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MindMap Gallery Topic 1 Overview of basic knowledge of computer networks

Topic 1 Overview of basic knowledge of computer networks

Basic knowledge of computer networks, introducing common network topologies, network system composition, functions and applications, Basic knowledge of data communications, Network classification, etc.

Edited at 2024-01-23 19:18:24

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Topic 1 Overview of basic knowledge of computer networks

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Outline

data
- 171
- 3
romaindias1998@gmail.com
A Structure of Cuet Phase
- 68
Mr. Romeel
Tree structure diagram of protocol
- 46
Liu Qian
Chapter Six Computer Network Basics
- 79
- 3
PlotWizard
physical layer
- 128
PlotWizard
Computer network network layer knowledge point mind map
- 320
- 3
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Computer Network Chapter 2
- 123
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computer network application layer
- 181
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Basic mind map of data communication and control network
- 101
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Advantages and Disadvantages of Packet Switching
- 48
Mason·Carter

Topic 1: Overview of basic knowledge of computer networks

1. Basic concepts of network

network definition

Computers with independent functions in different geographical locations are connected through communication lines, and under the management of network operating systems and communication protocols, resource sharing and data transmission are realized

Network development history

1. Terminal-oriented computer network

2. Computer communication network

3. Computer Internet Network

4. Broadband Integrated Services Digital Network

2. The composition, functions and applications of network systems

Network functions

1. Realize resource sharing of computer systems

2. Achieve rapid transmission of data information

3. Improve reliability - redundant backup system (RAID disk)

4. Provide load balancing and distributed processing capabilities-ICP (content provider)

5. Centralized management-ticket purchase system

6. Comprehensive information service-portal system

Network Applications

1. Office automation - OA system

2. Management information system

3. Process control

4.Internet applications

(1) Email (2) Information release

(3) E-commerce-E-C (EBG)

(4) Remote audio and video applications

5. New Internet technologies and applications

Internet of Things (IoT), cloud computing, cloud storage (Baidu Netdisk), Euroblockchain (digital RMB), software-defined network (SDN)

Network composition

Network nodes and communication links

Resource subnet and communication subnet

resource subnet

Host system - terminal controller - terminal

Communication subnet

center of picture

Network hardware system and network software system

Network system classification

6.OSI reference model

OSI Reference Model Overview

technical terms

The relationship between data units SDU, PDU, SAP, N and N 1

Connection-oriented and connectionless services

physical layer

Main functions of the physical layer

1. Establishment, maintenance and release of physical connections; 2. Transmission of physical layer service data units; 3. Physical layer management

Physical layer media and interconnect equipment

Transmission media: wired cable; equipment: repeaters, hubs, DTE, etc.

Data flow form

bitstream

data link layer

Main functions of data link layer

1. Link management; 2. Frame processing; 3. Addressing, etc.

Main protocols of data link layer

PPP (Point-to-Point Protocol)

Data link layer equipment

Network card (layer 1.2), bridge, switch (manufacturer)

Data flow form and addressing

Frame, MAC (48b)

Network layer

Network layer functions

1. Routing selection; 2. Flow control; 3. Congestion control, etc.

network layer services

Datagram (connection-oriented); virtual circuit (connection-oriented)

Routing

RIP(520),OSPF

Data flow form and addressing

Grouping, IP

Network layer equipment

Router (manufacturer)

transport layer

Transport layer characteristics

1. Connection and transmission; 2. Transport layer services; 3. Bridge between resource subnet and communication subnet

The main functions of the transport layer

1. Accept data from the session layer, 2. Provide establishment and termination of transmission connections, and implement corresponding services; 3. Provide reliable transparent data transmission to higher layers, with error control, flow control and fault recovery functions.

transport layer protocol

TCP (Transmission Control Protocol); UDP (User Datagram Protocol)

Addressing mode

port

session layer

Main functions of session layer

Responsible for establishing, managing, and terminating sessions between processes

Services provided by the session layer

1. Establishment and teardown of session connections; 2. Session management; 3. Data exchange; 4. Isolation; 5.

presentation layer

Main functions of presentation layer

1. Grammar conversion; 2. Transmission grammar selection; 3. General functions

Services provided by the presentation layer

1. Format encoding; 2. Data encryption and decryption (encryption methods DES and RSA); 3. Text compression

Application layer

Main functions of application layer

1. Virtual Terminal (VTP) 2. File transfer, access and management, 3. Email

7. Working principle of TCP/IP protocol and its layered model

TCP/IP concept

TCP/IP protocol is a set of network transmission protocols on the Internet.

Layered mode of TCP/IP protocol

The role of the network interface layer

Based on the services provided by the physical layer, it provides reliable data link transmission services to upper layer protocols.

