Unveiling the Internet: How Networks, Protocols, and Layers Power Our Digital World

1. What makes up a network?

The Internet is a massive graph of nodes (computers, hubs, switches, routers, etc.) connected by links (copper, fiber, wireless). Devices that connect to the network are called hosts or end systems , ranging from PCs and smartphones to refrigerators and traffic lights. By 2020, over 200 billion devices were online.

These nodes form local networks (home, corporate, mobile) that interconnect to become the global Internet.

2. Why can we enjoy Internet services?

Since 1993, government agencies stopped operating the Internet, and countless Internet Service Providers (ISPs) emerged (e.g., China Telecom, Unicom, Mobile). ISPs obtain blocks of IP addresses from regional registries and either build their own backbones or lease existing infrastructure. Users pay ISPs for IP usage to gain connectivity.

ISPs are organized hierarchically: national backbone ISPs, regional ISPs, and local ISPs. Multiple ISPs interconnect at Internet Exchange Points (IXPs) , allowing traffic to bypass expensive backbone links, reduce latency, and improve redundancy.

Content providers (ICP) such as BAT connect to ISPs via BGP (Border Gateway Protocol) to exchange routing information and deliver content efficiently.

3. How do computers in different countries understand each other?

Communication relies on standardized protocols . Protocols define message formats, sequencing, and actions for sending and receiving data. Hardware uses protocols to control bit streams on the physical medium, while software uses higher‑level protocols (TCP, UDP, HTTP, etc.) to ensure reliable communication.

Protocol : a set of rules that specify the format and order of messages exchanged between two or more communication entities.

Hardware uses link‑layer protocols to manage bit streams.

End systems use transport‑layer protocols to control packet flow.

Routers use network‑layer protocols to determine paths.

4. Why does my 100 M broadband rarely reach 100 M/s?

Broadband advertised as 100 Mbit/s translates to about 12 MB/s (1 byte = 8 bits). Real‑world speeds are lower due to shared bandwidth, protocol overhead, and network congestion.

In a shared‑bandwidth scenario, many users compete for the same upstream pipe, causing each user’s throughput to drop proportionally.

Upgrading to fiber or using dedicated lines (e.g., ADSL, LAN) can mitigate these limits.

Buy a Wi‑Fi amplifier to boost signal strength.

Run Ethernet cables to distant rooms and add a secondary router as a wireless access point.

5. Why does my computer get attacked?

The Internet connects billions of devices, making it a target for attackers seeking data, credentials, or disruption. Common attack vectors include viruses, worms, trojans, buffer overflows, DoS/DDoS, network protocol exploits, and credential theft.

Key security principles are:

Confidentiality : protect data from eavesdropping.

Endpoint authentication : ensure you are communicating with the intended party.

Integrity : prevent unauthorized modification of messages.

Basic defenses: use strong, unique passwords; enable firewalls; keep software updated; avoid opening suspicious attachments; prefer HTTPS (TLS) for encrypted transport.

6. Summary

This article answered nine fundamental questions about the Internet, covering network composition, ISP and IXP roles, routing and protocols, the OSI layered model, bandwidth sharing, and common security threats.

References

Thoughts on IXP – https://coding3min.com/go/1241/

ICP – https://coding3min.com/go/1240/

Multi‑line BGP – https://www.zhihu.com/question/266549604

BGP Wikipedia – https://coding3min.com/go/1239/

IDC – https://coding3min.com/go/1235/

SDN and IXP – https://www.cnblogs.com/pullself/p/10806054.html

Network Protocol – https://coding3min.com/go/1236/

Peer‑to‑Peer – https://coding3min.com/go/1237/

Routing Protocol – https://coding3min.com/go/1238/

Computer Networks notes – https://www.pianshen.com/article/4615873688/

Computer Networks – Top‑Down Approach (7th ed.)

Computer Networks – 6th ed.

ADSL vs LAN – https://coding3min.com/go/1245/

Shared bandwidth – https://coding3min.com/go/1242/

Switch vs Router – https://coding3min.com/go/1243/

Why switches work at Data Link layer – https://coding3min.com/go/1244/

Presentation & Session layers – https://www.zhihu.com/question/58798786

OSI model layers – https://blog.csdn.net/weixin_41738417/article/details/92796077

Network security attack analysis – https://zhuanlan.zhihu.com/p/50235996