Introduction to Internet

Introduction to the internet

IP Address and Domain Name System (DNS):

A computer network is a group of interconnected computers. Including the hardware and software used to communicate and provide users with accessibility to shared resources or a computer network is created when a several computers and terminals devices are connected together by data communication system.

Internet:

The internet is a network of network, linking computers to computers sharing the TCP/IP protocols. It consists of millions of smaller domestic, academic, business, and government networks.

The Internet is a global wide area network that connects computer systems across the world. It includes several high-bandwidth data lines that comprise the Internet "backbone". These lines are connected to major Internet hubs that distribute data to other locations, such as web servers and ISPs.

In order to connect to the Internet, you must have access to an Internet service provider (ISP), which acts the middleman between you and the Internet. Most ISPs offer broadband* Internet access via a cable, DSL*, or fiber connection. When you connect to the Internet using a public Wi-Fi signal, the Wi-Fi router is still connected to an ISP that provides Internet access. Even cellular data towers must connect to an Internet service provider to provide connected devices with access to the Internet.

*Broadband: This refers to high-speed data transmission in which a single cable can carry a large amount of data at once.

*DSL: Stands for "Digital Subscriber Line." DSL is a communications medium used to transfer digital signals over standard telephone lines. Along with cable Internet, DSL is one of the most popular ways ISPs provide broadband Internet access.

The Internet provides different online services. Some examples include:

Web: a collection of billions of webpages that you can view with a web browser

Email: the most common method of sending and receiving messages online

Social media: websites and apps that allow people to share comments, photos, and videos

Online gaming: games that allow people to play with and against each other over the Internet

Software updates: operating system and application updates can typically downloaded from the Internet

Intranet:

Intranet is a network inside an organization that uses internet technologies to provide an internet-like environment within the enterprise for the purpose of information sharing, communications, collaborations, and support of business process.

Advantages of Intranet:

1. Corporate information can stored centrally and accessed at any time from different location.
2. Resources can share and use same resources form different work place.
3. Accurate and consistent information can access by staffs which helps to enhance the level of customer services.
4. Data and information can store centrally and access by any place and printout the required documents which reduce the paperwork.

Disadvantage of Intranet:

1. It can create the fear of information management and control if data is in large volume.
2. Unauthorized access, denied of access, can make complexity of data security.
3. Information overload leads to lowers the productivity.

Extranet:

Extranets are networks that use internet technology to share the data and resources outside the organization. It interconnects the intranet of a business organization with the intranets of other business organizations, customers, suppliers.

Advantage of Extranet:

1. More integrated supply chains through the use of online ordering, order tracking, and inventory management.
2. It reduces costs by making documents available online to partners and customers.
3. It increases the effectiveness of collaboration with business partners.
4. Improve customer service and it leads customer satisfaction.
5. Extranet allows remote access of business information its leads work flexibility to the workers.

Disadvantage of Extranet:

1. It can be expensive to implement and maintain within an organization.
2. Information security problem can occurs when hosting valuable business information to public domain.

IP Address:

An IP address (internet protocol address) is a numerical representation that uniquely identifies a specific interface on the network.

Addresses in IPv4 are 32-bits long. This allows for a maximum of 4,294,967,296 (2³²) unique addresses. Addresses in IPv6 are 128-bits, which allow for 3.4 x 10³⁸ (2¹²⁸) unique addresses.

The total usable address pool of both versions is reduced by various reserved addresses and other considerations.

IP addresses are binary numbers but are typically expressed in decimal form (IPv4) or hexadecimal form (IPv6) to make reading and using them easier for humans. In binary notation, IP address if displayed as 32-bits and these 32-bits are represented in 4-octed (8-bites) address or 4-bytes address.

Example: 11000000.10101000.00000001.00000010

To make the IP address more compact and easier to read, IP address are usually written in decimal form with separating each bytes by a dot. Each number in dotted-decimal notation is between 0 and 255.

