What type of communication does TCP provide?
Reliable in-order connection-oriented byte-stream service.
What does full duplex mean in TCP?
Data flows both directions simultaneously.
What does the TCP sequence number represent?
The byte offset of the first byte in the segment + ISN.
What does the TCP acknowledgment number represent?
The next expected byte (cumulative ACK).
What does the Window field represent?
Receiver’s available buffer space for flow control.
What is inside a TCP SYN?
Initial sequence number and flow control window.
What is inside a TCP SYNACK?
Receiver ISN flow control window and ACK = senderISN+1.
Why is 2-way handshake not used?
It can create half-open connections.
What is SampleRTT?
Time from segment transmission to ACK arrival.
Why ignore RTT from retransmitted packets?
Ambiguous which transmission was ACKed (Karn’s Algorithm).
What is the EstimatedRTT formula?
EstimatedRTT = (1 - α) * EstimatedRTT + α * SampleRTT.
What is α for RTT smoothing?
0.125.
What is the DevRTT formula?
DevRTT = (1 - β) * DevRTT + β * |SampleRTT - EstimatedRTT|.
What is β for DevRTT?
0.25.
What is the TimeoutInterval formula?
Timeout = EstimatedRTT + 4 * DevRTT.
What is TCP flow control for?
Prevent sender from overwhelming receiver buffer.
What field carries flow control?
Advertised window.
When does sender stop sending?
When in flight data ≥ advertised window.
What is cwnd?
Congestion window (sender side).
What is ssthresh?
Threshold between slow start and congestion avoidance.
How does cwnd grow in Slow Start?
Doubles every RTT.
When does TCP leave Slow Start?
When cwnd exceeds ssthresh.
How does cwnd grow in Congestion Avoidance?
+1 MSS per RTT.
What does timeout indicate?
Severe congestion; set cwnd to 1 MSS.
