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
Email is considered a basic communication medium today.  It is not hard to learn and learning some basic information can make your use of email more efficient and productive.  This module presents information about the following areas related to email:
· Reading
· Composing
· Forwarding
· Replying
· Filtering
· Mailing lists
· Risks

Lecture Notes
Email Fundamentals
Email Servers and Clients
The basic client/server concept was explained in the "Networks" module.  This application may make the concept clearer.

Email Addresses
There is no standard format for the user name, other than it must be alphanumeric, and certain symbols and punctuation marks cannot be used.

Domain names may have more than three parts, but the names are limited to alphanumeric characters and periods cannot be used.

Upper- and lowercase letters don't matter generally in electronic mail addresses but can be used for readability.

Email Protocols
If you are using an email account set up for you by your employer or college, you will not be able to choose whether you use the POP3 or IMPA protocol.  If you are choosing an ISP yourself, you may want to check on which protocol it uses.

Introducing Email Clients
Getting an Account
Many people have several email accounts, such as one for private, home use and one for business use.  There are several advantages to this, including
· being able to send mail even if one account is down.
· providing a way to separate business and personal mail.
· having greater privacy.
· maintaining a permanent personal address, even if you change jobs or leave school.

Setting Up Your Email Client
Of course, you must supply your password when you want to access your email account, but you can do this in two ways:  (1) by storing your password permanently in memory, or (2) by typing it in each time you access email.  The first option is more convenient because when you access your email you will not be asked to enter your password each time, but if you share a computer with anyone else, they can also access your email without a password.

The permanent storage option is available when you set up your email.  If you want to change that option, check the "options" menu in your email client program.

Exploring Your Email Client's Window
If you have trouble finding any of the features mentioned on your program, check the Help function.

Composing, Receiving, and Forwarding Mail
If an incorrect address is used, the message will bounce back to the sender in a message sent by the system's software. Reasons for returned mail include no such user, unable to connect to remote system, and several problems due to either the local or remote system's mail software being configured incorrectly.  If you believe you have sent your message correctly, try again, perhaps after a brief wait.

Sending mail to the user named "postmaster" at a particular domain name should forward the message to the human user responsible for the mail software on that computer. Contacting the postmaster at a site can be useful if you have are having trouble with an electronic mail address at that site.

Some programs permit only one attachment per message, which can be inconvenient.

Managing Email
Because other people use filters, too, it is polite to use a descriptive subject line that will help your receivers sort your mail appropriately.

Also remember to delete email you have already read.  If you need a hard copy, print it out and then delete it.  This keeps your email account space on the server or on your own machine from becoming clogged.

Mailing Lists
If email can be compared to a letter which goes to a specific recipient, mailing lists can be compared to a mass mailing sent to many recipients whose names are on a mailing list.  An advantage of mailing lists is the ability to contact many people with similar interests at once.  This can be useful if you have a question about a particular topic but don't know exactly whom to ask; you can ask a large number of people at once!

Information on many mailing lists can be found at various Web sites, including http://www.reference.com and http://www.liszt.com, as well as many others.

Using Email Responsibly
Using Email at Work
Many employers now have user agreements that employees sign which state what rights employees have and do not have with regard to the use of Internet services at work.  Almost all of these agreements state that email is not private.  Even if your employer does not provide you with a user agreement, you must assume that email is not private.

Backup Tapes
In addition to backup tapes, some email systems are set up so that email is deleted in two steps.  In the first step, email disappears from your mail received list, but is still kept in a "recycle" area, like the recycle area on the Windows desktop.  Email in this area can be undeleted by the user, but it will still be available on backup tapes.

Additional Risks
You can check out email hoaxes on the web, where a search for "email hoax" or "Internet hoax" will provide many sites. Of course, this will not cover all hoaxes but will warn you of many, and also give you an idea of the type of messages to beware of.

How to Stay Out of Trouble
The most important principle is:  Be aware that email is not anonymous.