When a message other than SETUP, DISCONNECT, RELEASE or RELEASE COMPLETE is received which has one or more mandatory information elements missing, no action should be taken on the message and no state change should occur. A STATUS message is then returned with cause No. 96, mandatory information element is missing.
When a SETUP or RELEASE message is received which has one or more mandatory information elements missing, a RELEASE COMPLETE message with cause No. 96, mandatory information element is missing shall be returned.
When a DISCONNECT message is received with the cause information element missing, the actions taken shall be the same as if a DISCONNECT message with cause No. 31, normal, unspecified was received (see 5.3), with the exception that the RELEASE message sent on the local interface contains cause No. 96, mandatory information element is missing.
When a RELEASE COMPLETE message is received with a cause information element missing, it will be assumed that a RELEASE COMPLETE message was received with cause No. 31, normal, unspecified.
Information elements with a length indication of zero shall be treated as a missing information element.