My 3GPP TS 24.007 Notes

4 Introduction § 4.1 General

Five models are defined for Layer 3, one model for non-GPRS services, one for GPRS services supporting Class C MSs only, one model for GPRS-services supporting Class A and Class B MSs, one model for EPS services and one model for 5GS services over either 3GPP access or over non-3GPP access.

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The layer 3 for 5GS services is composed of three sublayers comprising:

• the 5GS radio resource management (5GRR) functions for NAS over 3GPP access or the non-3GPP access functions for NAS over non-3GPP access;
• the 5GS mobility management (5GMM) functions; and
• the 5GS connection management (5GCM) functions.

The 5GS mobility management (5GMM) sublayer is composed of a functional block for:

• the 5GS mobility management (5GMM) functions.

The 5GS connection management (5GCM) sublayer is composed of a functional block for:

• the 5GS session management (5GSM) functions.

NOTE: For NAS over non-3GPP access, the non-3GPP access functions can be supported through functionalities defined in IETF RFC 7296 [30].

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4 Introduction § 4.3 Technique of description

Layer 3 and its sub layers are specified by:

• their service specification, see clause 4.3.1;
• their protocol specification, see clause 4.3.3;
• the specification of functions, see clause 5.

4.3.1 Service description

The services of signalling layer 3 and its sublayers are described in terms of:

• services provided to upper (sub )layers at the service access points;
• services assumed from lower (sub )layers at the service access points.

Layer 3 and its supporting lower layers provide the Mobile Network Signalling (MNS) Service and User Data Transfer (UDT) Service (for GPRS services only) to the upper layers.

The service provided/assumed at the service access points are described by means of abstract service primitives and parameters as recommended in ITU-T Recommendation X.200.

4.3.3 Protocols and peer-to-peer communication

By use of the services provided by lower (sub )layers, peer entities in a (sub )layer in the MS and the network exchange information. Exchange of information between two peer entities is performed according to the corresponding (sub )layer protocols. A protocol is a set of rules and formats by which the information (control information and user data) is exchanged between the two peers. The information is exchanged by use of messages which are defined in the protocol. (Therefore, the messages are also called Protocol Data Units, PDUs).

There are several protocols of the RR sublayer, one protocol of the LLC sublayer, three protocols of the MM sublayer, and several protocols of the CM sublayer. For each functional block of the CM sublayer as defined in clause 4.1 there is one protocol. The CM protocols are specified in the Technical Specifications identified in clause 4.3.4.

In the model used in the present document, there are:

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5. for EPS services:
   • one RR entity in the MS and one RR entity in the network;
   • one EMM entity in the MS and one EMM entity in the network;
   • for each functional block of the CM sublayer as defined in clause 4.1 which is supported in the MS (in the network), there are, depending on the protocol, one or more entities in the MS (in the network). Two different entities of the same functional block in the MS (in the network) are called parallel entities. The entities of the same functional block in the MS correspond in a one-to-one relation to the entities of the functional block in the network. The corresponding entities are called peer entities.
6. for 5GS services:
   • one 5GRR entity in the MS and one 5GRR entity in the network for NAS over 3GPP access;
   • one non-3GPP access management entity in the MS and one non-3GPP access interworking entity in the N3IWF for the NAS over non-3GPP access;
   • one 5GMM entity in the MS and one 5GMM entity in the network;
   • for each functional block of the 5GCM sublayer as defined in clause 4.1 which is supported in the MS (in the network), there are, depending on the protocol, one or more entities in the MS (in the network). Two different entities of the same functional block in the MS (in the network) are called parallel entities. The entities of the same functional block in the MS correspond in a one-to-one relation to the entities of the functional block in the network. The corresponding entities are called peer entities.

As each sub layer entity is specified by one and only one protocol, it is also called a protocol entity or protocol control entity.

For GPRS-services supporting Class A and Class B MSs, the MM entities of the MM-sublayer are able to exchange information by means of GMM PDUs as well as MM PDU's. This means if a mobile is GPRS attached, non-GPRS mobility management procedures may make use of GRPS mobility management messages.

When two peer protocol entities exchange PDUs, a transaction is said to be established (or: to be active; or: to exist). It depends from the protocol when exactly a protocol entity considers the transaction to be active, normally this is the case:

• from the moment when it has passed the first suitable message to lower (sub-) layers or received the first suitable message from its peer entity;
• up to the moment when it has released the transaction.

4.3.4 Contents of layer 3 related Technical Specifications

-	The Radio Resource (RR) management protocol is defined in 3GPP TS 44.018;
-	the Mobility Management (MM) protocol is defined in 3GPP TS 24.008;
-	the Session Management (SM) protocol is defined in 3GPP TS 24.008;
-	the Call Control (CC) protocol is defined in 3GPP TS 24.008;
-	the Supplementary Services (SS) protocol is defined in 3GPP TS 24.010, 3GPP TS 24.08x, 3GPP TS 24.09x, and 3GPP TS 24.030;
-	the Short Message Service (SMS) protocol is defined in 3GPP TS 24.011;
-	the Group Call Control (GCC) protocol is defined in 3GPP TS 44.068;
-	the Logical Link Control (LLC) protocol is defined in 3GPP TS 44.064;
-	the GPRS Radio Resource (GRR) protocol is defined in 3GPP TS 44.060 and 3GPP TS 24.008;
-	the CTS Radio Resource (CTS-RR) sub-protocol is defined in 3GPP TS 44.056;
-	the CTS Mobility Management (CTS-MM) sub-protocol is defined in 3GPP TS 44.056;
-	the CTS additions to the Call Control (CC) protocol are defined in 3GPP TS 44.056;
-	the Location Services (LCS) protocol for a type A LMU is defined in 3GPP TS 23.271 and 3GPP TS 44.071;
-	the EPS Radio Resource (RR) management protocol is defined in 3GPP TS 36.331;
-	the EPS Mobility Management (EMM) protocol is defined in 3GPP TS 24.301;
-	the EPS Session Management (ESM) protocol is defined in 3GPP TS 24.301;
-	the 5GS Radio Resource management (5GRR) protocol is defined in 3GPP TS 38.331;
-	the 5GS Mobility Management (5GMM) protocol is defined in 3GPP TS 24.501;
-	the 5GS Session Management (5GSM) protocol is defined in 3GPP TS 24.501;
-	the UE policy delivery service is defined in 3GPP TS 24.501;
-	the non-3GPP access management protocol is defined in 3GPP TS 24.502;
-	the PC5 signalling protocol is defined in 3GPP TS 24.587;
-	the Time-Sensitive Networking (TSN) Application Function (AF) to Device-Side TSN Translator (DS-TT) and Network-Side TSN Translator (NW-TT) protocol is defined in 3GPP TS 24.519;
-	the Performance Measurement Function (PMF) protocol is defined in 3GPP TS 24.193;
-	the PC3 and PC5 signalling protocol for Proximity-based Services (ProSe) are defined in 3GPP TS 24.334.
-	the PC3a and PC5 signalling protocol for 5G Proximity-based Services (ProSe) are defined in 3GPP TS 24.554.
-	the signalling protocol between the Application Client on the constrained UE and the MSGin5G Client on the MSGin5G Gateway UE for Enabling MSGin5G Service is defined in 3GPP TS 24.538.

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