(1 marks) An IP datagram arrives at a router; how does the router know that the datagram has been in the Internet for a long time and must be discarded? b) (2 marks) A router receives an IP datagram from a network. Will the router change the sender IP address in the header of the IP datagram before forwarding the datagram to another network? Give reasons to support your answer. c) (2 marks) When will a host pass a received IP datagram from the host Internet layer to its transport layer? d) (2 marks) When will a router divide an IP datagram into smaller fragments? e) (3 marks) The computer network of a company has been assigned with a block of IP addresses (in the decimal-dot format) from 212.92.32.00 to 212.92.63.255. The company network gateway uses a 32-bit mask to recognise whether an incoming packet belongs to the company network or not. What is the value of the mask in the decimal-dot format? Give all your working details