Jan is having a busy day at the office. She needs to pick up her twins from preschool before 5:30 or face a stiff fine, but she also needs to get a birthday present for party they'll be going to on Saturday. No time to stop at a store because she can't leave work early, so she goes on line. (Don't tell the boss - this won't take long!)

She logs in to her favorite on-line megastore and does a quick search for educational toys. Lots to choose from in her budget range! The Young Scientist kit looks about right, and ships soon, too. With one mouse click she orders it; with a second she has it gift-wrapped, and with a third confirms shipping and payment. The gift is on the way - and so is she! (Best of all, the boss didn't notice the two minutes she took from work time to do it!)

This story - so commonplace today - would have been science fiction just a few years ago. We almost take it for granted now, but the technology that makes it possible is pretty spectacular. How does it all fit together? That's what we're going to look at in this module.

First of all, let's take a look at what's necessary to make this work. We need:

1. Communication Software
2. Network Interface
3. Communication Channel
4. Service Provider
5. Wide Area Network (WAN)
6. Server

1. Communication Software

Communication Software: The programmed instructions so your computer can communicate over a network.

2. Network Interface

Network Interface: The computer hardware for connecting with signals from the outside world.

3. Communication Channel

Communication Channel: The physical medium over which signals are transmitted, and the protocol used to encode the signals.

Definition: Protocol - a simple language and set of guidelines for communicating between machines.

4. Service Provider

Service Provider: An organization that runs communication devices and switches messages so they get to their destination. Service providers may also provide content, such as directories, chats, news, and Web sites.

5. Wide Area Network (WAN)

Wide Area Network (WAN): A system that allows signals to be transmitted over a variety of communication channels, and routes the signals to destinations distant from one another - that is, more than about 1 mile or 2 km.

6. Server

Server: a computer which is available to serve the needs of other computers on a network, providing files or other requested services to qualified requesters.

3. Local Services
   1. File Sharing
   2. Application Sharing
   3. Scheduling
   4. Directories
   5. Working Online
   6. Collaboration

4. Wide Area Services: The Internet
   1. World Wide Web
   2. Email
   3. On-line Help
   4. Web Services
   5. File Sharing
   6. Working Online
   7. Collaboration

All medium and large organizations now have local area networks which connect their employees' computers. They do this to better provide services to help people be more productive.

Here are some of the services most local area networks provide:

Rather than sending documents to colleagues on paper, you can now make them available through the local area network.

Application programs - the programs that allows to do productive work - are often installed on each individual computer. This is what we do at home. But in an organization with many computers, installing updates and patches on each computer is very time-consuming - and expensive.

So applications are stored on a server, and when needed on an individual machine, they can be quickly downloaded over the local area network and installed when they're needed. We to that in our classes and labs here at WCC.

One of the most frustrating and time-consuming tasks for middle and upper management in an organization is arranging meetings so that everyone who needs to be there can come. By making work-schedules available on the local area network, scheduling software can quickly find a time when everyone can attend, and send out reminders by email.

Phone directories are much more convenient on line - especially when the computer is connected to the phone system and can dial the number for you!

Enterprise databases are an extension of this concept. They can be used to find facts as well as people.

How about working at home, with all the information resources available at work? Improved network speed and security have made this possible, and many organizations are allowing their staff to work at home. This saves communing costs, congestion, and - if the organization sets itself up for it - saves costs of office space.

Local area networks make many types of on-line collaboration possible, from document-sharing to conferencing.

The main difference between local and wide area networks is their speed. It's technically easier to send signals rapidly over short distances, where signal strength is better and interference is usually less. This difference is shrinking as new transmission technologies are developed, and the differences shrink, so does the world. Soon, all the world will be covered by a "local area network".

Here are the services we generally associate with wide-area networks:

Many people don't realize that the World Wide Web is not the same as the Internet. The Internet is a system for transmitting messages; the Web is a type of message service that uses the Internet.

The boundaries between the Web and other Internet services are blurring, as Web browsers - the programs that display Web pages - are used to display many different types of services.

Electronic mail is one of the original services offered on wide area networks, and is still one of the most popular. Of course, you can send email locally, too!

