Module Six: Introduction to Internet and its various applications (Notes)
Local Area Networks (LANs)
A small network of computers in close proximity to each other. Roughly a single building’s worth of computers connected together usually via Ethernet, but other ways are possible (token ring, local talk, etc.)
Ethernet
Original design in 1973 by Bob Metcalf, Xerox PARC
How can I get bits from one computer to another cheaply, easily, and above all, quickly? Could have phone system style setup
Ethernet Design
Each computer has a unique address. All computers are connected to a single wire (but can be any medium, like radio) all computers listen to every message wait until the line is free to broadcast. If there is a collision, wait a random period of time then try again. This is the breakthrough.
Wide Area Networks (WANs)
Connect physically distant computers often connect physically distant LANs usually involve phone companies
There are a wide variety of ways to do this, but some significant companies include:
- Cisco Systems and 3Com (build hardware)
- AT&T and Sprint, TTCL (own the pipes)
WAN Design
- Probably very high bandwidth
- Probably fairly low latency
Pre-Internet, WANS were more or less all proprietary
Why make the distinction?
Because the issues are very different you have full control over the wires on a LAN. You probably have a contract with a phone company on a WAN
- LANs are relatively cheap to grow
- WANs are expensive to grow
What does it take to run a cable from one side of the street to the other?
Routers
> Connect two physically different networks
- An Ethernet and a token-ring network
- A modem connection and an Ethernet
- A LAN and a fiber optic cable
> Translate electrical requirements
> Translate between the two addresses
How Routers Work
- Look to other computers like just another machine on the LAN
- Looks at all packets on the LAN and forwards those destined for the outside world
- You often need the IP address of your local router when configuring your internet connection (the gateway)
The internet is a giant WAN
Many computers of various…
- Types: Intel, Sun, Palm Pilots, Atari, Apple, embedded systems, etc.
- Operating Systems: Windows 3.11, 95, 98, NT, 2000, UNIX, Linux, MacOS’s, etc.
- Sophistication: Space Shuttle to PCs
- Speeds: 16MHz 8086’s to 1 GHz machines
How do I get all of them talking together?
Protocol
A way for machines to talk to one another Like Korean or ASL or PASCAL. Hundreds of different protocols operate together to make the internet work properly
- Each is responsible for a different service
- Each is built on some protocol below
Internet Protocol (IP)
The most basic protocol of the Internet designed to get a single packet from one computer to another abstracts the physical connection between two machines
IP Addresses
Every computer on the Internet has one represented by four numbers between 0 and 255 (i.e. four bytes)
My home machine: 216.132.81.61
My office machine: 171.65.75.234
My office router: 171.64.75.1
More about IP
- IP actually promises to do very little try to get a single packet from one computer to another does not guarantee a packet’s arrival, timing, error free transmission and route
The problem with IP
32 bits long means that the maximum size of the Internet is 4,294,967,296 computers sounds like a lot, but isn’t ran out of addresses in late 1994 or early 1995 currently using tricks to circumvent that limit
A new version called IPv6 is coming to augment the current IPv4 128-bit addresses, other optimizations
How do I start using the Internet and Web?
Get to a Internet connected computer in order to use the Internet, you need to access to some computer that has access to the Internet.
Start up a Web browser
Once you have access to an Internet-connected computer, you can access the Web if that computer has Web browser software installed. Two popular Web browsers are Netscape Navigator and Microsoft Internet Explorer.
Use the Web browser
You use the Web browser typically through manipulating it with your mouse and cursor, and entering information from your keyboard.
To open a Web address (URL-Uniform Resource Locator), use your browser's menu and chose File->Open or File->Open Location. You might also be able to click on the text in the "Address" box at the top of your browser, alter or enter a URL there, and press the Enter key.
How do I email?
Use Web based mail your organization may supply you with Web-based mail. You can sign up for free, Web-based mail at sites such as http://www.mail.com/ or others.
To use Web-based mail, all you have to know is how to use your browser and follow the directions at the mail service's Web site to send and retrieve your email messages.
Searching the Internet or WWW
How do you find things on the Internet and Web?
The big adventure of the Net, to me, is the vast amount of content. Since 1994 when Net use began to really take off, there has been so much content added online--and good content that it is mind boggling.
Therefore, techniques and tools for searching are imperative (necessary) if you are going to find what you want. You'll need to learn to use tools, generically called "search engines
Types of Searching
a) Subject searching
b) Keyword searching
c) People searching
d) Portal searching: lycos.com, go.com, yahoo.com
Searching Tips
- Come up with key identifying words or phrases that would uniquely identify what you are trying to find and use these in search engines.
- Use bookmarks or "favorites" to quickly record the URL of resources that interest you.
- Take note of resources that are listed or cited often in annotated listings of resources; these popular resources may be very useful. Remember, everything changes on the Net.
- Use your information literacy skills to appropriately evaluate Internet based information.
- You can cite a Net resource in a paper; just include the URL in the citation and the date you visited the URL and the date stamp (if any) on the page.
Communication on the Net
How do people communicate on the Net?
- One to one communication: Email, chat-type systems large and small group communication:
- Social Networks
- Blogging
- Instant Messaging
- Chat
- Mail based discussion list
Mass communication:
> Net Video
> Net Audio
Using Internet Tools
The purpose of this lesson is to introduce you to Internet tools and utilities for information retrieval, besides the World Wide Web. What Tools Are on the Internet?
We've spent a good amount of time talking about the Web, and this is good because the Web dominates the Net. But there are other tools available on the Internet. In truth, because of the dominance of the Web, most of these tools are basically obsolete. But many Internet resources can still be reached by non Web means.
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