3.4-3.5

Question 1

What is Go Back N?

Answer 1

sender can have up to N unacked packets in pipeline
receiver only sends cumulative ack
sender has timer for oldest unacked packet
• when timer expires, retransmit all unacked packets

Question 2

What is selective repeat?

Answer 2

sender can have up to N unack’ed packets in pipeline
rcvr sends individual ack for each packet
sender maintains timer for each unacked packet
• when timer expires, retransmit only that unacked packet

Question 3

What is RTO?

Answer 3

Round Trip Timeout

Usually is RTT + some buffer time

if RTO has elapsed and an ACK hasn’t been received retransmission is triggered

Question 4

What is flow control?

Answer 4

receiver controls sender, so sender won’t overflow receiver’s buffer by transmitting too much, too fast