TCP and UDP

Questions 1 to 5 of 8

1. 1. A server is 80 ms away, so the round-trip time (RTT) is 80 ms. The client sends its request as soon as the handshake ends. When does the request reach the server?

   At 80 ms, when the SYN-ACK arrivesAt 120 ms, when the request reaches the serverAt 160 ms, one full round trip after the request startsAt 200 ms, after the request and the reply have both travelled
2. 2. True or false: the receiver has bytes 1001 to 1004 and bytes 1009 to 1012, but not 1005 to 1008. Its next ACK says 1013.

   False, because the ACK names the first byte it is missing, so it says 1005True, because the ACK moves past every byte the receiver holdsTrue, because the ACK always names the last byte received plus oneFalse, because the ACK can only name a byte after the handshake
3. 3. Put these steps from the HELLO WORLD example in the order they happen.

   Use the arrows to put the steps in order.

   1. 1.The sender resends the chunk that starts at byte 1005 after a timeout↑↓
   2. 2.The receiver's ACK moves to 1014, so all 13 bytes have arrived↑↓
   3. 3.The receiver sends ACK 1005, and repeats it for each later chunk that arrives↑↓
   4. 4.The client sends four chunks, and chunk 2 (O WO, starting at byte 1005) is lost↑↓
4. 4. A server program calls listen() but never calls accept(). A client calls connect() and gets no error. Why?

   The client's connect() returns after sending the SYN, before any replyThe server program accepted the connection when it called listen()The operating system finished the handshake and holds the connection in a waiting lineThe client sent its request before connecting, so the server already got it
5. 5. What does this program print? ``python import socket, threading srv = socket.socket() srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) srv.bind(("127.0.0.1", 9004)) srv.listen() def closer(): c, _ = srv.accept() c.sendall(b"partial") c.close() threading.Thread(target=closer).start() cl = socket.create_connection(("127.0.0.1", 9004)) print("read 1:", cl.recv(100)) print("read 2:", cl.recv(100)) cl.close() srv.close() ``

   read 1: b'partial', then read 2: b'partial'read 1: b'partial', then read 2: b''read 1: b'', then read 2: b'partial'read 1: b'partial', then read 2: TimeoutError