Originally, email was separate from the World Wide Web. Now, Web browsers are used to display and accept email, making it difficult for people to tell the difference.

New versions of popular operating systems now provide help through the Internet. In fact, only a limited amount of documentation is provided in many programs, and that makes it difficult for people without Internet connections to use even programs on their own computers.

The assumption behind this is that most people are connected to the Internet most of the time. There are lots of exceptions, though!

The World Wide Web was originally designed to provide information to human beings. It is now being extended to provide services to people and to other computers. Here are some examples:

For people:

• on-line shopping
• on-line banking and bill-payments
• government services
• interactive games
• gambling (this is a service???)

For computers:

• currency exchange rates
• sum, reduce, divide, multiply and power two number
• complete financial statements and ratios for more than 10,000 US public companies
• conversion functions to convert numbers into words (English), numbers into dollar amounts, and texts into title-cased texts
• ...and more: see XMethods, http://www.xmethods.net/

Just as you can share files locally, you can share them globally.

The original Internet file sharing service is called FTP - File Transfer Protocol. It's still used to transfer files over the Internet, expecially by people developing Web sites, in its newer version, SFTP - Secure File Transfer Protocol.

It is not as well known now, because most people access files via the Web using the HTTP protocol, but it's a bit faster for downloading large files.

For more information on FTP, see module NA30c.

With the right service provider, you could "commute" to a workplace halfway around the world - with zero fuel costs.

To learn more about working online, a good place to start is the Wikipedia article on Telecommuting.

With the growth of international business, collaboration long-distance is becoming more important. Some organizations use different time-zones to solve problems quickly without undue stress to their staff. Here's an example of "follow the sun" collaboration:

• A client has a big problem at 1 PM Pacific time. It's costing tons of money every hour, and needs to be solved ASAP. Client calls headquarters in Minneapolis.
• The Minneapolis office gets to work on the problem at 12 noon Central time
• 5 PM Central time: progress made, but problem not resolved. Details forwarded to the Wellington office in New Zealand, which gets to work on it at 8:30 AM New Zealand time.
• 5:30 PM New Zealand time: a tired team goes home after forwarding details of the problem and their progress to the Dublin office in Ireland.
• 9 AM Dublin time: Irish team gets to work and solves the problem by lunchtime. It's still only 6 AM Central time, 4 AM in the client's time zone - just 15 hours after the problem was discovered. The client will heave a sigh a relief, and nobody really broke a sweat to get the problem solved.

Let's take a quick look at how this all works. You may be amazed at how much goes on behind the scenes!

Let's say you're Jan, shopping on-line for a child's birthday present. What do you do first?

Start your browser, of course! This would be Microsoft Internet Explorer, Apple Safari, Mozilla Firefox, or one of a handful of other browsers.

Once your browser is running, you need to find the site. Jan does this by typing the URL - Uniform Resource Locator - into the address bar: www.MySuperToys.com.

The browser's first job is to figure out that when you type something into the address bar, you want to see a file from that Web site. It gets to work on that as soon as you hit the Enter key.

You've typed in a URL, but that's not enough to get the information you want. That's like asking your secretary to call Brittany Speares. She'll have to look up the number in a phone book.

The Internet's phone book is called the Domain Name Server system. Your computer does a quick lookup and comes back with an IP Address - a set of numbers that identifies each computer on the Internet.

Once it has that number, your computer knows exactly where to send a request to MySuperToys.com, and can go on to the next step.

Recall that a Protocol is a simple language and set of guidelines for communicating between machines. Each type of computer communication has its own protocol, and the one for the World Wide Web is HTTP, the HyperText Transfer Protocol.

The browser's next job is to translate your request into an HTTP message that the Web server can understand.

When we phone someone, we hear their phone ringing. The ringing is actually a request to initiate a communication session with the person we're calling.

In the same way, when your computer wants to talk to a server, it has to request a communication session. (No ringing bells, though.)

Since we want to shop - a financial transaction - we need to make sure nobody can listen in on our business and possibly pick up our credit card info. To keep the conversation secret, we'll set up a secure session with the server: we'll agree on a secret code to "scramble" the messages. Only the server and our own computer will be able to understand what's being transmitted.

