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Content for  TS 28.531  Word version:  17.1.0

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5  Specification level requirementsWord‑p. 11

5.1  Use casesWord‑p. 11

5.1.1  Network slice instance allocationWord‑p. 11

Use case stage Evolution/Specification <<Uses>> Related use
GoalTo satisfy request for allocation of a network slice instance with certain characteristics, by creation of new or using existing network slice instance; the request includes the network slice related requirements.
Actors and RolesA network slice provisioniong management service consumer.
NOP (Network Operator)
Telecom resourcesNetwork slice instance
Network slice subnet instance
Transport network A network slice provisioning management service provider.
A network slice subnet provisioning management service provider.
AssumptionsN/A
Pre-conditionsN/A
Begins whenThe network slice provisioning management service provider receives the request for allocation of the network slice instance with certain characteristics; the request contains network slice related requirements and the information indicating whether the requested NSI could be shared with other consumers.
The network slice provisioning management service provider have the capability to translate the network slice related requirements (e.g. SLA information from GSMA GST) and use it as input to the servie profile [6], the service profile can also be translated to the corresponding requirements for dedicated domains and NSSIs.
Step 1 (M)If the requested NSI can be shared and if an existing NSI can be used, the network slice provisioning management service provider decides to use the existing NSI.
Modification of the existing NSI may be needed to satisfy the network slice instance related requirements. Use case is completed go to "Step 8".
Otherwise, the network slice provisioning management service provider triggers to create a new NSI, for which the following steps 2 - 8 are needed.
Step 2 (M)The network slice provisioning management service provider decides on the constituent NSSIs and the topology of the NSI to be created using the information from service profile [6]. For the constituent NSSIs, the network slice provisioning management service provider derives network slice subnet related requirements from the network slice related requirements. If reconfiguration of the transport network is needed, the network slice provisioning management service provider derives transport network related requirements (e.g. latency, bandwidth) from the network slice related requirements.
Step 3 (M)For the required NSSI(s), the network slice provisioning management service provider sends network slice subnet related requirements to the network slice subnet provisioning management service provider to request allocation of the required NSSI(s).Network slice subnet instance allocation use case
Step 4 (M)The network slice provisioning management service provider receives the information of the allocated NSSI(s) (e.g. the management identifier of NSSI, service access point information of NSSI, external connection point information of NSSI) from NSSMF.
Step 5 (M)The network slice provisioning management service provider, via the network slice subnet provisioning management service provider, sends the transport network related requirements (e.g. external connection point, latency and bandwidth) to the TN Manager. The TN manager reconfigures the TN accordingly and responds to the network slice provisioning management service provider via the network slice subnet provisioning management service provider.
Step 6 (M)The network slice provisioning management service provider receives the response from TN Manager via the network slice subnet provisioning management service provider.
Step 7 (M)The network slice provisioning management service provider associates the NSSI(s) with the corresponding NSI (e.g. allocation of the management identifier of NSI and mapping the management identifier of NSI with the received management Identifier of NSSI(s)) and triggers to establish the links between the service access points of the NSSI(s).
Step 8 (M)The network slice provisioning management service provider notifies the network slice instance information of NSI (e.g., the management identifier of NSI).
Ends whenAll the steps identified above are successfully completed.
ExceptionsOne of the steps identified above fails.
Post-conditionsAn NSI is ready to satisfy the network slice related requirements.
TraceabilityREQ-PRO_NSSI-FUN-1, REQ-PRO_NSI-FUN-3.
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5.1.2  Network slice subnet instance allocationWord‑p. 13

