Section 3.6

Question 1

Fraction of packets retransmitted is equal to:

Answer 1

1-(lambda_out/lambda_in)

Question 2

The type of congestion control when The sender infers segment loss from the absence of an ACK from the receiver:

Answer 2

end-end

Question 3

The type of congestion control when Bits are set at a congested router in a sender-to-receiver datagram, and bits are in the returned to the sender in a receiver-to sender ACK, to indicate congestion to the sender

Answer 3

network-assisted

Question 4

The sender measures RTTs and uses the current RTT measurement to infer the level of congestion.

Answer 4

delay-based

Question 5

Which of the following actions are used in network-assisted congestion control (say versus end-end congestion control) to signal congestion. Check all that apply.

Answer 5

• A router marks a field in the datagram header at a congested router.
• A router sends an ICMP message to a host telling it to slow down its sending rate.

Question 6

Which of the following actions are associated with end-end congestion control (say versus network-assisted congestion control). Check all that apply.

Answer 6

• A router drops a packet at a congested router, which causes the transport-layer sender to infer that there is congestion due to the missing ACK for the lost packet.
• The transport-layer sender decreases its sending rate in response to a measured increase in the RTT.
• A datagram experiences delay at a congested network router, which is then measured by the sender and used to decrease the sending rate.
• A sender decreases its sending rate in response to packet loss detected via its transport-layer ACKing.