1. When the IVC for the AH protocol is computed, why are mutable fields set to 0 rather than omitted?

2. Section 11.4.4 discusses the use of SSL to provide confidentiality, authentication, and integrity security services for electronic mail and suggests that PEM is more appropriate. Consider a remote login protocol in the same context. In answering the following questions, please state explicitly any assumptions that you make.

a. One goal of the protocol is to provide user authentication from the client to the server. Which layer (application, transport, or network) would be most appropriate for providing this service? Why?

b. Another goal of the protocol is to provide host authentication between the client and the server, so the client knows which server it is communicating with, and vice versa. At which layer should these services be provided, and why?

c. Assume that the remote login protocol is connection-oriented. Which layer should supply message integrity and confidentiality services, and why?

d. Assume that the remote login protocol may use either a connection-oriented or a connectionless protocol (depending on various network factors determined when the client contacts the server). Which layer should supply message integrity and confidentiality services, and why?