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Content for  TS 23.558  Word version:  18.1.0

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6 Application layer architecture  6.1 General  6.2 Architecture  6.3 Functional entities  6.4 Service-based interfaces  6.5 Reference Points  6.6 Cardinality rules  6.7 Capability exposure for enabling edge applications 
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6  Application layer architecture  p. 22

6.1  General  p. 22

This clause provides the overall architecture description:
  • Clause 6.2 describes the functional architecture and corresponding to the functional architecture;
  • Clause 6.3 describes the functional entities;
  • Clause 6.4 describes the service-based interfaces;
  • Clause 6.5 describes the reference points;
  • Clause 6.6 describes the cardinality of functional entities and reference points; and
  • Clause 6.7 describes the capabilities exposed for enabling edge applications.
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6.2  Architecture  p. 22

This clause describes the architecture for enabling edge applications in the following representations:
  • A service-based representation, where the Edge Enabler Layer functions (e.g. ECS) enable other authorized Edge Enabler Layer functions (e.g. EES) to access their services. This representation also includes point-to-point reference points where necessary;
  • A service-based representation as specified in TS 23.501, where the Network Functions (e.g. NEF) enable authorized Edge Enabler Layer functions (e.g. ECS) i.e. Application Functions, to access their services;
  • A service-based representation, where the Core Network Northbound APIs as specified in TS 23.501 and TS 23.502, are utilized by authorized Edge Enabler Layer functions via CAPIF core function specified in TS 23.222; and
  • A reference point representation, where existing interactions between any two functions (e.g. EES, ECS) is shown by an appropriate point-to-point reference point (e.g. EDGE-6, EDGE-7).
Edge Enabler Layer functions shown in the service-based representation of the edge architecture shall only use service-based interfaces for their interactions.
Figure 6.2-1 illustrates the service based representation of architecture for enabling edge applications.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.2-1: Architecture for enabling edge applications - service-based representation
Figure 6.2-1: Architecture for enabling edge applications - service-based representation
(⇒ copy of original 3GPP image)
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The mechanisms for service discovery in the service-based representation depicted in Figure 6.2-1 are as follows:
  • The EES discovers the ECS via pre-configuration or by using CAPIF as specified in TS 23.222;
  • The EAS discovers the EES via pre-configuration or by using CAPIF as specified in TS 23.222;
  • The EAS discovers the other EAS(s) as specified in clause 8.8.3.2;
  • The EEC discovers the ECS as specified in clause 8.3.2; and
  • The EEC discovers the EES via service provisioning as specified in clause 8.3.3.
Figure 6.2-2 illustrates the service-based representation for utilization of the 5GS network services based on the 5GS SBA specified in TS 23.501.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.2-2: Utilization of 5GS network services based on the 5GS SBA - service based representation
Figure 6.2-2: Utilization of 5GS network services based on the 5GS SBA - service based representation
(⇒ copy of original 3GPP image)
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The ECS, EES and EAS acts as AFs for consuming network services from the 3GPP 5G Core Network entities over the Service Based Architecture specified in TS 23.501.
Figure 6.2-3 illustrates the service-based representation for utilization of the Core Network (5GC, EPC) northbound APIs via CAPIF.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.2-3: Utilization of Core Network Northbound APIs via CAPIF - service based representation
Figure 6.2-3: Utilization of Core Network Northbound APIs via CAPIF - service based representation
(⇒ copy of original 3GPP image)
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The ECS, EES and EAS act as authorized API invoker to consume services from the Core Network (5GC, EPC) northbound API entities like SCEF, NEF, SCEF+NEF which act as API Exposing Function as specified in TS 23.222.
The mechanism for northbound APIs discovery using the service-based interfaces depicted in Figure 6.2-3 is as specified in TS 23.222.
Figure 6.2-4 illustrates the reference point representation of the architecture for edge enabling applications.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.2-4: Architecture for enabling edge applications - reference points representation
Figure 6.2-4: Architecture for enabling edge applications - reference points representation
(⇒ copy of original 3GPP image)
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The EDN is a local Data Network. EAS(s) and the EES are contained within the EDN. The ECS provides configurations related to the EES, including details of the EDN hosting the EES. The UE contains AC(s) and the EEC. The EAS(s), the EES and the ECS can interact with the 3GPP Core Network. When SEAL notification management service is used, the EES and the ECS interacts with the SEAL notification management server and the SEAL EEC interacts with SEAL Notification management client.

