3GPP 24.501 v20.0.0 — the document's own text
7.5.1 Common procedures
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
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;
- an IE with an IEI unknown in the message, but encoded as "comprehension required" (see 3GPP TS 24.007 [11]); or
- an out of sequence IE encoded as "comprehension required" (see 3GPP TS 24.007 [11]) is received,
the UE shall proceed as follows:
If the message is not one of the messages listed in the UE procedures in clause 7.5.3, item a), b) or c), the UE shall return a status message (5GMM STATUS or 5GSM STATUS depending on the EPD) with cause #96 "invalid mandatory information";
the network shall proceed as follows:
If the message is not one of the messages listed in the network procedures in clause 7.5.3, item a), b) or c), 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 (5GMM STATUS or 5GSM STATUS depending on the EPD) with cause #96 "invalid mandatory information".