Friday, 12 June 2020

Unit-4 : The Internet (Notes of TU BSc. 4th Year Computer Science)

 The Internet
Syllabus: Definition; Internet Services (Electronic Mail, File Transfer, Telnet, Usenet News, and WWW); Uses of the Internet; Internet Address  


Internet is a global network providing a variety of information and communication facilities, consisting of interconnected networks using standardized communication protocols. The word internet comes from a combination between “interconnection” and “network”. The network is a collection of computers and devices connected via communication channels and transmission media allow to share resources (hardware, software, data, information). Generally, nobody owns the internet. Vinton Gray Cerf (also known as Vint Cerf) is the Father of the Internet.

Internet Services
The Internet allows us to access huge amounts of information such as text, graphics, sounds, and software across the world. Some of the internet services are Electronic Mail (E-mail), File Transfer, Telnet, Usenet News, and World Wide Web ( WWW).

  1. Electronic Mail: Electronic mail (E-mail) is used to send electronic messages over the internet. It provides services that allowed complex communication interaction. It provides the following facilities:
    - composing and sending/receiving a message.
    - Storing, forwarding, deleting, replying to a message.
    -Sending a single message to more than one person.
    -Sending text, voice, graphics, and videos.
  2. File Transfer: File transfer is the process of copying or moving a file from one computer to another over a network or Internet connection. It enables sharing, transferring, or transmitting a file or a logical data object between different users and/or computers both locally and remotely.
    A file transfer can be upload or download. File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), BitTorrent, and Simple File Transfer Protocol are the most common file transfer protocols used in computer networks and online.
    There are two main types of the file transfer:
    a) Pull-Based: The file transfer request is initiated by the receiver.
    b) Push Based: The file transfer request is initiated by the sender.
    Moreover, other than network or Internet, file transfer can be performed manually by copying a file to a new folder/drive in the same computer or by copying it on a USB pen drive, CD or other portable storage devices to be transferred to another computer.
  3. Telnet: It is used to log on to a remote computer that is attached to the internet. TELNET stands for Terminal Network. It is both TCP/IP applications. It provides direct access to various services on the Internet. Some of these services are available on your host, but Telnet is especially useful when these services are not available on your host.
  4. Usenet News/Newsgroup: It offers a forum for people to discuss topics of common interest. Usenet news service enables a group of internet users to exchange their views, ideas, information on some common topics of interest. Types of newsgroup a) moderated b) non-moderated
  5. World Wide Web (WWW): Commonly known as web, most popular internet service. It is a system of interlinked hypertext documents(called web pages) contained on the internet. A webpage contains text, graphics, animations, sounds, and videos.  All of the web pages maintained by an organization or individual are called a web site.  WWW uses Hypertext Transfer Protocol (HTTP) for fetching files on the internet. A web browser is a software application used to locate and display web pages. Some popular browsers are Microsoft Internet Explorer, Mozilla Firefox, Google Chrome, etc. Web server is a computer that delivers webpages. Every webpage on the internet has an address called Uniform Resource Locator (URL). URL is an addressing scheme used by web browsers to locate documents and other resources on the WWW.

Uses of the Internet
  • Online communication
  • Software sharing
  • Exchange of views on topics of common interest
  • Posting of information of general interest
  • Product promotion
  • Feedback about products
  • Customer support service
  • Online journals and magazines
  • Education and research
  • Entertainment
  • Exploring news and last technologies
  • Software downloading


Internet address
As we know, every device attached to the internet must be identified uniquely. For this, we need to provide an address to the devices attached to the internet. There are two types of addresses on the internet.
1) IP address
The numbered address provided to computers and other devices attached to the internet to identify them uniquely. Two versions of the internet protocol (IP) are in use, a) IP version 4 and b) IP version 6. Each version defines an IP address differently.
IP addresses can also be classified as Private IP addresses or Public IP addresses. An IP address that can be accessed over the internet is called a public IP address. A private IP address is any number or address assigned to a device on a private TCP/IP Local Area Network (LAN) that is accessible only within LAN.

2) Domain Name
As IP address are difficult to remember, domain names are named addresses provided to devices attached to the network. For example, www.fb.com is an example of a domain name.
Domain Name Server (DNS) helps to resolve the hostname to an address. It uses a hierarchical (tree) naming scheme and a distributed database of IP addresses and associated names.
A domain name is a symbolic string associated with an IP address. There are several domain names available. Some of them are generic such as .com, .edu, .gov, .net, etc. and some are country-level such as .np, .au, .in, .us, etc.



Some more Terms and Terminologies:

Information Retrieval Service: It involves browsing and information retrieval and provides customers the ability to find, view, download, and process information.

File Transfer Protocol (FTP): File Transfer Protocol is used to transfer files between computers over the network or the internet. It is commonly used to download a file from a server or to upload a file to a server by using the internet. FTP is an application protocol that uses the internet TCP/IP protocols. It includes many commands but only a few are used to retrieve files.

Protocol: Protocol is a set of guidelines or rules. A communication protocol is a formal description of message formats and the rules for exchanging those messages. A format that agreed to transfer data between two devices. Examples:
  1. Hypertext Transfer Protocol (HTTP)
  2. Internet Protocol (IP)
  3. Simple Mail Transfer Protocol (SMTP)
  4. Transmission Control Protocol (TCP)

Web Page: It is a document or resource of information that is suitable for the WWW and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML format and provides navigation to other webpages via hypertext links. It can contain texts, graphics, audio, video, and has built-in connections or links to other web documents.

Internet Protocol Address (IP address) is a 32 bits unique address that computing devices use to identify itself and communicate with other devices in the Internet Protocol network. There are 2 types of IP addresses. They are:
  1. Static IP address is an IP address that can be manually configured for a device and it will never change.
  2. Dynamic IP address is an IP address assigned by DHCP servers which can be changed automatically at any time.
Here is the Downloadable PDF of Unit-4 : The Internet


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