10.1 Overview

04.083GPPMobile radio interface Layer 3 specificationRelease 1998TS

Within the Layer 3 protocols defined in 3GPP TS 04.08, every message with the exception of the messages sent on the BCCH, downlink CCCH, SCH, RACH, and the HANDOVER ACCESS message, is a standard L3 message as defined in 3GPP TS 04.07 [20]. This means that the message consists of the following parts:

a) protocol discriminator;

b) transaction identifier;

c) message type;

d) other information elements, as required.

This organization is illustrated in the example shown in figure 10.1/3GPP TS 04.08.

8 7 6 5 4 3 2 1


│Transaction identifier │ Protocol discriminator│ octet 1

│ or Skip Indicator │ │


│ Message type │ octet 2


│ Other information elements as required │ etc…

+—– – – – – – – – – – – – – – – – – – – —–+

Figure 10.1/3GPP TS 04.08: General message organization example

Unless specified otherwise in the message descriptions of sub-clause 9, a particular information element shall not be present more than once in a given message.

The term "default" implies that the value defined shall be used in the absence of any assignment, or that this value allows negotiation of alternative values in between the two peer entities.

When a field extends over more than one octet, the order of bit values progressively decreases as the octet number increases. The least significant bit of the field is represented by the lowest numbered bit of the highest numbered octet of the field.