Content for TS 28.531 Word version: 18.1.0
5 Specification level requirements
5.1 Use cases
5.1.1 Network slice instance allocation
5.1.2 Network slice subnet instance allocation
5.1.3 Network slice instance deallocation
5.1.4 Network slice subnet instance deallocation
5.1.5 Obtaining network slice subnet instance information
5.1.6 Network slice feasibility check
5.1.7 Network slice instance activation
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5 Specification level requirements p. 11
5.1 Use cases p. 11
5.1.1 Network slice instance allocation p. 11
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | To satisfy request for allocation of a network slice instance with certain characteristics, by creating a new or using an existing network slice instance; the request includes the network slice related requirements. | |
| Actors and Roles | A network slice provisioniong management service consumer. | |
| Telecom resources | Network slice instance Network slice subnet instance Transport network A network slice provisioning management service provider. A network slice subnet provisioning management service provider. | |
| Assumptions | N/A | |
| Pre-conditions | N/A | |
| Begins when | The 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 has the capability toprocess the network slice related requirements (e.g. SLA information from GSMA GST) which are represented by service profile parameters [6]. The service profile can 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 when | All the steps identified above are successfully completed. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | An NSI is ready to satisfy the network slice related requirements. | |
| Traceability | REQ-PRO_NSSI-FUN-1, REQ-PRO_NSI-FUN-3. |
5.1.2 Network slice subnet instance allocation p. 13
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | Create 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 Roles | A network slice subnet provisioning management service consumer. | |
| Telecom resources | Network 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. | |
| Assumptions | Network slice subnet instance may include network functions which are virtualized. | |
| Pre-conditions | VNF Packages for virtualized network functions to be included in the network slice subnet instance have been already on-boarded. | |
| Begins when | The network slice subnet provisioning management service consumer sends to the network slice subnet provisioning management service provider a request for an 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 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 of TS 28.525, and the NFVO performs NS instantiation. (see note) | clause 6.4.3 of TS 28.525 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). The network slice provisioning management service provider associates the NSSI with the NSI. | |
| Ends when | All the steps identified above are successfully completed. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | A NSSI is ready to satisfy the network slice subnet related requirements. | |
| Traceability | REQ-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. | |
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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 deallocation p. 14
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | To deallocate a network slice instance.. | |
| Actors and Roles | A network slice provisioning management service consumer. | |
| Telecom resources | Network slice instance Network slice subnet instances A network slice provisioning management service provider. A network slice subnet provisioning management service provider. | |
| Assumptions | N/A | |
| Pre-conditions | N/A | |
| Begins when | The network slice provisioning management service provider receives the request indicating that an existing NSI is no longer needed to support a particular service. (identified by service profile Id) The NSI identification is included in the request. | |
| Step 1 (M) | Based on the request, the network slice provisioning management service provider deletes the corresponding slice profile and checks if there are 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; go to step 5. | 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 deallocation. | |
| Ends when | All the steps identified above are successfully completed or skipped per condition in the Step 1. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | The NSI has been or modified. | |
| Traceability | REQ-PRO_NSI-FUN-3 |
5.1.4 Network slice subnet instance deallocation p. 15
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | To deallocate a network slice subnet instance. | |
| Actors and Roles | Network slice subnet provisioning management service consumer. | |
| Telecom resources | Network slice subnet instance Network slice subnet provisioning management service provider. | |
| Assumptions | N/A | |
| Pre-conditions | N/A | |
| Begins when | The 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 to support a particular set of network slice subnet requirements identified by a slice profile id). The NSSI identification is included in the request. | |
| 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 that the NSSI should not be 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 from 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 when | All the steps identified above are successfully completed. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | The NSSI has been deallocated. | |
| Traceability | REQ-PRO_NSSI-FUN-8, REQ-PRO_NSSI-FUN-11 | |
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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 information p. 16
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | Enable the network slice subnet provisioning management service consumer to obtain network slice subnet instance information (e.g. Slice/Service type). | |
| Actors and Roles | Network slice subnet provisioning management service consumer. | |
| Telecom resources | Network slice subnet instance Network slice subnet provisioning management service provider. | |
| Assumptions | The 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-conditions | NSSI is created. | |
| Begins when | The 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 when | All the steps identified above are successfully completed. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | The network slice subnet provisioning management service consumer has obtained the network slice subnet instance information. | |
| Traceability | REQ-PRO_NSSI-FUN-7. |
5.1.6 Network slice feasibility check p. 17
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | To 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), and optionally reserve resources to satisfy the network slice requirements. | |
| Actors and Roles | Network slice management service consumer. For example, CSP providing NSaaS plays the role of network slice management service consumer. | |
| Telecom resources | Network slice management service provider. | |
| Assumptions | Network 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. Network slice management service consumer has optionally decided to request reservation of the resources to satisfy the network slice requirements. | |
| Pre-conditions | Network slice requirements have been derived or received by network slice management service consumer. | |
| Begins when | Network slice management service provider receives the request to evaluate the feasibility of provisioning a network slice and optionally reserve resources, 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. If the Network slice management service consumer has requested reservation of resources, then Network slice management service provider requests network slice subnet service provider(s) to reserve resources. | |
| 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). If the Network slice management service provider has requested reservation of resources, then Network slice subnet management service provider(s) reserves the resrources necessary to provision the network slice instance. | 5.1.21 Network slice subnet feasibility check |
| Ends when | Feasibility check results have been provided to network slice management service consumer. If the Network slice management service consumer has requested reservation of resources, then resources to satisfy the network slice requirements are reserved. | |
| Exceptions | One of the mandatory steps fails. | |
| Post-conditions | N/A | |
| Traceability | REQ-PRO_NSSI-FUN-12, REQ-PRO_NSSI-FUN-13, REQ-PRO_NSI-FUN-8. |
5.1.7 Network slice instance activation p. 18
| Use case stage | Evolution/Specification | <<Uses>> Related use |
|---|---|---|
| Goal | To activate an existing network slice instance which is inactive | |
| Actors and Roles | Network slice provisioning management service consumer. For example, CSP providing NSaaS plays the role of Network slice management service consumer. | |
| Telecom resources | Network slice instance Network slice provisioning management service provider. Network slice subnet provisioning management service provider. | |
| Assumptions | N/A | |
| Pre-conditions | An NSI has already been created and it is inactive. | |
| Begins when | The 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 NSI and sends response to the requesting consumer. | |
| Ends when | All the steps identified above are successfully completed. | |
| Exceptions | One of the steps identified above fails. | |
| Post-conditions | An NSI has been activated. | |
| Traceability | REQ-PRO_NSI-FUN-4 |
