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1. The units of data exchanged by a Data Link Layer protocol are called ?（）
A. Frames
B. Segments
C. Datagrams
D. Bit streams
2. Which of the following services can not offered by a Data Link Layer protocol?（）
A. Congestion control
B. Link Access
C. Error control
D. Framing
3. For the sliding window protocol, if the frame number uses a 3bit number, and the sending window size is 5, then the maximum receiving window size is ?（）
A. 2
B. 3
C. 4
D. 5
4.Using the selective repeat protocol, the sender has sent data frames numbered 0~3, and has received confirmation for frame 1. However, frames 0 and 2 have timed out. How many frames need to be resent ?（）
A. 1
B. 2
C. 3
D. 4
5.Using the go back N protocol, the sender has already sent data frames numbered 0~7. When the timer timeout, if the sender only receives confirmations for frames 0, 2, and 3, then, how many frames need to be resent ?（）
A. 2
B. 3
C. 4
D. 5
6.Assuming the transmission success rate of the physical channel is 95%, a network layer packet requires 10 data link layer frames to be sent. What is the success rate of sending network layer packets if the data link layer uses unconfirmed connectionless services ?（）
A. 40%
B. 60%
C. 80%
D. 95%
7. Which of the following is incorrect?（）
A. Selective repeat does not allow the sender to continuously send data frames without receiving confirmation.
B. Selective repeat only requires the sender to resend the error frames.
C. Under the same conditions, the efficiency of the go back N protocol is lower than that of the selective repeat protocol.
D. All of the above.
8. Which of the following is incorrect?（）
A. CRC is an error detection code.
B. CRC is an error correction code.
C. CRC can detect random errors.
D. CRC can detect burst errors.
9. Which is not a data link layer's function ?（）
A. Framing
B. Circuit management
C. Error control
D. Flow control
10. Which can be improved by increasing the signal-to-noise ratio ?（）
A. Random error
B. Burst error
C. Data loss
D. All of the above
11. In the following four descriptions about random access protocol, which one is not correct ?（）
A. In slotted ALOHA, nodes can transmit at random time.
B. In pure ALOHA, if a frame experiences a collision, the node will immediately retransmit it with probability p.
C. The maximum efficiency of a slotted ALOHA is higher than a pure ALOHA.
D. In CSMA/CD, one node listens to the channel before transmitting.
12. In the following descriptions about MAC address, which one is not correct ?（）
A. The MAC address is the address of one node’s adapter.
B. No two adapters have the same MAC address.
C. The MAC address doesn’t change no matter where the adapter goes.
D. MAC address has a hierarchical structure.
13. The value of Preamble field in Ethernet frame structure is ?（）
A. 10101010 10101010……10101010 1111111
B. 10101011 10101011……10101011 10101011
C. 10101010 10101010……10101010 10101011
D. 10101010 10101010……10101010 10101010
14. The most common Ethernet technologies are 10BaseT and 100BaseT. “10” and “100” indicate ?（）
A. the maximum length between two adapters.
B. the minimum length between two adapters.
C. the transmission rate of the channel.
D. the transmission rate of the node.
15. In the following four options, which service can not be provided by switch ?（）
A. filtering
B. self-learning
C. forwarding
D. optimal routing
16. MAC address is ( ) bits long.（）
A. 32
B. 48
C. 64
D. 128
17. Wireless LAN using protocol （）.
A. IEEE 802.3
B. IEEE 802.4
C. IEEE 802.5
D. IEEE 802.11
18.The following protocols are belonging to multiple access protocols except for（）.
A. channel partitioning protocols
B. routing protocols
C. random access protocols
D. taking-turns protocols
19. In the following four descriptions about CSMA/CD, which one is not correct?（）
A. node listens to the channel before transmitting
B. If someone else begins talking at the same time, stop talking
C. A transmitting node listens to the channel while it is transmitting
D. With CSMA/CD, the collisions can be avoided completely
20. Which of the following is correct ?（）
A. No two adapters have the same MAC address
B. MAC broadcast address is FF–FF–FF–FF–FF
C. A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes
D. All of the above
21. Because there are both network-layer addresses (for example, Internet IP addresses) and link-layer addresses (that is, LAN addresses), there is a need to translate between them. For the Internet, this is the job of （）.
A. RIP
B. OSPF
C. ARP
D. IP
22. Which device has the same collision domain ?（）
A. Hub
B. Switch
C. Router
D. Bridge
23. A ___ is a physical-layer device that acts on individual bits rather than on frames.（）
A. switch
B. hub
C. router
D. gateway
24. The network layer must determine the path taken by packets as they flow from a sender to a receiver. This action is called ?（）
A. Forwarding
B. Routing
C. Cut through
D. Examine
25. IP belongs to ____ layer ?（）
A. transport
B. Network
C. data link
D. physical
26. Which layer provides host-to-host services ?（）
A. transport
B. network
C. data link
D. physical
27. IPv4 has a ___ bit address ?（）
A. 16
B. 32
C. 48
D. 64
28. Most IPv4 datagram do not contain option field, how many bytes a header has in a typical IP datagram ?（）
A. 4 bytes
B. 8 bytes
C. 16 bytes
D. 20 bytes
29. The data field in IP datagram can carry many types of data except ?（）
A. TCP
B. UDP
C. ICMP
D. MAC
30. Suppose you receive an IP datagram from one link and check your forwarding table to determine the outgoing link, but this outgoing link has an MTU that is smaller than the length of IP datagram. Which technology will be used ?（）
A. resend
B. discard
C. fragment
D. none
31. A transport-layer protocol provides for logical communication between ?（）
A. Application processes
B. Hosts
C. Routers
D. End systems
32. In transport layer, the send side breaks application messages into ____, passes to network layer.（）
A. Frames
B. Segments
C. Datagrams
D. bit streams
33. Services provided by transport layer include ____.（）
A. HTTP and FTP
B. TCP and IP
C. TCP and UDP
D. SMTP
34. The port numbers ranging from ____ to ____ are called well-known port number and are restricted.（）
A. 0, 1023
B. 0, 65535
C. 0, 127
D. 0, 255
35. The SYN segment is used for ?（）
A. Closing a TCP connection
B. TCP flow control
C. TCP congestion control
D. TCP connection setup
36. Which of the following field is not used for connection setup and tear down ?（）
A. Sequence number
B. TST
C. SYN
D. FIN
37. —— is the byte sequence numbers of next byte expected from other side.（）
A. Sequence number
B. ACK number
C. Checksum
D. Port number
38. Suppose host A sends two TCP segments back to back to host B over a TCP connection. The first segment has sequence number 42, and the second has sequence number 110. If the first is lost and second arrives at host B. What will be the acknowledgment number?（）
A. 42
B. 43
C. 109
D. 110
39. ___ are two states in TCP congestion control.（）
A. slow start and congestion abandon
B. safe start and congestion avoidance
C. slow start and congestion avoidance
D. safe start and congestion abandon
40. The receive side of transport layer reassembles segments into messages, passes to ______ layer.（）
A. MAC
B. Networking
C. Physical
D. Application
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