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1. Multiple choice questions
1. The switching method with the smallest transmission delay time is (A)
A. Circuit switching B. Message switching C. Packet switching D. Cell switching
2. In the OSI seven-layer structure model, between the data link layer and the transport layer are (B)
A, physical layer B, network layer C, session layer D, presentation layer
3. Service and agreement are two completely different concepts. The following statement about them is wrong (D).
A. The protocol is horizontal, that is, the protocol is the rules governing the communication between peer entities. The service is vertical, that is, the service is provided by the lower layer to the upper layer through the interlayer interface.
B. Under the control of the protocol, the communication between two peer entities enables this layer to provide services to the upper layer. To implement the protocol of this layer, the services provided by the lower layer also need to be used.
C. The implementation of the protocol ensures that services can be provided to the upper layer.
D. OSI refers to the data unit exchanged between layers as a protocol data unit PDU.
4. In the OSI reference model, the data units transmitted by the data link layer and the physical layer are (C)
A, message (Message), bit (Bit) B, packet (Packet), message (Message)
C, Frame (Frame), Bit (Bit) D, Datagram (Datagram), Bit (Bit)
5. Among the following options, the one that does not belong to the layering of the OSI reference model is (B)
A. physical layer b. network interface layer c. data link layer d. Network layer
6. At the same time on the same channel, the communication method capable of two-way data transmission is (C)
A. Simplex B. Half-duplex C. Full-duplex D. None of the above three
7. If the multiplexing of the channel is distinguished by the time position (time slot) of the information in a frame, and no additional information header is required to mark the identity of the information, then this multiplexing method is (C) A, asynchronous time
division Multiplexing B, frequency division multiplexing C, synchronous time division multiplexing D, none of the above is correct
8. (C) has the best performance among the following transmission media.
A．twisted pair b. coaxial cable c. fiber d. All of the above are good.
9. There are several buildings surrounded by other power cables. If the buildings need to be connected to form a backbone campus network, (A) is more appropriate.
(A) Optical cable (B) Coaxial cable (C) Unshielded twisted pair (D) Shielded twisted pair
10. In the LAN architecture (B) is divided into two sublayers, MAC and LLC.
A, physical layer B, data link layer C, network layer D, transport layer
11. Among the following items, the one that is not a characteristic of datagram operation is (C)
A. Each packet itself carries enough information, and its transmission is processed separately.
B. During the entire transmission process, no virtual circuit needs to be established
C. Make all packets arrive at the destination end system in order
D. Network nodes must make routing choices for each packet
12. Hub is (C).
A, network card B, switch C, hub D, router
13. The following protocols do not belong to the protocol in the TCP/IP protocol suite (D)
A, ICMP B, TCP C, DNS D, HDLC
14. The transport layer of the TCP/IP model has two protocols. The first protocol TCP is a reliable connection-oriented protocol, and the second protocol UDP is (D).
A. A reliable connection-oriented protocol B. An unreliable connection-oriented protocol
C. A reliable connectionless protocol D. An unreliable connectionless protocol
15. The content of the message does not arrive at the destination node in order (D).
A. Circuit switching B. Message switching C. Virtual circuit switching D. Datagram switching
16. Which of the following does not belong to firewall technology is (D).
A IP filtering B Line filtering C Application layer proxy D Computer virus monitoring
17. The IP address of a certain computer is 132.121.100.1, so it belongs to (B) network.
A. Class A B. Class B C. Class C D. Class D
18. The basis of communication between various networks and various types of computers on the Internet is (D) protocol
(A) HTTP (B) IPX © X.25 (D) TCP/IP
19. The core protocol of the Internet is (B).
A. X.25 B. TCP/IP C. ICMP D. UDP
20. The transmission in the computer is (A) transmission, and the transmission on the communication line is transmission.
A, parallel, serial B, serial, parallel C, parallel, parallel D, serial, serial
21. The network topology that belongs to the centralized control mode is (A)
(A) star structure (B) ring structure© bus structure (D) tree structure
22. The following statement about network interconnection equipment is wrong (C).
A. Transponders and hubs can be used to extend the LAN at the physical layer.
B. A bridge can be used to extend the LAN at the data link layer.
C. An Ethernet switch is essentially a multi-port bridge, working at the network layer.
D. A router is used to interconnect different networks and is a network layer device.
23. The following statement about virtual local area network (VLAN) is wrong (D)
A. VLAN is a logical group composed of some LAN segments that has nothing to do with physical location.
B. VLAN can be realized conveniently by using Ethernet switches.
C. The workstations of each VLAN can be in different local area networks.
D. Virtual local area network is a new type of local area network.
24. The frame relay network is a kind of (A).
A. Wide area network B. Local area network C. ATM network D. Ethernet
25. Which of the following statements about IP address and hardware address is wrong ( D )
A. In LAN, hardware address is also called physical address or MAC address.
B. The hardware address is the address used by the data link layer and the physical layer. The IP address is used by the network layer and the above layers. C. The
IP address cannot be directly used for communication. It must be used to transmit data frames on the link of the actual network hardware address.
