6) Multicast [10 marks] a) (3 marks) What will a router do if it receives a multicast address in the source address field of an IP packet? (2 marks) Does a sender need to join a multicast group in order to send messages to that group? (5 marks) Describe reverse-path forwarding. What is it used for? b) c) 7) TCP [24 marks] a) (4 marks) If a receiving TCP system's buffer becomes full, what will it do? (5 marks) Why does TCP need a sophisticated calculation of the retransmission timer? (5 marks) How do Nagle's algorithm and Clarke's algorithm alleviate the problem of silly window b) c) d) (5 marks) What is the function of the TCP persistence timer? e) (5 marks) Describe the TCP slow start' process to control congestion. syndrome