4. a) Explain how the IPSec Tunnel mode works. (2 marks) b) Secure Socket Layer (SSL) and IP Security (IPSec) exchange their cryptographic algorithms at the beginning of the session establishment dialogue. State a strong justification if this can be exploited by a man-in-the-middle rival to force the parties to agree on a weak cryptographic suite even though both parties support a common (preferred) strong suite. Your answer must compare between SSL v2 and SSL v3. (5 marks) (CLO1:PLOI:C1)