OSI and tcp/ip protocol cluster

Catalog

Stratification thought

osi Seven layer model

  The function and analysis of each layer

 TCP/IP Protocol cluster

Data encapsulation and de encapsulation process

Common protocols and associations at all levels

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Stratification thought

Communication requirements ----> Define protocol standards

There are too many agreements needed to complete one thing    ——————> layered

Simplify complex problems

The same protocol is used between the same layers   The lower class serves the upper class

osi Seven layer model

  The function and analysis of each layer

   

(1). The physical layer

It specifies how to realize the lowest physical connection for network communication , And the machinery of physical equipment 、 electrical 、 Functional and process features . Such as ： How to use cables and connectors
type 、 Voltage used to transmit signals, etc . It should be noted that , Physical media required in the process of network communication ( Ethernet cable 、 Cable, etc ), In fact, it does not belong to the physical layer , Because of things
Management is actually a rule , Specify various specifications of these physical media devices when connecting to the network 、 Parameters and working mode . But at the same time , Twisted pair 、 Cable and other physics
Media is the realization of physical layer .
(2). Data link layer

Specifies how to address physical addresses 、 How to conduct data on physical lines ( frame frame) Reliable transmission and flow control . The data link layer protocols are SLIP Association
discussion 、CSLIP agreement 、PPP Agreements, etc . Switch , Decode the frame and send the data to the correct receiver according to the information contained in the frame , So the switch works on data
Link layer .
(3). The network layer

Specify which network nodes to pass 、 What kind of network path to send data ( Data packets ) From sender to receiver . In the network layer , Determined the slave node A Sending data
To the node B The network path of , Through which nodes . The network layer can be established LAN communication system , More importantly, it can be in WAN Establish communication in the network system , This is because
It has its own routing address structure , Through routing protocols ( Also known as routable protocol ) Route network communication .
(4). Transport layer

Responsible for overall data transmission and data control , Provide a mechanism for end-to-end data exchange . Transport layer for data ( paragraph ) Split and reorganize , And carry out flow control and
Determine the appropriate transmission rate according to the receiving capacity of the receiver . For example, Ethernet cannot handle greater than 1500 Byte packets , The transport layer divides data into data segments ,
And sequence number the small data segments . The receiver's transport layer will reorganize the data according to the sequence number . The transport layer protocol has TCP agreement 、UDP Agreements, etc .
(5). The session layer

Establish between two nodes in the network 、 Maintain and terminate Communications .
(6). The presentation layer

Format the data between the application and the network , So that it can be understood by the other party . That is, the presentation layer of the sender converts the abstract syntax of the application data into a net
Apply to OSI Transmission syntax of network transmission , The receiver is the opposite . besides , The presentation layer can also encrypt and decrypt data .
(7). application layer

Topmost OSI layer , Network services for applications . E-mail 、 The file transfer function provides protocol support . Application layer protocols include HTTP agreement 、FTP Association
discussion 、SMTP Agreements, etc .

 TCP/IP Protocol cluster

And osi The difference between

TCP/IP 5 Layer protocol cluster / Protocol stack

data /PDU                             application layer

Data segment / paragraph Fragment              Transport layer

message / package /IP package packet               The network layer

frame Frame                               Data link layer

The bit bit                                  The physical layer

8bit = 1Bvte byte

Data encapsulation and de encapsulation process

hypothesis from A towards B adopt QQ Send a message

Then the application layer is QQ 

The transport layer will add a TCP（ Comparison udp slow But it's safe ）/UDP（ fast , unsafe ） head      Target port number

Add one to the network layer IP baotou   primary IP And target IP

Data link layer Add MAC Sublayer FCS （ The switch doesn't know IP Know only MAC）

The physical layer   Become a bitstream

Common protocols and associations at all levels