Question: In 3GPP E-UTRA RRC protocol, what is the primary purpose of introducing extension markers within a SEQUENCE in size-critical messages (e.g., BCCH, BR-BCCH, PCCH, and CCCH)?
Option 1: To reduce the overall message size by eliminating unnecessary fields.
Option 2: To introduce new fields without altering the existing message structure, ensuring backward compatibility.
Option 3: To mandate the inclusion of all optional fields in every message transmission.
Option 4: To enable the addition of new information elements while maintaining crucial message structures and parameters relevant for a particular Radio Access Technology (RAT).
Explanation: Extension markers in SEQUENCE, especially in size-critical messages, are used to facilitate future extensions without disrupting existing structures. This is crucial for maintaining important information relevant to specific RATs while allowing for the evolution of the protocol.