a$)$ Consider a network in which packets are delivered reliable across each link.

That each, for each pair of adjacent nodes A $-$ B$,$ the datalink layer has an ARQ

protocol $($such as stop$-$and$-$wait$)$ that ensures packets sent by A do arrive at B$.$

In this network, why do you think is necessary for the transport layer to also

have its own ARQ protocol and do retransmissions of its packets?

b$)$ Consider a network in which the data$-$link layer protocol between two

machines in the network was replaced by a different data$-$link layer protocol.

In general, how will this affect the transport, session, presentation, and

application layers? PLEASE NO AI ANSWER