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Computer networking is a very large subject, but before we start diving into network security, we need to understand some basic concepts and principles. This chapter will cover the basic concepts of computer networks, including types of networks, how networks work, and some commonly used network technologies and protocols.
1. What is a computer network?
A computer network is a system of two or more computers connected together by a communication path (which can be wired, such as fiber optics, or wireless, such as radio waves) to share resources and information. At the most basic level, computer networks support a variety of applications that we use in our daily lives, such as email, social media, online shopping, and Internet telephony.
2. Types of computer networks
Computer networks can be divided into several types based on the size and scope of the network:
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Personal Area Network (PAN) : This is the smallest network that usually includes a person's personal devices, such as computers, cell phones, and printers. Bluetooth devices are an example of PAN.
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Local Area Network (LAN) : A local area network is a network of devices within a small geographical area (such as an office, school, or home). In a LAN, devices are usually connected via Ethernet or Wi-Fi.
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Wide Area Network (WAN) : A wide area network covers a larger geographical area and can span cities, countries, and even continents. The Internet is a huge WAN.
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Virtual Private Network (VPN) : A VPN is a private network created over a public network, such as the Internet. It uses encryption technology to ensure the secure transmission of data.
3. Working principle of computer network
Computer networks work based on rules called "network protocols." Network protocols define how devices on a network communicate and exchange data. There are many different network protocols, but the most common is TCP/IP.
TCP/IP is a protocol suite that includes several different protocols, each responsible for a different part of network communication. The name TCP/IP comes from two main protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP).
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Internet Protocol (IP) : The IP protocol is responsible for sending data packets from source address to destination address. Every device has a unique IP address on the network, just like every house has a unique mailing address.
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Transmission Control Protocol (TCP) : The TCP protocol manages the transmission of data packets. It ensures that packets arrive in the correct order and checks for any missing or corrupted packets.
For example, when you enter a URL (such as www.google.com) into your browser and press the Enter key, here's what happens:
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Your computer (client) sends a request to Google's servers. This request is sent via TCP/IP protocol.
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Google's servers receive your request and send a response back. The response contains the content of the web page you requested.
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Your computer receives the response and displays the content of the web page through your browser.
The process is so fast and seamless that we often don't realize how many complex interactions are happening in the background.
4. Common network technologies and protocols
In addition to TCP/IP, there are many other network technologies and protocols that support a variety of different network services and applications. Here are some of the most common ones:
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HTTP and HTTPS : These two protocols are used to send and receive web content on the Internet. HTTPS is a secure version of HTTP that uses encryption technology (such as SSL/TLS) to protect data transmission.
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DNS : The Domain Name System (DNS) is the “phone book” of the Internet. It converts domain names that are easy for people to remember (such as www.google.com) into IP addresses that machines can understand (such as 192.0.2.1).
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FTP : File Transfer Protocol (FTP) is used to transfer files over the network. It allows users to download files from the server or upload files to the server.
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SMTP, IMAP, and POP : These protocols are used to send and receive email. SMTP is used for sending mail, while IMAP and POP are used for receiving mail.
5. Conclusion
Computer networks are the basis of our daily lives and work. By understanding the basic concepts and principles of computer networks, we can better understand how networks work and how to protect our network security.
Before we dive into the topic of network security, I recommend that you take some time to familiarize yourself with these basic network concepts. Try to imagine how your data flows across a network, and how various network technologies and protocols make this possible. This will lay a solid foundation for our subsequent study.