D. RARP is to solve the problem of mapping the IP address and hardware address of the host or router on the same LAN.
26. Regarding the IP address in the Internet, the following statement is wrong (D)
A. The network numbers in the IP addresses of hosts or routers on the same LAN must be the same.
B. The network segments interconnected by bridges are still a local area network and can only have one network number.
C. A router always has two or more IP addresses.
D. When two routers are directly connected, the IP addresses must be specified at the interfaces at both ends of the connection.
27. Regarding CIDR with non-classified addressing, the following statement is wrong (C)
A. CIDR uses "network prefixes" of various lengths to replace the network number and subnet number in the classified address.
B. CIDR combines consecutive IP addresses with the same network prefix into a "CIDR" address block.
C. The shorter the network prefix, the fewer addresses the address block contains.
D. Using CIDR, multiple matching results may be obtained when searching the routing table, and the route with the longest network prefix should be selected from the matching results. Because the longer the network prefix, the more specific the route.
28. The path selection function is completed in (C) of the OSI model.
A, physical layer B, data link layer C, network layer D, transport layer
29. At the level of the TCP/IP protocol family, the problem of communication between computers is solved in (B).
A. Network interface layer B. Internet layer C. Transport layer D. Application layer
30. The type of service provided by the IP protocol is (B).
A. Connection-oriented datagram service B. Connectionless datagram service
C. Connection-oriented virtual circuit service D. Connectionless virtual circuit service
31. The twisted pair transmission medium is to twist two wires together, which can reduce (B).
A. Attenuation during signal transmission B. Interference of external signals
C. Signal leakage D. Mutual crosstalk between signals
32. The ICMP protocol is located in (A)
A, network layer B, transport layer C, application layer D, data link layer
33. In the OSI model, the relationship between the Nth layer and the N+l layer above it is (A).
A. Layer N provides services for Layer N + 1
B. Layer N + 1 adds a header to the information received from Layer N
C. Layer N utilizes the services provided by Layer N + 1
D. Layer N has no effect on Layer N + 1
34. The address "128.10.0.0" is the (B) address.
A, A class B, B class C, C class D, D class
35. The protocol to convert IP address to physical address is (C)
A, IP B, ICMP C, ARP D, RARP
36. In order to realize high-efficiency data transmission, TCP/IP adopts UDP protocol in the transport layer, and the reliability of its transmission is provided by (A).
A. Application process B. TCP C. DNS D. IP
37. At present, the wide area networks that actually exist and are used basically adopt (C)
A, bus topology B, ring topology C, mesh topology D, and star topology
38. In the OSI hierarchy, the actual communication is carried out between (A) entities.
A, physical layer B, data link layer C, network layer D, transport layer
39. The IP address 192.1.1.2 belongs to (C) and its default subnet mask is
Class A, B, 255.255.0.0 Class B, A, 255.0.0.0
Class C, C, 255.255.0.0 Class D, C, 255.255. 255.0
40. In TCP, the establishment of the connection adopts the method of (C) handshake.
A, once B, twice C, three times D, four times
2. Fill in the blanks
1. Computer network can be divided into wide area network, local area network and metropolitan area network according to the scope of function .
2. The wide area network is composed of some contact switches and links connecting these switches .
3. The packet level of the X.25 protocol is equivalent to the layer in the OSI reference model, and its main function is to provide multi-channel
network virtual circuit services to the host.
4. The session layer of OSI is above the services provided by the transport layer and provides services for the presentation layer.
5. Now we often refer to two network architectures: one is OSI , which is a theoretical standard; the other is TCP/IP , which is a de facto industry standard.
6. There are three ways to modulate a digital signal into an analog signal, namely frequency modulation, amplitude modulation, and phase modulation .
7. In the local area network, the hardware address is also called physical address and MAC address .
8. The three basic issues of the data link layer are encapsulation into frames, transparent transmission, and error monitoring
9. In the TCP/IP network, the TCP protocol works at the transport layer, and the FTP protocol works at the application layer.
10. The TCP/IP transport layer has two different protocols, namely User Datagram Protocol UDP and Transmission Control Protocol TCP .
11. In the TCP/IP network, the physical address is related to the data link layer, the logical address is related to the network layer, and the port address is related to the transport layer.
12. In the virtual circuit service, before any transmission starts, the connection must be established first .
13. Among classified IP addresses, Class D addresses are multicast addresses.
14. The dedicated IP address can only be used as a local address and cannot be used as a global address.
15. In the TCP/IP protocol family, the protocol ICMP is located at the network layer and can transmit error and control messages .
16. The protocols included in the third layer (network layer) of the TCP/IP hierarchical model mainly include IP, ICMP, ARP and RARP .
17. When the datagram is transmitted in the physical network, the IP address is converted into a physical address.
18. A TCP connection process is divided into three stages, namely, connection establishment, data transmission, and connection release .
