A brief introduction to TCP/IP protocol clusters

(i) OSI Brief introduction

(1) The OSI (Open System interconnect) features a simple description of each layer:

① Application layer: Provides an environment for the application to run and manages and executes the application;

② Presentation layer: Provides a set of rules and conventions for data encryption, decryption, compression, decompression, and terminal data format conversion before transmission;

③ Session Layer: The rules for qualifying and validating both sides of the conversation, as well as the way data is transmitted (full, half-duplex,

Single-mode transmission);

④ Transport Layer: Provide end-to-end reliable, transparent service, flow control, ensure the conversation layer to pass the information accurately;

⑤ Network layer: Addressing and routing, responsible for, maintaining and terminating the connection of intermediate devices;

⑥ Data Link layer: Encapsulates an IP datagram into a data frame, link management (build and release), processing of data reported during transmission

Error, the transmission and reception rate matching between peer layer;

⑦ Physical layer: Bitstream Transmission of data (0,1 binary).

(2) The disadvantages of the seven layer protocol included in the OSI:

① is more complex to implement, according to the seven-tier development of the actual network structure, the operating efficiency is relatively low;

② Seven layer protocol is not strictly divided, there are some functions in the layer between the duplication phenomenon.

(ii) TCP/IP protocol cluster Brief introduction

(1) The TCP/IP protocol cluster is proposed to solve the shortcomings of OSI seven layer protocol. The purpose is to solve the problem of heterogeneous computer network communication;

(2) The TCP/IP protocol cluster is an architecture and protocol standard for Internet development, which is synonymous with a set of communication protocols, a protocol cluster consisting of a series of protocols (the TCP/IP protocol contains a large number of protocols and applications, and several independently defined protocols are combined. ）

(3) functions between the layers of the TCP/IP protocol:

① Application layer: Services to Telnet, FTP, SMTP protocol, etc., is responsible for processing a specific application protocol;

② Transport layer: TCP protocol and UDP Protocol, TCP protocol is a reliable connection-oriented transport protocol, guaranteeing the word of a host

Throttle accurate transmission to the target host, UDP protocol is a non-connected service, no re-send and error correction function, does not guarantee the reliable transmission of data;

③ Network layer: including IP, ICMP and IGMP protocol, its main task is routing and addressing, so that each packet (message segment) to reach the destination independently;

④ Network interface layer: Also known as the data link layer, usually including network interface card (NIC) and device driver;

(4) The basic working principle of TCP/IP protocol:

Encapsulation: The message segment in the TCP protocol contains the port number of the source and target port (the equivalent of the house numbers, the range is small), the IP datagram contains the destination IP address (equivalent to the region address, the scope is large); Data link layer containing the AMC address of the network card, According to the Network Layer ARP protocol, the IP address of the target side is found to its corresponding AMC address, then the data transmission communication (each layer will contain a header information);

Unpacking: When the information is uploaded and encapsulated, the header information is removed and then passed up one layer at a time.