Security and QoS are two-thirds of a triumvirate, the third part of which is mobility. They are the major network-level areas of technical challenge that wireless IP must successfully handle to succeed. Of the triumvirate, security and QoS are more similar to each other than to mobility. Whereas mobility is for the most part an interesting problem only in the wireless case, security and QoS are among the most important areas of work and development for IP, whether wired or wireless. In both cases, there are challenging and interesting problems in the wired side, with additional challenges when wireless is considered.

One reason why security is so challenging is that it is a negative problem ^[1]. In many other problems in the wireless IP world, the objectives are to achieve something that can be verified with reasonable effort. For example, it is easy to verify that the objectives of a protocol like Mobile IP are met, when packets get forwarded to the correct locations of MHs. However, it is difficult to verify that a network is secure, because we would need to test it against a variety of different attacks. Even then, vulnerabilities might not be spotted, only to be revealed by yet another type of attack that the designer has not considered. Furthermore, in many other cases, a natural feedback mechanism exists when something fails the user can be expected to complain. However, if security fails, the person or persons with knowledge of the failure are typically the attackers,...