Fundamentals of Computer Networks: History, Protocols, and Core Concepts

The article begins by introducing the evolution of computers from mainframes to personal devices and explains how computer networks have progressed from isolated " 独立模式 " to interconnected " 网络互联模式 " architectures.

It distinguishes between WAN ( WAN(Wide Area Network, 广域网) ) and LAN ( LAN(Local area Network, 局域网) ) and illustrates their typical deployment scenarios with diagrams.

Computer Network Development Timeline

Batch Processing

Early computers operated in a batch‑processing stage where jobs were queued on tape and executed sequentially, limiting access to a single user at a time.

Time‑Sharing Systems

Time‑sharing introduced the "one‑machine‑per‑user" concept ( 一人一机 ) and provided a sense of exclusive use through shared resources.

Computer Communication

As computers became more affordable, the need for inter‑computer communication grew, leading to the realization that no computer should be an information island.

Birth of Computer Networks

In the 1980s, networks capable of interconnecting heterogeneous machines emerged, followed by the 1990s explosion of email, the World Wide Web, and other services that popularized the Internet.

High‑Speed Development

Recent advances in 3G/4G/5G and the transition from telephone‑based IP to modern IP‑based networking have accelerated network growth.

Network Security

The article notes the dual nature of the Internet, highlighting threats such as viruses, data leaks, and scams, and stresses the importance of secure connections for enterprises.

Internet Protocols

It explains that a protocol is a set of rules governing communication, using everyday analogies, and then introduces major Internet protocols: HTTP, IP, TCP, UDP, FTP, DNS, SMTP, ARP, ICMP, SLIP, PPP, and others.

OSI Reference Model

The OSI model’s seven layers (Physical, Data Link, Network, Transport, Session, Presentation, Application) are described, with each layer’s responsibilities and examples.

TCP/IP Protocol Suite

The TCP/IP suite simplifies the OSI model into four layers and groups many protocols under the "TCP/IP protocol suite" umbrella.

Core Network Concepts

Transmission Modes

Networks can be connection‑oriented or connection‑less, each with distinct setup requirements.

Packet Switching

Packets ( 报文(Message) ) are divided into smaller units ( 分组(Packets) ) that traverse communication links and switches, with concepts such as store‑and‑forward, queuing delay, and packet loss explained.

Circuit Switching

Circuit switching reserves resources end‑to‑end before data transfer, contrasting with packet switching’s on‑demand approach.

Delays and Throughput

The four primary delays—processing, queuing, transmission, and propagation—combine into total nodal delay, and the relationship between traffic intensity (La/R) and queuing delay is illustrated.

Throughput is discussed in terms of instantaneous and average rates, with formulas for calculating each.

Unicast, Broadcast, Multicast, Anycast

Different communication scopes are defined: unicast (one‑to‑one), broadcast (one‑to‑all), multicast (one‑to‑many selected group), and anycast (one‑to‑any of a group).

Physical Media

The article reviews common transmission media: twisted‑pair copper, coaxial cable, optical fiber, terrestrial wireless, and satellite links, describing their characteristics and typical use cases.

Conclusion

This is the first article in a series on computer networking fundamentals, inviting readers to like, comment, and share the content.