Question: In the context of Rx messages as per Policy and Charging Control, what is the significance of using NASREQ Diameter application alongside existing Diameter command codes?
Option 1: To leverage NASREQ's functional meaning for Network Access Server operations in Rx messaging.
Option 2: Solely for protocol purposes, without utilizing NASREQ's functional meaning, to identify Rx messages with specific AVPs and Auth-Application ID.
Option 3: To enable compatibility with older Diameter Base Protocol versions.
Option 4: For encrypting sensitive information within the Subscription-Id AVP.
Explanation: The correct answer highlights that NASREQ is utilized purely for its protocol structure in Rx messaging, not for its original functional purpose related to Network Access Servers. This distinction is crucial for understanding how Rx messages are formatted and identified (using specific AVPs and an Auth-Application ID) without misconstruing the role of NASREQ in this context.