8.5 EAS discovery

23.5583GPPArchitecture for enabling Edge ApplicationsRelease 18TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

8.5.1 General

Discovery procedures enable entities in an edge deployment to obtain information about EAS and their available services, based on specified criteria of interest.

EAS discovery enables the EEC to obtain information about available EASs of interest. The discovery of the EASs is based on matching EAS discovery filters provided in the request.

When multiple EASs are discovered for a specific AC, the EEC may select one or more EASs to enable AC communication with one of the selected EASs. The selection algorithm is outside the scope of this specification. Once the EAS is selected, the EEC may subscribe for the ACR event notifications at the EES of the selected EAS, as described in clause 8.8.3.5.2. The EDN configuration information received from ECS may be used for establishing a connection to EAS(s).

EAS discovery may be initiated by the EEC when a certain trigger condition at the UE is met. Some examples are as follows:

– AC related updates available at the EEC (e.g. due to AC installation/re-installation/activation), AC requesting application server access;

– Lifetime received via EAS discovery response specified in clause 8.5.3 is expired; or

– EEC detects the need of application context relocation as in clause 8.8.

NOTE: When the EEC decides to perform EAS discovery is up to EEC implementation.

8.5.2 Procedures

8.5.2.1 General

Following procedures are supported for EAS discovery:

– Request-response procedure;

– Subscribe-notify procedures for EAS discovery and EAS dynamic information subscription, comprising:

– Subscription procedure;

– Subscription update procedure; and

– Unsubscribe procedure;

8.5.2.2 Request-response model

Pre-conditions:

1. The EEC has received information (e.g. URI, IP address) related to the EES;

2. The EEC has received appropriate security credentials authorizing it to communicate with the EES as specified in clause 8.11; and

3. The EES is configured with ECSP’s policy for EAS discovery.

NOTE 1: Details of ECSP’s policy are out of scope.

Figure 8.5.2.2-1: EAS Discovery procedure

1. The EEC sends an EAS discovery request to the EES. The EAS discovery request includes the requestor identifier [EECID] along with the security credentials and may include EAS discovery filters and may also include UE location to retrieve information about particular EAS(s) or a category of EASs, e.g. gaming applications, or Edge Applications Server(s) available in certain service areas, e.g. available on a UE’s predicted or expected route.

2. Upon receiving the request from the EEC, the EES checks if the EEC is authorized to discover the requested EAS(s). The authorization check may apply to an individual EAS, a category of EASs or to the EDN, i.e. to all the EASs. If UE’s location information is not already available, the EES obtains the UE location by utilizing the capabilities of the 3GPP core network as specified in clause 8.10.3. If EAS discovery filters are provided by the EEC, the EES identifies the EAS(s) based on the provided EAS discovery filters and the UE location. If the EEC indicates that service continuity support is required, the EES shall take the indication which ACR scenarios are supported by the AC and the EEC and which of these are preferred by the AC into consideration. The EES may select one EAS and determine to perform application traffic influence for this AC based on AC’s service KPI or EAS’s service KPI in desired response time, when the EES does not perform traffic influence in advance.

When EAS discovery filters are not provided, then:

– if available, the EES identifies the EAS(s) based on the UE-specific service information at the EES and the UE location;

– EES identifies the EAS(s) by applying the ECSP policy (e.g. based only on the UE location);

NOTE 2: Details of the UE-specific service information and how it is available at the EES is out of scope.

NOTE 3: Both steps are evaluated prior to sending a response.

Upon receiving the request from the EEC, the EES may trigger the EAS management system to instantiate the EAS that matches with EAS discovery filter IEs (e.g. ACID) as in clause 8.12.

3. If the processing of the request was successful, the EES sends an EAS discovery response to the EEC, which includes information about the discovered EASs. For discovered EASs, this includes endpoint information. Depending on the EAS discovery filters received in the EAS discovery request, the response may include additional information regarding matched capabilities, e.g. service permissions levels, KPIs, AC locations(s) that the EASs can support, ACR scenarios supported by the EAS, etc. The EAS discovery response may contain a list of EASs. This list may be based on EAS discovery filters containing a Geographical or Topological Service Area, e.g. a route, included in the EAS discovery request by the EEC.