19. Every webpage (Home Page) on the WWW has an independent address, and these addresses are called Uniform Resource Locators (URL) .
20. There are two main protocols involved in e-mail: SMTP and POP3 .
3. Noun Analysis
1. Network architecture
Answer: The network architecture is to complete the communication and cooperation between computers, divide the functions of each computer interconnection into clearly defined levels, and stipulate the communication protocol between processes at the same level and the interfaces and services between adjacent ones. . These protocols for communication at the same layer and adjacent interfaces are collectively referred to as the network computer architecture.
2. LAN
Answer: LAN is the abbreviation of local area network. It is a general and popular local area network. Its main characteristics are: (1) geographical range; (2) high frequency bandwidth; (3) data transmission Reliable, low bit error rate; (4) Simple structure, easy to implement; (5) Network control tends to be distributed; (6) Usually owned by a single organization, it is easier to update equipment and introduce new technologies;
3. Network protocol
Answer: Protocol refers to a set of rules for managing data exchange between two communication devices. The network protocol is mainly composed of the following three elements: 1) grammar, that is, the structure or format of data and control information 2) semantics, that is, what kind of control information needs to be sent, what kind of operation to complete and what kind of response to make. 3) Synchronization, that is, a detailed description of the order in which events are implemented.
4. Multiplexing (Multiplexing)
Answer: In data communication or computer network systems, the bandwidth or capacity of transmission media often exceeds the requirements for transmitting a single signal. In order to effectively use communication lines, one channel can be used to transmit multiple signals. This method is called channel multiplexing, referred to as multiplexing (Multiplexing).
5. TCP/IP protocol
Answer: TCP/IP protocol is a communication protocol, including the standard of network communication on the Internet, as well as a set of network interconnection protocols and path selection algorithms. TCP is a transmission control protocol, which ensures that data is transmitted will not be lost; IP is a network protocol to ensure that data is transmitted to the designated location.
6. Router
Answer: A router is a key component for realizing packet switching, and its task is to forward received packets, which is the most important function of the core part of the network.
7. Transmission delay
Answer: Transmission delay: refers to the entire time required for a station to send a data frame from the beginning to the end of the data frame transmission, or it can be the entire time for the receiving station to receive the entire data frame.
4. Short answer questions
1. Briefly describe the main points of packet switching.
Answer: (1) Packets are grouped, adding headers (2) Stored and forwarded by routers (3) Combined at the destination
2. Discuss the results of computer networks according to different classification standards.
Answer:
According to the distribution of network nodes: LAN, MAN, WAN.
According to the network topology: bus, star, ring and mixed topology.
According to the transmission medium: wired network, optical fiber network, wireless network.
3. Briefly describe the simple functions of each layer of the OSI seven-layer model.
Answer:
1) Physical layer: transfer bit data stream (hardware interface, etc.)
2) Data link layer: transmission of data frames (node to node)
3) Network layer: transmission of data packets (routing, addressing, inspection, etc. )
4) Transport layer: transmission of data packets (end-to-end)
5) Session layer: responsible for the management of data units (connection, communication control, etc.)
6) Presentation layer: processing of data representation (encoding, encryption, decompression, etc. )
7) Application layer: application-oriented management (network and application interaction, etc.)
4. Briefly describe why the three problems of the data link layer must be solved?
Answer:
Frame delimitation is an inevitable requirement of packet switching;
transparent transmission avoids confusion between message symbols and frame delimitation symbols;
error detection prevents invalid data frames from wasting transmission and processing resources on subsequent routes.
5. Briefly describe the working principle of the media access control mode of Ethernet.
Answer: The medium access control method of Ethernet is CSMA/CD, and its working principle is:
1) Send data:
listen first and then send, listen while sending, stop conflict, extend and send again
2) Receive data:
all Ethernet networks The node has been continuously monitoring the data on the network. Once a carrier appears, it starts to intercept data from the network, and extracts the destination MAC address from the intercepted data. If the destination MAC address is itself, it deletes the MAC address and sends the data to the upper layer. Protocol delivery.
6. How is the IP address defined? How many categories are there? How to tell?
Answer:
IP address::={<network number>,<host number>}
The IP address is composed of the network number and the host number, with a total of 32 bits, which are divided into five categories: A, B, C, D and E.
Type A: The network number occupies 8 digits, and the first digit is 0, and the host number occupies 24 digits.
Type B: The network number occupies 16 digits, and the first two digits are 10, and the host number occupies 16 digits.
Type C: The network number occupies 24 digits, and the first three digits are 110, and the host number occupies 8 digits.
Type D: The first four digits are 1110, which is used for multicast.
Type E: the first four digits are 1111, reserved for future use
7. What is a subnet mask? What does 255.255.255.0 mean?
Answer: The subnet mask can indicate how the host address segment in the IP address divides the subnet address and host number. The subnet mask specifies that all 1s are the network number, and all 0s are the host number.
The subnet mask 255.255.255.0 represents the default subnet mask of a Class C IP address.
5. Final exam questions for colleges and universities
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