Fundamentals of the Internet

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Fundamentals of the Internet

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The Internet is a technology to connect people and computers throughout the world. With the help of the Internet, organizations can exchange data and information, people can communicate with each other in a faster and effective way, and researchers can gather information for their research from all over the word. Video conferencing is also possible through the Internet. With video conferencing, people can see each other while communicating, and organizations can arrange meetings even when the members are not in the same country. Shopping is also a growing feature of the Internet.

The Internet began in 1962 as a computer network for the US military. Over time, it has become a decentralized global network of millions of individual computers and computer networks. These individual computer networks may be of military, government agencies, educational institutions, nonprofit organizations, industrial and financial corporations, commercial enterprises, and even the private networks hosted by individuals. In short, the Internet is a worldwide network of computer networks that can be accessed via the computer by using a common set of communication protocols.

The Internet allows local computer users to find and use databases on computers of other academic institutions, research institutes, private companies, and government agencies. Other most commonly used features of the Internet are informative Web sites, electronic mail, discussion groups, on-line conversations, games, electronic commerce, and information gathering.

The terms frequently used in the concept of the Internet are as follows:

Web site: A Web site is a collection of Web pages on the World Wide Web. These Web pages are documents written or coded in languages that are supported by the Web such as HTML, DHTML, and XML. Web pages of a site are linked to each other and very often to a page of external sites by a hyperlink. The default page of the site is known as Home page. Every site and even each Web page has its unique address (URL).

Web pages may be of two types, namely static Web pages and dynamic Web pages. Static Web pages are those Web pages that do not change before being displayed in a Web browser. These Web pages are not interactive, i.e., visitors have no control over the information provided by these pages, and so the pages and information do not change with each visit.

Dynamic Web pages are those Web pages where the contents cannot be predetermined. In order to generate dynamic pages, a program such as ASP or PHP is required. These programs generate instructions to call up and construct the dynamic pages based on database contents or the information provided by the visitor.

To view a Web page, a specifically designed software known as a user agent or Web browser is needed. There are many different types of Web browsers available with various capabilities and a wide range of supported platforms.

Uniform Resource Locator (URL): Each Web page has its unique address that defines the route of a file on the Internet. These Web pages can be accessed directly by providing its address on the Web browser. This unique address is known as Uniform Resource Locator or URL.

Uniform Resource Locator (URL) is a string that supplies the Internet address of a Web site or a resource, on the World Wide Web, along with the protocol by which the site or resource is accessed. The most common URL type is http://, which gives the Internet address of a Web page. For example:

http://www.ucertify.com/about/about.html

Usually, a URL has three parts. In the above example, the first part is http. It means that the HTTP protocol is used for the transfer of contents of this Web site. The second part, www.ucertify.com, indicates the IP address of the site, where www shows that the site is on the World Wide Web, and .com is the domain name. The third and the last part /about/about.html represents the path of a specific Web page. It indicates that the file about.html is stored in the directory /about/.

Sometimes the URL looks like http://www.google.com/search?hl=en&q=ucertify&btnG=Google+Search. But here the URL is only http://www.google.com/search. hl=en, q=ucertify, and btnG=Google+Search are the parameters passing to the URL. Parameters are separated from the URL with a question mark (?), and they are separated from each other with ampersand (&). The Web page to be displayed by this string is a dynamic page, and it changes with every change in the parameters passing to the URL.

World Wide Web (www): World Wide Web is the most popular service provided by the Internet. The www stores and disseminates millions of Web sites that contain text, multimedia, animation, music, video, and graphics. Anyone can access this service through the Internet with the help of a Web browser.

IP Address: IP address is a unique identity number of a node, computer, or server on the Internet. It is like a phone number that is referred to by the network devices for sending information to each other.

An IP address is a four-byte number such as 134.32.202.16 that uniquely identifies a computer on a TCP/IP network. All four bytes are separated by a dot, and are made up of 32 bits of information. An IP address is divided into four sections, with each section containing one byte (8 bits), and each byte represented in 0 to 255 decimal numbers.

Each computer or network device on the TCP/IP network must be assigned a unique IP address. This is especially true in case of the Internet, which is a global network. To avoid IP address conflicts, a centralized regulatory authority named InterNIC issues the IP addresses for the devices on the Internet that are called public addresses.

InterNIC has also reserved certain IP addresses as private addresses for use with internal Web sites or intranets. These addresses are not routable on the public Internet, but are meant for the devices that reside behind a router or other Network Address Translation (NAT) devices or proxy server. These IP addresses are called private addresses.