If the EES is unable to determine the EAS information using the inputs in the EAS discovery request, UE-specific service information at the EES or the ECSP policy, the EES shall reject the EAS discovery request and respond with an appropriate failure cause.

If the EEC is not registered with the EES, and ECSP policy requires the EEC to perform EEC registration prior to EAS discovery, the EES shall include an appropriate failure cause in the EAS discovery response indicating that EEC registration is required.

If the UE location and predicted/expected UE locations, provided in the EAS discovery request, are outside the Geographical or Topological Service Area of an EAS, then the EES shall not include that EAS in the discovery response. The discovery response may include EAS(s) that cannot serve the UE at its current location if a predicted/expected UE location was provided in the EAS discovery request.

Upon receiving the EAS discovery response, the EEC uses the endpoint information for routing of the outgoing application data traffic to EAS(s), as needed, and may provide necessary notifications to the AC(s). The EEC may use the border or overlap between EAS Geographical Service Areas for service continuity purposes. The EEC may cache the EAS information (e.g. EAS endpoint) for subsequent use and avoid the need to repeat step 1. If the Lifetime IE is included in the response, the EEC may cache the EAS information only for the duration specified by the Lifetime IE.

NOTE 4: Within the duration specified by the Lifetime IE, the cached EAS Profile can be updated (e.g. according to notifications from the EES for changes of EAS information due to EAS status change) or the cached EAS Profile can be invalidated due to new EAS information discovery (e.g. due to UE mobility). The EEC can update or invalidate the cached EAS information (e.g. on PDU Session Release or Modification Command).

NOTE 5: The AC can cache the EAS information (e.g. EAS endpoint) for subsequent use. In the case of the cached information needing to be updated or invalidated, the mechanisms for the EEC to notify the AC is up to implementation and is not specified in the current release of the present document.

NOTE 6: The EEC can use the EAS information provided by the discovery procedure to perform service continuity planning, for example when ultra-low latency ACR is required.

If the EAS discovery request fails, the EEC may resend the EAS discovery request, taking into account the received failure cause. If the failure cause indicated that EEC registration is required, the EEC shall perform an EEC registration before resending the EAS discovery request.

8.5.2.3 Subscribe-notify model

8.5.2.3.1 General

Clause 8.5.2.3.2 and clause 8.5.2.3.3 together illustrate the EAS discovery procedure based on Subscribe/Notify model.

Clause 8.5.2.3.4 illustrates the EAS discovery update procedure.

Clause 8.5.2.3.5 illustrates the EAS discovery unsubscribe procedure.

8.5.2.3.2 Subscribe

Figure 8.5.2.3.2-1 illustrates the EAS discovery subscription procedure between the EEC and the EES. This subscription enables EES to inform EEC of various EAS discovery related events of interest to EEC (e.g. EAS discovery notification and EAS dynamic information).

Pre-conditions:

1. The EEC has received information (e.g. URI, IP address) related to the EES;

2. The EEC has received appropriate security credentials authorizing it to communicate with the EES as specified in clause 8.11;

3. The EES is configured with ECSP’s policy for EAS discovery; and

4. The EEC has optionally acquired a Notification Target Address to be used in its subscriptions to notifications.

NOTE 1: Details of ECSP’s policy are out of scope.

NOTE 2: How the EEC acquires the notification target address or a notification channel URI to receive the notifications is out of scope of this release. The notification target address can terminate at the EEC (e.g. in an IoT device) if the deployment supports EEC reachability, or it can terminate at a push notification service. Details of the push notification service are out of scope of this release.

Figure 8.5.2.3.2-1: EAS discovery subscription

1. The EEC sends an EAS discovery subscription request to the EES. The EAS discovery subscription request includes the EECID along with the security credentials, Event ID, and may include EAS discovery filters and EAS dynamic information filters to subscribe to information about particular EAS(s) or a category of EASs (e.g. gaming applications) or dynamic information about EAS(s).

