NSSF comprises of various microservices deployed in Kubernetes based Cloud Native Environment (CNE, example: OC-CNE) . Some common services like logs or metrics data collection, analysis and graphs or charts visualization, etc. is provided by the environment. The microservices integrates with them and provide them necessary data. The following diagram describes the overall architecture of the NSSF:

Figure 4-1 Network Slice Selection Function Architecture Diagram

The solution has the following components:

• NS-Gateway (NSG): This microservice is responsible for receiving the ingress traffic for NSSF and distribute the traffic to the appropriate NSSF Function (NSSelection, NSAvailability). NSG is also responsible to pegging traffic related measurements.

  Note:

  API Gateway Ambassador is used to implement NS-Gateway.

• NS-Selection MicroService (NSS): This microservice receives all traffic for NS Selection Service. The microservice validates and pre-processes NS Selection query requests before forwarding it to NSPolicy service. NSS parses and validates Get request parameters for initial registration and PDU session establishment messages. It also forwards response back to NS-Gateway.

• NS-Availability MicroService (NSA): This microservice receives all traffic for NS Availability Service. The microservice maintains a list of allowed/rejected S-NSSAIs per TAI. It also provides AMF to get authorizes S-NSSAI list per TAI based on the S-NSSAIs supported by AMF.

• NS-Policy MicroService (NSP): This microservice performs the following functionalities:
  • This microservice performs the policy decision based on operator configured policy rules.

  • Initial Register/UE-Config-Update:

    • Based on incoming requested NSSAI , Subscriber-NSSAI, PLMN, TAC, and AMF_ID, NSSF selects allowed and rejected network slices per access type.

    • In case of successful selection of network slice, this service runs Discovery query to NRF to get candidate AMF list.

  • PDU Session Establishment:

    • Based on incoming requested NSSAI, PLMN, TAC, and AMF_ID, AMF runs policy rules to find a single network slice.

• NS-Subscription MicroService (NSS): This microservice sends notifications to NF service consumer (AMF) which have subscribed for "S-NSSAI_STATUS_CHANGE_REPORT" if there is any change of allowed NSSAI on subscribed TAI list.

• NS-Configuration MicroService (NSC):

  This microservice provides REST interface to configure NSS managed objects. For information on managed objects and REST APIs, See the OCNSSF Cloud Native User's Guide.

• NS-Registration MicroService (NSR):

  This microservice registers with the NRF and sends periodic heartbeats.

  1.NRF Regisration and Heartbeat

  In this level, first the Registration profile is configured using helm. Then Performance service calculates load and capacity of NF. NsRegistration requests load and capacity from performance service and send it to NRF with heartbeat.

  2.NRF Subscription

  NSSF subscribes to NRF for AMF based on Target AMF Set and Region ID for Registration/Deregistration and load update.