A key challenge in a ubiquitous network society is the design of effective authentication and access control schemes that adequately meet the unique security issues posed by the context-aware service paradigm. Despite recent advances in Web services security approaches, issues remain that impede the development of context-aware authentication and access control framework for the ubiquitous computing environment. In this paper, we propose a distributed system based on authentication and access control agents characterized by autonomic policy decision, network federation and dynamic access control for context-aware services. We will describe the travel navigation service system implementation as one of the context-aware services and also report unresolved issues, which include network mobility support, trust relationship among agents and device interconnection.