TCP — end of module

What this checks. That you can follow sequence and acknowledgement arithmetic, name the state each end is in, and tell a refusal apart from a silence. You need 3 of 4 to pass, and every option is explained afterwards — including the ones you did not pick.

1. 1/4A client sends a SYN with sequence number 1000. What acknowledgement number does the server's SYN-ACK carry?

   Work out a value

   1001

   1000

   It depends on the server's own initial sequence number
2. 2/4A client's SYN reaches a host that has nothing listening on the port. What comes back?

   Predict what happens next

   RST, within about one round-trip time

   Nothing — the SYN is silently discarded

   SYN-ACK with the window set to zero
3. 3/4What is the difference between the receive window and the congestion window?

   Tell two ideas apart

   The receive window is advertised by the other end and protects the receiver; the congestion window is the sender's own estimate and protects the network

   They are the same value, seen from each end

   The congestion window is negotiated during the handshake
4. 4/4Which capture contents best prove a segment was lost rather than merely delayed?

   Choose the evidence

   The same sequence number sent twice, with duplicate acknowledgements for the byte before it in between

   A gap in the timestamps

   A RST at the end of the conversation