## 6 Conclusions and Future Work  
The rise of new paradigms like NFV in the context of the 5 th generation of mobile networks has provided new ways to enable the development and deployment of network services. In this regard, microservice platforms assist in the optimisation and orchestration of network functions in distributed infrastructures. However, these platforms have some limitations due to the flat networking approach that they implement for the communication of their workloads (containers) in order to build a complex application. Furthermore, these solutions can also have some limitations for connectivity with other infrastructures, requiring networking abstractions that could prevent communicating network functions between clusters or other platforms. To address these issues, this paper has presented L2S-M as a solution that enables link-layer connectivity as a service in cloud-native ecosystems. L2S-M provides a programmable data plane that microservice platforms (like K8s) can use to create virtual networks that can be used by the containers to communicate at the link-layer level, since they will see the rest of the containers as if they were located in the same local area network (even though they might be distributed in different locations, depending on the cluster and the underlying infrastructure). Using these virtual networks, L2S-M provides the necessary network isolation required to deploy network and vertical specific functions in microservice platforms, which current solutions cannot easily provide. Furthermore, since L2S-M uses SDN technology to establish the paths between pods in a cluster, other SDN applications can be flexibly deployed to support traffic engineering and optimise traffic distribution, using an alternative network path across the L2S-M overlay. This paper also provides a first exploration of the potential of L2S-M to provide inter-cluster communications between containers using virtual networks, enabling the direct communication of network functions between heterogeneous infrastructures managed by different platforms, which can implement different virtualisation techniques, or even run bare-metal functions. This paper also presented the use implementation of L2S-M in a complex Smart Campus scenario, deploying a CDN to distribute multimedia content in a complex, distributed and heterogeneous scenario. The tests performed in the validation of this paper showed that L2S-M is suitable to deploy complex NSes based in microservices that require the use of multiple isolated virtual networks for their proper functionality, interconnecting workloads located in different infrastructures over geographically distributed locations. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Cache Enabled** & **Throughput (Mb/s)** & **Download Time** \\ \hline Off & 4.207 & 3:20 \\ On & 4.780 & 3:05 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Download throughput and time used for retrieving content using Wi-Fi. Moreover, these tests depicted the flexibility of L2S-M to incorporate new infrastructures, like Wi-FI access points, to extend the functionality of the NSes in the use cases. Our future work for the advancement and further development of L2S-M includes the implementation of the overlay manager figure in the solution to dynamically modify the overlay network. Furthermore, we will also explore the implementation of L2S-M with SR-IOV interfaces to enable its direct use with the physical switching equipment commonly present in data centre infrastructures. This future work will also involve the exploration of alternative SDN controllers to increase the functionality and isolation aspects of L2S-M, as well as the development and application of SDN algorithms to apply traffic engineering mechanisms. Finally, we want to contribute to the relevant open-source communities with L2S-M. In this regard, we are working on a feature in OSM to support the creation of virtual networks in K8s clusters, using L2S-M as the reference operator [49]. Funding acquisition, F.V. ; Investigation, L.F.G., I.V.