Use case stage Evolution/Specification <<Uses>> Related use
GoalCreate a new network slice subnet instance or use an existing network slice subnet instance to satisfy the network slice subnet related requirements; provide the provisioning service consumer with identity of the NFVO which the consumer can use for further access to the information of the involved VNFs, PNFs and NSs.
Actors and RolesA network slice subnet provisioning management service consumer.
Telecom resourcesNetwork Slice Subnet instance
Network Service instance
A network slice subnet provisioning management service provider.
The operator deployed NFVO to manage the lifecycle of VNFs and interconnection between the VNFs and PNFs in terms of the NS instances.
AssumptionsNetwork slice subnet instance may include network functions which are virtualized.
Pre-conditionsVNF Packages for virtualized network functions to be included in the network slice subnet instance have been already on-boarded.
Begins whenThe network slice provisioning management service provider sends to the network slice subnet provisioning management service provider a request for a NSSI to be associated with the NSI; the request contains network slice subnet related requirements including the SliceProfile [6].
The network slice subnet provisioning management service provider receives request for a network slice subnet instance. The request contains network slice subnet related requirements. The request may include guidance for use of particular NFVO(s) when VNFs and PNFs in certain part of the network are involved. The request may also include query of the identity of the NFVO to be used.
Step 1 (M)Based on the network slice subnet related requirements received, the network slice subnet provisioning management service provider decides to create a new NSSI or use an existing NSSI.
Step 2 (M)If an existing network slice subnet instance is decided to be used, the network slice subnet provisioning management service provider may trigger to modify the existing network slice subnet instance to satisfy the network slice subnet related requirements. Go to "Step 8".
Otherwise, the network slice subnet provisioning management service provider triggers to create a new NSSI, the following steps are needed.
Step 3 (O)If the required NSSI contains constituent NSSI(s) managed by other network slice subnet provisioning management service provider (s), the first network slice subnet provisioning management service provider derives the requirements for the constituent NSSI(s) and sends those requirements to the corresponding network slice subnet provisioning management service provider (s) which manages the constituent NSSI(s).
The first network slice subnet provisioning management service provider receives the constituent NSSI information from the other network slice subnet provisioning management service provider (s) and associates the constituent NSSI(s) with the required NSSI.
Step 4 (M)Based on the network slice subnet related requirements received and SliceProfile [6], the network slice subnet provisioning management service provider decides that to satisfy the NSSI requirements, the part of the network controlled by certain NFVO should be involved. The network slice subnet provisioning management service provider determines the NS related requirements (i.e. information about the target NSD and additional parameterization for the specific NS to instantiate, see clause 7.3.3 in ETSI GS NFV-IFA013 [3]).
Step 5 (M)Based on the NS related requirements, the network slice subnet provisioning management service provider triggers corresponding NS instantiation request to NFVO via Os-Ma-nfvo interface as described in clause 6.4.3 in TS 28.525, and the NFVO performs NS instantiation. (see note)TS 28.525, Clause 6.4.3 NS instance use cases
Step 6 (M)The network slice subnet provisioning management service provider associates the NS instance with corresponding network slice subnet instance (e.g. allocation of the management identifier of NSSI and mapping with the corresponding identifiers).
Step 7 (M)The network slice subnet provisioning management service provider is using the NF provisioning service to configure the NSSI constituents.
In case of RAN NSSI, the configuration contains RRM policy information for individual Radio cells. In the cells shared by multiple NSSIs such policy includes guidance for split of Radio resources between the NSSIs.
NF provisioning service
Step 8 (M)The network slice subnet provisioning management service provider notifies the provisioning service consumer with the NSSI information (e.g. the management identifier of NSSI) and the NFVO identity when relevant. The network slice provisioning management service provider associates the NSSI with the NSI.
Ends whenAll the steps identified above are successfully completed.
ExceptionsOne of the steps identified above fails.
Post-conditionsA NSSI is ready to satisfy the network slice subnet related requirements.
TraceabilityREQ-PRO_NSSI-FUN-2, REQ-PRO_NSSI-FUN-3, REQ-PRO_NSSI-FUN-4, REQ-PRO_NSSI-FUN-5, REQ-PRO_NSSI-FUN-6, REQ-PRO_NSSI-FUN-14.
NOTE:
According to the TS 28.525, for the PNFs, NS instantiation includes only establishment of interconnection with other NFs.
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5.1.3  Network slice instance deallocationWord‑p. 14

