What is Stateful Packet Inspection (SPI)

This chapter describes various firewall conventions, and how these technologies operate when deployed on a corporate network. Terms associated with firewalls, as well as related concepts, are also discussed. Highly neglected internal security mechanisms utilizing firewall technologies are presented, including host-based firewalls and the more novel distributed firewall implementation. Finally, a section on how to perform a cost-benefit analysis when deciding which firewall technologies to implement is included. The chapter is designed as an introductory tutorial to the underlying concepts of firewall technologies. This understanding should provide a starting point for both systems support specialists implementing network security and researchers who are interested in firewall technologies.