Question: What happens when a mandatory or conditionally required Information Element (IE)/IE Group (with the condition being true) is not included in a received S1AP message?
Option 1: The receiver ignores the missing IE/IE Group and processes the rest of the message.
Option 2: The receiver sends a request for the missing IE/IE Group before proceeding.
Option 3: An abstract syntax error occurs due to the missing IE/IE Group.
Option 4: The message is queued pending further instructions from the network.
Explanation: According to S1AP protocol specifications, if an IE/IE Group with a mandatory or conditional (with the condition being true) presence field is not included in a received message, it results in an abstract syntax error. This ensures protocol integrity and prevents potential misinterpretations due to missing critical information. In telecom networks, such errors are crucial for diagnosing and resolving communication issues between network elements, like eNodeBs and MMEs in E-UTRAN.