2. Upon receiving the request from the EEC, the EES checks if the EEC is authorized to subscribe for information of the requested EAS(s). The authorization check may apply to an individual EAS, a category of EASs or to the EDN, i.e. to all the EASs. The EES may utilize the capabilities (e.g. UE location) of the 3GPP core network as specified in clause 8.10.3. If the request is authorized, the EES creates and stores the subscription for EAS discovery.

3. If the processing of the request was successful, the EES sends an EAS discovery subscription response to the EEC, which includes the subscription identifier and may include the expiration time, indicating when the subscription will automatically expire. To maintain the subscription, the EEC shall send an EAS discovery subscription update request prior to the expiration time. If an EAS discovery subscription update request is not received prior to the expiration time, the EES shall treat the EEC as implicitly unsubscribed.

If the EES is unable to determine the EAS information using the inputs in the EAS discovery subscription request, UE-specific service information at the EES or the ECSP policy, the EES shall reject the EAS discovery subscription request and respond with an appropriate failure cause.

If the EAS discovery subscription request fails, the EEC may resend the EAS discovery subscription request again, taking into account the received failure cause. If the failure cause indicated that EEC registration is required, the EEC shall perform an EEC registration before resending the EAS discovery subscription request.

8.5.2.3.3 Notify

Figure 8.5.2.3.3-1 illustrates the EAS discovery notification procedure between the EEC and the EES.

Pre-conditions:

1. The EEC has subscribed with the EES for the EAS discovery information as specified in clause 8.5.2.3.2.

Figure 8.5.2.3.3-1: EAS discovery notification

1. An event occurs at the EES that satisfies trigger conditions for notifying (e.g. to provide EAS discovery information or EAS dynamic information) a subscribed EEC. If UE’s location information is not already available, the EES obtains the UE location by utilizing the capabilities of the 3GPP core network as specified in clause 8.10.2. If EAS discovery filters were provided by the EEC during subscription creation, the EES identifies the EAS(s) based on the provided EAS discovery filters and the UE location. If the EEC indicates that service continuity support is required, the EES shall take the indication which ACR scenarios are supported by the AC and the EEC and which of these are preferred by the AC into consideration.

If EAS discovery filters were not provided, then:

– if available, the EES identifies the EAS(s) based on the UE-specific service information at the EES and the UE location;

– EES identifies the EAS(s) by applying the ECSP policy (e.g. based only on the UE location);

NOTE 1: Details of the UE-specific service information and how it is available at the EES is out of scope.

NOTE 2: Both steps are evaluated prior to sending a response.

If the UE is located outside the Geographical or Topological Service Area of an EAS, then the EES shall not include this EAS in the EAS discovery notification.

2. The EES sends an EAS discovery notification to the EEC with the EAS information determined in step 1.

8.5.2.3.4 Subscription update

Figure 8.5.2.3.4-1 illustrates the EAS discovery subscription update procedure between the EEC and the EES.

Pre-conditions:

1. The EEC has subscribed with the EES for the EAS discovery information as specified in clause 8.5.2.3.2

Figure 8.5.2.3.4-1: EAS discovery subscription update

1. The EEC sends an EAS discovery subscription update request to the EES. The EAS discovery subscription update request includes the security credentials and the subscription identifier. It may also include EAS discovery filters, EAS dynamic information filters and/or proposed expiration time for the updated subscription.

2. Upon receiving the request from the EEC, the EES checks if the EEC is authorized to update the subscription information. The EES may utilize the capabilities (e.g. UE location) of the 3GPP core network as specified in clause 8.10.3. If the request is authorized, the EES updated the stored subscription for EAS discovery.

3. The EES sends an EAS discovery subscription update response to the EEC, which may include the expiration time, indicating when the updated subscription will automatically expire. To maintain the subscription, the EEC shall send an EAS discovery subscription update request prior to the expiration time. If an EAS discovery subscription update request is not received prior to the expiration time, the EES shall treat the EEC as implicitly unsubscribed.

8.5.2.3.5 Unsubscribe

Figure 8.5.2.3.5-1 illustrates the EAS discovery unsubscribe procedure between the EEC and the EES.

