An exam question about reliable protocol.

Question

Consider the following file transport application, which uses the protocol defined below to reliably service a client’s request.

The protocol has the following characteristics:

• The protocol runs across a network with a 1050 byte MTU, a 20 ms one-way latency.

• Each transferred packet consists of a total of 50 bytes of packet headers plus the payload.

• The client initiates a three-way handshake, piggybacking a 100 byte request on the third packet of the handshake.

• The server has a maximum transmission window of three MTU (3000 Bytes).

• The client sends one cumulative acknowledgment after every two data packets arrive.

• After the last packet in the file has been acknowledged, the server sends a FIN, which the client must acknowledge before closing the connection.

Suppose that packet 3 is lost on its way to the client but all other packets get through. Which packet arrival subsequent to packet 3 triggers an acknowledgment and what would the client acknowledge when that packet arrives?

Answer 1

If "packet 3" is not 3rd packet of handshaking but file data (sure, otherwise server won't send FIN): 1.Which packet arrival subsequent to packet 3 triggers an acknowledgment - FIN-ACK sent by server 2. what would the client acknowledge when that packet arrives - (if "that packet" is "packet 3" then FIN-ACK, otherwise FIN).