This set of Data communication and Networking Multiple Choice Questions and Answers (MCQs) focuses on “X.25 protocol ”.
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1. The size of the header of a long data packet at the PLP level is ___________ bytes
- 3
- 4
- 5
- none of the above
B. 4
2. In the short format, the size of an RR packet is _________ bytes.
- 3
- 5
- 4
- none of the above
A. 3
3. In the long format, the size of an RR packet is _________ bytes.
- 3
- 5
- 4
- none of the above
C. 4
4. X.25 is a _______ protocol.
- LAN
- WAN
- MAN
- none of the above
B. WAN
5. In the short format, the size of the RNR packet is _________ bytes.
- 3
- 5
- 4
- none of the above
A. 3
6. X.25 has _________ layers.
- three
- two
- one
- four
A. three
7. In the long format, the size of an RNR packet is _________ bytes.
- 3
- 5
- 4
- none of the above
C. 4
8. X.25 protocol uses ____________.
- its own physical layer
- the physical layer of Ethernet
- the physical layer of Token Ring
- none of the above
A. its own physical layer
9. In the short format, the size of an REJ packet is _________ bytes.
- 3
- 4
- 5
- none of the above
A. 3
10. The PLP packet is used in the _______ layer of the X.25 protocol.
- physical
- data link
- network
- transport
C. network
11. In the long format, the size of an REJ packet is _________ bytes.
- 3
- 5
- 4
- none of the above
C. 4
12. X.25 uses the ___________ protocol at the data link layer.
- LAPD
- LAPB
- PLP
- LAPX
B. LAPB
13. When a DTE receives a corrupted PLP packet, it sends an _________ control packet to the sender DTE.
- RR
- RNR
- REJ
- none of the above
C. REJ
14. The LAPB protocol is a version of the _________ protocol.
- SDLC
- BSC
- HDLC
- none of the above
C. HDLC
15. When a DTE receives an error-free PLP packet and is ready to receive more packets, it sends an _________ control packet to the sender DTE.
- RR
- RNR
- REJ
- none of the above
A. RR
16. Which layer in X.25 handles connection establishment?
- Physical
- Frame
- Network
- Transport
C. Network
17. When a DTE receives an error-free PLP packet, but is not ready to receive more packets, it sends an _________ control packet to the sender DTE.
- RR
- RNR
- REJ
- none of the above
B. RNR
18. X.25 uses _______ connections.
- SVC
- PVC
- both SVC and PVC
- none of the above
C. both SVC and PVC
19. When X.25 uses the short format, the number of PLP packets in transition can be up to __________.
- 7
- 127
- 1
- none of the above
A. 7
20. End-to-end addressing for X.25 is done by the _______ protocol.
- X.3
- X.121
- X.28
- none of the above
B. X.121
21. When X.25 uses the long format, the number of PLP packets in transition can be up to __________.
- 7
- 127
- 1
- none of the above
B. 127
22. The Triple-X protocols associated with X.25 are_____________.
- X.12, X.8, and X.121
- X.3, X.8, and X.122
- X.3, X.8, and X.121
- none of the above
D. none of the above
23. A DTE receives PLP packets with sequence numbers 23, 24, 27. What control packet should be sent to the sender?
- RR with sequence number 28.
- REJ with sequence number 27.
- REJ with sequence number 25.
- none of the above
C. REJ with sequence number 25.
24. The virtual circuit identifier in X.25 is called the _______.
- LNC
- LCN
- PVC
- SVC
B. LCN
25. A DTE receives PLP packets with sequence numbers 23, 24, 25. What control packet should be sent to the sender if the receiver is ready to receive more packets?
- RR with sequence number 28.
- REJ with sequence number 27.
- RNR with sequence number 25.
- none of the above
D. none of the above
26. The LCN in X.25 is _______ bits.
- 25
- 12
- 14
- 16
B. 12
27. A DTE receives PLP packets with sequence numbers 23, 24, 25. What control packet should be sent to the sender if the receiver is not ready to receive more packets?
- RR with sequence number 28.
- REJ with sequence number 27.
- RNR with sequence number 25.
- none of the above
D. none of the above
28. The LCN in X.25 can define theoretically up to ___________ virtual circuits.
- 1000
- 4000
- 2000
- 4096
D. 4096
29. A DTE using the short format sends a PLP packet with P(S) = 7. What is the sequence number of the next packet?
- 8
- 0
- 1
- none of the above
B. 0
30. Hop-to-hop flow and error control in X.25 is done at the _______ layer
- physical
- frame
- packet
- b and c
B. frame
31. A DTE wants to send a PLP data packet to another DTE. The packet should be encapsulated in an _______
- I-frame
- S-frame
- U-frame
- none of the above
A. I-frame
32. End-to-end flow and error control is done at the ____________ layer
- physical
- frame
- packet
- b and c
C. packet
33. A DTE wants to send a PLP RR packet to another DTE. The packet should be encapsulated in an _______ at the data link layer.
- I-frame
- S-frame
- U-frame
- none of the above
A. I-frame
34. A DTE which is connected to a DCE can use _______ LCN(s) to create connections for 10 application programs.
- only one
- 5
- 10
- 2
C. 10
35. A DTE wants to send a PLP call request packet to another DTE. The packet should be encapsulated in an _______ at the data link layer
- I-frame
- S-frame
- U-frame
- none of the above
A. I-frame
36. Multiplexing in X.25 is done at the _______ layer.
- physical
- data link
- network
- transport
C. network
37. An acknowledgment at the PLP layer is encapsulated in _________ at the data link layer.
- an I-frame
- an S-frame
- a U-frame
- none of the above
A. an I-frame
38. The window size for a short packet at the PLP layer is _________.
- 16
- 7
- 128
- none of the above
B. 7
39. A control packet such as a registration request at the PLP layer is encapsulated in _________ at the data link layer.
- an I-frame
- an S-frame
- a U-frame
- none of the above
A. an I-frame
40. The window size for a long packet at the PLP layer is _________.
- 16
- 7
- 127
- none of the above
C. 127
41. When a DTE wants to acknowledge the receipt of a frame from the local DCE, it uses ______________
- an I-frame
- an S-frame
- a U-frame
- none of the above
B. an S-frame
42. The size of the header of a short data packet at the PLP level is ___________ bytes
- 3
- 5
- 4
- none of the above
A. 3
43. Every PLP packet is encapsulated in ___________ at the data link layer.
- an I-frame
- an S-frame
- a U-frame
- none of the above
A. an I-frame
44. An I-frame carries ____________.
- a PLP data packet
- a PLP control packet
- a or b
- none of the above
C. a or b
45. An S-frame carries ____________.
- a PLP data packet
- a PLP control packet
- a or b
- none of the above
D. none of the above
46. A U-frame carries ____________.
- a PLP data packet
- a PLP control packet
- a or b
- none of the above
D. none of the above
47. Which of the following is true?
- A U-frame carries management information from the PLP layer.
- A U-frame carries management information from the frame level
- a or b
- none of the above
B. A U-frame carries management information from the frame level
48. Which of the following is true?
- An S-frame carries control information from the PLP level.
- An S-frame carries management information from the frame level
- a or b
- none of the above
D. none of the above