Pre-conditions:

1. The EEC has subscribed with the EES for notification (e.g. EAS discovery information and EAS dynamic information) as specified in clause 8.5.2.3.2

Figure 8.5.2.3.5-1: EAS discovery unsubscribe

1. The EEC sends an EAS discovery unsubscribe request to the EES. The EAS discovery unsubscribe request includes the security credentials of the EEC along with the subscription identifier.

2. Upon receiving the request, the EES performs an authorization check to verify whether the EEC has authorization to perform the operation. If authorized, the EES cancels the subscription for provisioning as requested in step 1.

3. The EES responds with an EAS discovery unsubscribe response.

8.5.3 Information flows

8.5.3.1 General

The following information flows are specified for EAS discovery:

– EAS discovery request and response;

– EAS discovery subscription, notification, subscription update and unsubscribe; and

– EAS dynamic information subscription, notification, subscription update and unsubscribe.

8.5.3.2 EAS discovery request

Table 8.5.3.2-1 describes information elements for the EAS discovery request. Table 8.5.3.2-2 provides further detail about the EAS Discovery Filter information element.

Table 8.5.3.2-1: EAS discovery request

Information element	Status	Description
Requestor identifier	M	The ID of the requestor (e.g. EECID)
UE Identifier	O	The identifier of the UE (i.e. GPSI or identity token)
Security credentials	M	Security credentials resulting from a successful authorization for the edge computing service.
EAS discovery filters	O	Set of characteristics to determine required EASs, as detailed in Table 8.5.3.2-2.
UE location	O	The location information of the UE. The UE location is described in clause 7.3.2.
Target DNAI (NOTE)	O	Target DNAI information which can be associated with potential T-EAS(s)
EEC Service Continuity Support	O	Indicates if the EEC supports service continuity or not. The IE also indicates which ACR scenarios are supported by the EEC or, if this message is sent by the EEC to discover a T‑EAS, which ACR scenario(s) are intended to be used for the ACR.
EES Service Continuity Support (NOTE)	O	The IE indicates if the S-EES supports service continuity or not. The IE also indicates which ACR scenarios are supported by the S-EES or, if the EAS discovery is used for an S‑EES executed ACR according to clause 8.8.2.5, which ACR scenario is to be used for the ACR.
EAS Service Continuity Support (NOTE)	O	The IE indicates if the S-EAS supports service continuity or not. The IE also indicates which ACR scenarios are supported by the S-EAS or, if the EAS discovery is used for an S‑EAS decided ACR according to clause 8.8.2.4, which ACR scenario is to be used for the ACR.
NOTE: This IE shall not be included when the request originates from the EEC.

Table 8.5.3.2-2: EAS discovery filters

Information element	Status	Description
List of AC characteristics (NOTE 1)	O	Describes the ACs for which a matching EAS is needed.
> AC profile (NOTE 2)	M	AC profile containing parameters used to determine matching EAS. AC profiles are further described in Table 8.2.2-1.
List of EAS characteristics (NOTE 1, NOTE 3)	O	Describes the characteristic of required EASs.
> EASID	O	Identifier of the required EAS.
> EAS provider identifier	O	Identifier of the required EAS provider
> EAS type	O	The category or type of required EAS (e.g. V2X)
> EAS schedule	O	Required availability schedule of the EAS (e.g. time windows)
> EAS Geographical Service Area	O	Location(s) (e.g. geographical area, route) where the EAS service should be available.
> EAS Topological Service Area	O	Topological area (e.g. cell ID, TAI) for which the EAS service should be available. See possible formats in Table 8.2.7-1.
> Service continuity support	O	Indicates if the service continuity support is required or not.
> Service permission level	O	Required level of service permissions e.g. trial, gold-class
> Service feature(s)	O	Required service features e.g. single vs. multi-player gaming service
NOTE 1: Either "List of AC characteristics" or "List of EAS characteristics" shall be present. NOTE 2: "Preferred ECSP list" IE shall not be present. NOTE 3: The "List of EAS characteristics" IE must include at least one optional IE, if used as an EAS discovery filter.

8.5.3.3 EAS discovery response

Table 8.5.3.3-1 describes information elements for the EAS discovery response from the EES to the EEC.