Private IP addresses are used either to hide systems from the public Internet or to provide an additional range of addresses to the organizations that do not have sufficient public IP addresses to distribute on their network. Organizations can use these numbers to assign internal IP addresses without having to worry about an IP address conflict or having to obtain a new block of IP addresses. An IP address in the private address range is never assigned as a public address, so the private addresses never duplicate public addresses. Private addresses can be repeated, but two public addresses cannot be the same.

Private address range:

Name	IP address range	Number of IPs	Classful description	Largest CIDR block
24-bit block	10.0.0.0 - 10.255.255.255	16 777 215	single class A	10.0.0.0/8
20-bit block	172.16.0.0 - 172.31.255.255	1 048 576	16 contiguous class Bs	172.16.0.0/12
16-bit block	192.168.0.0 - 192.168.255.255	65 535	256 contiguous class Cs	192.168.0.0/16

Also, IP addresses in the range of 169.254.0.0 -169.254.255.255 are reserved for Automatic Private IP Addressing. These IPs should not be used on the Internet.

Public address range: Except the private address range, all IP addresses are public addresses.

In a TCP/IP network, communications are based on IP addresses. All devices in a network use IP addresses to communicate with each other. Computers or network devices (such as routers) process IP addresses easily and work accordingly, whereas human beings (or users) find it difficult to remember these 32-bit IP addresses. For example, it is difficult for a user to remember 66.223.125.240 than www.ucertify.com for a communication address. This is why user-friendly names are associated with computers, sites, file system shares, e-mail addresses, etc., so as to help users remember them. Whenever a user uses these names to send information, the computer converts the name of the destination computer into its IP addresses. The system followed for converting the IP address is known as Domain Name System, and the process is known as resolution of the domain name.

Domain: A domain is a set of network resources that are part of a network and share a common directory database. A domain is administered as a unit with common rules and procedures. Each domain has a unique name. Users just have to log on to a domain to access the network resources within it.

Domains are usually computers, which are grouped together for administrative purposes. Each of the domains has a domain name.

Domain Name: A domain name is the name by which a domain is identified on the network e.g., www.ucertify.com is the domain name for the uCertify site, where www.ucertify is the unique name for uCertify's server on the World Wide Web, and com is the domain name that depicts the type of work this organization performs. In this case, ucertify.com is a commercial business organization.

The domain name part of a DNS name is hierarchical and can consist of two or more words separated by a dot (.). The domain name space has a root at the top, and beneath the root, there are top-level domains. Under these domains, there are second-level domains. This chain can be stretched to any extent. At the end of the chain is a host computer. For example, in the fully qualified name www.ucertify.com, www is a host name (or computer) that is placed in the ucertify domain. The ucertify is a sub-domain of top-level domains named com.

Top-level domain is the last part of the domain name that is separated by the dot from the URL. Top-level domain is mainly categorized into two types. They are geographical and generic top-level domains.

1. Geographical top-level domain: Countries and geographical areas like dependent territories use these top-level domain names. For example:
   
   

   Domain Name	Description
   .in	Used for sites that belong to India
   .my	Used for sites that belong to Malaysia
   .uk	Used for sites that belong to U.K.
   .de	Used for sites that belong to Germany
   .sg	Used for sites that belong to Singapore
   .fr	Used for sites that belong to France
   .au	Used for sites that belong to Australia



2. Generic top-level domain: These top-level domains are used by a particular category of organizations. For example:
   
   

   Domain Name	Description
   .com	Used for Commercial sites
   .edu	Used for Educational sites
   .gov	Used for Government sites
   .org	Used for Organizational sites
   .mil	Used for US military sites
   .net	Used for Network sites
   .ac	Used for Academic sites

There is another category of top-level domain names known as infrastructure top-level domain. Top-level domain arpa is the only one that comes under this category.

Each level of domain has its own DNS server to resolve host names. The domains at each level maintain information about the domains at the next level, lower in the hierarchy. When a request comes to a DNS server, and the server is unable to resolve the query, it forwards the request to a DNS server of the next level, higher in the hierarchy. This process is known as referral.

Domain Name System: Domain Name System (DNS) is a hierarchical naming system used for locating domain names on private TCP/IP networks and the Internet. It provides a centralized service for mapping DNS domain names to IP addresses and vice versa.

DNS consists of a hierarchical namespace, a collection of name servers, and DNS clients. DNS clients are also called resolvers. Each server in a collection contains information for a small part of the namespace, which is known as the authoritative source for that part of the namespace. Whenever resolvers send queries to the DNS server, the server tries to retrieve information from its own database to resolve the IP addresses associated with the request names. If the entries are not found in its own database, it passes on the requests to other DNS servers for name resolution.



