Q3. Consider the following network. Fig. Q3 (a) State the names and one function of all layers of the OSI model including any sub-layers. (8 marks) (b) Computer A attempts to send a message to computer B. The message is encapsulated as it passes through the different layers of the OSI model. Describe the main headers added at the Transport and Network layers. ( 3 marks) (c) The message generated by computer A has arrived at Router 1. State the source and destination IP and MAC addresses that appear on the data packet. Describe the mechanism used by computer A to obtain the MAC address of Router 1. Assume that computer A knows the IP address of its default gateway. (7 marks) (d) Assume that computer A obtains its IP address and configuration parameters from a DHCP server. State two advantages of performing IP configuration with the aid of DHCP