One of the most important Smart Grid Control Protocols is MMS over IEC 61850, which is predicted a great future after its extension for usage over Wide Area Networks and its generalization for other Smart Grid and industrial applications. Nevertheless the protocol stack of IEC 61850, which is used for MMS, originated from the 80s of the last century, is outdated and overloaded. It contains a complete ISO/OSI protocol stack of all layers. Nowadays the requirements are different not only under application aspects but also under the aspect of critical infrastructures, which should be able also to communicate over networks with limited capacities. This paper proposes a new slimmed protocol stack for IEC 61850 including improved security services for application oriented security and against denial of service attacks. The proposal is compared with the existing solution, and results are given based on simulations showing the benefits of a rejuvenation cure of the protocol stack for MMS.