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9. Multicast 12 marks] (a) [3 marks] Consider a network containing three hosts , H2, and H3. The network consists of a multicast router R running IGMP version 1. The list of currently active groups and the associated delay timers is as follows H1 H2 H3 Group timer tl Group /A Group B timer t2 Group timer t4 roup C timer t:5 mer t Group A timer t6 Group C timer t Note 11 = 6,2-16. t3 12, t4 20, t5 = 4, t6 = 15, t7-8. Describe the sequence of responses that will occur in response to router R's query message. (b) 2 marks] Although DVMRP has been deployed in the multicast backbone and in other intra-domain multicast networks, some rather severe scalability issues prevent it from being used in large-scale multicast environments. What are these issues? Explain. (c) 5 marks] How is the DVMRP forwarding table different from DVMRP routing table? List and explain the fields tabulated in these tables. Why is there a need for these two different tables? (d) 2 marks] Because of route suppression mechanism, IGMP routers cannot keep track of individual hosts joined to a multicast group on a subnet. Furthermore, even if the router could keep track of all active members, doing so would not be desirable. Why