Failover functionality for client-related security association

There are provided measures for a failover functionality for a client-related security association. Such measures exemplarily comprise providing a failover functionality at a proxy function and/or facilitating provision of a failover functionality at a servicing call state control function, wherein the respective failover functionality relates to a first proxy function, the serving function is for servicing the first proxy function and a second proxy function, the first proxy function has a security association with a client, and the first proxy function and the second proxy function are reachable with the same network address.