name: GCS
full_form: Group Controlling Server
context: Editor's Note: It is for FFS how to deal with more than one BM-SC. 1) GCS AS has received data for distribution to the group. 2) GCS AS provides the group key (MSK) and the group identifier among other MBMS specific data to the BM-SC. 3) GCS AS provides the data for distribution to the group to BM-SC indicating that no protection has been applied and requests BM-SC to apply MBMS data protection mechanisms before broadcasting. 4) BM-SC uses the group key (MSK) provided and encrypts the Multicast/Broadcast data according to the MBMS security scheme with MTKs (resulting in SRTP packets). In addition BM-SC generates MIKEY messages that secure the delivery of the MTKs. 5) BM-SC sends UDP/SRTP, UDP/MIKEY data and other MBMS specific data received by GCS AS to the MBMS GW. NOTE: There is no need that MTKs are known to the GCS AS. GCS AS trusts BM-SC to securely distribute the data via Multicast/Broadcast. How GCS AS generates the MSK is out of scope of Rel-12.
description: The Group Controlling Server (GCS) manages and distributes multicast/broadcast data to groups within the MBMS (Multimedia Broadcast/Multicast Service) architecture. It interacts with other network functions, such as the BM-SC (Broadcast Multicast Service Center), to ensure secure delivery of multimedia content.
explanation: The GCS controls and manages a specific aspect of network operations: distributing multicast/broadcast data within the MBMS architecture. Its interactions with other network functions like the BM-SC further solidify its role as a Network Function.
section_title: 6.3.4.3.2.3	Multicast/Broadcast downlink
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