6.3  Functional entities  p. 25

6.3.1  General  p. 25

This clause describes the functional entities of the architecture for enabling edge applications.

6.3.2  Edge Enabler Server (EES)  p. 25

EES provides supporting functions needed for EASs and EEC.
Functionalities of EES are:
  1. provisioning of configuration information to EEC, enabling exchange of application data traffic with the EAS;
  2. providing API invoker and API exposing functions as specified in TS 23.222;
  3. interacting with 3GPP Core Network for accessing the capabilities of network functions either directly (e.g. via PCF) or indirectly (i.e. SCEF/NEF/SCEF+NEF);
  4. exposing events related to ACT;
  5. EEC context transfer between EESs;
  6. supporting external exposure of 3GPP network and service capabilities to the EAS(s) over EDGE-3;
  7. registration functions (i.e., registration, update, and de-registration) for the EEC(s) and the EAS(s);
  8. triggering the EAS instantiation on demand; and
  9. supporting ACR related operations (e.g. ACR launching, ACR information notification, EELManagedACR).
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6.3.3  Edge Enabler Client (EEC)  p. 25

EEC provides supporting functions needed for AC(s).
Functionalities of EEC are:
  1. retrieval of configuration information to enable the exchange of Application Data Traffic with the EAS;
  2. discovery of EASs available in the EDN; and
  3. detecting UE mobility events.

6.3.4  Edge Configuration Server (ECS)  p. 25

ECS provides supporting functions needed for the EEC to connect with an EES.
Functionalities of ECS are:
  1. provisioning of Edge configuration information to the EEC. The Edge configuration information includes the following:
    1. the information for the EEC to distinguish amongst the EESs (e.g. EDN service area); and
    2. the information for establishing a connection with EESs (such as URI);
    3. providing the T-EES information to the S-EES;
    4. supporting the functionalities of registration (i.e., registration, update, and de-registration) for the EES(s);
    5. supporting the functionalities of API invoker and API exposing function as specified in TS 23.222; and
    6. interacting with 3GPP Core Network for accessing the capabilities of network functions either directly (e.g. via PCF) or indirectly (i.e. SCEF/NEF/SCEF+NEF).
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6.3.5  Application Client (AC)  p. 26

AC is the application resident in the UE performing the client function. Depending on how ACR is implemented, the AC might be required to decide whether to initiate ACR. Other details of the AC are out of scope of this specification.

6.3.6  Edge Application Server (EAS)  p. 26

EAS is the application server resident in the EDN, performing the server functions. The AC connects to the EAS in order to avail the services of the application with the benefits of Edge Computing.
It is possible that the server functions of an application are available only as an EAS.
However, it is also possible that certain server functions are available both at the edge and in the cloud, as an EAS and an Application Server resident in the cloud respectively. The server functions offered by an EAS and its cloud Application Server counterpart may be the same or may differ; if they differ, the Application Data Traffic exchanged with the AC may also be different.
The EAS can consume the 3GPP Core Network capabilities in the following ways, all of which are optional to support:
  1. invoking 3GPP Core Network capabilities via the edge enabler layer through the EES
  2. invoking 3GPP Core Network function (e.g. PCF) APIs directly, if it is an entity trusted by the 3GPP Core Network; and
  3. invoking the 3GPP Core Network capabilities through the capability exposure functions i.e. SCEF/NEF/SCEF+NEF.
The EAS can support processing ACR related operations (e.g. ACR status update, selected target EAS declaration).
The EAS can expose its Service API(s) (i.e., EAS Service API(s)) towards the other EASs by supporting API provider domain functions as specified in TS 23.222; and the EAS can consume the EAS Service API(s) exposed by the other EAS(s) by supporting API invoker functionalities as specified in TS 23.222.
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6.3.7  Notification management client |R18|  p. 26

Notification management client is as specified in TS 23.434.

6.3.8  Notification management server |R18|  p. 26

Notification management server is as specified in TS 23.434.

