List three design goals for a firewall. List four techniques used by firewalls to control access and enforce a security policy. What information is used by a typical packet filtering firewall? What are some weaknesses of a packet filtering firewall? What is the difference between a packet filtering firewall and a stateful inspection firewall? What is an application-level gateway? What is a circuit-level gateway? What are the common characteristics of a bastion host? Why is it useful to have host-based firewalls? What is a DMZ network and what types of systems would you expect to find on such networks? What is the difference between an internal and an external firewall?