Introduction to the Internet

What is the Internet?

• It is the world's largest computer network linking billions of users.
• The word "Internet" came from combining "interconnection" with "network".
• It is a collection of connected computers and devices for sharing resources.
• Resources include hardware, software, data, and information.

Birth of the Internet

• It started in 1969 with ARPA which is the Advanced Research Project Agency.
• The Internet was built on the concept of decentralized, equal nodes.
• The term "internet" emerged in 1982.
• In 1986 the first "free net" was created at Case Western Reserve University in USA.
• Vinton Gray Cerf is recognized as one of "the fathers of the Internet" and developed TCP/IP.

Major Components of the Internet

• Server
• IP (Internet Protocol) Address
• Browser
• Domain Name System (DNS)
• Internet Service Provider (ISP)

Server

• It is a computer program that provides a service to another computer program and its user.

Type Server

• Application Server: Provides business logic for programs, it manages applications and acts as a liaison between users, databases, and backend systems.
• Examples of application servers are Apache Tomcat, JBoss (WildFly), IBM WebSphere Application Server, Oracle WebLogic Server, and Microsoft Internet Information Services (IIS).
• Web Server: Serves HTML pages and files, it hosts websites and delivers web pages to users, processes requests from clients, and sends back the requested content.
• Examples of web servers are Apache HTTP Server, Nginx, and IIS (Internet Information Services, LiteSpeed Web Server
• Proxy Server: It acts as an intermediary between devices, and is a system or router that provides a gateway between users and the internet to help prevent cyber attacks.
• Examples of proxy servers are Apache (with mod_proxy or Traffic Server), HAProxy, IIS configured as proxy (e.g., with Application Request Routing), Nginx, Privoxy, Squid, Varnish (reverse proxy only), WinGate, Ziproxy, Tinyproxy, RabbIT and Polipo
• Mail Server: Handles incoming and outgoing email and is a computer system that manages the sending, receiving, and storage of emails working with email clients like Outlook or Gmail.
• Examples of mail servers are Microsoft Exchange Server, Postfix, Sendmail, Dovecot, Exim, MailEnable, Zimbra and Hmail Server.
• File Server manages centralized file storage and access, stores and shares files across a network, and can be a microcomputer or a computer with a large disk drive and specialized software.
• Examples are Windows File Server or Server Message Block (SMB), Linux File Server or Network File System (NFS), and cloud storage services like Dropbox, GoogleDrive, OneDrive, Azure Files, and Amazon FSx.
• Policy Server offers security and authorization, uses rules and policies to control access, manage networks, and ensure security in a variety of applications like access control, network management, and service quality.
• Microsoft's Network Policy Server (NPS), Websense Policy Server and RADIUS Server are policy servers.

How application servers work

• They provide the runtime environment for running applications.
• They process requests and data flow.
• They integrate different components of an application, such as databases, web servers, and business logic.
• They support multiple users simultaneously.

How web servers work

• A user enters a URL into their browser.
• The browser sends an HTTP request to the web server.
• The web server responds with the requested web page or an error message.

How proxy servers work

• When you request a website, your computer sends the request to the proxy server instead of directly to the website.
• The proxy server uses its own IP address when communicating with the website, concealing your actual IP address.
• The proxy server then forwards your request to the intended website
• Once the website sends back the requested data, the proxy server receives it and then forwards it back to your computer.

How a mail server works

• It uses email protocols to process incoming requests, forward messages, and deliver them to the correct recipient
• Delivers emails, reduces the chances of lost or undelivered messages
• Can try to resend messages if something goes wrong
• Informs the sender if an email doesn't have a valid recipient

How does a file server work

• A file server is connected to a network and provides a centralized location for storing files
• Users can access files and folders on the file server from connected devices
• File servers use file-sharing protocols like SMB, NFS, FTP, or HTTP to enable clients to access files
• Users can open, read, change, and delete files and folders on the file server

How policy servers work

• Receive inputs from sensors and services.
• Policy servers trigger policies, which are computer-interpreted rules that automatically execute when events occur.
• Process access control requests against a set of statements that define how resources are allocated.
• Return access control responses.

IP Address

• It is a numerical label assigned to each device, provides identity to a network device and is a unique number that identifies a device on the internet.
• 192.168.123.132: An example of an IP address in dotted-decimal format
• 168.212.226.204: An example of an IP address that is represented as a 32-bitbinary number
• 192.158.1.38: An example of an IPv4 address

Web Browser

• It is a software program that lets you access and view websites on the internet acting like a gateway that allows you to interact with the online world, and also is used to interpret HTML and other web technologies.
• Examples are Google Chrome, Safari, Firefox, Edge, Internet Explorer, Vivaldi, Tor Browser, UC Browser etc.

Domain Name System (DNS)

• It is a system for naming computers and services on the internet that translates domain names into IP addresses, which allow browsers to access websites and other internet resources.
• Examples include RSU.edu.ph, Youtube.com, Google.com, Spotify.com, Gmail.com and Redcross.org etc.

Internet Service Providers (ISPs)

• They are companies that provide internet access to users and businesses and offer a variety of services, including internet access, email, and domain registration.
• Examples are PLDT, Converge, Globe, Sky Broadband, AT&T, Google Fiber, Smart BroadBand, Dito Telecom, Sky Cable etc.

Learn about the Internet, the world's largest computer network linking billions of users. Discover its origins with ARPA in 1969 and the emergence of the term "internet" in 1982. Understand the major components such as servers, IP addresses, browsers, DNS, and ISPs.