An Overview of Computer Network of 1500 Word Paper Format Template
This paper expounds the software and hardware of computer network, so that people can have an overall understanding of the structure and equipment of computer network, so that they will not be helpless in the face of network problems in their future work and study, and improve the efficiency of work and study.
Keywords: computer network; Network composition; Network function; network equipment
China Library ClassificationNo.: TP3 15 Document ID: DocumentNo.:1671-7597 (2012) 0101.
1 Definition of computer network
Computer network is a system that uses communication equipment and communication lines to interconnect a number of computer systems with independent functions located in different geographical locations into a large-scale and powerful network system according to the agreed communication protocol, and uses network software with perfect functions (namely, network communication protocol, information exchange mode and network operating system, etc.). ) realize interactive communication, resource sharing, information exchange, comprehensive information service, collaborative work and online processing.
2 the classification of computer networks
1) computer networks are divided into four types according to geographical scope: local area network, metropolitan area network, wide area network and internet; 2) According to the topological structure, it is divided into bus, star, ring, tree and mesh networks; 3) According to the switching mode, it is divided into circuit switching network, store-and-forward switching network and hybrid switching network; 4) Divided into baseband network and broadband network according to transmission bandwidth; 5) According to the operating system used in the network, it is divided into NetWare network, Windows NT network and Unix network. 6) According to transmission technology, it is divided into broadcast network, non-broadcast multiple access network and point-to-point network.
3 the composition of the computer network system
Computer network system usually consists of three parts: resource subnet, communication subnet and communication protocol. The resource subnet directly faces the users in the computer network; The communication subnet is responsible for data communication and application-oriented data processing in the computer network. The rules and conventions that communication parties must abide by are called communication protocols, and their existence is the fundamental difference between computer networks and general computer interconnection systems.
4 The main functions of computer network
Resource * * * Enjoy: The main purpose of computer network is to * * * enjoy resources. * * * The resources enjoyed are: hardware resources, software resources and data resources. Among them, sharing data resources is the most important purpose of computer network.
Data communication: Data communication refers to the use of computer networks to realize data transmission between computers in different geographical locations, and the use of technical means to realize information transmission between networks. This is the most basic function of computer network, and it is also the basis for realizing other functions. Such as e-mail, fax, remote data exchange, etc.
Distributed processing: When a computer system in a computer network is overloaded, it can transfer its own tasks to other computer systems in the network to improve the utilization rate of the whole system. For large-scale comprehensive scientific computing and information processing, tasks are distributed to different computer systems in the network through appropriate algorithms. Promote the development of distributed data processing and distributed database. Using network to realize distributed processing, a high-performance and high-reliability distributed database system is established.
Comprehensive information service: In today's information society, all walks of life are producing a lot of information all the time, which needs to be processed in time, and computer network plays a very important role in it.
5 Common equipment of computer network
Network Interface Card (NIC): inserted in the slot of the computer motherboard, it is responsible for converting the data to be transmitted by users into a format that can be recognized by other devices on the network, and transmitting it through the network medium.
Hub: It is a single-bus device that provides many network interfaces and is responsible for connecting multiple computers in the network. The so-called * * * sharing means that all ports of hub * * * use a data bus, so the average data volume and rate transmitted by each user (port) are limited by the total number of active users (ports).
Switch: Also called switching hub. It also has many interfaces, providing multiple network nodes for interconnection. However, its performance is much better than that of * * * shared hub: it is equivalent to having multiple buses, so that each port device can transmit data independently without being affected by other devices, which means that each port has an independent and fixed bandwidth in front of users. In addition, switches also have functions that hubs lack, such as data filtering, network segmentation and broadcast control.
Cable: the distance expansion of the network needs to be realized by cable. Different networks have different connecting cables, such as optical fiber, twisted pair and coaxial cable.
* * * Telephone network: Public Switched Telephone Network (PSTN) with the rate of 9600 bps ~ 28.8 kbps, which can reach 1 15.2kbps after compression. The transmission medium is an ordinary telephone line.
