You are charged to protect the machine of Alice from receiving unwanted traffic from machines on a blacklist.

(1) If the access control can only be done on the machine of Alice, will the implementation of access control be an Access Control List, or a directory? Explain briefly.

(2) If the access control can only be done on the senders of all traffic, will the implementation of access control be an Access Control List, or a directory? Explain briefly.

(3) If the access control can only be done by having the traffic carry certain information, what will be the access control implementation you would choose? Explain briefly.