9.11.1 General

The different formats (V, LV, T, TV, TLV, LV-E, TLV-E) and the five categories of information elements (type 1, 2, 3, 4 and 6) are defined in 3GPP TS 24.007 [11].

The first octet of an information element in the non-imperative part contains the IEI of the information element. If this octet does not correspond to an IEI known in the message, the receiver shall determine whether this IE is of type 1 or 2 (i.e. it is an information element of one octet length) or an IE of type 4 or 6 (i.e. that the next octet is the length indicator or, for a type 6 IE, the next 2 octets are the length indicator indicating the length of the remaining of the information element) (see 3GPP TS 24.007 [11]).

NOTE: This requirement for the receiver is not applicable for information elements included in a Type 6 IE container information element. Any IE in the Type 6 IE container information element is of type 6 with format TLV-E; therefore, the rules for the IEI value encoding defined in 3GPP TS 24.007 [11], clause 11.2.4, are not applicable.

This allows the receiver to jump over unknown information elements and to analyse any following information elements of a particular message.

The definitions of information elements which are:

• common for the 5GMM and 5GSM protocols;
• used by access stratum protocols; or
• sent to upper layers

are described in clause 9.11.2.

The information elements of the 5GMM or 5GSM protocols can be defined by reference to an appropriate specification which provides the definition of the information element, e.g. "see clause 10.5.6.3A in 3GPP TS 24.008 [12]".