Seven network interconnection framework ISO / OSI ISO's
Level (5-7) - end-
transporting layer (4) - end to end
network hardware layer (1-3) - chained
Application layer:
The most direct services, application management communication user experience (such as e-mail, browse the Web, etc.).
Presentation Layer:
Representation of data communication between processes (such as syntax conversion, data format conversion, encryption and decryption, etc.).
Session Layer
Providing a session between different machines in the process of communication, such as the creation, management, and other processes remove the session.
Transport Layer
To-end through the logical interface (port number, gateway) service to the upper layer byte stream data, and error control, flow control mechanism, any changes in network hardware technology is invisible to the top, i.e. without considering the underlying high-level design details, transport layer functions as "nexus" effect.
(TCP, UDP protocol)
Network layer
It provides two types of network services to the transport layer:
1. connection-oriented (similar to play), focusing on how to establish a link;
2. No connection :( similar high moral map to check the line, take a look at a war battle, lines, variable speed ), focus: to establish a detailed routing table at each station.
Network layer four major tasks:
1. Routing: discover routes, selecting a path;
2 congestion control: Avoid / relieve congestion;
3. LAN interconnection: The solution faced packet size, network speed, adjust so protocol the difference between two data networks package successfully delivered;
4. statistics and control: more statistics which users need network traffic, frequently visited sites, etc., accounting functions.
The most well-known layer protocol (IP) - (router)
data link layer
On the basis of the physical layer provided by the "bit" on the service provided between adjacent network nodes to a data "frame" units, plus start, end, error checking code, etc., is formed with a fixed data format. It is also responsible for traffic control data link error control, error correction, where possible, can choose retransmission can not be corrected.
The network layer provides a "simple communication link" (e.g., cable, WiFi, network card), is a closed path, except at both ends, no other entrances.
Physical Layer
The most basic transmission channel, establish, maintain, cancel physical connections.
