Implementing access control mechanisms, such as a firewall, to protect the network is an example of which of the following network defense approach?

Which of the following encryption techniques do digital signatures use?

Which of the following protocols is described as a connection-oriented and reliable delivery transport layer protocol?

Which of the following is a firewall that keeps track of the state of network connections traveling across it?

Larry is a network administrator working for a manufacturing company in Detroit. Larry is responsible for the entire company's network which consists of 300 workstations and 25 servers.
After using a hosted email service for a year, the company wants to cut back on costs and bring the email control internal. Larry likes this idea because it will give him more control over email.
Larry wants to purchase a server for email but he does not want the server to be on the internal network because this might cause security risks. He decides to place the email server on the outside of the company's internal firewall. There is another firewall connected directly to the Internet that will protect some traffic from accessing the email server; the server will essentially be place between the two firewalls. What logical area is Larry going to place the new email server into?