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. Based on the transmission frequency band, it is divided into baseband and broadband signals.
3. What is the model structure adopted by the computer network? 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
Another zip code. -------- The repeater acts as the station of the central signal 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 a different path for data transmission
Transport Layer: network port addressing; find the mailbox from the mailbox according to the specific 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 lan must have one of the hubs and routers as an intermediate connection.
5. What is Ethernet? What is its biggest feature?
Ethernet is a communication protocol standard dedicated to lan. It adopts 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 IP addresses to the data header to form an IP packet, so that more data can be transmitted;
TCP, transmission control protocol, and Transport Control Protocol are protocols running on the transport layer. They are mainly used to check data packets so that 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 addresses are 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 number that can be allocated under the network number is segmented, you can divide the host address into the prepared subnet number + host number 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. The World Wide Web is a multimedia sharing platform running 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 URL (Uniform Resource Locator, Uniform Resource Locator) entered by the user for website 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: contains 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: Web server; Baidu.com is 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 the Web Server:
The communication process is as follows:
Enter URL in the browser -- DNS resolution domain name return IP -- the browser establishes a TCP connection with port 80 of the IP address (HTTP's default TCP port is 80) -- in the response URL of the server
Path and file information -- send the information to the browser through the 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 the user name, And email.szu.edu.cn is the mail server name of Shenzhen University.
The Protocol for receiving mail is SMTP Simple Mail Transfer Protocol, which belongs to the TCP/TP protocol cluster. It is mainly used based on the domain name of the recipient's 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 of the Post Office Protocol. This protocol is mainly used to connect to the server and download emails while allowing users
Delete emails from the server.
14. Where Are FTP applications?
FTP, file transfer protocol, and file transfer protocol
15. What are common Chinese and English search engines?
Google Baidu AltaVista Yahoo
16. What databases does literature search have?
Commonly used include SCI, EI, CNKI, and CSSCI.
Chapter 7 data security and computer security
1. What is a computer virus? What about Trojans?
Computer viruses. See biological virus comparison.
Reproducibility: A computer virus is a program or command that replicates and transmits data when execution conditions are met.
Destructive: Data damage or function impact.
Trojans are derived from Trojans, which are hidden in Trojans and then cause attacks. Network Trojans refer to seemingly beneficial programs that actually hide a lot of information about users and control computer ports.
Programs are mainly hacker attacks, but 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 (destroyed only when certain conditions are met)
4. How to protect against computer viruses? How does the firewall and gateway play a protective role?
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, firewalls are classified into many categories,
1) A router at the network layer is a relatively low-level firewall. its working principle is to detect 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: Execute the software on the gateway to take data and analyze and store part of the information as the implementation detection.
