ECT215 Practice Test III

Instructions: There are 20 questions on this test. It is written in a style very similar to the REAL exam #2. Choose the best answer from among those given. Click the GRADE button on the bottom of the form when you want the exam graded.

Note: You can practice this test as many times as you desire; the system will cook you up a fresh batch of questions each time you access this page.

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1. What is the meaning of the control signal NAK in an ARQ system?

a) Bad data detected; resend the data again
b) Receiver unreachable; no connection was possible
c) Too many retries in transmitting the data; abort
d) None of these

2. Which BCC value below is the correct EVEN longitudinal parity for the data block {$02, $03}? The values are in hexadecimal.

a) $af
b) $01
c) $04
d) None of these

3. What is the purpose of a block check character in data communications?

a) It contains redundant information for check the accuracy of the data
b) It contains a duplicate of all the information within the data block
c) It holds the address of the sender and receiver units
d) None of these

4. Given G(x) = X^5 + X^3 + X^2 + 1, what size CRC (in bits) will result?

a) 2
b) 3
c) 5
d) 8
e) None of these

5. In a Hamming encoder for 4-bit data, the checkbits would be in what positions?

a) C1, C2, C3
b) C2, C3, C4
c) C2, C4, C5
d) C1, C2, C4
e) None of these

6. In the process of calculating a CRC, the BCC is what arithmetic result?

a) Remainder
b) Divisor
c) Dividend
d) Quotient
e) None of these

7. Which BCC value below is the correct 8-bit checksum for the data block {$42, $C3}? The values are in hexadecimal.

a) $27
b) $FF
c) $05
d) None of these

8. If a terminal doesn't respond to a host poll or select command in a 3270 network, what will likely happen next?

a) The host will exclude the device on subsequent rounds; the terminal is locked out
b) The host will try communicating with the device for about 150 seconds before giving up
c) The host will skip the device and try it again on the next loop
d) None of these

9. When IBM3270 is running in multidrop mode, what response does a terminal provide to a poll when it has no data for the host?

a) EOT
b) ACK0
c) ACK1
e) None of these

10. If a terminal is busy or has a full memory buffer when it is selected by a host, how might it respond to a select command in the IBM 3270 protocol?

a) ACK0
b) ACK1
d) RVI
e) None of these

11. Which of these gives the correct order of operations for a 3270 point-to-point network?

a) Bid, communicate, release
b) Communicate, release, poll
c) Poll, communicate, Bid
d) Select, communicate, release
e) None of these

12. When a terminal unit is selected in IBM 3270 protocol (and is ready for data), what is its normal response?

b) ACK1
c) NAK
d) None of these

13. What is the correct response to the 5th valid data block in an IBM3270 "conversation?"

a) ACK0
c) ACK1
d) NAK
e) None of these

14. You're troubleshooting an IBM 3270 network that seems to be locked - no communications is occuring and host has locked out all the remote terminal units. On the host modem you notice that the DCD light is steadily lit. What is likely wrong?

a) The host modem is defective and unable to receive any signal from the network
b) The host modem is stuck in transmit mode and unable to receive any signals
c) One of the remote units is stuck in transmit mode
d) None of these

15. What is the advantage of the windowing system used in the HDLC protocol?

a) Better detection of multiple-bit (burst) errors in the transmitted data stream
b) Less time (bandwidth) used for generating acknowledgement messages
c) Simplification of the receiver-transmit handshaking method
d) None of these

16. What is a "piggybacked acknowledge?"

a) An acknowledge that is sent within an information frame
b) An acknowledge that confirms reception of several consecutive frames
c) An acknowledge that confirms that at least 50% of the data in a frame is correct
d) None of these

17. In the HDLC protocol, what pattern marks the beginning and end of data frames?

b) BCC
c) FCS
d) LRC
e) None of these

18. What is the maximum number of frames that can be sent without an immediate acknowledge in HDLC?

a) 1
b) 2
c) 3
d) 4
e) 5
f) 6
g) 7
h) 8

19. A primary unit sends the following frame. What will probably happen next on the network?

RR A=02 P/F=1 NR=03

a) Secondary unit 03 will stop responding to any further host requests
b) All units on the network will get ready to receive the subsequent broadcast data frame(s)
c) Secondary unit 02 will respond with a frame for the host
d) None of the above

20. The following HDLC exchange occured on a network:

RR A=7E P/F=1 NR=07

                    I A=7E P/F=0 NR=06 NS=07
                    I A=7E P/F=1 NR=06 NS=00

What will the host respond with if all the frames have been correctly received (assuming that the host doesn't have any data to send to unit $7E.)

a) RR A=7E P/F = 1 NR=02
b) RNR A=7E P/F = 1 NR=07
c) RR A=7E P/F = 0 NR=01
d) None of these

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