Suppose that packets sent between Alice and Bob are encrypted and integrity protected by Alice and Bob with a symmetric key known only to Alice and Bob. a. Which fields of the IP header can be...

Suppose that packets sent between Alice and Bob are encrypted and integrity protected by Alice and Bob with a symmetric key known only to Alice and Bob.

a. Which fields of the IP header can be encrypted and which cannot?

b. Which fields of the IP header can be integrity protected and which cannot?

c. Which of the firewalls—packet filter, stateful packet filter, application proxy—will work in this case, assuming all IP header fields that can be integrity protected are integrity protected, and all IP header fields that can be encrypted are encrypted? Justify your answer.