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心智圖資源庫 Topic 1 Overview of basic knowledge of computer networks
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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.
編輯於2024-01-23 19:18:24
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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