6.4  Service-based interfaces  p. 26

The architecture for enabling edge applications contains the following service-based interfaces:
Eecs:
Service-based interface exhibited by ECS.
Eees:
Service-based interface exhibited by EES.

6.5  Reference Points  p. 26

6.5.1  General  p. 26

This clause describes the reference points of the architecture for enabling edge applications.

6.5.2  EDGE-1  p. 27

EDGE-1 reference point enables interactions between the EES and the EEC. It supports:
  1. registration and de-registration of the EEC to the EES;
  2. retrieval and provisioning of EAS configuration information;
  3. discovery of EASs available in the EDN; and
  4. service continuity procedures (e.g. ACR initiation).

6.5.3  EDGE-2  p. 27

EDGE-2 reference point enables interactions between the EES and the 3GPP Core Network functions and APIs for retrieval of network capability information. It supports:
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6.5.4  EDGE-3  p. 27

EDGE-3 reference point enables interactions between the EES and the EASs. It supports:
  1. registration of EASs with availability information (e.g. time constraints, location constraints);
  2. de-registration of EASs from the EES;
  3. discovery of T-EAS information to support ACT;
  4. providing access to network capability information (e.g. location information);
  5. requesting the setup of a data session between AC and EAS with a specific QoS and receiving QoS related information; and
  6. service continuity procedures (e.g. ACR status).
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6.5.5  EDGE-4  p. 27

EDGE-4 reference point enables interactions between the ECS and the EEC. It supports:
  1. provisioning of Edge configuration information to the EEC.

6.5.6  EDGE-5  p. 27

EDGE-5 reference point enables interactions between AC(s) and the EEC.

6.5.7  EDGE-6  p. 27

EDGE-6 reference point enables interactions between the ECS and the EES. It supports:
  1. registration of EES information to the ECS;
  2. de-registration of EES information from the ECS; and
  3. retrieval of the T-EES information from the ECS.

6.5.8  EDGE-7  p. 28

EDGE-7 reference point enables interactions between the EAS and the 3GPP Core Network functions and APIs for retrieval of network capability information. It supports:
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6.5.9  EDGE-8  p. 28

EDGE-8 reference point enables interactions between the ECS and the 3GPP Core Network functions and APIs for retrieval of network capability information. It supports:
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6.5.10  EDGE-9  p. 28

EDGE-9 reference point enables interactions between two EESs. EDGE-9 reference point may be provided between EES within different EDN (Figure 6.5.10-1) and within the same EDN (Figure 6.5.10-2).
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.5.10-1: Inter-EDN EDGE-9
Figure 6.5.10-1: Inter-EDN EDGE-9
(⇒ copy of original 3GPP image)
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Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.5.10-2: Intra-EDN EDGE-9
Figure 6.5.10-2: Intra-EDN EDGE-9
(⇒ copy of original 3GPP image)
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EDGE-9 supports:
  1. discovery of T-EAS information to support ACR;
  2. EEC context relocation procedures; and
  3. transparent transfer of the application context during EELManagedACR.

6.5.11  NM-UU |R18|  p. 29

NM-UU reference point is as specified in TS 23.434.

6.5.12  NM-S |R18|  p. 29

NM-S reference point is as specified in TS 23.434, where EES or ECS acts VAL server.

6.5.13  NM-C |R18|  p. 29

NM-C reference point is as specified in TS 23.434, where EEC acts as VAL client.

6.6  Cardinality rules  p. 29

6.6.1  General  p. 29

The cardinality rules are applied to the architecture specified in clause 6.2. The cardinality rules are classified as functional entity cardinality and reference point cardinality. The functional entity cardinality specifies the multiplicity of the functional entity that can exist as per the architecture. The reference point cardinality specifies the multiplicity of source and target functional entities that can exist in a relationship defined by the reference point in the architecture.
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6.6.2  Functional Entity Cardinality  p. 30

6.6.2.1  General  p. 30

6.6.2.2  AC  p. 30

The following cardinality rules apply for ACs:
  1. one or more ACs may be located in a UE.

6.6.2.3  EEC  p. 30

The following cardinality rules apply for EECs:
  1. One or more EEC(s) may be located in a UE.

