Computer Networks

1. Computer Networks Intranet: An intranet is a private computer network that uses “Internet Protocol” technologies to securely share any part of an organization's information or network operating system within that organization.

2. Computer Networks Internet: The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic and optical networking technologies.

3. Computer Networks Internet (cont’d): The internet was invented by a British engineer and computer scientist named, ‘Sir Timothy John Berners-Lee. The first proposal for the internet was submitted in March 1989. Communication was to be established using the “Hypertext Transfer Protocol” (HTTP). The first communication between an HTTP client and a server was done on December 25, 1990. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents of the “World Wide Web” (WWW) and the infrastructure to support the the distribution of electronic mail.

4. Computer Networks Internet Protocol: IP Addresses Every machine on the Internet has a unique identifying number, called an IP Address. The IP stands for Internet Protocol, which is the language that computers use to communicate over the Internet. A protocol is the pre-defined way that someone who wants to use a service talks with that service. The "someone" could be a person, but more often it is a computer program like a Web browser.

5. Computer Networks Internet Protocol: IP Addresses (cont’d) A typical IP address looks like this: 216.27.61.137 To make it easier for us humans to remember, IP addresses are normally expressed in decimal format as a dotted decimal number like the one above. But computers communicate in binary form. The IP address shown above, expressed in binary format look like this: 11011000.00011011.00111101.10001001

6. Number Systems Number Systems: Decimal (0, 1 ,2 , …9) Binary (0 and 1) Hexadecimal (0,1,2, …9, A, B… F) Octal (0, 1, 2, …7)

7. Computer Networks Internet Protocol: IP Addresses (cont’d) 11011000.00011011.00111101.10001001 The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers. Since each of the eight positions can have two different states (1 or zero), the total number of possible combinations per octet is 28 or 256. So each octet can contain any value between zero and 255. Combine the four octets and you get 232 or a possible 4,294,967,296 unique values!

8. Computer Networks Internet Protocol: IP Addresses (cont’d) Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses. For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.

9. Computer Networks Internet Protocol: IP Addresses (cont’d) The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need. The octets are split into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet. There are five IP classes plus certain special addresses.

10. Computer Networks 11011000.00011011.00111101.10001001 Servers and Client machines: There are two general classifications for computers on an Intranet, the Internet, or if the computer is a stand-alone PC: - Servers - Client Machines Last Octet (Host) First Octet (Net)

11. Computer Networks Servers and Client machines (cont’d): Server: A server computer is a computer, or series of computers, that link other computers or electronic devices together. They often provide essential services across a network, either to private users inside a large organization or to public users via the internet. For example, when you enter a query in a search engine, the query is sent from your computer over the internet to the servers that store all the relevant web pages. The results are sent back by the server to your computer.

12. Computer Networks Servers and Client machines (cont’d): Client: A client or thin client (sometimes also called a lean or slim client) is a computer or a computer program which depends heavily on some other computer (its server) to fulfill its traditional computational roles. This stands in contrast to the traditional fatclient, a computer designed to take on these roles by itself. The exact roles assumed by the server may vary, from providing data storage, to actual information processing on the client's behalf. Thin clients occur as components of a broader computer infrastructure, where many clients share their computations with the same server.

13. Electronic Mail (email) Client PC: Email Server: demo@intdbsys.com Internet Connection Electronic Mail (email), is an exchange of information between two email servers, and several client computers. Electronic messages (email) are transmitted from one computer to another in a matter of seconds. Email Server: hgilchan@yahoo.com

14. Accessing Email There are two standard ways to view email: Webmail (aol.com, my.earthlink.net… etc) Email program (Microsoft Outlook) In order to access any ‘Webmail’, you need to start Internet Explorer then type in the ‘web address’ of your mail server. ‘Microsoft Outlook’ allows you to create/add an account that will automatically retrieve your email when you start up the program. Configure Outlook to access test email.

15. Accessing Email Before you start your email program, make sure that you have the following information from your ‘Internet Service Provider (ISP): E-mail address (demo@intdbsys.com) Account Name (A name relating to the account) Password In older versions of Outlook, you had to provide the name of the outgoing server ‘Simple Mail Transfer Protocol’ (SMTP) and the name of the incoming server ‘Post Office Protocol’ ( POP3). Outlook 2007 and 2010 will automatically search for (SMTP) and (POP3), using the email address and a password.