Example: 192.168.1.2

Domain Name System (DNS):

Domain Name System is an internet service that translates domain names into IP addresses. Simply the DNS is a TCP/IP application service that converts user-friendly names into IP address. Because domain name is alphabetic, they are easier to remember. When you enter domain name in the browser url then DNS server maps this domain to the corresponding IP address and reached to the correct destination.

For example: the domain name www.example.com might be translated into 192.168.1.10

The last three character of the DNS address indicate the type of the domain.

• Commercial organization as .com
• Educational institutions as .edu
• Governmental organization as .gov
• Network service provider as .net
• Organizations as .org

There are some international domains which assign for different countries as

• Nepal as .np
• Australia as .au
• France as .fr
• Japan as .jp
• United States as .us
• China as .cn
• United Kingdom as .uk

Following figure demonstrates the hierarchy of DNS.

Fig: Hierarchy of DNS

Client-Server Architecture:

Client/server architecture is a computing model in which the server hosts, delivers and manages most of the resources and services to be consumed by the client. This type of architecture has one or more client computers connected to a central server over a network or internet connection. This system shares computing resources.

Client/server architecture is also known as a networking computing model or client/server network because all the requests and services are delivered over a network.

Client/server architecture works when the client computer sends a resource or process request to the server over the network connection, which is then processed and delivered to the client. A server computer can manage several clients simultaneously, whereas one client can be connected to several servers at a time, each providing a different set of services. In its simplest form, the internet is also based on client/server architecture where web servers serve many simultaneous users with website data.

Fig: Client-Server Architecture

HTML:

It stands for "Hypertext Markup Language". HTML is the language used to create webpages. "Hypertext" refers to the hyperlinks that an HTML page may contain. "Markup language" refers to the way tags are used to define the page layout and elements within the page.

The example below is HTML used to define a basic webpage with a title and a single paragraph text.

<!doctype html>

 Title of Webpage

This is an example of a paragraph in HTML. 

The first line defines what type of contents the document contains. "<!doctype html>" means the page is written in HTML5. Properly formatted HTML pages should include,, andtags, which are all included in the example above. The page title, metadata (Metadata describes other data. It provides information about a certain item's content), and links to referenced files are placed between thetags. The actual contents of the page go between thetags.

The web has gone through many changes over the past few decades, but HTML has always been the fundamental language used to develop webpages. Interestingly, while websites have become more advanced and interactive, HTML has actually gotten simpler. If you compare the source of an HTML5 page with a similar page written in HTML 4.01 or XHTML (Extensible Hypertext Markup Language) 1.0, the HTML5 page would probably contain less code. This is because modern HTML relies on cascading style sheets or JavaScript to format nearly all the elements within a page.

Many dynamic websites generate webpages on-the-fly, using a server-side scripting language like PHP (Hypertext Preprocessor) or ASP (Application Service Provider). However, even dynamic pages must be formatted using HTML. Therefore, scripting languages often generate the HTML that is sent to your web browser.

Some of the key advantages of learning HTML:

Create Web site - You can create a website or customize an existing web template if you know HTML well.

Become a web designer - If you want to start a career as a professional web designer, HTML and CSS designing is a must skill.

Understand web - If you want to optimize your website, to boost its speed and performance, it is good to know HTML to yield best results.

Learn other languages - Once you understand the basic of HTML then other related technologies like JavaScript, php, or angular are become easier to understand.

Hyper Text Transfer Protocol (HTTP):

It stands for "Hypertext Transfer Protocol". HTTP is the protocol used to transfer data over the web. It is part of the Internet protocol suite and defines commands and services used for transmitting webpage data.

HTTP uses a Client-Server model. A client, for example, may be a home computer, laptop, or mobile device. The HTTP server is typically a web host running web server software, such as Apache or IIS (Internet Information Services). When you access a website, your browser sends a request to the corresponding web server and it responds with an HTTP status code. If the URL is valid and the connection is granted, the server will send your browser the webpage and related files.

