Notes on network principles (five layer network)

1、TCP/UDP And OSI

① The physical layer ( Ethernet cable )





② Data link layer （mac）









③ The network layer （IP）





④ Transport layer 【 port 】（TCP/UDP）





⑤ application layer 、 The presentation layer 、 The session layer ：

( adopt IP Address and port for communication )





2. Understand hierarchical relationships

Each level is only responsible for communicating with its own upper and lower nodes





3.IP Address