Peer-to-Peer Protocols and Local Area Networks - Week 1
In networks where errors are infrequent, which approach is favored for efficiency?
a, Hop-by-hop approach
b, End-to-end approach
c, Either one of the above
d, Neither one of the above ✔️b
Which of the following statements is true about the stop-and-wait ARQ protocol?
a, Stop-and-wait is only efficient if the link delay-bandwidth product is small
b, Stop-and-wait is only efficient if the link delay-bandwidth product is large
c, Stop-and-wait is only efficient if the link bandwidth is low
d, Stop-and-wait is only efficient if the link bandwidth is high ✔️a
Consider a situation where an interactive application produces a packet to send each keystroke from the
client and the server echoes each keystroke that it receives from the client. Which of following
strategies for sending ACK frames in a Go-Back-N is appropriate for the situation?
a, send an ACK frame immediately after each frame is received
b, send an ACK frame after every other frame is received
c, send an ACK frame when the next piggyback opportunity arises
d, Any one of the above
** Since each keystroke is echoed, there will always be a piggyback opportunity. Thus, the piggyback
method should be used. Indeed, the echo packet constitutes an acknowledgment. ✔️c
Consider a bulk data transfer application where a server sends a large file that is segmented in a number
of full-size packets that are to be transferred to the client. Assume the channel has a low probability of
error. Which of following strategies for sending ACK frames in a Go-Back-N is appropriate for the
situation?
a, Any one of the above
, b, send an ACK frame when the next piggyback opportunity arises
c, send an ACK frame after every other frame is received
d, send an ACK frame immediately after each frame is received
** The upstream traffic to a server is generally much less than the downstream traffic. Thus, the
piggybacking method is non-ideal in this case. If the channel has a low probability of error, the
alternating ACK method is better, as it saves bandwidth. ✔️c
Consider Selective Repeat ARQ flow control protocol. In the following scenario, what should be the
value of frame number x at receiver B?
a, 3
b, 2
c, 4
d, None of the above
** Even if frame 3 is received, frame 2 is still missing in the receiver's buffer. Therefore, receiver
acknowledges frame 2, meaning it expects the next frame to be frame 2 after the current sending
window. ✔️c
ARQ protocols combine error detection, retransmission and sequence numbering to provide reliability
a, True
b, False ✔️a
A service model specifies a level of performance that can be expected in the transfer of information.
a , True
b, False ✔️a
A service offered at a given layer can include which of the following feature(s)
a, Sequencing
b, Reliability
In networks where errors are infrequent, which approach is favored for efficiency?
a, Hop-by-hop approach
b, End-to-end approach
c, Either one of the above
d, Neither one of the above ✔️b
Which of the following statements is true about the stop-and-wait ARQ protocol?
a, Stop-and-wait is only efficient if the link delay-bandwidth product is small
b, Stop-and-wait is only efficient if the link delay-bandwidth product is large
c, Stop-and-wait is only efficient if the link bandwidth is low
d, Stop-and-wait is only efficient if the link bandwidth is high ✔️a
Consider a situation where an interactive application produces a packet to send each keystroke from the
client and the server echoes each keystroke that it receives from the client. Which of following
strategies for sending ACK frames in a Go-Back-N is appropriate for the situation?
a, send an ACK frame immediately after each frame is received
b, send an ACK frame after every other frame is received
c, send an ACK frame when the next piggyback opportunity arises
d, Any one of the above
** Since each keystroke is echoed, there will always be a piggyback opportunity. Thus, the piggyback
method should be used. Indeed, the echo packet constitutes an acknowledgment. ✔️c
Consider a bulk data transfer application where a server sends a large file that is segmented in a number
of full-size packets that are to be transferred to the client. Assume the channel has a low probability of
error. Which of following strategies for sending ACK frames in a Go-Back-N is appropriate for the
situation?
a, Any one of the above
, b, send an ACK frame when the next piggyback opportunity arises
c, send an ACK frame after every other frame is received
d, send an ACK frame immediately after each frame is received
** The upstream traffic to a server is generally much less than the downstream traffic. Thus, the
piggybacking method is non-ideal in this case. If the channel has a low probability of error, the
alternating ACK method is better, as it saves bandwidth. ✔️c
Consider Selective Repeat ARQ flow control protocol. In the following scenario, what should be the
value of frame number x at receiver B?
a, 3
b, 2
c, 4
d, None of the above
** Even if frame 3 is received, frame 2 is still missing in the receiver's buffer. Therefore, receiver
acknowledges frame 2, meaning it expects the next frame to be frame 2 after the current sending
window. ✔️c
ARQ protocols combine error detection, retransmission and sequence numbering to provide reliability
a, True
b, False ✔️a
A service model specifies a level of performance that can be expected in the transfer of information.
a , True
b, False ✔️a
A service offered at a given layer can include which of the following feature(s)
a, Sequencing
b, Reliability
