Section: 8.5 Non-semantical mandatory information element errors
Content: When on receipt of a message, - an "imperative message part" error; or - a "missing mandatory IE" error; is diagnosed or when a message containing: - a syntactically incorrect mandatory IE; or - an IE unknown in the message, but encoded as "comprehension required" (see 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [20]); or - an out of sequence IE encoded as "comprehension required" (see 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [20]) is received, the mobile station shall proceed as follows: If the message is not one of the messages listed in subclauses 8.5.1, 8.5.2, 8.5.3, 8.5.4 and 8.5.5 a), b) , f) or h), the mobile station shall ignore the message except for the fact that, if an RR connection exists, it shall return a status message (STATUS, MM STATUS depending on the protocol discriminator) with cause # 96 "Invalid mandatory information". If the message was a GMM message the GMM-STATUS message with cause #96 " Invalid mandatory information" shall be returned. If the message was an SM message the SM-STATUS message with cause # 96 "invalid mandatory information" shall be returned. - the network shall proceed as follows: When the message is not one of the messages listed in subclause 8.5.3 b), c), d) or e) and 8.5.5 a), c), d), e) or g), the network shall either: - try to treat the message (the exact further actions are implementation dependent), or - ignore the message except that it should return a status message (STATUS, or MM STATUS (depending on the protocol discriminator), GMM STATUS, or SM STATUS) with cause # 96 "Invalid mandatory information".