6.6.2.4  ECS  p. 30

The following cardinality rules apply for ECSs:
  1. One or more ECS(s) may be deployed to support one EDN;
  2. One ECS may be deployed to support one or more EDN(s);
  3. One or more ECS(s) may be deployed by a PLMN operator; and
  4. One or more ECS(s) may be deployed by an ECSP.

6.6.2.5  EES  p. 30

The following cardinality rules apply for EES:
  1. One or more EES(s) may be located in an EDN; and
  2. One or more EES(s) may be located in an EDN per ECSP.

6.6.2.6  EAS  p. 30

The following cardinality rules apply for EASs:
  1. One or more EAS(s) may be located in an EDN.

6.6.3  Reference Point Cardinality  p. 30

6.6.3.1  General  p. 30

6.6.3.2  EDGE-1 (Between EEC and EES)  p. 30

The following cardinality rules apply for EDGE-1:
  1. One EEC may communicate with one or more EES(s) for one or more AC concurrently; and
  2. One EES may communicate with one or more EEC(s) concurrently.

6.6.3.3  EDGE-3 (Between EAS and EES)  p. 30

The following cardinality rules apply for EDGE-3:
  1. One EAS may communicate with only one EES within the same EDN; and
  2. One EES may communicate with one or more EAS(s) concurrently.

6.6.3.4  EDGE-4 (Between EEC and ECS)  p. 31

The following cardinality rules apply for EDGE-4:
  1. One EEC may communicate with one or more ECS(s) concurrently; and
  2. One ECS may communicate with one or more EEC(s) concurrently.

6.6.3.5  EDGE-5 (Between AC and EEC)  p. 31

The following cardinality rules apply for EDGE-5:
  1. One AC may communicate with only one EEC; and
  2. One EEC may communicate with one or more AC(s) concurrently.

6.6.3.6  EDGE-6 (Between EES and ECS)  p. 31

The following cardinality rules apply for EDGE-6:
  1. One EES may communicate with one or more ECS(s) concurrently; and
  2. One ECS may communicate with one or more EES(s) concurrently.

6.6.3.7  EDGE-9 (Between EES and EES)  p. 31

The following cardinality rules apply for EDGE-9:
  1. One EES may communicate with one or more EES(s) concurrently.

6.7  Capability exposure for enabling edge applications  p. 31

6.7.1  General  p. 31

The Figure 6.7.1-1 shows the capability exposure for enabling edge applications.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 6.7.1-1: Capability exposure for enabling edge applications
Figure 6.7.1-1: Capability exposure for enabling edge applications
(⇒ copy of original 3GPP image)
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Capability exposure includes the 3GPP core network (i.e. 5GC, EPC), ECS and the EES capability exposure, to fulfil the needs of the edge service operations. The capability exposure functionality is utilized by the functional entities (i.e. EES, EAS and ECS) depicted in the architecture for enabling the edge applications.

6.7.2  APIs provided by the Edge Enabler Layer  p. 32

Table 6.7.2-1 summarizes the APIs exposed by the ECS.
API Name Known Consumers References
Eecs_ServiceProvisioningEEC 8.3
Eecs_EESRegistrationEES 8.4.4
Eecs_TargetEESDiscoveryEES 8.8.3.3
Table 6.7.2-2 summarizes the APIs exposed the EES.
API Name Known Consumers References
Eees_EECRegistrationEEC 8.4.2
Eees_EASRegistrationEAS 8.4.3
Eees_EASDiscoveryEEC 8.5
Eees_UELocationEAS 8.6.2
Eees_ACRManagementEventEAS 8.6.3
Eees_AppClientInformationEAS 8.6.4
Eees_UEIdentifierEAS 8.6.5
Eees_SessionWithQoSEAS 8.6.6
Eees_TargetEASDiscoveryEAS, EES 8.8.3.2
Eees_AppContextRelocationEEC, EAS 8.8.3.4
Eees_ACREventsEEC 8.8.3.5
Eees_EELManagedACREAS 8.8.3.6
Eees_EECContextPullEES 8.9.4.2
Eees_EECContextPushEES 8.9.4.3
Eees_SelectedTargetEASEAS 8.8.3.7
Eees_ACRStatusUpdateEAS 8.8.3.8
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