Table 8.5.3.3-1: EAS discovery response

Information element	Status	Description
Successful response	O	Indicates that the EAS discovery request was successful.
> Discovered EAS list	O	List of discovered EAS(s). Each element includes the information described below.
>> EAS profile	M	Profile of the EAS. Each element is described in clause 8.2.4
>> Lifetime	O	Time interval or duration during which the information elements in the EAS profile is valid and supposed to be cached in the EEC (e.g. time-to-live value for an EAS Endpoint)
Failure response	O	Indicates that the EAS discovery request failed.
> Cause	O	Indicates the cause of EAS discovery request failure.

8.5.3.4 EAS discovery subscription request

Table 8.5.3.4-1 describes the information elements for EAS discovery subscription request from the EEC to the EES.

Table 8.5.3.4-1: EAS discovery subscription request

Information element	Status	Description
EECID	M	Unique identifier of the EEC.
UE Identifier	O	The identifier of the UE (i.e. GPSI or identity token)
Event ID	M	Event ID: – EAS availability change – EAS dynamic information change
Security credentials	M	Security credentials resulting from a successful authorization for the edge computing service.
Notification Target Address	O	The Notification target address (e.g. URL) where the notifications destined for the EEC should be sent to.
EAS discovery filters	O	Set of characteristics to determine matching EASs (as detailed in Table 8.5.3.2-2). Applicable for "EAS availability change" event
EAS dynamic information filters	O	List of dynamic information changes (as detailed in Table 8.5.3.4-2) about EAS, the EEC is interested in. Applicable for "EAS dynamic information change" event
EEC Service Continuity Support	O	Indicates if the EEC supports service continuity or not. The IE also indicates which ACR scenarios are supported by the EEC.
Proposed expiration time	O	Proposed expiration time for the subscription

Table 8.5.3.4-2: EAS dynamic information filters

Information element	Status	Description
List of dynamic information filters	M	List of EAS dynamic information required by the EEC per EAS.
> EASID	M	Identifier of the EAS
> ACIDs	O	Flag to notify change in list of ACIDs served by the EAS
> EAS Description	O	Flag to notify change in description of the EAS.
> EAS Endpoint	O	Flag to notify change in EAS endpoint
> EAS Features	O	Flag to notify any change in features provided by the EAS
> EAS Schedule	O	Flag to notify change in availability schedule of the EAS (e.g. time windows)
> EAS Service Area	O	Flag to notify change in change in geographical service area that the EAS serves
> EAS Service KPIs	O	Flag to notify change in characteristics of the EAS.
> EAS Status	O	Flag to notify change in the status of the EAS (e.g. enabled, disabled, etc.)
> Service continuity support	O	Flag to notify change in EAS support for service continuity.

8.5.3.5 EAS discovery subscription response

Table 8.5.3.5-1 describes the information elements for EAS discovery subscription response from the EES to the EEC.

Table 8.5.3.5-1: EAS discovery subscription response

Information element	Status	Description
Successful response	O	Indicates that the subscription request was successful.
> Subscription ID	M	Subscription identifier corresponding to the subscription.
> Expiration time	O	Indicates the expiration time of the subscription. To maintain an active subscription, a subscription update is required before the expiration time.
Failure response	O	Indicates that the subscription request failed.
> Cause	O	Indicates the cause of subscription request failure

8.5.3.6 EAS discovery notification

Table 8.5.3.6-1 describes the information elements for EAS discovery notification from the EES to the EEC.

Table 8.5.3.6-1: EAS discovery notification

Information element	Status	Description
Subscription ID	M	Subscription identifier corresponding to the subscription stored in the EES for the request
Event ID	M	Either EAS discovery notification or EAS dynamic information notification
EAS list	O	List of EAS profiles. Each element includes the information described below.
> EAS profile	M	Profile of the EAS. Each element is described in clause 8.2.4
> Lifetime	O	Time interval or duration during which the information elements in the EAS profile is valid and supposed to be cached in the EEC (e.g. time-to-live value for an EAS Endpoint)

8.5.3.7 EAS discovery subscription update request

Table 8.5.3.7-1 describes the information elements for EAS discovery subscription update request from the EEC to the EES.

