# On the Rollout of Network Slicing in Carrier Networks: A Technology Radar
## 8 Oss Domain
### Oam  
The life cycle of a network slice is articulated into four different phases: preparation (slice design, slice on-boarding and network set-up), commissioning (slice instantiation and configuration), operation (slice activation, modification, reporting/supervision and de-activation) and decommissioning (slice termination) [17]. The operator's main role is to manage the life cycle of all slices running in the network. In this endeavor, the operator makes use of OAM tools available in the OSS layer, as illustrated in Figure 2.  
This section outlines the main solutions that enable the OSS to conduct network slice life cycle management. Their position in the radar (see Figure 9) makes it clear that the trend is to evolve towards a fully digital OSS stack, wherein design, data management, assurance and orchestration processes all need to be aligned and integrated across physical, virtual and cloud assets. This journey needs to be accompanied with new levels of automation, extending them further up the stack, into the E2E service and network management domain. The first stop of the journey is the as-is ring of the radar. Today's OSS consists of isolated, monolithic systems passing through specialized applications that require complex integration. In addition, automation is quite limited (only present in specific parts of the OSS, and not covering all the management domains) and with many silos (part of the automation is often developed as standalone scripts used by separate domain teams, with each team creating and managing automation using its own environment). However, with the edge computing and 5G SA technologies just around the corner, most of the operators have already integrated a **MANO stack** in their OSS, using SOL005 [25]. Apart from the monetization of Infrastructure as a service (IaaS) services, the MANO stack allows operators to move carrier-grade functions and services to the cloud, leveraging NFV technology. This is critical for a cost-efficient delivery of some NSA slicing solutions, like the ones represented in Figure 10C-E, where there is a need to deploy multiple instances of the same network functions. The second stop is the deploy ring of the radar. Coinciding with the early rollout of 5G SA networks and the commercialization of the first B2C slices, operators need to integrate slicing logic into their OSS. The short-term focus is on basic slice provisioning. In this regard, the following solutions are needed. * **NST/NSST**. The Network Slice Template (NST) and Network Slice Subnet Template (NSST) are pre-configured service descriptors that help create a blueprint to ease replicability (i.e., design once, deploy everywhere) of offered network slices and slice subnets. For example, the NSST corresponding to a 5 GC slice could include the following information: (i) the type of services that the 5 GC slice supports, (ii) the 5 GC slice topology, and (iii) the 5 GC slice placement policy. Based on the fact that a network slice subnet can be deployed as an ETSI NFV network service (see Figure 1), the information given in (ii) is a pointer to the corresponding Network Service Descriptor (NSD), while the information captured in (iii) is the specification of the PoP type where individual network service components can be deployed, and their affinity/anti-affinity rules. For the construction of the NST, the approach is similar, but including pointers to the NSSTs. The design, development, testing and validation of NSTs/NSSTs/NSDs, and their subsequent onboarding to the catalogs, are activities that formally belong to the network slice preparation phase. * **Lite Slice NRM fragment**. As seen in Figure 1, the 3 GPP information model for network slicing is complex, with a high number of classes and different containmenting relationships across them. Furthermore, this model is in continuous evolution, as long as the work in 3 GPP SA2 and GSMA GST/NEST evolves. For this reason, it is preferable to have a life version of the slice NRM fragment in the short term.