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Content for  TS 23.558  Word version:  17.4.0

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8.5  EAS discoveryWord‑p. 68

8.5.1  GeneralWord‑p. 68

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.
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8.5.2  ProceduresWord‑p. 69

8.5.2.1  GeneralWord‑p. 69

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 modelWord‑p. 69

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.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 8.5.2.2-1: EAS Discovery procedure
Figure 8.5.2.2-1: EAS Discovery procedure
(⇒ copy of original 3GPP image)
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Step 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.
Step 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.
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);
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.
Step 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.
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.
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8.5.2.3  Subscribe-notify modelWord‑p. 70

8.5.2.3.1  GeneralWord‑p. 70
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.
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8.5.2.3.2  SubscribeWord‑p. 71
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.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 8.5.2.3.2-1: EAS discovery subscription
Figure 8.5.2.3.2-1: EAS discovery subscription
(⇒ copy of original 3GPP image)
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Step 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).
Step 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.
Step 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 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 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.
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8.5.2.3.3  NotifyWord‑p. 72
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.
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 8.5.2.3.3-1: EAS discovery notification
Figure 8.5.2.3.3-1: EAS discovery notification
(⇒ copy of original 3GPP image)
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Step 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);
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.
Step 2.
The EES sends an EAS discovery notification to the EEC with the EAS information determined in step 1.
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8.5.2.3.4  Subscription updateWord‑p. 72
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
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 8.5.2.3.4-1: EAS discovery subscription update
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Step 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.
Step 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.
Step 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.
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8.5.2.3.5  UnsubscribeWord‑p. 73
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
Copy of original 3GPP image for 3GPP TS 23.558, Fig. 8.5.2.3.5-1: EAS discovery unsubscribe
Figure 8.5.2.3.5-1: EAS discovery unsubscribe
(⇒ copy of original 3GPP image)
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Step 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.
Step 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.
Step 3.
The EES responds with an EAS discovery unsubscribe response.

8.5.3  Information flowsWord‑p. 74

8.5.3.1  GeneralWord‑p. 74

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 requestWord‑p. 74

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.
Information element Status Description
Requestor identifierMThe ID of the requestor (e.g. EECID)
UE IdentifierOThe identifier of the UE (i.e. GPSI or identity token)
Security credentialsMSecurity credentials resulting from a successful authorization for the edge computing service.
EAS discovery filtersO Set of characteristics to determine required EASs, as detailed in Table 8.5.3.2-2.
UE locationOThe location information of the UE. The UE location is described in clause 7.3.2.
Target DNAI (NOTE)OTarget DNAI information which can be associated with potential T-EAS(s)
EEC Service Continuity SupportOIndicates 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)OThe 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)OThe 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.
Information element Status Description
List of AC characteristics (NOTE 1)ODescribes 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)ODescribes the characteristic of required EASs.
> EASIDOIdentifier of the required EAS.
> EAS provider identifierOIdentifier of the required EAS provider
> EAS typeOThe category or type of required EAS (e.g. V2X)
> EAS scheduleORequired availability schedule of the EAS (e.g. time windows)
> EAS Geographical Service AreaOLocation(s) (e.g. geographical area, route) where the EAS service should be available.
> EAS Topological Service AreaO 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 supportOIndicates if the service continuity support is required or not.
> Service permission levelORequired level of service permissions e.g. trial, gold-class
> Service feature(s)ORequired 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.
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8.5.3.3  EAS discovery responseWord‑p. 76

Table 8.5.3.3-1 describes information elements for the EAS discovery response from the EES to the EEC.
Information element Status Description
Successful responseOIndicates that the EAS discovery request was successful.
> Discovered EAS listOList of discovered EAS(s). Each element includes the information described below.
>> EAS profileMProfile of the EAS. Each element is described in clause 8.2.4
>> LifetimeOTime 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 responseOIndicates that the EAS discovery request failed.
> CauseOIndicates the cause of EAS discovery request failure.
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8.5.3.4  EAS discovery subscription requestWord‑p. 76

Table 8.5.3.4-1 describes the information elements for EAS discovery subscription request from the EEC to the EES.
Information element Status Description
EECIDMUnique identifier of the EEC.
UE IdentifierOThe identifier of the UE (i.e. GPSI or identity token)
Event IDMEvent ID:
  • EAS availability change
  • EAS dynamic information change
Security credentialsMSecurity credentials resulting from a successful authorization for the edge computing service.
Notification Target AddressOThe Notification target address (e.g. URL) where the notifications destined for the EEC should be sent to.
EAS discovery filtersO 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 filtersO 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 SupportOIndicates if the EEC supports service continuity or not. The IE also indicates which ACR scenarios are supported by the EEC.
Proposed expiration timeOProposed expiration time for the subscription
Information element Status Description
List of dynamic information filtersMList of EAS dynamic information required by the EEC per EAS.
> EASIDMIdentifier of the EAS
> ACIDsOFlag to notify change in list of ACIDs served by the EAS
> EAS DescriptionOFlag to notify change in description of the EAS.
> EAS EndpointOFlag to notify change in EAS endpoint
> EAS FeaturesOFlag to notify any change in features provided by the EAS
> EAS ScheduleOFlag to notify change in availability schedule of the EAS (e.g. time windows)
> EAS Service AreaOFlag to notify change in change in geographical service area that the EAS serves
> EAS Service KPIsOFlag to notify change in characteristics of the EAS.
> EAS StatusOFlag to notify change in the status of the EAS (e.g. enabled, disabled, etc.)
> Service continuity supportOFlag to notify change in EAS support for service continuity.
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8.5.3.5  EAS discovery subscription responseWord‑p. 77

