FTS3 Token Support for a Proxy-less WLCG World

The File Transfer Service (FTS) is a key middleware service responsible for orchestrating data transfers within the WLCG. This paper presents the FTS changes as part of the larger Worldwide LHC Computing Grid (WLCG) decision to move away from Grid User certificates towards token-based authentication and authorization. We report on the token approach chosen by the FTS service, as well as delve into the technical implementation of said solution. The paper describes experiences from running FTS token support in production, as well as concluding with remarks on future directions.