Question: Which of the following is a primary purpose of the E-RAB MODIFY REQUEST message sent by the MME to the eNB in an E-UTRAN?
Option 1: To establish new S1 connections for initial attach procedures.
Option 2: To modify allocated resources (Uu and S1) for one or several E-RABs, or to change the S-GW.
Option 3: To release all existing E-RABs due to a UE's detachment.
Option 4: To request eNB capability information for handover preparations.
Explanation: The correct answer is Option 2 because the E-RAB MODIFY REQUEST message, as initiated by the MME towards the eNB, is specifically utilized to adjust (i.e., modify) the resources allocated on both the Uu and S1 for one or more Evolved Radio Access Bearers (E-RABs), or to facilitate a change in the Serving Gateway (S-GW). This aligns with managing and optimizing existing radio access bearer configurations, rather than establishing new connections, releasing resources due to detachment, or requesting capability information.