Question: What is the primary purpose of using a Filler Information Element (IE) in the User Data Header of an SMS message?
Option 1: To introduce new security features by encrypting the replaced IEs
Option 2: To compress the User Data Header while maintaining its original length indicators
Option 3: To insert additional routing information for special message types
Option 4: To replace existing IEs without altering the original TP-User-Data-Header-Length (UDHL) and TP-User-Data-Length (TP-UDL) values
Explanation: The Filler IE is used to replace existing Information Elements in the User Data Header while ensuring that the original lengths remain unchanged, maintaining compatibility and preventing errors during message processing.