ISDN (Integrated Services Digital Network) is a dial-up connection mode. The low-speed interface is 128kbps (the high-speed can reach 2M), and the ISDN line is used through the telecommunication bureau or the ISDN service is added to the ordinary telephone line. ISDN is a digital transmission mode, which has the characteristics of fast connection and reliable transmission, and supports the identification of the other party's number.
Dedicated line: leased line, called DDN in China, is a point-to-point connection mode, and the speed is generally 64 kbps ~ 2.048 Mbps. The advantage of private line is that data transmission is well guaranteed and the bandwidth is constant.
X.25 network: it is a WAN mode that appeared earlier and is still widely used today. Its speed is 9600 bps ~ 64 kbps. It has redundant error correction function and high reliability, but its side effects are slow speed and long delay.
Asynchronous transmission mode: ATM(Asynchronous Transfer Mode) is a cell switching network, which is characterized by high speed, small delay and guaranteed transmission quality. ATM mostly uses optical fiber as the connection medium, and the speed can reach thousands (109bps).
Modem: As a device for signal conversion between terminal system and communication system, it is one of the essential devices in WAN. There are synchronous and asynchronous, which are used to connect the synchronous and asynchronous serial ports of the router respectively. Synchronization can be used for private line, frame relay, X.25, etc. Asynchronous PSTN connection in the era of computer network.
6 conclusion
People's use of computers and the Internet is bound to penetrate into all aspects of social production and life. Through the functions of computers and the Internet, it will bring great convenience to the production and business activities of enterprises and the work and life of ordinary people. With the connection and dissemination of the Internet, the speed of information dissemination will accelerate, and the dependence of enterprises and individuals on network information will deepen. Departments with relatively large information needs will become industries that create high added value in the future society. And through them, it will promote the progress and development of related knowledge industries, even the optimization and adjustment of the whole social and economic structure, and promote the all-round social and economic progress.
The development of today's computer network is a sign that human civilization has entered a higher stage, which has promoted the development of human society in a more modern direction and promoted the arrival of the era of knowledge economy. Through the connection of computer network, people have broken the original time-space barrier, invisibly narrowed the distance between people and expanded our living space to some extent. The network has brought us great convenience and success. However, the network has also brought more challenges to society. It requires us to face the new life and environment at a higher level, while constantly changing our thinking and behavior. We should seize the opportunities brought by the Internet age and constantly strive to promote the development of human society to a higher stage.
This paper is about the 12th Five-Year Plan of Hunan Province. Project approval number: xjk011czj010.
References:
[1] Xie Xiren, Computer Network (4th Edition).
1500 word paper format template Part II Computer network security
How to construct a closed logical environment in the open computer network physical environment to meet the actual needs of countries, groups and individuals has become a realistic problem that must be considered. In order to overcome these security problems and make the use of computer networks safer, computer network security came into being.
Keyword encryption technology; Firewall technology; Network security strategy
0. overview
Network system security involves communication security, computer system security, storage security, physical security, personnel security and many other factors, which is the sum of technical security, structural security and management security related to people, network and environment.
1. Threats to computing networks
The main reasons for network security defects are: the fragility of TCP/IP, the insecurity of network structure, the vulnerability to eavesdropping and the lack of security awareness.
2. Computer network security strategy
2. 1 physical security policy
Suppressing and preventing electromagnetic leakage (that is, TEMPEST technology) is the main problem of physical security strategy.
2.2 access control strategy
Access control is the main strategy of network security prevention and protection, and its main task is to ensure that network resources are not illegally used and accessed.
2.2. 1 network access control
Network access control provides the first layer of access control for network access. It controls which users can log on to the server and get network resources, and controls when users are allowed to access the network and at which workstation they are allowed to access the network.
2.2.2 Network access control
Network access control is a security protection measure against illegal network operations. Users and user groups are given certain rights.
2.2.3 Directory-level security control
The network should allow users to control their access to directories, files and devices. There are usually eight kinds of access rights to directories and files: administrator, read, write, create, delete, modify, file scan and access control.
2.2.4 Attribute security control
When using files, directories and network devices, the network system administrator should specify the access attributes of files, directories, etc. Attributes can often control the following permissions: writing data to files, copying files, deleting directories or files, viewing directories and files, executing files, hiding files, * * enjoying, system attributes, etc.
