Intermediary-based services and performance optimizations are increasingly being considered, by network service providers, with a view towards offering value-added services and improving the user experience of wireless mobile clients at reduced costs. However, in the presence of an end-to-end security mechanism such as IPsec, it is impossible to offer such services without fully compromising end-to-end security. We propose a new architecture to enable intermediarybased services for wireless mobile users while maintaining an acceptable level of end-to-end security. As a part of our architecture, we present a new IPsec option called Encapsulating Security Variable Payload (ESVP). We identify several important issues related to the architecture and discuss methods for addressing them. Categories and Subject Descriptors C.2.1 [Computer-Communication Networks]: Network Architecture and Design; C.2.2 [ComputerCommunication Networks]: Network Protocols General Terms Design, Security Keywor...