【Information I】Information and Communication Networks and Data Utilization: The Perfect Master Guide
Hello everyone! In this chapter, we are going to learn about how the internet we use every day works and how we can make the most of vast amounts of data. Terms like "protocol" and "IP address" might sound difficult because they are technical, but if we compare them to things we see in our daily lives, they are actually quite simple. It might feel a bit tough at first, but you'll be just fine if you take it one step at a time!
1. Network Basics: How We Connect
LAN and WAN
Networks are broadly divided into two types based on their scale:
● LAN (Local Area Network): A network covering a limited, small area, like inside your school or home.
● WAN (Wide Area Network): A wide-area network that connects separate LANs using communication carriers' lines.
Analogy: Think of a LAN as a "hallway inside your house," and a WAN as the "roads connecting your house to the outside world."
Protocols (Communication Rules)
A "common set of rules" that allows computers to talk to each other is called a protocol. If one person spoke Japanese and the other spoke English, a conversation wouldn't work, right? It's the same for computers—they need to follow the same rules.
● The most important protocol for the internet is TCP/IP.
【Key Point】The TCP/IP 4-Layer Model
The communication process is divided into four layers, each with a specific role (let's compare this to the process of sending a letter):
1. Application Layer: Specific services like email or web browsing (writing the letter).
2. Transport Layer: Ensures data reliability. The representative protocol is TCP (confirming that the letter arrived).
3. Internet Layer: Delivers data to the destination. The representative protocol is IP (looking at the address and transporting it).
4. Network Interface Layer: Physical communication. This involves LAN cables or Wi-Fi (the act of physically carrying the letter).
【Summary】
Networks are categorized as LAN or WAN depending on their size, and it is precisely because of protocols (common rules) that computers all over the world can communicate with each other.
2. Internet Addresses: IP Addresses and DNS
IP Addresses
An IP address is a number used to identify a computer on a network. It acts like an address on the internet.
● IPv4: Can create about 4.3 billion addresses (\( 2^{32} \)). It is expressed as four numbers, such as "192.168.0.1".
● IPv6: Introduced because IPv4 addresses were running out. It can create almost an infinite number of addresses (\( 2^{128} \)).
DNS (Domain Name System)
IP addresses (long strings of numbers) are hard for humans to remember, right? DNS is a system that translates human-friendly names (domain names) like "google.com" into IP addresses.
Example: It’s just like looking up a "phone number" from a "name" in a phone book.
【Trivia】
The HTTP found in website addresses (URLs) like "https://" is also a protocol. It’s simply the set of rules for exchanging web data!
3. Protecting Information: Security and Encryption
The internet is convenient, but there are risks of eavesdropping or tampering with information. Encryption is what prevents this.
Symmetric Key Encryption vs. Public Key Encryption
● Symmetric Key Encryption: Uses the same key for both encryption and decryption (returning it to the original). It is fast, but there is a risk that the key could be stolen while being sent to the other party.
● Public Key Encryption: Data is encrypted using a public key that anyone can use, and decrypted using a private key that only you possess. It’s safer because you don't have to share the key, but it takes more time to process.
Hybrid Encryption
Modern web communications (like HTTPS) combine both methods to achieve "secure and fast" communication.
Digital Signatures and Authentication
● Digital Signature: Proves that the sender is who they say they are and that the data has not been tampered with.
● Digital Certificate: A "digital ID" issued by a trusted third-party organization (Certificate Authority).
【Common Mistake】
Thinking that "data encrypted with a public key can be decrypted with the same public key" is wrong! Data encrypted with a public key can only be decrypted with its paired private key. This is a point often tested in exams!
4. Data Utilization and Society
In modern society, we analyze the vast amounts of collected data (Big Data) to make our lives more convenient.
Databases
A collection of large amounts of data organized to be easily used is called a database. Specifically, Relational Databases (RDB), which manage data in a table format, are the most common.
Data Formats
● CSV: A simple text format where items are separated by commas (,). It can be opened by many different programs.
● JSON: A format that is easy to handle with programming. It is frequently used for web services.
Information Design and Visualization
To communicate analysis results clearly, it is important to use graphs and diagrams (visualization). Choose the right tool for your purpose: bar graphs (for comparisons), line graphs (for changes over time), or pie charts (for proportions).
【Point: Data Credibility】
When looking at data, you must check "when, by whom, and for what purpose it was collected" and be careful about potential biases (Media Literacy).
Final Thoughts
In the field of information and communication networks, your understanding will deepen significantly once you start paying attention to how terms are connected.
Try to imagine the behind-the-scenes of your daily habit of "viewing a site in a browser": DNS looks up the address, TCP/IP carries the data, and HTTPS encrypts it...
These "connections between mechanisms" are often tested in national exams. Start by firmly grasping the basic terms. I'm rooting for you!