Protocols and the TCP/IP model
| English | Chinese | Pinyin |
|---|---|---|
| protocol | 协议 | xié yì |
| TCP | 传输控制协议 | chuán shū kòng zhì xié yì |
| layering | 分层 | fēn céng |
| UDP | 用户数据报协议 | yòng hù shù jù bào xié yì |
| connection-oriented | 面向连接 | miàn xiàng lián jiē |
| connectionless | 无连接 | wú lián jiē |
Rules for talking
- A protocol 协议 is a set of rules for how devices communicate — both ends must follow the same ones.
- Networking is split into layers, each with one focused job.
- The internet runs on the TCP 传输控制协议/IP suite of four layers.
Why protocols and layers
- A protocol defines the format, order, meaning, timing and error handling of messages — without it, communication fails (like two people with no shared language).
- Layering 分层 splits the work so each layer talks only to the ones above and below. Benefits: modularity (swap Ethernet for Wi-Fi without touching the rest), standardisation, and abstraction.
The four layers of the TCP/IP protocol suite
A protocol is the shared rules: format, order, timing and errors
A network protocol is:
A protocol defines the format, order, meaning, timing and error handling of messages — both ends must agree.
A benefit of splitting networking into layers is:
Each layer has one job and a clear interface, so (e.g.) Ethernet can be swapped for Wi-Fi without touching higher layers.
The TCP/IP layers
| Layer | Purpose | Examples |
|---|---|---|
| Application | what the user program does | HTTP, FTP, SMTP |
| Transport | end-to-end delivery between processes | TCP, UDP 用户数据报协议 |
| Internet | routing packets between networks | IP |
| Link | sending bits over the physical medium | Ethernet, Wi-Fi |
A cable modem connects a home network to the internet provider
Tap the four layers of the TCP/IP model
Explore each layer. Data travels DOWN the stack as it's sent (each layer adds its header) and back UP as it's received — and any layer can be swapped without touching the others.
Match each TCP/IP layer to its job.
Application = user protocols; Transport = TCP/UDP delivery; Internet = IP routing; Link = bits on the medium.
TCP vs UDP
- TCP is connection-oriented 面向连接: it sets up a connection, ensures all data arrives in order, and retransmits lost packets — reliable, but with overhead. Used by HTTP, email, FTP.
- UDP is connectionless 无连接: send-and-forget, no acknowledgements or ordering — low overhead, no guarantees. Used for streaming, DNS and gaming, where speed beats reliability.
A satellite dish sends and receives data by radio over a long distance
- Network protocols are organised as a stack of layers.
How does TCP differ from UDP?
TCP sets up a connection and ensures reliable, ordered delivery (with overhead); UDP is fire-and-forget.
TCP is connection-oriented and guarantees ordered, complete delivery (with overhead), while UDP is fire-and-forget — faster but with no delivery guarantee.
That's why UDP suits live streaming, gaming and DNS, but TCP is used for files, email and secure web pages where every byte must arrive.
You've got it
- a protocol = agreed rules (format, order, meaning, timing, errors)
- layering gives modularity, standardisation and abstraction
- TCP/IP layers: Application → Transport → Internet → Link
- TCP = reliable, ordered, connection-oriented; UDP = fast, connectionless, no guarantees