# On the Rollout of Network Slicing in Carrier Networks: A Technology Radar
## 1 Introduction
A clear example of this mismatching can be observed on the priorities that different SDOs set in relation to which slicing features need to be worked out in each release. In fact, these priorities are quite different across SDOs, both in time and scope. * **Scalability burdens**. The higher the number of slices running in parallel, the heavier the burden on the operator's OSS (Operations Support System) in terms of scalability. In fact, having a high number of instantiated tiny network slices, each requiring separate control and management, may well imply a strong impact on OSS functions (orchestration, assurance, etc.). This requires the operator to find the right balance in the slice design and activation patterns, looking to minimize this impact while properly addressing service demands. The introduction of advanced configuration and automation capabilities in OSS assets is also a must, in order to reduce the number of touches, especially in the assurance phase. * **Multi-provider solutions**. Upcoming 5G commercial networks are to be built out of solutions from multiple technology providers. The reason for this approach is essentially related to the dangerous effect of monoculture. Single-vendor dependency is a killer for innovation, as it restricts open collaboration from the broader 5G ecosystem of companies developing new technology, use cases, and services that the market expects. In this multi-vendor ecosystem, the challenge for operators will be in the appropriate combination of pieces from different providers and in ensuring they work together, within and across domains. The high integration efforts on the operator side to achieve multi-provider interoperability can be partially relieved by selecting solutions which are standards-compliant, i.e., based on the use of open interfaces. * **Brownfield environments**. Carrier networks are formed of already available equipment and functions (legacy is the common term for them), aimed at offering services from previous generations and even former releases of the current one. The need to keep this legacy up and running shall be combined with the introduction of the slicing functionality, avoiding the creation of silos. Unlike greenfield environments (e.g., private 5G networks), where network slicing can be easily launched as soon as commercial products are available, in carrier networks the operator needs to carefully upgrade its assets in such a way that the the legacy and slicing features can coexist. This process needs to be conducted in a cost-efficient way, ensuring that the upfront CAPEX behind every required upgrade will be compensated with a large mass of customers willing to consume the added slicing features. The above challenges outline the main issues that operators need to work out to fulfill the promise of E2E network slicing, in 5G and beyond. However, solving these issues towards this ultimate goal may require years, specially for the first issue (i.e., the different slicing readiness across the different domains). In the meantime, operators need to look for workarounds to start commercializing and monetizing network slicing, incorporating solutions in their portfolio according to the set of slicing capabilities available in their networks by then. The population of the portfolio is not an easy task, given the quite fragmented landscape in standards and literature, with plenty of ad-hoc solutions that cover particular slicing aspects from different domains and under different assumptions. Defining a network slicing rollout plan based on the current collection of solutions is a critical activity for operators to succeed in the market. This activity consists of two steps. First, identifying all relevant solutions and positioning them in a common space, with multiple dimensions that reflect the E2E conception of network slicing. Secondly, defining a go-to-market strategy [3], based on deciding which solutions will be made available, when, for which customers, and under which business models.