Some common HTTP status codes include:

200 - Successful request (the webpage exists)

400 – Bad request (invalid request message parameters)

401 - Unauthorized request (authorization required)

403 - Forbidden (access is not allowed to the page or directory)

404 – Request not found.

500 - Internal server error (often caused by an incorrect server configuration)

HTTP also defines commands such as GET and POST, which are used to handle form submissions on websites. The CONNECT command is used to facilitate a secure connection that is encrypted using SSL (Secure Sockets Layer). Encrypted HTTP connections take place over HTTPS (Hyper Text Transport Protocol Secure), an extension of HTTP designed for secure data transmissions.

URLs that begin with "http://" are accessed over the standard hypertext transfer protocol and use port 80 by default. URLs that start with "https://" are accessed over a secure HTTPS connection and often use port 443.

Email:

Email, short for "electronic mail," is one of the most widely used features of the Internet, along with the web. It allows you to send and receive messages to and from anyone with an email address, anywhere in the world.

Email uses multiple protocols within the TCP/IP suite. For example, SMTP (Simple Mail Transfer Protocol) is used to send messages, while the POP (Post Office Protocol) or IMAP (Internet Message Access Protocol) protocols are used to retrieve and filter messages from a mail server. When you configure an email account, you must define your email address, password, and the mail servers used to send and receive messages. Fortunately, most webmail services configure your account automatically, so you only need to enter your email address and password. However, if you use an email client like Microsoft Outlook or Apple Mail, you may need to manually configure each account. Besides the email address and password, you may also have to enter the incoming and outgoing mail servers and enter the correct port numbers for each one.

The original email standard only supported plain text messages. Eventually, email evolved to support rich text which supports text formatting, such as bold, italics, and underlining, as well as different fonts, font sizes, and colored text. Rich text documents can also include page formatting options, such as custom page margins, line spacing, and tab widths. Today, email supports HTML, which allows emails to be formatted the same way as websites. HTML email messages can include images, links, and CSS layouts. You can also send files or "email attachments" along with messages. Most mail servers allow you to send multiple attachments with each message, but they limit the total size. In the early days of email, attachments were typically limited to one megabyte, but now many mail servers support email attachments that are 20 megabytes in size or more.

Email was originally written "e-mail," but is now more commonly written as "email" without the dash.

Email Netiquette

Netiquette is short for "Internet etiquette". Just like etiquette is a code of polite behavior in society, netiquette is a code of good behavior on the Internet. This includes several aspects of the Internet, such as email, social media, online chat, web forums, website comments, multiplayer gaming, and other types of online communication.

When composing an email message, it is important to use good netiquette. For example, you should always include a subject that summarizes the topic of the email. It is also helpful to begin each message with the recipient's name and end the message with your name or "signature." A typical signature includes your name, email address, and/or website URL. A professional signature may include your company name and title as well. Most email programs allow you to save multiple signatures, which you can insert at the bottom of an email.

If you want to send an email to multiple recipients, you can simply add each email address to the "To" field. However, if the email is primarily intended for one person, you should place the additional addresses in the "CC" (carbon copy) field.

If you are sending an email to multiple people that don't know each other, it is best to use the "Bcc" (blind carbon copy) field. This hides the email addresses of each recipient, which helps prevent spam.

FTP:

It stands for "File Transfer Protocol". FTP is a protocol designed for transferring files over the Internet. Files stored on an FTP server can be accessed using an FTP client, such as a web browser, FTP software program, or a command line interface.

An FTP server can be configured to enable different types of access. For example, an "anonymous FTP" configuration allows anyone to connect to the server. However, anonymous users may only be allowed to view certain directories and may not be able to upload files. If anonymous FTP access is disabled, users are required to log in in order to view and download files.

