Question: In the context of Short Message Service (SMS) support on the mobile radio interface, what is the primary purpose of the Short Message Relay Protocol (SM-RP) used between an SMR entity in the Mobile Station (MS) and an SMR entity in the Mobile Switching Center (MSC)?
Option 1: To manage mobility-related functions for SMS delivery
Option 2: To facilitate peer-to-peer communication between SMR entities for Short Message Relay Layer services
Option 3: To handle billing and charging for SMS services
Option 4: To encrypt SMS content for secure transmission
Explanation: The Short Message Relay Protocol (SM-RP) is used for facilitating peer-to-peer communication between SMR entities in the MS and MSC, providing Short Message Relay Layer services. This highlights its importance in the technical implementation of SMS support, focusing on service provision rather than mobility management, billing, or encryption.