Most messages on the Internet are coded using TCP, the Transmission Control Protocol. This breaks long messages up into smaller chunks, and puts them in an "envelope" of information necessary to transmit the message accurately. The resulting packet - the data envelope and enclosed message - is then ready to be sent over the Internet.

Message packets seldom go directly to their destination. Instead, they're passed from one point on the Internet to another until they get to the right server.

The system for routing these messages, the Internet Protocol (IP), is at the heart of how the Internet works. (You can find more detail on how IP works in module NG03c, "What is the Internet?".)

Finally, your message has gotten through to the toy store's Web server. If it's not too busy, the server will "answer the phone" by agreeing to set up a communication session with you, and go through the process of setting up an encryption code to keep the conversation private.

Now that your computer is "talking" to the server, it can work on your request. Usually, this is a request to log in, but over the course of the conversation, the server will decode several more of your messages, plus answer them with encoded messages back to you.

Once a message is decoded, the server's job is to try to fulfill your request.

• In many cases, the request is simply asking to be sent a file of text, which we call a "Web page" when the browser has displayed it.
• In addition to the text of the Web pages, there are images stored in separate files. Your browser will request these, and the server will try to send them, too.
• If you're shopping, you'll probably be using the company's database. This involves sending requests to search for information, and the server needs a special program to handle that. Once the information is found (or not found) the results are set up like a Web page before being sent back. This is how you find the Young Scientist kit for your twins' friend.

Hopefully, you'll get a response you like, but it might be "404 - File not found" or something like that. Considering how many hoops a message has to jump through, and how many things can go wrong, it's amazing how often it all works right.

How long did it take to do steps 2-10? Probably less than 2 seconds. We take it all for granted, but from this you see how complicated networking really is.

Signals can be transmitted over many different communication channels, but only three physical media are widely used to carry the signals. We can take a look at them here:

Copper wire still caries the majority of signals. Many protocols are used over wires, because wire a number of advantages:

• Inexpensive - the technology for making wire has been around for nearly 200 years. Not necessarily cheap, but compared to fiber, wire is a bargain.
• Immune to interference - lots of wires can be laid in a small space, and their messages don't interfere with one another or with other kinds of messages, thanks to shielding techniques. There are very minor emission which can be picked up by sensitive devices, however.
• Fast - signals can be pumped through wires at a good rate of speed.
• Flexible - compared to optical fiber, copper wire can be coiled and bent in relatively tight curves.

Fiber optic cable uses very thin, flexible strands of glass to guide light waves over long distances with relatively little loss. This has only been possible since the development of special types of glass, and the invention of lasers to create strong, coherent light waves. Fiber has these advantages:

• The fastest transmission rate of any medium. Most high-traffic channels now use optical fiber to carry the largest number of signals at the highest possible speed.
• Totally non-interfering - better than even best-shielded copper wire. And it's impossible to eavesdrop on the fiber transmissions even with the most sensitive equipment, because no electromagnetic radiation at all escapes from it.

Radio transmission is used in several types of communication channel to carry signals.

Networking is one of the most rapidly-changing fields of technology. We can't predict the future, but here are some emerging trends:

Networks make a lot of good things possible, but bad people can also use them for their purposes. One of these purposes is to steal information from people and organizations, often to enable them to steal money.

This trend is on the rise, and the experts predict that there will be an ongoing battle between "bad guys" and "good guys" over the security of our networks.

Wireless networking is growing faster than any other type. In part, that's because of how inexpensive it is: with relatively little trouble, one wireless access point can serve 50-60 computers. It would have taken hours to install wires for them all.

Using cell phones has also whetted people's appetite for mobile communication. Uniting cell phones and laptops to more rapid mobil communication channels is one of the main goals of research and experimentation.

It's those cell phones again. People just love little gadgets you can clip to your belt or drop in your bag, then whip out to communicate with.

There's a limit to how small a computer can get and still be usable - unless you're actually wearing it. Research has been on-going to develop wearable computers, and we're seeing them gradually emerge.

The biggest challenges are getting information and commands into small computers, and getting information back out. Several techniques for overcoming these challenges have been tried. The leading contenders now include:

• speech recognition for input
• projection via eyeglasses for output