16. Accessing Email When someone sends you an email message, it does not suddenly appear on your screen. The message sits on your ISP’s mail server, until you connect and retrieve your message(s). Outlook 2007 and 2010 will automatically connect to the designated mail server and retrieve your message(s). You can set Outlook to check for new mail every minute or every few hours, and you can specify exactly the accounts you want checked (you can even set different intervals for different accounts).

17. Accessing Email Most email programs, organize the user interface into several folders: Inbox Sent Items Saved Spam Archive Deleted Items

18. Email Etiquette A protocol has been established over the years regarding sending and receiving email: Never type in upper case letters ( considered as shouting) Do not send sarcastic remarks (flame) Avoid sending messages about the latest viruses. Avoid attachments that you consider as being private.

19. Email Attachments Files and images can be attached to an email message. There is a limit on the size of the attachment, this is dependent on your ISP server specifications. Typical sizes range from a maximum of 2M Bytes to 4M Bytes.

20. The Web The single most exciting part of the Internet is the “World Wide Web” (or web for short). The web is a loose collection of interconnected documents stored on computers all over the world. Each page on a web site may contain one or more links to another page on the same computer, or to computer down the block, across the country, or overseas. You can move from continent to continent by clicking on these links. Going from page to page using links is sometimes called surfing the web.

21. The Web Web documents contain pictures, sounds, video clips, animation, and even interactive programs. The web contains a vast amount of information, far more than even the world's largest libraries. For example, you can read news stories and movie reviews, check airline schedules, see street maps, get the weather forecast for your city, or research a health condition. Reference sources, such as dictionaries and encyclopedias, are widely available, as are historical documents and classic literature.

22. The Web Most companies, government agencies, nonprofit organizations, museums, and libraries have websites with information about their products, services, or collections. Many individuals publish websites with personal journals called blogs (short for web logs) about their hobbies and interests.

23. The Web Not all Information on the Web is Accurate Even though the web is great for research, not all information on the web is reliable. Information on some websites might be inaccurate, out of date, or incomplete. Before you trust information, make sure it comes from an authoritative source, and check other sources to verify the information.

24. The Web Communication - Instant messaging Instant messaging (IM) allows you to have a real-time conversation with another person or a group of people. When you type and send an instant message, the message is immediately visible to all participants. Unlike e‑mail, all participants have to be online (connected to the Internet) and in front of their computers at the same time.

25. The Web Communication - Newsgroups and web-based forumsNewsgroups and web-based forums allow you to participate in text-based discussions with a community of other people who are interested in the same topic. For example, if you are having trouble using a program, you could post a question in a discussion group for users of that program.

26. The Web Shopping: The web is the world's biggest shopping mall. You can browse and purchase products—books, music, toys, clothing, electronics, and much more—at the websites of major retailers (usually a credit card is required). You can also buy and sell used items through websites that use auction-style interfaces.

27. The Web Sharing (Facebook): You can upload (copy) pictures from your digital camera to a photo-sharing website. Invited friends and family members can then visit the website to view your photo albums.

28. The Web Games: You can play games of every type on the web, often against other players—no matter where they are in the world. Many games are free, and you can download others for a fee. You can also listen to Internet radio stations, watch movie clips, and download or purchase music, videos, and even some TV shows.

29. Connecting to the Internet The Internet is a worldwide network of computers that can communicate with one another and share resources. The computers are all connected by a massive collection of fiber optic cables, phone lines, and wireless signals that enable the Internet to transfer data at lightening-fast speeds. The network of cables, phone lines. and wireless connections that carry the data are known as the Internet’s backbone. In order to plug into this network and tap it’s resources, it needs a modem and an ISP.

30. Connecting to the Internet To connect your computer to the Internet, you must first sign up with an Internet service provider (ISP). An ISP provides access to the Internet, usually for a monthly fee. You sign up for an account with an ISP just as you do for telephone service or utilities. To find an ISP in your area, try looking in your telephone directory under "Internet Service Providers“, or use another computer to shop on-line for an ISP in your area. Your ISP functions as a communication hub between your PC and the Internet.