Table 8.5.3.7-1: EAS discovery subscription update request

Information element	Status	Description
Subscription ID	M	Subscription identifier corresponding to the subscription to be updated
Security credentials	M	Security credentials resulting from a successful authorization for the edge computing service.
Proposed expiration time	O	Proposed expiration time for the subscription
EAS discovery filters	O	Set of characteristics to determine required EASs, as detailed in Table 8.5.3.2-2.
EAS dynamic information filters	O	List of dynamic information about EAS, the EEC is interested in, as detailed in Table 8.5.3.4-2.
EEC Service Continuity Support	O	Indicates if the EEC supports service continuity or not. The IE also indicates which ACR scenarios are supported by the EEC.

8.5.3.8 EAS discovery subscription update response

Table 8.5.3.8-1 describes the information elements for EAS discovery subscription update response from the EES to the EEC.

Table 8.5.3.8-1: EAS discovery subscription update response

Information element	Status	Description
Successful response	O	Indicates that the subscription update request was successful.
> Expiration time	O	Indicates the expiration time of the updated subscription. To maintain an active subscription, a subscription update is required before the expiration time.
Failure response	O	Indicates that the subscription update request failed.
> Cause	O	Indicates the cause of subscription update request failure

8.5.3.9 EAS discovery unsubscribe request

Table 8.5.3.9-1 describes the information elements for EAS discovery unsubscribe request from the EEC to the EES.

Table 8.5.3.9-1: EAS discovery unsubscribe request

Information element	Status	Description
Subscription ID	M	Subscription identifier corresponding to the subscription to be unsubscribed
Security credentials	M	Security credentials of the EEC

8.5.3.10 EAS discovery unsubscribe response

Table 8.5.3.10-1 describes the information elements for EAS discovery unsubscribe response from the EES to the EEC.

Table 8.5.3.10-1: EAS discovery unsubscribe response

Information element	Status	Description
Successful response	O	Indicates that the unsubscribe request was successful.
Failure response	O	Indicates that the unsubscribe request failed.
> Cause	O	Indicates the cause of unsubscribe request failure

8.5.4 APIs

8.5.4.1 General

Table 8.5.4.1-1 illustrates the API for EAS discovery.

Table 8.5.4.1-1: Eees_EASDiscovery API

API Name	API Operations	Operation Semantics	Consumer(s)
Eees_EASDiscovery	Request	Request/Response	EEC
	Subscribe	Subscribe/Notify	EEC
	Notify
	UpdateSubscription
	Unsubscribe

8.5.4.2 Eees_EASDiscovery_Request operation

API operation name: Eees_EASDiscovery_Request

Description: The consumer requests for one time EAS discovery information.

Inputs: See clause 8.5.3.2.

Outputs: See clause 8.5.3.3.

See clause 8.5.2.2 for details of usage of this operation.

8.5.4.3 Eees_EASDiscovery_Subscribe operation

API operation name: Eees_EASDiscovery_Subscribe

Description: The consumer subscribes for EAS discovery information.

Inputs: See clause 8.5.3.4.

Outputs: See clause 8.5.3.5.

See clause 8.5.2.3.2 for details of usage of this operation.

8.5.4.4 Eees_EASDiscovery_Notify operation

API operation name: Eees_EASDiscovery_Notify

Description: The consumer is notified with EAS discovery and/or EAS dynamic information.

Inputs: See clause 8.5.3.6.

Outputs: None.

See clause 8.5.2.3.3 for details of usage of this operation.

8.5.4.5 Eees_EASDiscovery_UpdateSubscription operation

API operation name: Eees_EASDiscovery_UpdateSubscription

Description: The consumer updates an existing subscription for EAS discovery information.

Inputs: See clause 8.5.3.7.

Outputs: See clause 8.5.3.8.

See clause 8.5.2.3.4 for details of usage of this operation.

8.5.4.6 Eees_EASDiscovery_Unsubscribe operation

API operation name: Eees_EASDiscovery_Unsubscribe

Description: The consumer cancels an existing subscription for EAS discovery information.

Inputs: See clause 8.5.3.9.

Outputs: See clause 8.5.3.10.

See clause 8.5.2.3.5 for details of usage of this operation.