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Seven layer network architecture

2022-07-06 09:09:00 【~Pompeii】

Seven layer network architecture

1. Why is it divided into seven layers

Support the interconnection of heterogeneous networks .

2. The seven layers are respectively responsible for （ function ）

OSI The model divides the work of network communication into 7 layer , From bottom to top are The physical layer 、 Data link layer 、 The network layer 、 Transport layer 、 The session layer 、 Indicating layer and stress

(1) The physical layer

	  Mission ： Transparently transmit the bitstream .

function ： Provide data transmission path for data segment equipment

Transmission unit ： The bit

The implemented hardware ： A hub , Repeater

（2） Data link layer

Mission ： Transmitting the network layer IP Datagram assembly into frame

	  function ：a.  Establishment of link connection 、 Remove and separate 

		       b.  Frame delimitation and frame synchronization 

		       c. Error detection

Transmission unit ： frame

The implemented hardware ： Switch 、 bridge

agreement ：PPP,HDLC、SDLC、STP、ARQ

(3) The network layer

Mission ：a. Encapsulate the message segments transmitted from the transport layer into packets

b. Choose the right route , So that the packets transmitted from the transport layer can be delivered to the destination host

function ：a. Provide services for the transport layer

		      b.  Packing and unpacking

c. Routing

d. Congestion control

Transmission unit ： Data segment

The implemented hardware ： Router

agreement ：ICMP、ARP、RARP、IP、IGMP、OSPF

(4) Transport layer

Mission ： Responsible for the communication between two processes in the host

function ：

	     a.  Provide reliable services for end-to-end connections 

	     b.  Provide flow control for end-to-end connections 、 Error control 、 Service quality management services 

 Transmission unit ： Message segment （TCP） Or user datagram （UDP）

agreement ：TCP、UDP

(5) The session layer

 Mission ： Dialogue between processes on different hosts

function ： Manage session processes between hosts , Including the establishment of 、 Manage and terminate inter process sessions . It's an end-to-end service

(6) The presentation layer

Responsible for handling the representation format of information exchanged between two communication systems with different internal data representation structures , Provide necessary data compression and decompression functions for data encryption and decryption and improving transmission efficiency .

(7) application layer

Mission ： Provide the interface between the system and users

function ：

a. File transfer