Chapter 6 data communication and computer network
(Data communication, data transmission rate, bandwidth, modulation mode, etc. in the channel, mainly about computer networks)
1. What is a computer network?
Simply put, a computer network is a network that connects a single machine to a data line through a communication device.
Data sharing and information exchange.
2. What are the most common computer networks?
Lan and Internet. According to the transmission frequency band, it is divided into baseband and broadband signals.
3. What is the model structure of the computer network routing? What is the role of each layer, and what is the hardware associated with each layer?
The computer network is designed based on the layer-7 OSI design, that is, the Open System Interconnection model.
The layer-7 OSI includes protocols supported in message transmission.
The layer-7 models are:
Physical Layer: defines the transmission characteristics between the interface and the physical media, which is equivalent to picking up the email package from the mailbox to the shuttle bus and sending it
There is also a zip code. -------- The repeater acts as a central signal website to enlarge the signal source
-------- Hub, scattered multi-channel signals
Data link layer: receives data from the physical layer for frame separation, physical addressing, traffic control, and other processing.
. ---------- Bridge, connected to different LAN
Network Layer: transmits data from the link layer through multiple paths. It is equivalent to sending the mail package to the specified
The mail box of the address. ---------- Vro, select data transmission in different paths
Transport Layer: network port addressing; find the mailbox from the mailbox according to the detailed geological
---------- Gateway, spread between networks of different architectures
Session Layer: the user contacts the transmitter to receive the email
Presentation Layer: Thank you
Application Layer: read emails by unpacking.
4. What is lan construction?
A local area network must be composed of a hub and a router as an intermediate connection.
5. What is Ethernet? What is its biggest feature?
Ethernet is a communication protocol standard dedicated to local area networks. The principle of the refer is the carrier conflict detection technology. General Constant
The speed can reach 10 Mbps.
6. What is Internet? As the world's largest Interconnected Network, what are the key technologies of its protocol?
The Internet connects various networks around the world to achieve resource sharing and information communication. TCP/IP protocol.
7. What is the TCP/IP protocol? What is the process of implementing the Protocol? What about its functions?
TCP/IP protocol is a protocol that can be applied to multiple communication networks, ensuring the smoothness of Internet interconnection.
The IP protocol is an Internet Protocol that runs at the network layer. It is mainly used to add data headers to IP addresses to form an IP packet, which can transmit many other data;
The TCP protocol, transmission control protocol, and Transport Control Protocol are the protocols executed at the transport layer. They are mainly used to check data packets and ensure data transmission is correct;
7. Briefly describe the domain name hierarchy.
Domain Name, from left to right, the permission management organization is growing, and the rightmost is the top-level domain name; for example, szu.edu.cn Edu: cernet cn: China;
8. How are IP addresses classified? How are network numbers and host numbers differentiated?
An IP address consists of IPv4 addresses and 4 bytes. Generally, an IP address consists of a network address and a host address. Based on the preceding data, the IP address is divided into A, B, C, and other network addresses.
A: The highest bit is 0, SO 2 ^ 7-2 network numbers and 2 ^ 24 host addresses;
B: The highest bit is 10. Therefore, there are 2 ^ 14-2 network numbers and 2 ^ 16 host addresses;
C: The highest bit is 110, and so on.
Then, because the host numbers below the network numbers can be allocated in segments, the host addresses can be divided into the preparation of subnet numbers + host numbers to expand the port. This subnet number
It is called subnet encoding;
To distinguish between a network number and a host number, use a shielding code.
For example, the shielding code of the Class A network address is 255.0.0.0 B: 255.255.0.0 C: 255.255.255.0.
9. What is the difference between the World Wide Web and the Internet? How is the WWW Service model established?
Internet is a network interconnection mode, and the World Wide Web is a multimedia sharing platform on the Internet;
WWW Service is built on C/S;
Server: WWW server. A lot of Web information is displayed in text, and the text on the Web page points to other web pages. Therefore, Web information is displayed in hypertext;
Client: that is, the browser. Its main function is to accept the user input URL (Uniform Resource Locator, unified Resource Locator) for site navigation and display
Text Information. XML eXtensible Markup Language, The extensible markup language is the language for displaying web page information;
10. How does a URL explain the URL Information?
URL: including the protocol, server, path, file name, and other information;
For example, the common URL: http://www.baidu.com explanation: HTTP is hypertext transmission protocol, Hypertext Transfer Protocol; www: webserver; Baidu.com for Baidu
Server name.
11. Introduction to how HTTP works.
HTTP is an application layer protocol that works on TCP. The service mode is c/s, that is, communication between the browser and Webserver:
The communication process is roughly as follows:
Enter URL in the browser -- DNS resolution domain name return IP -- the browser establishes a TCP connection with the 80 port of the IP address (the default HTTP tcpport is 80) -- in the response URL of the server
Path and file information -- send the information to the browser through TCP connection.
12.html and XML
Hypertext Markup Language: hypertext markup language. It is the structure and text language used to write web pages.
13. What are the meanings of the mailbox names of the protocols in the email system for receiving and sending mails respectively?
For example, the mailbox name [email protected], 2010130285 is username, and email.szu.edu.cn is the name of the mail server of Shenzhen University.
The Protocol for receiving mail is SMTP Simple Mail Transfer Protocol, which belongs to the TCP/TP protocol cluster. It mainly serves to receive the Domain Name of the mailbox
Convert to an IP address and send the email to this address.
The mail sending protocol is POP3, post office protocol3, and the third version number of the Post Office Protocol. This protocol is mainly used to connect to the server and download emails. At the same time, users are allowed
Delete emails from the server.
14. Where Are FTP applications?
FTP, file transfer protocol, and file transfer protocol
15. What are frequently used Chinese and English search engines?
Google Baidu AltaVista Yahoo
16. What databases does literature search have?
Frequently used: SCI, EI, CNKI, CSSCI, etc.
Chapter 7 data security and computer security
1. What is a computer virus? What about Trojans?
Computer viruses, which can be compared with biological viruses.
Reproducibility: A computer virus is a program or command that replicates and transmits data when the running conditions are met.
Destructive: Data damage or function impact.
Trojans are derived from Trojans that are hidden in Trojans and then cause attacks. Network Trojans refer to seemingly deliberate programs that actually hide a lot of user information and control computer ports.
Programs are mainly hacker attacks, but they are not capable of self-replication.
2. What are hacker behaviors?
Attackers can steal data or damage computer functions.
3. What are the characteristics of computer viruses?
Infectious, destructive, and latent (damage occurs only when certain conditions are met)
4. How to protect against computer viruses? How does the firewall and gateway play a protective role?
It is often used to install anti-virus software without browsing insecure plug-ins.
Firewall: a firewall that separates different buildings to prevent the spread of fire. A firewall in a computer refers to the software and hardware built between two different networks to prevent virus infection.
Total. In fact, there are many firewall categories,
1) A router at the network layer is a relatively low-level firewall. its working principle is to check and renew IP headers and security networks to remove insecure data packets. However, the router at the application layer cannot be processed.
Layer viruses or virtual IP packets.
2) Personal Firewall:
3) proxy server:
4) status listener: the software that runs the token on the gateway to retrieve data and analyze and store some information as the implementation token.
Computer network and security
