Why network like internet popular and reliability

Hierarchy in Network

1.       Physical Layer is the basic, for transfer signal bit from one machine to another.

2.       Link Layer is dealing with collision for sharing physical layer.

3.       Network Layer is building scalable network exert sub-network in filtering and forwarding.

4.       Up Layer is for convenience programmer coding, such as Port in process.

From mention before, network is clearly separate into several layers with different character. In TCP/IP it can separate into three layers and the OSI is seven layers. But as a programmer over operating system, we exploit socket mechanism for processing connection without setup our own network stack, like I have mentioned layers. Yet, known more about the detail of network is also helpful to develop a correct network programme.