Use case stage Evolution/Specification <<Uses>> Related use
GoalTo terminate or modify an existing NSI which was used to support a particular service, but is no longer needed.
Actors and RolesA network slice provisioning management service consumer.
NOP Operator
Telecom resourcesNetwork slice instance
Network slice subnet instances
A network slice provisioning management service provider.
A network slice subnet provisioning management service provider.
AssumptionsN/A
Pre-conditionsN/A
Begins whenThe network slice provisioning management service provider receives the request indicating that an existing NSI is no longer needed to support particular service. The NSI identification is included in the request.
Step 1 (M)Based on the request, the network slice provisioning management service provider checks if there are no other services to be supported by the NSI. If there are none the network slice provisioning management service provider may decide to terminate the NSI; then proceed to Step 2.
Otherwise, the network slice provisioning management service provider may decide to trigger to modify the NSI or to do nothing.
The use case is completed; skip the remaining steps.
NSI modification use case
Step 2 (M)If the NSI to be terminated is active, the network slice provisioning management service provider de-activates the NSI. Then, the NSI to be terminated is inactive.NSI de-activation use case
Step 3 (M)The network slice provisioning management service provider identifies the network slice subnet instances used by the NSI, and for every such NSSI sends the request to the corresponding network slice subnet provisioning management service provider (s) indicating that the NSSI(s) are no longer needed for the NSI. The network slice subnet provisioning management service provider (s) may decide to terminate or modify the NSSI(s) based on the request and disassociates them with the NSI.
Step 4 (M)The network slice provisioning management service provider receives the response from the network slice subnet provisioning management service provider (s) and terminates the NSI.
Step 5 (M)The network slice provisioning management service provider notifies its consumer of the NSI termination.
Ends whenAll the steps identified above are successfully completed or skipped per condition in the Step 1.
ExceptionsOne of the steps identified above fails.
Post-conditionsThe NSI has been or modified.
TraceabilityREQ-PRO_NSI-FUN-3
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5.1.4  Network slice subnet instance deallocationWord‑p. 15

Use case stage Evolution/Specification <<Uses>> Related use
GoalTo terminate or disassociate an existing NSSI which was used by the NSI or NSSI, but is no longer needed
Actors and RolesNetwork slice subnet provisioning management service consumer.
Telecom resourcesNetwork slice subnet instance Network slice subnet provisioning management service provider.
AssumptionsN/A
Pre-conditionsN/A
Begins whenThe network slice subnet provisioning management service provider receives network slice subnet related request from its authorized consumer indicating that an existing NSSI is no longer needed.
Step 1 (M)Based on the request, the network slice subnet provisioning management service provider decides whether the NSSI should be terminated.
If the decision is the NSSI should be terminated, go to the Step 2.
If the decision is the NSSI is not terminated (e.g., the NSSI is shared or the network slice subnet provisioning management service provider decides to keep the NSSI for later use), the network slice subnet provisioning management service provider disassociates the NSSI from its consumer and provides feedback to the authorized consumer, maybe with removing its consumer's configuration or not. Go to Step 5.
Step 2 (M)If the NSSI consists of constituent NSSIs that are not managed directly by the network slice subnet provisioning management service provider, the network slice subnet provisioning management service provider sends a request to other network slice subnet provisioning management service provider(s) indicating that the constituent NSSIs are no longer needed for the NSSI.
Step 3 (M)If the NSSI is associated with NSI, the network slice subnet provisioning management service provider disassociates the NSI with the NSSI to be terminated, and the network slice subnet provisioning management service provider may trigger request to NFVO for terminating or updating (e.g. scaling-in) the NS instance. . (see note).
Step 4 (M)If there exists a transport network segment used by the NSSI, the network slice subnet provisioning management service provider may indicate that the transport network segment is no longer needed to support the NSSI.
Step 5 (M)The network slice subnet provisioning management service provider sends response to its consumer.
Ends whenAll the steps identified above are successfully completed.
ExceptionsOne of the steps identified above fails.
Post-conditionsThe NSSI has been terminated or disassociated.
TraceabilityREQ-PRO_NSSI-FUN-8, REQ-PRO_NSSI-FUN-11
NOTE:
In case where the NS instance is not dedicated for the NSSI, the network slice subnet provisioning management service provider does not terminate the NS instance.
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5.1.5  Obtaining network slice subnet instance informationWord‑p. 16

