a$)$ Which layers in the Internet protocol stack does a router process? Which layers does a link$-$layer switch process? Which layers does a host process?

b$)$ Describe the different wireless technologies you use during the day and their

characteristics. If you have a choice between multiple technologies, why do you prefer one over another?

c$)$ List the four broad classes of services that a transport protocol can provide. For each of the service classes, indicate if either UDP or TCP $($or both$)$ provides such a service.

d$)$ How can websites keep track of users? Do they always need to use cookies?

e$)$ Is it possible for an application to enjoy reliable data transfer even when the application runs over UDP? If so$,$ how?