OSI knowledge sorting

OSI： Open system interconnection , It's divided into seven layers

1、 Control level ： application layer The presentation layer The session layer

2、 Data level ： Transport layer The network layer Data link layer The physical layer

application layer ： Accept user data , Interface of human-computer interaction , Application oriented .

The presentation layer ： Logic language （ programing language , Software language ） Convert to machine language （ Binary language ）----- translate , encryption

The session layer ： For each type of data transmitted （ management ： establish 、 maintain 、 End ） A virtual link （ To prevent different types of data from affecting each other .

Transport layer ：

effect ：1、 Distinguish traffic 2、 Define the data transmission mode

1、 Distinguish traffic

Port number ： Static port , Dynamic port

Port number ：port ID, Range of values 1-65535

Static port ： Also known as port Range 1-1023

Dynamic port ： Range 1024-65535

Common port numbers ：

HTTP（ Hypertext transfer protocol ）---80 ,TCP 

HTTPS---443,TCP  （ More secure ）

Telnet（ Remote login service ）--- 23 ,TCP

SSH( Remote login （ High security , encryption , authentication )---22 ,TCP

RIP---520,UDP

DNS（ Domain name resolution ）---53 ,TCP and UDP

TCP： Reliable transmission , Transmission control protocol , It's a kind of Connection oriented The reliable transmission protocol

How to ensure reliability ？

1、 Acknowledgement mechanism

2、 Retransmission mechanism

Three times mobile phone system ： Ensure connection oriented , Also known as TCP Three handshakes of

Acknowledgement mechanism ： Display mechanism , Implicit mechanism

Optimization mechanism ： Mobility mechanism （ Sliding window mechanism ）; Reorder

UDP： Unreliable transmission , User datagram protocol , It's a kind of Non connection oriented Unreliable transport protocol for

Unreliable transmission mode and flow characteristics ：

1、 Large flow

2、 High real-time performance

3、 Insensitive to data loss

Segmented transmission of data ： When transmitting large data, follow MTU Value for segmented transmission .

MTU： Maximum transmission unit , The default is 1500 byte , You can modify （ Modification is not recommended ）

PDU： Protocol data unit --- Refers to the unit of data passed between peer-to-peer levels

4 layer PDU：segment piecewise Fragmentation

The network layer ：network  Addressing Addressing

Address ：

Preparation agreement ：IP（IPV4  IPV6） IPX   apple talk   novell   NSAP

IPV4： use 32 Binary addressing .

A binary be called 1 position bit

IP Address ：32 It's binary ,0 and 1 constitute , For addressing

Network mask ：32 It's binary , Successive 1 And continuous 0 constitute , Successive 1 On behalf of network bit , Successive 0 Represents the host bit .

Network bit                       Host bit

1101 1000.0001 0001.0000 0001.0000 0001---------216.17.1.1

Network mask

1111 1111.1111 1111.0000 0000.0000 0000-----------255.255.0.0

Write a complete IP Address time ：IP Address + Network mask

Address classification

A Class address ： The first is fixed as 0

0XXX XXXX---0-127（ Available as 1-126）, The netmask defaults to ：255.0.0.0

B Class address ： The first two are fixed as 10

10XX XXXX---128-191 , The netmask defaults to ：255.255.0.0

C Class address ： The first three are fixed 110

110X XXXX---192-223, The netmask defaults to 255.255.255.0

D Class address ： The first four are fixed as 1110

1110 XXXX----224-239, Multicast address , No mask

E Class address ： The first four are fixed as 1111

1111 XXXX----240-255, Scientific research address

Special address ：

1、0.X.X.X  Invalid address （ Reserved address ）,0.0.0.0 Invalid address     placeholder

2、127.0.0.1 Local testing （127.X.X.X Address of the test ）

3、 network number , The network bit remains unchanged All hosts are 0 The address of （ Describe a network segment ）

162.1.1.1---------------162.1.0.0 

255.255.0.0

4、 Restricted broadcast address ,255.255.255.255 

5、 directional （ direct ） Broadcast address , The network bit remains unchanged , All hosts are 1

200.1.1.1 ---------200.1.1.255

255.255.255.0

6、 Local link address ：link-local  { 169.254.0.0 255.255.0.0 }

Public address ： Globally unique identification address

Private address ： Address without unique identification

10.0.0.0  255.0.0.0 

172.{16-31}.0.0  255.255.0.0

192.168.X(0-255).0  255.255.255.0

Three layers PDU：packet package

A B C Class addresses are called unicast addresses

unicast ： One to one transmission

Multicast ： One to many transmission

radio broadcast ： One to all transmission modes

Data link layer ： LAN （ Ethernet Ethernet） 

Wide area network （PPP HDLC ATM FR）

Second floor address ：Mac Address （ Media access control ）----- Physical address Hardware address Burn address

LLC layer ： Logical link control sublayer

MAC layer ： Media access control sublayer

Mac Address structure ： 48 It's binary , Writing uses 12 Hexadecimal （ A hexadecimal needs to use 4 individual Binary representation ） The way of writing ： Subtractive hexadecimal or dotted hexadecimal

60-F2-62-3C-E3-53------- terminal   host mobile phone   The server

60F2.623C.E353------- Connect to the device      Router A firewall   ASA 

front 24 position ： manufacturer ID ----OUI（ Uniform resource identifiers ）

after 24 position ： product ID ----interface ID （ Interface identifier ）

On the second floor PDU ：frame  frame

The physical layer ： Pay attention to the mechanical characteristics of network hardware Optical properties   Electrical characteristics

First floor PDU：bit        Bit stream

Transmission medium ： Optical fiber    、 Twisted pair （RJ45）

Twisted pair ：

568A Linear sequence ： Green and white 、 green 、 Orange white 、 blue 、 Bluish white 、 orange 、 Brown and white 、 Brown

568B Linear sequence ： Orange white 、 orange 、 Green and white 、 blue 、 Bluish white 、 green 、 Brown and white 、 Brown

Parallel lines ： Also known as the through line , Same line sequence . Parallel lines are used for different layers of equipment

Cross line ： The line sequence is different . Cross lines are used for equipment on the same floor .

All negative ： also called console Line , Configuration line , The line sequence is opposite , Network equipment for user control .