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1. 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

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. Given G(x) = X^7 + X^3 + X^2 + 1, what is the hexadecimal value of the divisor?

a) $CB
b) $8D
c) $1E
d) $5A
e) None of these

4. A group of data sent together is called a/an:

a) Block check character
b) Frame
c) Block
d) (B) or (C)
e) None of these

5. 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

6. When a Hamming data receiver half-adds (exclusive-ORs) the received checkbits with the regenerated checkbits, what is the meaning of the result?

a) The count of bits in the word that were in error
b) The checksum of the all the data in the block
c) The address of the bit in error
d) None of these

7. 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

8. Where is the address contained within a 3270 message?

a) After the STX character within the message
b) Within the header
c) After the BCC
d) None of these

9. 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
c) WACK
d) RVI
e) None of these

10. 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

11. 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

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

a) WACK
b) ACK1
c) NAK
d) None of these

13. 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
d) WACK
e) None of these

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

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

15. The following HDLC exchange occured on a network:

RR A=43 P/F=1 NR=07

                    I A=43 P/F=0 NR=06 NS=07
                    I A=43 P/F=0 NR=06 NS=00
                    I A=43 P/F=0 NR=06 NS=01
                    I A=43 P/F=1 NR=06 NS=02
RR A=43 P/F=1 NR=00

What will happen next on the network?

a) The primary unit will service the next terminal in the poll list
b) Secondary unit 43 will transmit frames 0,1,2
c) Secondary unit 43 will transmit only frame 0
d) The host will lock secondary unit 43 off the network, no longer polling it

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. 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

18. The NR/NS acknowledgment system of HDLC could be classified as functioning in what OSI model layer?

a) 1 - Physical
b) 2 - Data Link
c) 3 - Network
d) 4 - Transport
e) 5 - Session
f) 6 - Presentation
g) 7 - Application

19. Within the zero-stuffed area of an HDLC data frame, how will the data pattern %1111 1111 be represented?

a) 1111 10101
b) 1111 10111
c) 1010 11101
d) 0001 11110
e) None of these

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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