Question: What happens when a mandatory or conditionally required (with the condition being true) Information Element (IE)/IE group is not included in a received RANAP message on the UTRAN Iu interface?
Option 1: The message is ignored, but no error is triggered.
Option 2: An abstract syntax error occurs due to the missing IE/IE group.
Option 3: The receiver automatically requests retransmission of the omitted IE/IE group.
Option 4: The message is processed with default values for the missing IE/IE group.
Explanation: According to RANAP signalling specifications for the UTRAN Iu interface, if an IE/IE group with a mandatory or conditional (where the condition is true) presence field is not included in a received message, it results in an abstract syntax error due to the missing element. This ensures protocol integrity and consistency across the network.