## 5 Practical Experience with L2S-M  
### Description of the Testbed  
This section describes the testbed that is considered to validate the implementation of the design introduced in Section 3. This testbed mimics the infrastructure that could be deployed in a university Smart Campus environment. Universities, due to the nature of the academic and research activities that they perform on a daily basis, must have a powerful, reliable and secure infrastructure that allows them to flexibly deploy various applications used by the members of the university. These applications, ideally, should be able to effectively use the resources provided by the university infrastructure, as well as having good scalability properties (to adapt the service to the possible demands, which can dynamically be modified) and be resilient to temporary failures and/or service cut-offs. In this regard, microservices are able to provide most of these characteristics. Unfortunately, some of these services require networking capabilities that solutions like K8s are not able to provide. One prominent example of this situation is the use case presented in this paper: the implementation of a content-delivery network (CDN) for the distribution of academic content in a Smart Campus scenario. Generally, universities are composed of several campuses spread in distributed geographical locations. Each campus has its own size and importance inside the structure of the university, especially regarding the resources that they are able to provide for their own cloud environments for content distribution. This can potentially be an issue since a pure centralised model might impact the performance needed to effectively send content to remote campuses, possibly being a more desirable solution to move the content closer to the users to avoid overloading the main infrastructure of the network, which in turn may reduce latency as well. A centralised model can also introduce a single point of failure if the main infrastructure is down and/or link disruptions occur. Finally, it is important to mention that the network infrastructures of these campuses should be able to be dynamically modified to accommodate the demand that each campus may require at each moment, without interfering with the functionality. Microservice solutions like K8s are not usually able to provide the necessary tools to implement a distributed scenario due to its flat networking approach and the limitations of inter-cluster communications. However, L2S-M will be used in this paper to provide a CDN to distribute content across different campuses of a wide variety of characteristics located across geographically distributed regions, while also allowing to easily accommodate new infrastructures and members to fit the necessities of the university (for instance, setting up a temporary network for an event). This use case includes four different sites distributed along two campuses to prove the effectiveness of the solution in an intra-campus scenario and of the NEDs for the inter-cluster communications. Each campus is designed to include different resources to showcase the interaction between heterogeneous infrastructures. Accordingly, there are two different sites inside each campus, resembling the cloud and edge of each campus, where each site can have its own infrastructure and implementation, to validate the initial statements. The scenario presented in this paper can be seen in Figure 8. The first campus in the scenario (on the right) is composed of two different sites: one central campus environment, and one temporary edge site, which is set up only if an event is performed in the university facilities (e.g., a conference or a workshop). The central infrastructure of this campus is regarded as the main cloud of the whole organisation, holding most of the software and teaching resources available to the students and teachers. In consequence, the representation of this site is conducted through two VMs (since these are considered \"heavier\" machines in terms of available resources).