Internet is simply network of networks. When several computers are interconnected to one another they form a network. When you connect through an internet service provider (ISP) you become part of their network. Several large companies like internet service providers have dedicated backbones to link several regions. In each region the companies have point of presence (POP).The POP is a point where local users access the company's network often through a dedicated link. There is no overall controlling of the network but instead there are several high level networks connecting to each other through Network Access Points or NAPs.To illustrate how the internet works we can look at the example below.
An Internet service provider named KK builds its network in the major cities in the world. All their internet servers are placed at a building and are inter linked using the fiber as the backbone between the buildings in that city. All the customers are able to communicate via the servers placed at that particular building in that city. The KK Company is able to control the communication between the customers. A different ISP company named YY within the same city is not able to communicate with the customers of the KK Company because they have different networks and (Point of Presence) from theirs. Since the two companies cannot intercommunicate they make a special arrangement to connect to Network Access Points in various cities. Data flows between individual networks through Point of Presence that are interlinked at the NAP points. Different Internet Service Providers interconnect at Network Access Points and this in turn makes all the computers be able to communicate with each other all over the world. This is how the internet works. For the computers to communicate with each other through the internet they need IP address. The ip address is expressed as decimals for example 192.168.9.30. Networks, routers, NAPs, ISPs, DNS and powerful servers all make the Internet possible.
HOW MESSAGES ARE TRANSFERRED ACROSS THE INTERNET
The messages are sent across the internet using e-mail. This is the short form of electronic mail. It is a method of exchanging digital messages from an author to one or more recipients. The email contains four parts: envelope, header and body. The header contains control information like originator's email address one or more of the recipients' addresses. When a person composes mail using her Mail User Agent (MUA) she enters the email address of the correspondent. She then presses the "send "button. Her MUA formats the message in email format and uses the Submission Protocol (a profile of the Simple Mail Transfer Protocol (SMTP) to send the mail to Local mail submission agent (MSA) run by the Internet Service Provider for example smtp.kasnetafrica.co.ke.The MSA looks at the destination address provided in the SMTP protocol (not from the message header). In an email address the part before @ sign represents the local address and the part after represents the domain name. The MSA resolves a domain name to determine the fully qualified domain name of the mail exchange server in the Domain Name System (DNS).The DNS server responds with any MX records listing the mail exchange servers for that domain. The message is sent to the exchange server using the SMTP. This server may need to forward the message to other MTAs before the message reaches the final message delivery agent (MDA).The correspondent presses the "get mail" button in his MUA, which picks up the message using either the Post Office Protocol (POP3) or the Internet Message Access Protocol (IMAP4).Domains usually have several mail exchange servers so that they can continue to accept mail when the main mail exchange server is not available by using web mail service.
MAIN FEATURES OF HTML
HTML has the ability to work with multiple folders and sub-folders. You can include files from any location on your computer and define their virtual path to access them in e-books.It has a compiler that creates three types of e-books and digital publications: Self-Extracting, Internet Explorer-based browser and Stand-alone HTML Viewer. Compiled HTML publications and graphics' source files are not reusable by end users. Internet Explorer and HTML Viewer publications do not require files to be extracted for displaying them. Your websites are protected against external modifications and truncated downloads because publications check their integrity before running. All website files are stored inside the .exe ebook file so you do not need to distribute them. HTML turns your websites into single Windows executable files, real applications called ebooks or digital publications - for easy, secure and fast distribution to your customers, colleagues, friends, and other users. HTML creates compact ebooks without losing performance. Your website files are strongly compressed using algorithms.HTML Viewer publications have built-in HTML browser functionality and are similar to Web browsers because users are familiar with the navigation interface. They do not require any external Web browser and can run on any computer with or without a Web browser: therefore, they are truly stand-alone.
DIFFERENCE BETWEEN INTERNRET, INTRANET AND XTRANET
Internet is a worldwide system of computer networks - a network of networks in which users at any one computer can, if they have permission, get information from any other computer. It is a network based on standards including Internet Protocol (IP), Simple Mail Transfer Protocol (SMTP) and the Domain Name System (DNS), which enables global communications between all connected computing devices. It provides the platform for web services and the World Wide Web.
An Intranet is a network based on the internet TCP/IP open standard. It belongs to an organization, and is designed to be accessible only by the organization's members. It is a private network that is contained within an enterprise. An extranet is a private network that uses Internet protocols, network connectivity. An extranet can be viewed as part of a company's intranet that is extended to users outside the company, usually via the Internet. A virtual network tying a company to outside organizations, often through the Internet.
WORK CITED
http://en.wikipedia.org/wiki/Email
J. Myers, SMTP Service Extension for Authentication. 1985.
J. De winter, Service Extension for Remote Message Queue Starting, The Internet Society (August 1996)
J. Klensin. Simple Mail Transfer Protocol. The Internet Society (October 2008)
Partridge, Craig. The Technical Development of Internet Email New York: 2008. Print
voicendata.ciol.com/content/goldbook/goldbook03/103033102.asp
www.volresource.org.uk/swit/webterm.htm
