Chapter 01 Getting Started with Computer Networks
01-1 Why You Need to Know Computer Networks
Network of networks, the Internet
Why Developers Need to Know Computer Networks
- When utilizing network knowledge in program creation work
- When utilizing network knowledge in the task of maintaining programs
Key points summarized in two keywords
Verification problem

01-2 A Macro-View of the Network
Basic structure of the network
- Host
- Network equipment
- Communication media
- message
Network classification by scope
- LAN
- WAN
Network classification by message exchange method
- Circuit switching method
- Packet switching method
[Learn more] Transmission method based on address and destination type
Key points summarized in six keywords
Verification problem

01-3 A Microscopic Look at Networks
Protocol
Network Reference Model
- OSI model
- TCP/IP model
Encapsulation and decapsulation
- Encapsulation
- Reverse encapsulation
PDU
[Learn more] OSI 7-layer and TCP/IP 4-layer don't actually do anything.
[Learn More] Traffic and Network Performance Metrics
- Processing rate
- Bandwidth
- Packet loss
Key points summarized in 7 keywords
Verification problem

Chapter 02 Physical Layer and Data Link Layer
02-1 Ethernet
Ethernet standard
Communication media notation format
Types of communication media
Ethernet frame
- Preamble
- Destination MAC address and source MAC address
- Type/length
- Data
- FCS
[Learn more] Token Ring
Key points summarized in four keywords
Verification problem

02-2 NIC and Cable
NIC
- Appearance of NIC
- The role of NIC
twisted pair cable
- Appearance of twisted pair cable
- Classification of twisted pair cables according to shielding
- Classification of twisted pair cables by category
fiber optic cable
- Appearance of fiber optic cables
- Single-mode fiber optic cable
- Multimode fiber optic cable
Key points summarized in 5 keywords
Key points summarized in a table
Verification problem

02-3 Hub
Physical layer without address concept
Herb
- Features of herbs
- Collision Domain
CSMA/CD
Key points summarized in 5 keywords
Verification problem

02-4 Switch
switch
- Switch Features
MAC address learning
VLAN
- Port-based VLAN
- MAC-based VLAN
Key points summarized in four keywords
Verification problem

Chapter 03 Network Layer
03-1 Network Layer Beyond LAN
Limitations of the data link layer
Internet Protocol
- IP address format
- IP functions
- IPv4
- IPv6
ARP
[Learn More] How to Avoid IP Fragmentation
Key points summarized in 7 keywords
Verification problem

03-2 IP address
Network address and host address
Classful addressing system
Classless addressing scheme
- Subnet mask
- Subnetting: bitwise AND operation
- Subnet mask notation: CIDR notation
Public IP address and private IP address
- Public IP address
- Private IP addresses and NAT
Static IP addresses and dynamic IP addresses
- Static allocation
- Dynamic allocation and DHCP
[Learn more] Reservation Address: 0.0.0.0 vs. 127.0.0.1
Key points summarized in 9 keywords
Verification problem

03-3 Routing
router
Routing table
Static Routing and Dynamic Routing
- Static routing
- Dynamic routing
routing protocol
- IGP: RIP and OSPF
- EGP: BGP
Key points summarized in 5 keywords
Verification problem

Chapter 04 Transport Layer
04-1 Transport Layer Overview: IP Limitations and Ports
Unreliable and connectionless communication
Transport layer that complements the limitations of IP
Port, a bridge connecting to the application layer
- Definition of port
- Classification of ports
Port-based NAT
- NAT translation table
- NAPT
[Learn more] Port Forwarding
[Learn more] ICMP
Key points summarized in six keywords
Verification problem

04-2 TCP and UDP
TCP communication stages and segment structure
- Control bits
- Sequence number and confirmation response number
TCP connection establishment and termination
- Connection establishment: Three-way handshake
- Connection terminated
TCP status
- Connection not established
- Connection establishment status
- Connection terminated
UDP datagram structure
Key points summarized in 9 keywords
Verification problem

04-3 TCP Error, Flow, and Congestion Control
Error Control: Retransmission Techniques
- Error detection and retransmission
- ARQ: Retransmission technique
- Stop-and-Wait ARQ
- Go-Back-N ARQ
- Selective Repeat ARQ
Flow Control: Sliding Window
congestion control
[Learn More] ECN: Explicit Congestion Notification
Key points summarized in six keywords
Verification problem

Chapter 05 Application Layer
05-1 DNS and Resources
Domain name and name server
Hierarchical name server
URI that identifies the resource
- URL
- URN
[Learn more] DNS record types
Key points summarized in 7 keywords
Verification problem

