I. Multiple choice questions

The basic structure and technology of 1 The Internet originated in ()

A.DECnet B.ARPANET C.NOVELL D.ALOHA

2. The transmission mode used in WAN is ()

A. broadcast B. store and forward C. centralized control D. distributed control

3. The part of the computer network that is responsible for the communication task between nodes is called ().

A. node switching network B. node communication network C. user subnet D. communication subnet

4. The main function of the modem is ().

A.b. digital signal shaping

C. Conversion between analog signal and digital signal D. Coding of digital signal

5. If the line bandwidth of the noise-free channel is 3kHz and the number of discrete values that each symbol can take is 8, the maximum data transmission rate of the channel can reach ().

a . 24 kbps b . 48 kbps c . 12 kbps d . 18 kbps

6. In the modem with symbol rate of 2400 baud, the data transmission rate can be obtained by using 8PSK phase technology.

Used for ()

A. 2400 BP b. 4800 BP c. 7200 BP d. 1200 BP

7. Divide the total bandwidth of a physical channel into several subchannels with the same bandwidth as transmitting a single signal, and each channel transmits a signal. This channel multiplexing technique is called ().

A. spatial multiplexing B. time multiplexing C. frequency multiplexing D. none of the above is true.

8. In the T 1 carrier standard, 8 is proposed. CCITT, the number of bits contained in each frame and the time required to transmit a frame are () respectively.

A. 193，250 s B. 193， 125 s。

In 256 BC, 125 south latitude, 256 south latitude and 250 south latitude.

9. Two states in which two carrier signals with different amplitudes are used to represent binary values are called ().

A. amplitude shift keying method B. frequency shift keying method C. phase shift keying method D. amplitude-phase modulation

10. The sound signal is coded by pulse code modulation (PCM). If the sampling frequency is 8000 times per second and the quantization level is 256, then the data transmission rate should reach ().

a . 64 kbps b . 48 kbps c . 56 kbps d . 32 kbps

1 1. The typical code that can extract the synchronization signal from the data signal waveform is ().

A. non-return-to-zero code B. Manchester code C.BCD code D. cyclic redundancy code

12. Asynchronous Transfer Mode (ATM) is actually a combination of two switching technologies, which are ().

A. packet switching and frame switching circuit switching and packet switching

C. Packet switching and message switching D. Circuit switching and message switching

13. If you dial the extension by pulse dialing, the other party's number is 6275 1890, and the dialing command of the modem should be ().

A.ATDT0，6275 1890 B

C.ATDP6275 1890

14. electrical characteristic specification logic of EIA RS-232c? 0? The level range of is ()

A.0V to +5V B.-5V to 0V C.+5V to+15V D.- 15V to -5V.

15. Using HDLC protocol, the information transmission operation between combined stations is called ().

A. Asynchronous operation B. Synchronous operation C. Balanced operation D. Unbalanced operation

The BRI interface of 16.ISDN provides two B (payload) channels and one D (signaling) channel, and the highest transmission rate that users can use is ().

a . 64 kbps b . 128 kbps c . 144 kbps d . 1.544 Mbps

17. In the X.25 packet-level protocol, the packet type flag consists of the third byte of the header. If the lowest bit of this byte is? 0? , which means that the grouping is ()

A. data packet B. call request packet C. call indication packet D. confirmation packet

18.OSI defines five protocol levels for the transport layer, namely, level 0 ~ level 4, of which the lowest level of complexity is ().

A.4, b. 3 or 2, c. 0, d. 1.

19. In the header format of ATM, VPI and VCI fields are used for ().

A. Error control B. Flow control C. Congestion control D. Routing

20. About the token bus network, the following statement is true ().

A. it can't produce conflict. B. There will be conflicts.

C. conflicts can be avoided, but they still exist. D there is no conflict under light load, but there will be conflict under heavy load.

Second, fill in the blanks

2 1. Computer networks can be divided into message switching networks, packet switching networks and _ _ _ _ _ _.

22. With the Hamming code check method, if the information bit is 10 bit, the redundant bit is at least _ _ _ _ _ _ _ _.

23.OSI includes telegraph definition, protocol specification and _ _ _ _ _ _ three-level abstraction.

24. The commonly used operation methods of HDLC are normal response mode NRM, asynchronous balance mode ABM and _ _ _ _ _ _ _ _.

25. When the data link layer uses the sliding window mechanism to describe the GO-back-N method, its _ _ _ _ _ _ _ window is equal to 1, and its _ _ _ _ _ _ window is greater than 1.

26. Static routing is based on certain fixed rules and can be divided into three algorithms: flood routing, fixed routing and _ _ _ _ _ _ _.

27. Two common deadlocks are store-and-forward deadlocks and _ _ _ _ _ _ _ _.

28. Commonly used congestion control methods include buffer pre-allocation, packet loss and _ _ _ _ _ _ _.

29. In the five transport protocol levels defined by OSI, _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ refers to

30. A service is formally described by a set of _ _ _ _ _ _ _.

3 1. The inner bridge is called the inner bridge for short, and it exists in _ _ _ _ _ _ _ _; The outer bridge, referred to as the outer bridge for short, was built on _ _ _ _ _ _ _ _.

32. The lower five layers of the OSI environment provide transparent data transmission. _ _ _ _ _ _ _ _ _ _ is responsible for processing semantics, and _ _ _ _ _ _ _ is responsible for processing grammar.

33. When users use telephone lines and modems to access the network, or when two distant networks are interconnected by dedicated data lines, they need to run a special _ _ _ _ _ _ _ _ _ _ _ _ _ protocol at the data link layer.

34.IEEE 802.3 standard provides a functional description of the MAC sublayer, which mainly includes two aspects: data encapsulation and _ _ _ _ _ _ _.

35. Commonly used routers are divided into _ _ _ _ _ _ _ and _ _ _ _ _ _.

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