This paper presents a proposal for a flexible agent mobility architecture based on IEEE-FIPA standards and intended to be one of them. This proposal is a first step towards interoperable mobility mechanisms, which are needed for future agent migration between different kinds of platforms. Our proposal is presented as a flexible and robust architecture that has been successfully implemented in the JADE and AgentScape platforms. It is based on an open set of protocols, allowing new protocols and future improvements to be accommodated in the architecture. With this proposal we demonstrate that a standard architecture for agent mobility capable of supporting several agent platforms can be defined and implemented.