Multicast security researches have been going on for a decades. In representative, some standard documents have been submitted by IETF Working Group (WG) MSEC. The reason that multicast group security is more difficult than one-to-one security is because all group members must share single group key at the same time. Whenever members join and leave, the group key must be updated and distributed to all members to keep forward and backward secrecy. At this time, ‘1 affects n’ problem occurs. For a practical multicast security service in an actual world, it is not sufficient that membership state is divided into only two parts: join and leave. This paper describes different features between multicast and multicast security, and suggests the SLEEP state for the practical multicast security service.