Computer Network

Architecture of Computer Network.

A network is $$\text{Network}=\text{Nodes}+\text{Links}+\text{Protocols},$$logical 逻辑上（transparent） physical 实现 Remember that $$\text{Computer Network}=\text{Protocol Stack}+\text{Addressing}+\text{Routing},$$ base on which we build the Internet to connect everything. Architecture & Layering The network architecture, equivalently, the protocol stack, organizes communication into layers, each providing services to the layer above while hiding implementation details from the layer below. A simple example is the OSI model, which partitions the communication process into seven layers: $$\text{Physical}\to\text{Data Link}\to\text{Network}\to\text{Transport}\to\text{Session}\to\text{Presentation}\to\text{Application}.$$ The OSI model provides a conceptual framework; it does not define specific protocols. Now consider the TCP/IP model, which condenses these into four layers: ...