05-2 HTTP
Characteristics of HTTP
- Request-response based protocol
- Media independent protocol
- Stateless protocol
- Persistent Connection Protocol
HTTP message structure
HTTP method
- GET - Please bring it to me
- HEAD - Please bring me only the header
- POST - Please process
- PUT - Please overwrite
- PATCH - Please make some corrections
- DELETE - Please delete it
HTTP status code
- 200s: Success status code
- 300s: Redirection status code
- 400s: Client error status code
- 500s: Server error status code
[Learn More] The Evolution of HTTP: From HTTP/0.9 to HTTP/3.0
Key points summarized in four keywords
Verification problem

05-3 HTTP Headers and HTTP-Based Technologies
HTTP header
- HTTP headers used in requests
- HTTP headers used in response
- HTTP headers used in both requests and responses
Cash
cookie
Content negotiation and expression
Key points summarized in four keywords
Verification problem

Chapter 06 Network Review through Practice
06-1 Wireshark Installation and Usage
Installing Wireshark
- Windows
- macOS
How to use Wireshark
- Packet capture
- Wireshark screen configuration
- Packet filtering
- Saving and opening capture files
Key points summarized in two keywords
Verification problem

06-2 Protocol Analysis with Wireshark
IP Analysis
- IPv4 fragmentation + ICMP
- IPv6 fragmentation + UDP
TCP Analysis
- TCP connection establishment
- TCP connection termination
- TCP retransmission
HTTP Analysis
Key points summarized in 5 keywords
Verification problem

Chapter 07 Network Deepening
07-1 Technology for Stability
Availability
Duplication
load balancing
[Learn more] Forward and reverse proxies
Key points summarized in four keywords
Verification problem

07-2 Technology for Safety
Passwords and Certificates
- Symmetric key encryption and public key encryption
- Certificates and digital signatures
HTTPS: SSL and TLS
Key points summarized in 8 keywords
Verification problem

07-3 Wireless Network
Radio waves and frequencies
Wi-Fi and 802.11
AP and service set
Key points summarized in 9 keywords
Verification problem

Answer and explanation
Search

When you want to properly learn network structure and principles
When you want to gain the network knowledge required by developers
When you want to easily get started with the network on your own

》 One, a solid learning design that systematically repeats following the '7-step structure tailored for beginners'!
This book is structured to help you naturally memorize the core network structure and principles by repeatedly learning them in seven steps.
Through “Key Keywords” and “Before You Begin,” you can learn the representative concepts and key learning content to be learned in each section in advance, and through “Speech Bubbles,” “Diagrams,” and “Learn More,” you can learn the concepts repeatedly and in-depth.
Finally, we will review what you have learned through the “Key Keywords” and “Confirmation Questions” at the end of each section and help you properly understand unfamiliar terms that can be a learning obstacle for beginners.

》 Two, learning to remember and understand the network structure and operating principles by following them with your eyes!
Networking is not something you learn by installing something or writing code, by its theoretical nature.
Learning about complex theories can easily feel boring or difficult, but this book presents the principles of network operation with step-by-step diagrams and analogies, allowing readers to visually grasp and mentally understand the concepts.
Also, in the final advanced chapter, you can practice using the program with the author, so don't miss it and give it a try.

》 3. Video lectures and a learning site to help you learn alone or together, and a network to communicate with authors.
For readers who still find it difficult to understand through books alone, we provide direct lecture videos by the author.
Additionally, if you have any questions while studying, you can ask the author questions at any time through the learning site.
Through the author's answers, you can learn about what you don't know and understand what you already know more clearly.
We also run a self-study group for readers who want to study alone but lack confidence.
With the Honkong Study Group, you can complete the course without giving up.
▶ Learning site: https://hongong.hanbit.co.kr
Author's GitHub: https://github.com/kangtegong/self-learning-cs2

》 Net, [Honey Glossary] provided that can be viewed easily anytime, anywhere!
We provide a [Honkong Terminology Note] that organizes only the key concepts and terms that you must remember.
Unfamiliar terminology is a learning obstacle for beginners.
Repetitive learning is important to understand and become familiar with unfamiliar terms.
"The Self-Study Network" highlights key words to be learned in each section, reiterates them using keyword emphasis and speech bubble elements, and finally organizes them into a glossary of terms to help you review them repeatedly until the very end.
Whenever you have trouble remembering a term or concept, feel free to open the [Honkong Terminology Note].
Go ahead and add your own terms to complete your own glossary.

Who is this book for?
》 I want to become a web developer, but I am a non-major with no knowledge of networking.
》 Beginner programming user who is confused by network terminology
》 Undergraduate students who have difficulty following network class content
》 A junior developer who lacks basic network knowledge while developing a web