1 Introduction

1.1 Overview

This section describes the role of Oracle Communications Network Slice Selection Function (NSSF) in the 5G Service Based Architecture (SBA).

Network slices enable the users to select customized networks with different functionalities (such as mobility) and performance requirements (such as latency, availability and reliability). Network slices differ in features supported and network function optimizations. In such cases, network slices may have different S-NSSAIs with different slice and service types. The user can deploy instances of multiple network slices delivering the same features but for different groups of User Equipments (UEs). These instances deliver different committed services as they are dedicated to a customer, the network slices may have different S-NSSAIs with the same slice or service type but different slice differentiators. The NSSF fulfills the requirement for determining the individual network function pertaining to a slice.

Note:

The performance and capacity of the NSSF system may vary based on the call model, Feature or Interface configuration, and underlying CNE and hardware environment.
NSSF is a functional element that supports the following functionalities:
  • NSSF enables the Access and Mobility Management Function (AMF) to perform initial registration and Protocol Data Unit (PDU) session establishment.
  • AMF can retrieve NRF, NSI ID, and target AMFs as part of UE initial registration and PDU establishment procedure.
  • NSSF uses an NF Service Consumer (AMF) to update the S-NSSAI(s) that AMF supports and notifies of any changes in the status.
  • NSSF selects the network slicing instance (NSI) and determines the authorized Network Slice Selection Assistance Information (NSSAIs) and AMF to serve the UE.
  • NSSF interaction with NRF allows retrieving specific NF services to be used for registration request.

NSSF provides the following information when queried by the AMF:

  • Allowed NSSAIs
  • Configured NSSAIs
  • Restricted NSSAIs
  • Candidate AMF List (in case of registration)
  • Network Slice instance ID (for PDU session establishment)
  • Slice-level NRF information (for PDU Connectivity)

NSSF supports the above functions through the following NSSF services:

  • NSSelection service (Nnssf_NSSelection): This service is used by an NF Service Consumer (AMF) to retrieve the information related to network slice. It enables network slice selection in the serving Home Public Land Mobile Network (HPLMN).
  • NSAvailability Service (Nnssf_NSAvailability): This service stores and maintains list of supported S-NSSAIs per TA. It allows NF service Consumer (AMF) to update and subscribe the above data and get notifications for any addition or deletion of supported S-NSSAIs.

NSSF Availability

Oracle Communications Cloud Native Core, Network Slice Selection Function (NSSF) availability is dependent on many factors. NSSF applications are designed to achieve 99.999% availability, according to the applicable Telecommunications Industry Association TL9000 standards, with the following deployment requirements:

  • Deploy on a Cloud Native Environment with at least 99.999% Availability.
  • Deploy with n + k application redundancy, where k is greater than or equal to one.
  • Maintain production software within n-3 software releases, where n is the current general availability release.
  • Apply bug fixes, critical patches, and configuration recommendations provided by Oracle promptly.
  • Maintain fault recovery procedures external to the applications for the reconstruction of lost or altered files, data, programs, or Cloud Native environment.
  • Install, configure, operate, and maintain NSSF as per Oracle’s applicable installation, operation, administration, and maintenance specifications.
  • Maintain an active support contract and provide access to the deployed NSSF and your personnel to assist Oracle in addressing any outage.
NSSF availability is measured for each calendar year and is calculated as follows:

Table 1-1 Measuring NSSF Availability

Availability Description
Planned Product Availability (Product available time in each month) less (Excluded Time (defined below) in each month).
Actual Product Availability (Planned Product Availability) less (any Unscheduled Outage).
Product Availability Level (Actual Product Availability across all Production instances divided by Planned Product Availability across all Production instances) x 100.

Note:

Excluded Time means:
  • Scheduled maintenance time.
  • Lack of power or backhaul connectivity, except to the extent that such lack of backhaul connectivity was caused directly by the CNC NF.
  • Hardware failure.
  • Issues arising out of configuration errors or omissions.
  • Failures caused by third-party equipment or software not provided by Oracle.
  • Occurrence of any event under Force Majeure.
  • Any time associated with failure to maintain the recommended architecture and redundancy model requirements above.

1.2 References

  • Oracle Communications Cloud Native Core, Network Slice Selection Function Installation, Upgrade, and Fault Recovery Guide
  • Oracle Communications Cloud Native Core, Network Slice Selection Function Network Impact Report
  • Oracle Communications Cloud Native Core, Network Slice Selection Function REST Specification Guide
  • Oracle Communications Cloud Native Core, Cloud Native Environment Installation, Upgrade, and Fault Recovery Guide
  • Oracle Communications Cloud Native Core, Automated Testing Suite Guide
  • Oracle Communications Cloud Native Core, cnDBTier User Guide
  • Oracle Communications Cloud Native Core, Data Collector User Guide