Nowadays, P2P file-sharing systems have gained a large acceptance among the Internet users. However, there has been little relatively work done in access control for P2P networks, where security is a critical requirement for broader applications of the technology not only in the current but also in the future. In this work, a new architecture is presented in this paper, it integrates the aspects of credential, identity and role-based access control policies to provide scalable, efficient and fault-tolerance access control services. It also preserves the decentralized structure of the P2P platform by employing primary/backup strategy, and resolves the two kinds of interoperability conflicts while mapping role from foreign domain to local domain without centralized authority. We believe that the proposed architecture is realistic, secure and preserves P2P decentralized structure.