https://www.youtube.com/watch?v=-ZIULmY5SJg
8.1. Which of the following features are usually expected to be provided by transport protocol ?
(a) Guaranteed message delivery
(b) Delivers messages in the same order they were sent
(c) Delivers at least one copy of each message
(d) Supports finite length of messages
(e) Allows the receiver to apply flow control to the sender
8.2. Which of the following are typical limitations of the network service (like IP of Internet) on which transport protocol will operate ?
(a) Drop messages
(b) Deliver only one copy of a given message
(c) Reorder messages
(d) Limit messages to some finite size
(e) Deliver messages within a bounded delay
Transport-Protocols-2
https://www.youtube.com/watch?v=jNVaRifMH20
8.3. Which of the following statements are correct for “Transport Control Protocol (TCP)” ?
(a) TCP provides unreliable service
(b) TCP is a connection oriented protocol
(c) TCP is a connectionless protocol
(d) TCP is a byte-oriented service protocol, and each byte has a sequence number
(e) TCP is a packet-oriented service protocol and each packet has a sequence number.
8.4. Which of the following statements are correct for “flow control and congestion control” ?
(a) Flow control involves preventing senders from overrunning the capacity of the receivers
(b) Flow control involves preventing senders from overrunning the capacity of the networks.
(c) Congestion control involves preventing senders from overrunning the capacity of the networks.
(d) Congestion control involves preventing senders from overrunning the capacity of the receivers.
(e) Congestion control involves preventing senders from overrunning the capacity of the receivers and networks.
Transport-Protocols-3
8.5. Which of the following statements are correct for “TCP segments” ?
(a) When the sender sends bytes to a TCP connection, the TCP will forward these bytes immediately as a TCP segment.
(b) TCP does not transmit individual bytes over the Internet.
(c) The source TCP buffers enough bytes from the sending process to fill a reasonably sized segment and then sends out this segment.
(d) The destination TCP puts the contents of the received segment into a receive buffer, and the receiving process reads from this buffer.
(e) When the destination TCP receives a segment, it will deliver the segment to receiving process immediately.
https://www.youtube.com/watch?v=sAP0CTaj400
8.6. Which of the following fields of TCP header are involved in TCP's sliding window algorithm ?
(a) Acknowledgment,
(b) AdvertisedWindow
(c) Destination port number
(d) SequenceNum,
(e) Source port number
8.7. Which of the following statements about “sequence number” of TCP are correct ?
(a) TCP is a byte-oriented protocol and each byte of data has a sequence number.
(b) TCP is a byte-oriented protocol and each segment of data has a sequence number.
(c) The SequenceNum field of TCP header contains the sequence number for the first byte of data carried in that segment.
(d) The SequenceNum field of TCP header contains the sequence number for the last byte of data carried in that segment.
(e) The SequenceNum field of TCP header has a length of 16 bits.
8.8. The TCP header includes six flags: SYN, FIN, RESET, PUSH, URG, and ACK. Which of the following statements about these flags are correct ?
(a) The SYN and FIN flags are used when terminating and establishing a TCP connection, respectively.
(b) The ACK flag is set any time the Acknowledgment field is valid, implying that the receiver of this segment should pay attention to it.
(c) The URG flag signifies that this segment contains urgent data and the urgent data is contained at the bottom of the segment body.
(d) The PUSH flag signifies that the sender invoked the push operation, which indicates to the receiving side of TCP that it should notify the receiving process of this fact.
(e) The RESET flag signifies that the receiver wants to abort the connection.
8.9. The Checksum field in TCP header is computed over the TCP header, the TCP data, and the “pseudoheader”. Which of the following fields are included in the “pseudoheader”?
(a) Source IP address of IP header
(b) Destination IP address of IP header
(c) Length field of IP header.
(d) Source port of TCP header
(e) Destination port of TCP header
Transport-Protocols-5
8.10. The TCP uses three-way handshaking mechanism to establish a connection. Consider the following timeline chart for three-way handshaking mechanism. Assume that
“1” represents the “SYN” flag is set
“2” represents the “ACK” flag is set,
“3” represents both the “SYN” and “ACK” flags are set.
“4” represents the “FIN” flag is set
“5” represents the “RESET” flag is set
Then for this timeline chart, we have
a = 1
b = 3
c = 2
d = 101
e = 201
8.11. Consider the following timeline chart for closing a TCP connection, starts from the client. Assume that
“1” represents the “SYN” flag is set
“2” represents the “ACK” flag is set,
“3” represents both the “SYN” and “ACK” flags are set.
