Reliable Communication

Question	Answer
How can you check for errors?	- Check the bitsum - use sequence numbers
what is ARQ?	an error-control protocol that automatically initiates a call to retransmit any data packet or frame after receiving flawed or incorrect data. When the transmitting device fails to receive an acknowledgement signal to confirm the data has been received, it usually retransmits the data after a predefined timeout and repeats the process a predetermined number of times until the transmitting device receives the acknowledgement.
stop-and-wait ARQ	It has one frame at a time sent with no additional frames sent until reception of the previous one is confirmed via an acknowledgement signal.
Why pick selective repeat over go back-N?	go back-N is good if errors are rare, otherwise it wastes a lot of bandwidth resending all those frames
What is the congestion window in TCP?	Congestion Window (cwnd) is a TCP state variable that limits the amount of data the TCP can send into the network before receiving an ACK.
What is the Receiver Window (rwnd)?	is a variable that advertises the amount of data that the destination side can receive.
What is TCP Slow Start?	During slow start the congestion window size is doubled after each round trip time (almost exponential increase). The transmission rate will be increased until either a loss is detected, or the receiver's window (rwnd) is the limiting factor, or the slow start threshold (ssthresh) is reached

Resource summary

	Created by Emma Tysk over 6 years ago