The standard FTP protocol is not encrypted, meaning it is vulnerable to packet sniffers (sniffer is a program that monitors and analyzes network traffic, detecting bottlenecks and problems) and other types of snooping (snooping is trying to find someone’s confidential information) attacks. Therefore, the FTPS and SFTP protocols were developed to provide secure FTP connections. FTPS (FTP with SSL security) provides SSL (Secure Socket Layer) encryption for all FTP communication. SFTP (SSH File Transfer Protocol) is a secure version of FTP that uses SSH (Secure Shell is the method of securely communicate with other computer) to encrypt all data transfers.

To you connect to an FTP server, you first need to enter the server name and port number. The server name often starts with "ftp," such as "ftp.example.com." The standard port number for FTP is 21, while SFTP uses port 22 (SSH). If you connect via FTPS, you might be required to enter a custom port number, but the most common one is 990. In order to access an SFTP or FTPS server, you will also need to enter a username and password.

WWW:

It stands for "World Wide Web." It is important to know that this is not a synonym for the Internet. The World Wide Web, or just "the Web," as ordinary people call it, is a subset of the Internet. The Web consists of pages that can be accessed using a Web browser.

The Internet is the actual network of networks where all the information resides. Things like Telnet, FTP, Internet gaming, Internet Relay Chat (IRC), and e-mail are all part of the Internet, but are not part of the World Wide Web.

The Hyper-Text Transfer Protocol (HTTP) is the method used to transfer Web pages to your computer. With hypertext, a word or phrase can contain a link to another Web site. All Web pages are written in the hyper-text markup language (HTML), which works in conjunction with HTTP.

TELNET (Remote Login):

This is a program that allows you log in to a Unix computer via a text-based interface. If you have an account on a Telnet server, you can access certain resources on the system such your home directory, your e-mail account, FTP files, etc. The downside of Telnet is that, to use it, you need to use Unix commands, which can be a challenge.

Static and Dynamic Webpage:

Static Webpages contains fixed content. Each page is coded in HTML and displays the same information to every visitor. Static sites are the most basic type of website and are the easiest to create. Unlike dynamic webpages, they do not require any Web programming or database design. A static site can be built by simply creating a few HTML pages and publishing them to a Web server.

Since static Web pages contain fixed code, the content of each page does not change unless it is manually updated by the webmaster. This works well for small websites, but it can make large sites with hundreds or thousands of pages difficult to maintain.

Therefore, larger websites typically use dynamic pages, which can be updated by simply modifying a database record. Static sites that contain a lot of pages are often designed using templates. This makes it possible to update several pages at once, and also helps provide a consistent layout throughout the site.

Dynamic webpages are generated in real-time. These pages include Web scripting code, such as PHP (Hypertext Preprocessor) or ASP (application service provider). When a dynamic page is accessed, the code within the page is parsed on the Web server and the resulting HTML is sent to the client's Web browser.

Most large websites are dynamic, since they are easier to maintain than static websites. This is because static pages each contain unique content, meaning they must be manually opened, edited, and published whenever a change is made.

Dynamic pages, on the other hand, access information from a database. Therefore, to alter the content of a dynamic page, the webmaster may only need to update a database record. This is especially helpful for large sites that contain hundreds or thousands of pages. It also makes it possible for multiple users to update the content of a website without editing the layout of the pages.

Dynamic websites that access information from a database are also called database-driven websites.

Search Engines:

Google, Excite, Lycos, AltaVista, Infoseek, and Yahoo are all search engines. They index millions of sites on the Web, so that Web surfers like you and me can easily find Web sites with the information we want. By creating indexes, or large databases of Web sites (based on titles, keywords, and the text in the pages), search engines can locate relevant Web sites when users enter search terms or phrases.

When you are looking for something using a search engine, it is a good idea to use words like AND, OR, and NOT to specify your search. Using these Boolean operators, you can usually get a list of more relevant sites.