“4” represents the “FIN” flag is set
“5” represents the “RESET” flag is set
Then for this timeline chart, we have
a = 4
b = 2
c = 4
d = 2
8.12. Consider the following TCP client state diagram. Assume that
“1” represents the “receive ACK and send nothing”
“2” represents the “send SYN” ,
“3” represents the “receive SYN/ACK and send ACK”
“4” represents the “wait 30 seconds”
“5” represents the “receive FIN and send ACK”
“6” represents the “send nothing”
“7” represents the “send FIN”
Then for this TCP client state diagram, we have
a = 2
b = 3
c = 7
d = 1
e = 5f = 4
Transport-Protocols-6
https://www.youtube.com/watch?v=NJp1MoMmoWU
8.13. Consider the following TCP server state diagram. Assume that
“1” represents the “receive ACK and send nothing”
“2” represents the “send SYN” ,
“3” represents the “receive SYN/ACK and send ACK”
“4” represents the “wait 30 seconds”
“5” represents the “receive FIN and send ACK”
“6” represents the “send nothing”
“7” represents the “send FIN”
“8” represents the “receive SYN and send SYN/ACK”
Then for this TCP server state diagram, we have
a = 6
b = 8
c = 1
d = 5
e = 7f = 1
Transport-Protocols-7
https://www.youtube.com/watch?v=2AutJrL_Qyc
8.14 In TCP fast retransmission mechanism, when a packet arrives out of order, the TCP resends the same acknowledgment it sent last time. This second transmission of the same acknowledgment is called a “duplicate ACK”. Which of the following statements are correct ?
(a) When the sending side sees a duplicate ACK, it knows that the other side must have received a packet out of order.
(b) When the sending side sees a duplicate ACK, it is also possible that the earlier packet has only been delayed rather than lost
(c) When the sending side sees a duplicate ACK, it knows that the other side must have received a packet out of order, and the packet was already lost.
(d) When the sending side sees a duplicate ACK, it is NOT possible that the earlier packet has only been delayed rather than lost
(e) When the sending side sees a duplicate ACK, it knows that the packet was already lost, and will retransmit the packet immediately
8.15 In TCP fast retransmission mechanism, when a packet arrives out of order, the TCP resends the same acknowledgment it sent last time. This second transmission of the same acknowledgment is called a “duplicate ACK”. How many duplicate ACKs the TCP will wait before retransmitting the packet ?
Ans : 3
Transport-Protocols-8
https://www.youtube.com/watch?v=rxFs37YBk8c
Transport-Protocols-9
https://www.youtube.com/watch?v=cOlkc497keM
8.16 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, how to determine the value for “CongestionWindow” ?
(a) The receiving side of TCP will send a suitable CongestionWindow to the sending side of TCP.
(b) No one will send a suitable CongestionWindow to the sending side of TCP.
(c) TCP source sets the CongestionWindow based on the congestion level it observed.
(d) TCP source increasing the CongestionWindow when the level of congestion goes up
(e) TCP source decreasing the CongestionWindow when the level of congestion goes down.
8.17 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, how does the TCP source determine that the network is congested ?
(a) TCP interprets “packet lose” as a sign of congestion.
(b) The receiving side of TCP will send a “congested notification” packet to the sending side of TCP.
(c) The routers in the Internet who dropped packets will send a “congested notification” packet to the sending side of TCP.
(d) When the TCP source receives 3-duplicate ACKs
(e) When “timeout” happens in the TCP source.
8.18 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, what is the action when the TCP source receives 3-duplicate ACKs ?
(a) The source sets CongestionWindow to 1/2 of its previous value.
(b) The source sets CongestionWindow to 1/3 of its previous value.
(c) The source sets CongestionWindow to 1/4 of its previous value.
(d) The source sets CongestionWindow to 1/5 of its previous value.
(e) The source sets CongestionWindow to 1 MSS (maximum segment size).
8.19 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, the TCP source increases the congestion window when the newly capacity of network is available. Which of the following statements are correct ?
(a) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds the equivalent of 1 packet of MSS to CongestionWindow.
(b) Every time the source successfully sends a packet (the sent packet has been ACKed), it adds the equivalent of 1 packet of MSS to CongestionWindow.
(c) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds the equivalent of 1/2 packet of MSS to CongestionWindow.
