$2$A$)($i$)$ Explain what type of OSPF link state is advertised in each of the following cases:

$1.$ A router needs to advertise the existence of another router at the end of a point$-$to$-$point link.

$2.$ A router needs to advertise the existence of two stub networks and one transient network.

$($ii$)$ OSPF messages and ICMP messages are directly encapsulated in an IP datagram. If we intercept an IP datagram, how can we tell whether the payload belongs to OSPF or ICMP?

$($iii$)$ Distinguish between link state and distance vector routing protocols.

$($iv$)$ Distinguish between Frequency Division Multiplexing and Time Division Multiplexing.