This chapter covered the basic overview of the Cisco IDS 4.0 architecture. The mainApp application starts and stops all other IDS applications. Then, the chapter presented an overview of communications protocols used by several outside devices to manage and collect event information from the sensors. This chapter introduced the new communication protocol called RDEP, which is used by IEV and Security Monitor to pull XML documents across an encrypted HTTPS connection from the sensors. Last, you learned about the different privilege levels with which you can create user accounts and the special service-level account that you should only create with the help of the Cisco TAC.