(d) Every time the source successfully sends a packet (the sent packet has been ACKed), it adds the equivalent of 1/2 packet of MSS to CongestionWindow.
(e) Every time the source successfully sends a CongestionWindow’s worth of packets (all packets sent out during the last RTT have been ACKed), it adds the equivalent of 3 packets of MSS to CongestionWindow.
8.20 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, TCP does not wait for an entire window’s worth of ACKs to add 1 packet’s worth to the congestion window, but instead increments CongestionWindow by a little (denoted as increment) for each ACK. Which of the following is correct for this increment ?
(a) Increment =1/CongestionWindow
(b) Increment = 1/MSS
(c) Increment = MSS/CongestionWindow
(d) Increment = MSS (MSS/CongestionWindow)
(e) Increment = MSS/(CongestionWindow+MSS)
Transport-Protocols-10
https://www.youtube.com/watch?v=Deg0Y-KoobE
8.21 Which of the following statements are correct for “slow start” in TCP congestion control ?
(a) Slow start effectively increases the congestion window linearly
(b) Slow start is used to increase the congestion window rapidly from a cold start
(c) When the ACK for a packet arrives TCP source, the TCP source adds 1 packet size of MSS to CongestionWindow
(d) When the ACK for a packet arrives TCP source, the TCP source doubles the size of CongestionWindow
(e) Slow start effectively doubles the number of packets the TCP source has in transit every RTT
8.22 For the Additive Increase Multiplicative Decrease (AIMD) mechanism used in TCP congestion control, what is the action when the TCP source happens “timeout” ?
(a) The source sets CongestionWindow to 1/2 of its previous value.
(b) The source sets CongestionWindow to 1/3 of its previous value.
(c) The source sets CongestionWindow to 1/4 of its previous value.
(d) The source sets CongestionWindow to 1/5 of its previous value.
(e) The source sets CongestionWindow to 1 MSS (maximum segment size).
8.23 Which of the following statements are correct for a TCP source to handle the “packet lost” in congestion control ?
(a) After receives 3 duplicate ACKs, the CongestionWindow is cut in half and then grows linearly.
(b) After receives 3 duplicate ACKs, the CongestionWindow is set to 1 MSS and then grows linearly.
(c) After timeout event happes, the CongestionWindow is set to 1 MSS; the window then grows exponentially to a threshold, and then grows linearly.
(d) After timeout event happes, the CongestionWindow is set to 1 MSS; the window then grows linearly.
(e) After timeout event happes, the CongestionWindow is cut in half; the window then grows exponentially to a threshold, and then grows linearly.
8.24 Which of the following statements are correct for the “Threshold” used in TCP congestion control ? Please note that we said sender is in “slow-start phase” when the CongestionWindow is below Threshold, and in “congestion-avoidance phase” when the CongestionWindow is above Threshold.
(a) When a sender is in slow-start phase, its window grows exponentially.
(b) When a sender is in congestion-avoidance phase, its window grows linearly.
(c) When a triple duplicate ACK occurs, the Threshold is set to CongWin/2 and CongWin is set to Threshold.
(d) When timeout occurs, the Threshold is set to CongWin/2 and CongWin is set to Thresheld.
(e) When timeout occurs, the Threshold is set to CongWin/2 and CongWin is set to 1 MSS.
Transport-Protocols-11 12
https://www.youtube.com/watch?v=QWEj0NQ01e4
8.25 Consider the following figure to demonstrate the growth of CongestionWindow size for different “packet lost” events in TCP congestion control. We can use the following events to “describe” the curve in this figure. Initially, the connection is in slow start period with CongestionWindow size = 1 (1MSS).
Event 1: 3-duplicate ACKs happens at 5th RTT
Event 2: Timeout happens at 10th RTT
Event 3: 3-duplicate ACKs happens again at 18th RTT.
And we have a = 16 (window size), b = 8 (window size), c = 12 (window size), d = 6 (Threshold), e = 10 (window size), f = 5 (Threshold) as shown in the figure.
Event 1: 3-duplicate ACKs happens at 4th RTT
Event 2: Timeout happens at 17th RTT
Event 3: 3-duplicate ACKs happens again at 25th RTT.
Then we have
a =8(window size),
b =4(window size),
c =16(window size),
d =8(Threshold),
e =12(window size),
f =6(Threshold).
And what is the CongestionWindow size at the following points?
At 3rd RTT :4
At 17th RTT :16
At 22th RTT :9
At 30th RTT :10
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