Internet layer functions, protocols

Protocol: 1.ICMP (Internet Control Message Protocol) 2.IP (Internet Protocol) 3.ARP (Address Resolution Protocol) 4.RARP (Reverse Address Resolution Protocol) 5.IGMP (INTERNET Group Management Protocol)

Transport layer functions, protocols

Protocol: 1.TCP (Transmission Control Protocol), connection-oriented and reliable, after three-way handshake 2.UDP (User Datagram Protocol) connectionless and unreliable

Application layer functions, protocols

Protocol: 1. FTP (File Transfer Protocol, 20/21) TELNET (Remote Login Protocol, 23) 3. SMTP (Simple Mail Transfer Protocol, 25) 4. HTTP (Hypertext Transfer Protocol, 80) 5. RIP (Routing Information Protocol, 520) 6.NFS (Network File System, 111) 7.DNS (Domain Name Service, 53) 8.DHCP (Dynamic Host Configuration Protocol, 67/68) 9.TFTP (Trivial File Transfer Protocol, 69) 10.POP3 (Post Office Protocol version 3,110) 11.SNMP (Simple Network Management Protocol, 161/162)

5. Common network topologies

Main types of computer network topology

1. Bus topology 2. Star topology 3. Ring topology 4. Tree topology 5. Mesh topology

Overview of bus topology, advantages, disadvantages

Advantages: 1. Strong scalability 2. Low cost 3. High reliability. Disadvantages: 1. Not strong real-time performance 2. Difficulty in fault diagnosis and isolation

Star topology overview, advantages, disadvantages

Advantages: 1. Easy to expand 2. Simple structure 3. Convenient fault inspection and isolation 4. Small network delay and low transmission error. Disadvantages: 1. The central node is overburdened 2. The line utilization rate is not high

Ring topology overview, advantages, disadvantages

Advantages: 1. Good real-time network performance 2. Optical fiber available. Disadvantages: 1. Difficulty in expansion 2. Node failure causes network-wide failure 3. Difficulty in fault diagnosis

Overview of other types of topologies, advantages, disadvantages

(Tree) Advantages: 1. Low cost and easy to promote 2. Convenient fault isolation. Disadvantages: 1. Too much dependence on roots. (Mesh) Advantages: High reliability. Disadvantages: 1. Complex structure 2. High cost 3. Difficult to manage and maintain

Topology selection principles

1. Reliability 2. Scalability 3. Cost

4. Basic knowledge of data communication

basic concept

information and data

Information is a reflection of objective things, in the form of numbers, text, etc. Data is digital information

Channels and channel capacity

Channel: the channel for information transmission, channel capacity: the maximum capacity of the channel to transmit information

code elements and codewords

code element, code word

Main Specifications

1. Bit rate 2. Baud rate 3. Bit error rate 4. Throughput 5. Channel bandwidth

Bandwidth and data transfer rates

Bandwidth: is an important indicator of network transmission capability, the difference between the highest frequency and the lowest frequency (HZ), data transmission rate: the speed of data transmission per unit time (bps)

Data transmission method

Data communication system model

DTE, DCE

Data line communication method

1.Simplex 2.Half duplex 3.Full duplex and examples

Data transmission method

1. Baseband 2. Frequency band 3. Broadband (multiple logical channels)

data exchange technology

circuit switching

Advantages: 1. Good real-time performance, communication speed 2. Simple equipment 3. High exclusivity. Disadvantages: 1. Low line utilization 2. Physical connection must be established before transmission

message exchange

Advantages: 1. High line utilization 2. Both parties do not need to work at the same time. Disadvantages: 1. Long network delay 2. Not suitable for communication and interactive situations

packet switching

(Datagram) Advantages: 1. For short message data, communication transmission is relatively high. Disadvantages: large transmission delay

(Virtual circuit) Advantages: 1. High communication rate for large data 2. Short delay 3. Data is not easily lost. Disadvantages: greater dependence on the network

cell exchange

Connection-oriented asynchronous transmission, 53 = 48 5, can be used in WAN and LAN

Error checking and correction

Internal factors: noise, attenuation, delay, etc. External factors: electromagnetic interference, sun, industrial noise

parity check

It is the simplest method of error checking

Cyclic redundancy code check CRC

It is a commonly used check code with error detection and correction capabilities.

3. Classification of networks

Sort by coverage

1. Personal network (PAN) 2. Local area network (LAN) 3. Metropolitan area network (MAN) 4. Wide area network (WAN)

Topology classification

1. Bus 2. Star 3. Ring 4. Tree 5. Mesh Basic model, typical equipment, advantages and disadvantages of each topology

Ownership Classification

1.Public network 2.Private network

The status of computers

1.Peer-to-peer network 2.(C/S) 3.B/S