2.2.5 network server security control
The security control of network server includes setting a password to lock the server console to prevent illegal users from modifying, deleting important information or destroying data; You can set the time limit for server login and the time interval for illegal visitor detection and shutdown.
2.2.6 Monitoring and locking control
Network administrators should monitor the network, and servers should record users' access to network resources. For illegal network access, the server should give an alarm in the form of graphics, text or sound to attract the attention of the network administrator.
2.2.7 Security control of network ports and nodes
The ports of servers in the network are usually protected by automatic callback devices and silent modems, and the identity of nodes is identified in encrypted form.
3. Information encryption strategy
The basic process of data encryption is to process the original plaintext file or data according to some algorithm, making it an unreadable code, usually called "ciphertext", so that its original content can be displayed only after the corresponding key is input. In this way, the purpose of protecting data from being stolen and read by illegal personnel can be achieved. The reverse process of this process is decryption, that is, the process of converting encoded information into its original data.
Encryption technology is usually divided into three categories: symmetry, asymmetry and single item.
Symmetric encryption means that encryption and decryption use the same key, which is usually called "session key". This encryption technology is widely used at present.
Asymmetric encryption means that encryption and decryption do not use the same key. There are usually two keys, called "public key" and "private key", which must be used in pairs, otherwise the encrypted file cannot be opened.
Single item encryption is also called hash encryption. This kind of encryption uses hash algorithm to convert some information with different lengths into 128 bits of garbled code, which is called hash value.
4. Firewall technology
Network firewall technology is a special network interconnection equipment, which is used to strengthen the access control between networks, prevent external users from illegally entering the internal network through the external network, access the internal network resources, and protect the internal network operating environment.
4. 1 classification of firewall
According to the different technologies adopted by firewalls, we can divide them into four basic types: packet filtering, network address translation ――NAT, proxy and monitoring.
4.2 Packet Filtering Types
Packet filtering product is the primary product of firewall, and its technical basis is packet transmission technology in the network.
4.3 Network Address Translation NAT
Network address translation is a standard for converting IP addresses into temporary, external and registered IP addresses. It allows internal networks with private IP addresses to access the Internet.
4.4 Agent Type
Proxy firewall can also be called proxy server, which is more secure than packet filtering products and has begun to develop to the application layer. The proxy server is located between the client and the server, which completely blocks the data exchange between them.
4.5 Monitoring types
Monitoring firewall is a new generation product, and this technology has actually surpassed the original definition of firewall. The monitoring firewall can actively monitor the data at all levels in real time. Based on the analysis of these data, monitoring the firewall can effectively judge the illegal intrusion at all levels.
5. Precautionary measures for computer network security
5. 1 Whether the structural design of the network system is reasonable is the key to the safe operation of the network.
Because the LAN uses Ethernet based on broadcast technology, the communication packets between any two nodes will also be intercepted by the network card of any node on the same Ethernet. The application of network segmentation technology will eliminate the hidden danger of the network from the source, and replacing the * * * shared hub with the switching hub will be another way to eliminate the hidden danger.
5.2 Strengthening computer management is the guarantee of network system security.
(1) Strengthen equipment management to ensure the physical security of computer network system. Establish and improve the safety management system to prevent illegal users from entering the computer control room and all kinds of illegal acts; (2) Strengthen access control to ensure the normal operation of computer network system. (3) Establish the authority control module of the network. Network access control is a security protection measure against illegal network operations. (4) Establish an attribute security service module. Attribute security control can associate a given attribute with files, directories and network devices of a network server. (5) Establish the security setting module of the network server. (6) Establish the file information encryption system. (7) Establish a network intelligent log system. (8) Establish a perfect backup and recovery mechanism.
With the development of computer technology and communication technology, computer network will increasingly become an important means of information exchange in industry, agriculture and national defense, and penetrate into all fields of social life. Therefore, it will be very important to recognize the vulnerability and potential threats of the network and adopt strong security strategies to ensure the security of the network. I believe that in the next decade, network security technology will definitely make greater progress.
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