DNS servers keep the information in the DNS database in the form of resource records.

The major function of the Internet is to communicate messages and information between an individual computer and networks. For communication, a common set of rules is used known as protocols.

Protocol: To enable two computers to communicate with each other effectively and efficiently, a common set of rules and regulations are required. The Protocol is a set of rules, which is accepted globally. TCP/IP is a suite of various protocols utilized for communicating messages and information among computers. They are used as a standard for transmitting the data over various networks.



The primary protocols in the suite are as follows:

Internet Protocol (IP): This protocol deals with the addresses of the computers. It decides the addresses of the destination computers to be labeled on the packet. It also ensures that the various computers and intermediate nodes correctly read the address and route the packet to the destination.

Transmission Control protocol (TCP): TCP is one of the most important protocols of TCP/IP networks. This protocol deals with the packets in transferring them from one end to the other over the networks. TCP allows two hosts to establish a connection and exchange data. It ensures that the data is delivered at the right place and the packets in the same order in which they were being sent.

Packets are small pieces of data meant for effective and efficient communication over the network. For sending a bulk of data on the Web, the data is divided into various pieces, and the pieces are known as packets. These packets follow different paths to reach their destination. This process is called routing. The size of the packet depends upon the network capability.

TCP is a reliable, connection-oriented protocol operating at the transport layer. This protocol can transmit large amounts of data. Application-layer protocols such as HTTP and FTP utilize the services of TCP to transfer files between clients and servers.

File Transfer Protocol (FTP): Transferring a file from one computer to another is the most essential function allowing us to share the resources on the Internet. The File Transfer Protocol (FTP) is the one of the oldest protocols used for transferring files over the TCP/IP network. It is also utilized for uploading the Web pages from a local computer on the Internet. FTP can be used for transferring any type of file such as software programs, text, audio, video, pictures, images, graphics, etc., from the host computer to other computers. FTP transfer can be started with the Web browser by typing ftp:// followed by URL of the file. After that, a user can enter the Get or Put command and specify the file name to be transferred.

1. Get filename


2. Put filename

This act will transfer the specific file permanently into your computer.

Note: It is better to compress all the files before transferring them.

The File Transfer Protocol command is used to update, delete, rename, move, and copy files between a local computer and any other computer over the Internet. The FTP command is mostly used to distribute files over the Internet. In Linux, the FTP command requires the FTPD daemon that is started by INETD by default.

Hyper Text Transport Protocol (HTTP): Hypertext Transfer Protocol (HTTP) is a client/server TCP/IP protocol used on the World Wide Web (WWW) to display Hypertext Markup Language (HTML) pages. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when a client application or browser sends a request to the server using HTTP commands, the server responds with a message containing the protocol version, success or failure code, server information, and body content, depending on the request. HTTP uses TCP port 80 as the default port.

HTTP Vs. FTP: The HTTP protocol is used for sending a request and transmiting the files on the browser. Unlike the FTP, it does not transfer text and binary files permanently between a host computer and a local computer over the Internet . The HTTP protocol is similar to the FTP protocol in the way they transfer files and support binary files.

Hypertext Transfer Protocol Secure (HTTPS): HTTP protocol is a protocol used in the Universal Resource Locater (URL) address line to connect to a secure site. If a site has been made secure by using the Secure Sockets Layer (SSL), HTTPS, instead of HTTP protocol, should be used as a protocol type in the URL. It directs the message towards the secure port member instead of the default Web port member.

Simple Mail Transfer Protocol (SMTP): Simple Mail Transfer Protocol is used for the delivery of e-mail. The functions of this protocol are as follows.

1. Identifies the sender


2. Specifies the recipient of mail


3. Transfers the e-Mail

It verifies the e-mail address of the receiver. It also facilitates the sender to keep a copy of the e-mail with him till the mail is delivered.

Gopher: Gopher is a service over the Internet that allows accessing the resources available on the Web. It is a protocol used for searching and retrieving the information from the sites by using TCP/IP protocol. It is also considered as a program that searches file names and other resources on the Internet. Gopher is based on client server architecture. It presents the information in hierarchical menus. These Menus can call other Gopher menus.

Telnet: The telnet is a protocol that allows you to access the computer on the Internet to which you have the access permission. It is a service presented by the Internet that enables the host computer to act as a terminal of the remote computer. It provides a facility to the host computer to access any other computer and get full control over it. You can use software, other programs installed in it, and even the files stored in the remote computer just like you use your own computer. It may be used to get massive information from a public library or public database. Telnet is mainly used for accessing those information, software, and programs that are not available on the host computer.