Use case stage Evolution/Specification <<Uses>> Related use
GoalEnable the network slice subnet provisioning management service consumer to obtain network slice subnet instance information (e.g. Slice/Service type, network slice subnet capability information).
Actors and RolesNetwork slice subnet provisioning management service consumer.
Telecom resourcesNetwork slice subnet instance Network slice subnet provisioning management service provider.
AssumptionsThe network slice subnet provisioning management service consumer is authorized to obtain the network slice subnet instance information from the network slice subnet provisioning management service provider.
Pre-conditionsNSSI is created.
Begins whenThe network slice subnet provisioning management service consumer wants to obtain the network slice subnet instance information.
Step 1 (M)The network slice subnet provisioning management service consumer sends a request to the network slice subnet provisioning management service provider to obtain the network slice subnet instance information.
The indication on which information needs to be obtained may be included in the request.
Step 2 (M)The network slice subnet provisioning management service provider processes this request.
Step 3 (M)The network slice subnet provisioning management service provider sends the result of network slice subnet instance information to the network slice subnet provisioning management service consumer.
Ends whenAll the steps identified above are successfully completed.
ExceptionsOne of the steps identified above fails.
Post-conditionsThe network slice subnet provisioning management service consumer has obtained the network slice subnet instance information.
TraceabilityREQ-PRO_NSSI-FUN-7.
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5.1.6  Network slice feasibility checkWord‑p. 17

Use case stage Evolution/Specification <<Uses>> Related use
GoalTo check the feasibility of provisioning a network slice to determine whether the network slice requirements can be satisfied at a particular point in time (e.g., in terms of resources)
Actors and RolesNetwork slice management service consumer. For example, CSP providing NSaaS plays the role of network slice management service consumer.
Telecom resourcesNetwork slice management service provider.
AssumptionsNetwork slice management service consumer has decided to check the feasibility of provisioning a network slice based on, for example, internal decision or to facilitate an external service requests.
Pre-conditionsNetwork slice requirements have been derived or received by network slice management service consumer.
Begins whenNetwork slice management service provider receives the request to evaluate the feasibility of provisioning a network slice according to the network slice requirements at a particular point in time.
Step 1 (M)Network slice management service provider identifies the network slice subnets according to the requirements.
Step 2 (M)Network slice management service provider obtains the information necessary to evaluate the feasibility of provisioning a network slice by requesting the network slice subnet service provider(s) to evaluate the availability of resources under their contol.
Step 3 (M)Network slice subnet management service provider(s) checks the feasibility of provisioning a slice subnet(s) by analysing network constituents to ensure that their capabilities, e.g., resources, management services, etc. are (or will be) adequate to provision network slice instance, satisfying all requirements without impacting existing services. For the purpose of checking the feasibility of provisioning a network slice subnet(s) of the network slice , network slice subnet management service provider(s) may obtain information from the network (e.g., current or predicted load level information from the NWDAF).5.1.21 Network slice subnet feasibility check
Ends whenFeasibility check results have been provided to network slice management service consumer.
ExceptionsOne of the mandatory steps fails.
Post-conditionsN/A
TraceabilityREQ-PRO_NSSI-FUN-12, REQ-PRO_NSSI-FUN-13, REQ-PRO_NSI-FUN-8.
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5.1.7  Network slice instance activationWord‑p. 18

Use case stage Evolution/Specification <<Uses>> Related use
GoalTo activate an existing network slice instance which is inactive
Actors and RolesNetwork slice provisioning management service consumer. For example, CSP providing NSaaS plays the role of Network slice management service consumer.
Telecom resourcesNetwork slice instance Network slice provisioning management service provider. Network slice subnet provisioning management service provider.
AssumptionsN/A
Pre-conditionsAn NSI has already been created and it is inactive.
Begins whenThe network slice provisioning management service provider decides to activate an NSI based on the received network slice related request from its authorized consumer.
Step 1 (M)The network slice provisioning management service provider checks whether NSSIs associated with the NSI are all active, if there is an inactive NSSI, the network slice provisioning management service provider requests the network slice subnet provisioning management service provider to activate the corresponding NSSI.Network slice subnet instance activation use case
Step 2 (M)The network slice provisioning management service provider receives response from the network slice subnet provisioning management service provider indicating that the NSSI is active.
Step 3 (M)The network slice provisioning management service provider activates the state of the NSI and sends response to the requesting consumer.
Ends whenAll the steps identified above are successfully completed.
ExceptionsOne of the steps identified above fails.
Post-conditionsAn NSI has been activated.
TraceabilityREQ-PRO_NSI-FUN-4
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