31. Your Computer Cable Modem Connecting to the Internet ISP

32. Connecting to the Internet Different ISPs offer different connection types and speeds.There are three basic types of connections: A broadband connection is a high-speed Internet connection. With a broadband connection, you are connected to the Internet at all times and can view webpages and download files very rapidly. Two common broadband technologies are Digital Subscriber Line (DSL) and cable technology. These require a DSL or cable modem, which is often provided by your ISP.

33. Connecting to the Internet A dial-up connection uses a dial-up modem to connect your computer to the Internet through a standard telephone line. Dial-up is slower and requires you to establish a new connection each time you want to use the Internet, however, dial-up is less expensive.

34. Connecting to the Internet The term Wi-Fi suggests Wireless Fidelity. A Wi-Fi enabled device such as a personal computer, video game console, smartphone or digital audio player can connect to the Internet when within range of a wireless network connected to the Internet. The coverage of one or more (interconnected) access points — called hotspots — can comprise an area as small as a few rooms or as large as many square miles. Coverage in the larger area may depend on a group of access points with overlapping coverage.

35. Connecting to the Internet Just as every residence has a unique street address, every webpage has its own web address. That address is called the “Universal Resource Locator” (URL). For example, the URL for the Microsoft’s website is http://www.microsoft.com.

36. Browser The user interface to the Internet is done using a “Graphical User Interface (GUI)” program called a ‘browser’ or ‘web browser’. There are several types of browsers available: Internet Explorer (IE) (Windows) Mozilla Firefox (Windows, Linux, Unix) Safari (Apple PC’s, Unix) Chrome ( Developed by Google) Opera (Windows, Linux, Unix) All of these browsers can be downloaded to your PC.

37. Browser Language All browsers communicate using a standard language. HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. A markup language is a set of markup tags, and HTML uses markup tags to describe web pages. HTML is written in the form of HTML elements consisting of "tags" surrounded by angle brackets (like <html>) within the web page content. HTML tags normally come in pairs like <b> and </b>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags).

38. Browser Language The purpose of a web browser is to read HTML documents and display them as web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page. HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It can embed scripts in languages such as JavaScript which affect the behavior of HTML webpages

39. Browser The browser will always start at the ‘default’ start page. If your PC is not connected to the Internet, a message will be displayed:

40. Browser Default Page Change the default page by clicking on ‘Tools’, then ‘Internet Options’. Then click ‘Use current’, ‘Use default’, or ‘Use blank’.

41. Cookies When you visit some websites, they automatically send an electronic passport, called a cookie to your computer. As you browse the site, use it’s tools, or order products, the site “stamps” your passport to keep track of your interests, passwords, and any product you order. Whenever you revisit the site, the cookie stored on your machine is used to identify you. For example, if you buy programming books from ‘Amazon.com’, anytime you revisit the site, a list of programming books will be presented to you.

42. Cookies Because cookies are used to track your web habits, some people are suspicious of them. However, most cookies are designed to enhance your web browsing experience and allow web sites to target advertisements to your tastes. All browsers have tools for regulating how the browser handles cookies.

43. Cookies In Windows Internet Explorer (IE), take the following steps to set your preferences: Click Tools, Internet Options Click the Privacy tab Click the Advanced button Check “Override automatic cookie handling” Select your choice Cookies can also be deleted using your browser ‘Tools’ setting.

44. Cookies Cookie settings:

45. Cookies Deleting cookies:

46. Search Engines There are several search engines available to find information on the Internet: Google Yahoo Bing Alta Vista Ask.com

47. Browsers Windows XP, Vista and Windows 7, use the Microsoft “Internet Explorer” web browser. Mozilla ‘Firefox’ also runs in the ‘Windows’ environment.

48. Downloading and Uploading Files Downloading means taking a file from another machine and copying it to your PC. Examples downloads: - Device driver (scanner, printer, sound card, etc..) - Picture Images (‘.jpeg’, ‘.gif’…etc) - Files (forms, manuals) etc - Music - Movies

49. Downloading and Uploading Files Uploading is the reverse of downloading; there is more security involved with uploading. One of the most common uses of uploading is to publish a website (making it available on the internet).

50. Social Media Social media is one of the most popular evolution of the internet; it connects friends, relatives, employees, and colleagues by using tools for sharing and conversing with each other.