Question: In IMS session-based messaging, what is the primary transport protocol requirement for messages within a message session between two UEs or involving intermediate nodes?
Option 1: Connectionless Best-Effort Transport Protocol
Option 2: Connection-Oriented Reliable Transport Protocol with Guaranteed QoS
Option 3: Connectionless Reliable Transport Protocol with Optional QoS
Option 4: Connection-Oriented Reliable Transport Protocol
Explanation: According to IMS architectural principles for session-based messaging, messages within a message session should be transported over a connection-oriented reliable transport protocol. This ensures that messages are delivered reliably and in order, which is crucial for maintaining the integrity of the messaging session, especially when involving intermediate nodes like chat servers or Application Servers for charging purposes. While QoS (Quality of Service) might be beneficial, it's not explicitly required for the messaging media component itself, making Option 2 less fitting as the primary requirement. Options 1 and 3 do not align with the specified need for a connection-oriented reliable protocol.