User Datagram Protocol (UDP): This is a connectionless, unreliable transport-layer protocol. UDP is used primarily for a brief exchange of requests and replies.

Internet Control Message Protocol (ICMP): This is a diagnostic and error-reporting protocol that is carried within IP datagrams.

Address Resolution Protocol (ARP): This is an Internet protocol for resolving an IP address into a physical layer address.

Point-to-Point Protocol (PPP): This is a data link-layer protocol designed to create a direct connection between two TCP/IP computers, typically using telephone lines.

Protocols are not sufficient for making connections to the Internet. There is also a requirement of an IP address and a proper port number. Port is an interface through which data can be sent and received between two computers across the world. In other words, port is a number that a protocol uses to transfer data to and from a program. Different protocols use different ports for transmitting the data. Following are the some main protocols and their default ports:

Protocol	Default Port
HTTP	80
HTTPS	443
FTP	21
Telnet	23
SMTP	25

The use of the Internet is unrestricted, and they are increasing day by day. Some major functions of the Internet are gathering information with the use of browsers and search engines, sending messages or information immediately with the help of e-mail and managing the users' personal information.

Web browsers: A Web browser is an application that enables a user to view Hypertext Markup Language (HTML), XML, XHTML, and other Web support language documents on the World Wide Web, on another network, or on his computer. Internet Explorer is an example of a browser application. The Web browsers are mainly of two types, GUI-based and Text-based. A GUI-based Web browser allows you to use the mouse within the browser window, and also permits you to click on the hypertext present in Web sites and the button of the tool bar. During surfing, the Web browser acts as a client and connects you with the server of URL address mentioned on browsers. The Web browser also has some user customization features such as preferences, cookie, and caching.

1. Preferences: Preferences are the options provided by the program to the user. These options can be changed. It is a user customization feature that can change the user interface according to the way he wants to perceive his data. By this, the user can also control the routine action to the program. In case the user does not modify it, default setting will be followed.



2. Cookie: A cookie is a small text file that is placed on a computer by the Web sites, which are visited by users. It contains information about a user and his or her computer such as which operating system is being used, the logon name, the user's preferences, the user's personal identifiable information, etc. A Web site reads this information automatically the next time a user visits the site, letting the site keep track of the user's preferences. If cookies are deleted from a computer, a user will have to re-enter the information retained by them, every time he visits a site.



3. Caching: Web caching is a method for minimizing performance bottlenecks and reducing network traffic by serving locally cached Web contents. Web caching helps in reducing bandwidth utilization during periods of high network traffic. High network traffic is usually caused when a large number of users use the network at the same time. With a caching solution in place, users' requests will be returned from the cache without having to travel over a WAN link to the destination Web server.

E-mail: Electronic Mail, usually known as E-mail, is a means of transferring messages in electronic form over a communication system, mostly to the Internet. A user can also transfer large messages with attachment that may include image, graphics or animation, and even voices. In this process, the sender composes a message at his computer, which is received at the recipient's computer when he connects through the Internet.

The most important requirement to send an e-mail is to have an e-mail account with an e-mail provider's Web site. That site provides the user a unique identifiable address that is known as e-mail address. A user can receive his e-mails through a mail program such as Microsoft Outlook or by visiting the Web site on which he has created his e-mail account. With the mail program, a user can get his e-mail directly on his computer, but the disadvantage of this program is that the user can view his e-mail only on the computer on which the program is installed. With the Web-based e-mail method, the user can check his e-mail from anywhere in the world on any computer with Internet facility. The disadvantage of this method is that the user has to visit his e-mail account provider's site.

FTP vs. E-Mail: E-mail supports only ASCII text. For including other file types such as images, graphics, animation, multimedia, programs, etc., in an e-mail message, they have to be rehabilitated into binary format and attached to the e-mail. On the other hand, FTP was designed to handle binary files directly as well as ASCII text. So it does not involve any encoding and decoding of the data.

Web search engine: Web search engine is a Web site that is used to retrieve the information from the public Web. Since there are thousands of sites on the Web, it is very difficult to obtain the information on a required topic or find the appropriate site. With the search engine, you can get them easily. The only thing you have to do is to open the search engine site and put the keyword you are searching for. The search engine will present a number of sites on the related keyword.

Personal Information Management (PIM): Personal Information Management is a software that contains names, addresses, and notes for fast retrieval. The major function of this software is to maintain a telephone list with automatic dialing, calendar, scheduler, and tickler. PIM allows you to note down any text in it, and provides a facility to search it by any of the words written in the text. PIM facilitates the user to manage the information on a daily basis.

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