Shulou(Shulou.com)06/03 Report--

ISO:internet standard orgnization, International Organization for Standardization

OSI Model-Open system Interconnection reference Model

Open system Internet reference module

IOS:internet operating system, Internet operating system

TCP/IP model OSI model:

Function: to provide a unified reference standard for network interconnection

Structure: divided into 7 layers, each layer defines and implements different functions

7-Application layer (application)

This layer represents a variety of network applications.

Agreement: all kinds of language

Product: software

6-presentation layer (presentation)

Can be understood as a translator.

5-session layer (session)

Creation, management, and deletion of sessions

4-Transport layer (transport/transmit/transmition)

Function: to protect the data transmission and ensure the stable and effective data transmission

Protocol: TCP/UDP

Products:

3-Network layer

Purpose: addressing and routing data

Protocol: IP

Implementation: router, multilayer switch

2-data Link layer

Function: responsible for the establishment and removal of logical links, responsible for the formation of frames

Protocol: Ethernet (Ethernet)

Products: bridge, switch

1-physical layer

Function: responsible for setting standards for the physical and electrical characteristics of network equipment

Protocols: electrical protocols, industrial design standards

Products: network cable, repeater, hub

Frame frame check checksum Fcs tail

7-3 floor plus tail

2 layers plus head and tail

High voltage 0 low voltage 1 serial

Data encapsulation (decapitation)

Send, transmit and receive

Transmission media:

Wireless

Satellite, laser, Bluetooth

Wired

Network cable, optical fiber

Network cable

Function:

Composition:

8 copper wire cables

Signal:

Signals 0 and 1 are represented by voltage, that is, high voltage and low voltage.

Type:

Line sequence: 568A and 568B

568B: orange white, orange, green white, blue, blue white, green, brown white, brown

568A: green white, green, orange white, blue, blue white, orange, brown white, brown

1, 2: send data

3, 6: receive data

4578: prevent data transmission interference

Network cable is also called "twisted pair".

Straight-through line: both sides of the line order is the same, connect different equipment crossing lines: both sides of the line order is different, connect the same device reversal line: the two sides of the line order is completely opposite-equipment control line-console line is sold in all major online stores IT male essential speed: 10Mbps 100Mbps 1000Mbps1G 10000Mbps10G wire: the higher the level, the harder 55e: Super Category 5 6 7 UTP unshielded twisted pair STP shielded twisted pair

Optical fiber: single mode (other colors)

Multimode (× ×)

Layer 1-0pm 1 bit stream

Layer 2-data frame, frame

Layer 3-packet, packet

Layer 4-data segment, segment

Layer 7-data flow, flow

@ base

Binary system

Of all the numerical components, there are only two basic elements, 0 and 1.

Decimal

Of all the numerical components, there are only 10 basic elements, 0-9.

Hexadecimal system

Of all the numerical components, there are only 16 basic elements, 0-9 mai amurf.

Note:

1 hexadecimal equals 4 binary

2 hexadecimal equals 1 byte

All hexadecimal systems are preceded by a 0x

An IP address has 4.3 billion bit

Conversion between binary systems

one

two

four

eight

sixteen

thirty-two

sixty-four

one hundred and twenty eight

two hundred and fifty six

five hundred and twelve

1024

@ unit

Bit, bit

Byte, byte, 1 Byte, byte, 1 Byte equals 8bit

Kbit, 1000bit

Mbit, 1000Kbit

Gbit, 1000Mbit

Tbit, 1000Gbit

Pbit, 1000Tbit

=

Layer 3 address (IP address)

Implementation protocol: IP (/ IPx/AppleTalk)

Function: within a certain range, unique, identification, a network device; (characteristics, uniqueness, limitations)

Also known as logical address, which can be changed at will

It is equivalent to the name of a person in the human world; provided that, within a certain range,

Structure: network bit + host bit, total 32bit, that is, 4 Byte (bytes)

Representation:

1, 2 base, let the equipment see.

Base 2, 10, for people to see.

Dotted decimal, such as x.x. X is decimal.

X represents 8 bit, with values ranging from 0 to 255,

For example: 192.168.100.79 → 11000000 (.) 10101000 (.) 01100100 (.) 01001111

1001 # 9 0001 1001 # 25

Features:

IP address must be combined with subnet mask for it to work

Subnet Mask-netmask

Function:

Distinguish between network bits and host bits in IP addresses.

Structure:

The left side is always 1 and the right side is always 0.

Length is 32bit, that is, 4Byte bytes

Represents: pure binary

Dotted decimal system

/ n-→ n represents the number of ones in the subnet mask

Implementation: 1. 1 IP address, which must correspond to a subnet mask

2. Both of them are 32bit, corresponding one to one

3. The bits in the IP address corresponding to 1 in the subnet mask are called network bits.

4. The bits in the IP address corresponding to 0 in the subnet mask are called host bits.

Features:

1. The left side is always 1, and the right side is always 0

2, 0 and 1, never cross.

Related concepts:

Reverse mask, that is, the 0 and 1 in the subnet mask are reversed.

Special IP address: (cannot be configured for use on the device)

Network IP address: represents an IP network range and does not represent any hosts

Definition:

The address of the host bit, which is all 0, is called the network address

Broadcast IP address: represents all devices in a range and is not unique.

Definition:

The address of the host bit, all 1, is called the broadcast address

For example: 192.168.78.6 255.255.255.0

Network address-192.168.78.0 / 24

Broadcast address-192.168.78.255 / 24

0. IP address must appear at the same time as subnet mask

1. Distinguish the network bits from the host bits of the IP address by the subnet mask. 2. Change all the host bits to 0, and then write the IP address-network address

3. Replace all the host bits with 1, and then some IP addresses-broadcast addresses

192.168.65.32

11000000.10101000.01000001.00100000

255.255.255.128

11111111.11111111.11111111.10000000

IP classification

Classification is carried out in order to facilitate the management of IP addresses.

Principles:

Based on the fixed bit of the first few bytes in the IP address

A

The first bit in the first byte, fixed, with an address of 0

The first byte is: 0XXX XXXX

B

The first two bit in the first byte, fixed, with an address of 10

The first byte is: 10XXX XXXX

C

The first three bit in the first byte, fixed with the address of 110,

The first byte is: 110X XXXX

D

The first four bit in the first byte, fixed, with an address of 1110

The first byte is 1110 XXXX

E

The rest are in Class E.

Note: IP address classification is not based on subnet mask

There are two special IP addresses in each network segment that cannot be used.

Special addresses in Class A cannot be configured on network devices

Those that begin with 0 cannot be configured to use

Those that begin with 127 cannot be configured to use

The IP address space contains 32 addresses of 2, that is, 4294967296, about 4.3 billion.

-notice in the next section--

The IP address is limited, with the development of the network, there are more and more networking, and the IP address is wasted, so the IP address space is exhausted very quickly.

So we need to propose corresponding mitigation solutions and solutions:

1. The division of public address and private address

2. Subnetting (this is the most difficult)

3. Develop IPv6; (represented by 128bit, so IPv6 has a total of 2 to the 128th)

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