3GPP 24.501 v20.0.0 — the document's own text
D.8.1 General
Taught in 5. Finding your way around TS 24.501 (CT1 — the group that writes what your phone says, in depth), 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The procedures specified in the clause apply to those messages which pass the checks described in this clause.
This clause also specifies procedures for the handling of unknown, unforeseen, and erroneous UPDS data by the receiving entity. These procedures are called "error handling procedures", but in addition to providing recovery mechanisms for error situations they define a compatibility mechanism for future extensions of the UPDS.
Clauses D.8.1 to D.8.8 shall be applied in order of precedence.
Detailed error handling procedures in the network are implementation dependent and may vary from PLMN to PLMN. However, when extensions of UPDS are developed, networks are assumed to have the error handling which is indicated in this clause as mandatory ("shall") and that is indicated as strongly recommended ("should").
Also, the error handling of the network is only considered as mandatory or strongly recommended when certain thresholds for errors are not reached during a dedicated connection.
For definition of semantical and syntactical errors see 3GPP TS 24.007 [11], clause 11.4.2.