Question: In the context of Mission Critical (MC) services, as per 3GPP standards, which plane is responsible for establishing associations between users involved in an MC service, such as an MCPTT call, and utilizes the services of the bearer plane?
Option 1: Application Plane - Responsible for providing all services required by the user, including media conferencing and tones.
Option 2: Bearer Plane - Defines the bearers supporting the other planes, specifically outlined for LTE in related standards.
Option 3: Signalling Control Plane - Provides necessary signalling support for MC service associations and accesses services across MC services.
Option 4: Resource Control Plane - Oversees resource allocation as defined in Policy and Charging Control Architecture specifications.
Explanation: The correct answer is the Signalling Control Plane because it provides signalling necessary to establish user associations for Mission Critical services, such as MCPTT calls, relying on the Bearer Plane for underlying transport infrastructure.