Recommendation ITU-T Q.3627 v.1 specifies requirements for supplementary service such as a closed user group (CUG) to be provided on the IMS platform. The version number, v.1, indicates that this is version one of Recommendation ITU-T Q.3627, and that it relates to Release 10 of the relevant 3GPP/ETSI standard. This Recommendation endorses ETSI TS 124 654 V10.3.0 (2013-04) "Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); LTE; Closed User Group (CUG) using IP Multimedia (IM) Core Network (CN) subsystem, Protocol Specification (3GPP TS 24.654 version 10.3.0 Release 10)".