uses a network of links instead of a single end-to-end circuit, but within the network it establishes a fixed route that reduces latency.  It is fast enough to support data, voice, and video traffic-such as multimedia-at extremely high transfer rates.

Protocols
Protocols include baud rate and other important details which permit the two computers to exchange data. Most communications software programs have a feature called a script file that allows you to create and store the settings for each individual system you communicate with, as well as each computer's telephone number and the information you need to connect on-line.  In most cases where one computer is directly connected to another, their communications protocols must be set to match.

Synchronizing two communicating computers is called handshaking.  Some communications applications are designed to work on many different brands of computers to overcome hardware incompatibility and expand communications capabilities.

The concept of open vs. proprietary standards emerges here again, and can be compared to its appearance in earlier topics such as hardware connections and data storage.

Network Layers
The logic behind dividing the job of preparing and sending messages between various protocol layers is that each layer can focus on one aspect of a complex job.  This makes the software of the layers easier to write, debug, and maintain.  In addition, it means that changes can be made to one layer of the protocol without affecting the other layers, as long as the interface between them remains the same.

Local Area Networks (LANs):  Limited Reach, Fast Connections
Networking Hardware:  Network Interface Cards (NICs)

Some computers, such as Macintosh, are pre-wired to be able to hook up to a LAN.  If not, a NIC provides the additional circuitry needed.

Networking Software
In a peer-to-peer network, all computers run the same network software.  In a client/server network, all clients run the same network software, but the server runs a different program because it has additional network responsibilities and capabilities.

Media
The choice of physical media depends on the distance between machines, the budget for the network, the transmission speed required, and other performance needs.

LAN Topologies
Because only the machine with the token can send a message, and there is only one token in a network, two computers can never attempt to transmit messages at the same time.  Therefore, no contention access is needed.

Ring topologies are also called "token ring" networks.  When capitalized, Token Ring refers to the specific ring network protocol developed by IBM.

Note that in the topology diagrams, any of the workstations depicted could also be another machine, such as a printer.

LAN Technologies
Lower layer protocols refer to those that actually transmit the message across the network, including verifying the connection between machines and actually sending the data.  Ethernet is the most popular physical layer because it is relatively easy and inexpensive to implement, but it is still reasonably fast.

LAN Protocols
The TCP/IP protocol, most commonly associated with the Internet, is increasingly being used for other LANs.  This is especially convenient when the LAN will also be connected to the Internet, as many LANs are.

Wide Area Networks (WANs):  Long-Haul Carriers
How WANs Work
When a business wants to use a WAN, it generally selects a service provider who sells it the right to hook up through a POP to its backbone.  Just as with telephone service, companies can often choose among a variety of providers who compete for business.  The organization itself provides the physical connection to the POP, and the quality and speed of that connection often determine the overall quality and speed of the organization's WAN access, since the backbone lines are always very high speed.

How WANs Are Organized
The physical connections for a WAN (the PDNs) are owned by private, profit-making companies.  Two of the largest are owned by MCI (Tymnet) and Sprint (Telenet), which use them for their voice telephone long-distance service as well as for WAN connections.

WAN Protocols
The advantage of point-to-point connection over packet switching is speed.

WAN Applications
Companies which use WANs for transaction acquisition can respond more quickly to sales trends by re-ordering inventory or moving it from one location to another to meet demand.  Analysis of transactions can also be used to identify over- or under-performing stores and to predict income and cash flow.

An open standard for EDI called the X12 makes it easier for companies to ensure that their systems will be compatible.  As more and more large companies ask the smaller companies that supply them to adopt EDI, the small companies will benefit, too, since it ensures that they will receive payment quickly and automatically.  These financial benefits may outweigh the startup costs associated with EDI.

EDI is being used by healthcare providers and insurers to transmit treatment and payment information, for travel companies and customers to arrange and pay for bookings, and for automated tax reporting.

Right click on the link below to download a file, which overviews chapter 9.  This is a rich text file and can be opened by any word processing software.

Chapter 9 Overview