OSI Model 開放式系統互聯通訊參考模型

OSI - Open System Interconnection
Open System Interconnection reference model 開放式系統互聯通訊參考模型 (Wikipedia/維基百科)

Layer 7 - Application 應用層

Layer 6 - Presentation 表達層/展示層

Layer 5 - Session 會議層/交談層

Layer 4 - Transport 傳輸層
Example: TCP (Transmission Control Protocol). Connection-oriented links for conveying segments of data.
Example: UDP (User Datagram Protocol). Connectionless transmission model. For Multimedia traffic.

Layer 3 - Network 網路層 Example: IP (Internet Protocol). Data transported as packets.

Layer 2 - Data Link 資料鏈結層
Logical Link Control (LLC) sublayer
Media Access Control (MAC) sublayer - e.g. CSMA/CD (802.3), CSMA/CA (802.11)

Layer 1 - Physical 實體層

References:

Communication Systems (4th Edition) by Simon Haykin, Wiley 2001, p11-12.
What is the difference between TCP and IP protocols?
Transmission Control Protocol(Wikipedia)
User Datagram Protocol(Wikipedia)
OSI七層簡介