Between computer networks to communicate with what rules, it is to study the problem of network models.
Network models generally refers to:
OSI (Open System Interconnection Open Systems Interconnection) Reference Model
TCP / IP reference model
Network model layer 7 Overview:
1. Physical layer: The main criteria defining the physical device, such as a cable interface types, the interface of the optical fiber type, transmission rate and other transmission media. Its main role is the transmission bit stream (1,0 is made into the current strength to be transmitted, the destination after conversion to 1,0, that is, we often say that the digital to analog conversion and analog to digital conversion). This layer is called the data bits.
2. The data link layer: The main physical layer receives data from the MAC address (the address of the NIC) encapsulation and decapsulation. This layer is often called a data frame. In the device of this layer is to work the switch, data transmission through the switch.
3. Network layer: The main underlying data received from the IP addresses (for example 192.168.0.1) encapsulation and decapsulation. In this layer devices routers work is often referred to this layer of data packets.
4. Transport Layer: defines the protocol and port number (WWW port 80, etc.) for transmitting data, such as: the TCP (Transmission Control
Protocol, transmission efficiency is low, high reliability, high transmission reliability for the data amount of data), the UDP (User Datagram Protocol, TCP characteristics and on the contrary, for the less demanding transmission reliability, a small amount of data data, such as QQ chat data is transmitted in this manner). Segment is primarily from the lower layer receiving and transmitting data to the destination address after restructuring. Often this layer is called a data segment.
5. Session Layer: establishing a data transmission path: through the transport layer (transmission and receive ports of port number). In your main
Initiating a session between the system or accept the session request (need to recognize each other device may be a MAC or IP host name)
6. Presentation layer: mainly received data is interpreted, encryption and decryption, compression and decompression, and the like (i.e., the computer recognizes what adults can be converted to recognize something (such as pictures, sound, etc.).
7. Application Layer: The main application of some terminals, such as FTP (file download all kinds), WEB (IE browser), QQ like (it can be understood as what we can see on the computer screen is. terminal application).
