The present invention describes a novel method, radio access node and system for specifying and interpreting identifiers in a telecommunications system. In the method of the present invention, an RNC identifier extension element extending the RNC identifier is created and one or more radio access network nodes are specified with the RNC identifier and RNC identifier extension element extending the RNC identifier in the first and/or second interface instance. In a preferred embodiment, the RNC identifier and RNC identifier extension element extending the RNC identifier specify a radio network access server and an IP base station in the second interface.