# On the Rollout of Network Slicing in Carrier Networks: A Technology Radar
## 5 CN Domain
### Functionality
Business-to-Business (B2B) slice types, used for the provisioning of non-public networks (NPNs) [44], in particular for public network integrated NPNs (PNI-NPNs) [45]. Figure 11 captures a representative number of these 5 GC slices types. On the one hand, there is the _B2C category_ (Figure 11A,B). This category includes 5 GC slices (i) designed for end user consumption, so there is no need to have in-slice dedicated control plane functions; and (ii) to be entirely built on the 5G public network infrastructure (PLMN). Within this category, two different slice types can be found. * **5 GC slice Type A1 (shared UPF)**: deployment flavor wherein the 5 GC slice does not have a dedicated UPF; indeed, the in-slice UPF instance is also shared with other 5 GC slices. * **5 GC slice Type A2 (dedicated UPF)**: deployment flavor wherein the 5 GC slice is allocated with a separate UPF. In the B2C category, the first 5 GC slices to be launched may be of Type A2, with few slices hosting premium communication services that end users can subscribe to. With a commercial model based on offering VIP service experiences, the operator looks to keep existing users and attract new ones, generating moderate revenues from their subscriptions in the short term. For Type A1 slices, the situation is rather different. Unlike Type A2 slices, where traffic isolation across them is preserved with the provision of dedicated UPFs, in Type A1 slices the UPF is shared among them. In this context, operators expect that one UPF can support multiple 5 GC slices, which means that one UPF shall be able to manage user plane resources (e.g., UE IP addresses, GTP-U Fully Qualified TEIDs, CPU, memory, bandwidth, etc.) at the S-NSSAI granularity. Unfortunately, the ability for a UPF to perform resource management (e.g., resource separation, resource allocation, resource usage report) per 5 GC slice is not yet available in the standards due to technology limitations inherent to UPF internals, though 3 GPP have already started working on solutions to solve this [46]. Being a Rel-17+ feature, we are still years away from seeing Type A1 slices running in production networks. However, their availability will mark a major turning point in operator B2C slicing strategies, with the ability to deploy 5 GC slices at a much wider scale,  
Figure 11: 5 GC slice types. (**A,B**) represents B2C slice types. (**C–E**) represents B2B slice types. offering performance levels similar to Type A2 slices, but using a much lower number of UPFs. Additionally, the operator can use Type A1 slices to aggregate users with similar performance profiles, all this in a transparent manner, in search of creating efficiency improvements. This use of slicing, which allows the operator to streamline network management operations, is referred to as 'Network Slicing for Network Operator internals' in [17]. On the other hand, there is the _B2B category_ (Figure 11C-E), which covers all the 5 GC slices which are intended for industry customers. Examples of these customers include verticals and hyperscalers. Unlike the B2C category, the 5 GC slices belonging to this new category will be used to host services for private use (i.e., only available for the customer's subscribers), which typically span beyond the operator's service footprint. This means that (i) every slice shall have dedicated control plane functions, so that the isolation of traffic management can be preserved across slices, and (ii) not all the in-slice functions will be hosted by PLMN; indeed, some of them might be deployed at customer facilities (e.g., UPF). Within this category, three different 5 GC slice types are worth mentioning. * **5 GC slice Type B1 (baseline CP)**: deployment flavor wherein 5 GC slice is provided with dedicated UPF and a dedicated SMF. This ensures that in-slice traffic flows have an independent management and configuration, completely separated from other 5 GC slices. * **5 GC slice Type B2 (advanced CP)**: represents a 5 GC slice Type B1 provisioned with dedicated PCF.