Table 8.5.3.5-1 describes the information elements for EAS discovery subscription response from the EES to the EEC.
Information element Status Description
Successful responseOIndicates that the subscription request was successful.
> Subscription IDMSubscription identifier corresponding to the subscription.
> Expiration timeOIndicates the expiration time of the subscription. To maintain an active subscription, a subscription update is required before the expiration time.
Failure responseOIndicates that the subscription request failed.
> CauseOIndicates the cause of subscription request failure
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8.5.3.6  EAS discovery notificationWord‑p. 77

Table 8.5.3.6-1 describes the information elements for EAS discovery notification from the EES to the EEC.
Information element Status Description
Subscription IDMSubscription identifier corresponding to the subscription stored in the EES for the request
Event IDMEither EAS discovery notification or EAS dynamic information notification
EAS listOList of EAS profiles. Each element includes the information described below.
> EAS profileMProfile of the EAS. Each element is described in clause 8.2.4
> LifetimeOTime 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)
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8.5.3.7  EAS discovery subscription update requestWord‑p. 78

Table 8.5.3.7-1 describes the information elements for EAS discovery subscription update request from the EEC to the EES.
Information element Status Description
Subscription IDMSubscription identifier corresponding to the subscription to be updated
Security credentialsMSecurity credentials resulting from a successful authorization for the edge computing service.
Proposed expiration timeOProposed expiration time for the subscription
EAS discovery filtersO Set of characteristics to determine required EASs, as detailed in Table 8.5.3.2-2.
EAS dynamic information filtersO List of dynamic information about EAS, the EEC is interested in, as detailed in Table 8.5.3.4-2.
EEC Service Continuity SupportOIndicates if the EEC supports service continuity or not. The IE also indicates which ACR scenarios are supported by the EEC.
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8.5.3.8  EAS discovery subscription update responseWord‑p. 78

Table 8.5.3.8-1 describes the information elements for EAS discovery subscription update response from the EES to the EEC.
Information element Status Description
Successful responseOIndicates that the subscription update request was successful.
> Expiration timeOIndicates the expiration time of the updated subscription. To maintain an active subscription, a subscription update is required before the expiration time.
Failure responseOIndicates that the subscription update request failed.
> CauseOIndicates the cause of subscription update request failure
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8.5.3.9  EAS discovery unsubscribe requestWord‑p. 78

Table 8.5.3.9-1 describes the information elements for EAS discovery unsubscribe request from the EEC to the EES.
Information element Status Description
Subscription IDMSubscription identifier corresponding to the subscription to be unsubscribed
Security credentialsMSecurity credentials of the EEC
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8.5.3.10  EAS discovery unsubscribe responseWord‑p. 78

Table 8.5.3.10-1 describes the information elements for EAS discovery unsubscribe response from the EES to the EEC.
Information element Status Description
Successful responseOIndicates that the unsubscribe request was successful.
Failure responseOIndicates that the unsubscribe request failed.
> CauseOIndicates the cause of unsubscribe request failure
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8.5.4  APIsWord‑p. 79

8.5.4.1  GeneralWord‑p. 79

Table 8.5.4.1-1 illustrates the API for EAS discovery.
API Name API Operations Operation Semantics Consumer(s)
Eees_EASDiscoveryRequestRequest/ResponseEEC
SubscribeSubscribe/NotifyEEC
Notify
UpdateSubscription
Unsubscribe
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8.5.4.2  Eees_EASDiscovery_Request operationWord‑p. 79

API operation name:
Eees_EASDiscovery_Request
Description:
The consumer requests for one time EAS discovery information.
Inputs:
Outputs:
See clause 8.5.2.2 for details of usage of this operation.

8.5.4.3  Eees_EASDiscovery_Subscribe operationWord‑p. 79

API operation name:
Eees_EASDiscovery_Subscribe
Description:
The consumer subscribes for EAS discovery information.
Inputs:
Outputs:
See clause 8.5.2.3.2 for details of usage of this operation.

8.5.4.4  Eees_EASDiscovery_Notify operationWord‑p. 79

API operation name:
Eees_EASDiscovery_Notify
Description:
The consumer is notified with EAS discovery and/or EAS dynamic information.
Inputs:
Outputs:
None.
See clause 8.5.2.3.3 for details of usage of this operation.

8.5.4.5  Eees_EASDiscovery_UpdateSubscription operationWord‑p. 80

API operation name:
Eees_EASDiscovery_UpdateSubscription
Description:
The consumer updates an existing subscription for EAS discovery information.
Inputs:
Outputs:
See clause 8.5.2.3.4 for details of usage of this operation.

8.5.4.6  Eees_EASDiscovery_Unsubscribe operationWord‑p. 80

API operation name:
Eees_EASDiscovery_Unsubscribe
Description:
The consumer cancels an existing subscription for EAS discovery information.
Inputs:
Outputs:
See clause 8.5.2.3.5 for details of usage of this operation.

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