# Stochastic Model Driven Performance and Availability Planning for a Mobile Edge Computing System
## 3 Architecture Overview  
Figure 1 illustrates the proposed MEC architecture that was considered to construct the SPN model. Such a base architecture is widely adopted to describe the MEC infrastructure \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Related** & **Metrics** & **Master-Slave** & **Sensitivity** & **Context** & **Use of Component** \\
**Work** & **Metrics** & **Variation** & **Analysis** & **Dependency** \\ \hline [20] & Energy consumption and data transferring & No & No & Egde & No \\ \hline [21] & Energy consumption & No & No & Edge & No \\ \hline [22] & Energy consumption & No & No & Edge & No \\ \hline [9] & Energy consumption and Execution time & No & No & Cloud/Edge & No \\ \hline [23] & Communication cost and Reallocation execution & No & No & Edge & No \\ \hline [24] & Energy consumption, Execution time, Migration cost, User cost and Co-location & No & No & Edge & No \\ \hline [25] & Energy consumption and Execution time & No & No & Edge & No \\ \hline [26] & Availability & No & No & Cloud & No \\ \hline [27] & Availability & No & Yes & Cloud & No \\ \hline [28] & Availability & No & No & Cloud & No \\ \hline [29] & Availability & No & No & Cloud & No \\ \hline [30] & Availability & No & No & Cloud & No \\ \hline [31] & Availability & No & Yes & Cloud/Edge/Fog & No \\ \hline [32] & Availability & No & No & Edge & No \\ \hline This work & MRT, Resource utilization, Discard probability and Availability & Yes & Yes & Edge & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Related works. in several works [21; 33; 34] with a MEC server for processing incoming data streams. These data are generated and sent by applications running on mobile devices, for example, user-health monitoring applications, game rendering, etc. In the context of this work, we focus on applications with a high level of user interactivity, including peripherals such as smartphones or tablets. In more detail, in the edge computing layer, we have two servers, a master server and a server with the slave nodes (which will perform the processing itself). Slaves are micro-services that run in containers. In this work, each container is configured to run on a server core. Therefore, if there are 16 cores, 16 containers will be executed. The use of containers in the MEC context is still not very common. The use of containers allows greater flexibility to scale the computational power of the architecture according to the volume of tasks and also restrictions of applications' response times. The master server is responsible for receiving requests from mobile devices and distributing them between slave servers. At first, the master server runs the management service with the service running in bare metal (non-virtualized) mode and using threads. However, nothing prevents the analyst from virtualizing the master server service as well. To manage the containers, we consider that a container orchestrator (e.g., Kubernetes (Kubernetes: [[https://kubernetes.io/](https://kubernetes.io/)]([https://kubernetes.io/](https://kubernetes.io/)), accessed on 20 December 2020) or Swarm (Swarm: [[https://docs.docker.com/engine/swarm/](https://docs.docker.com/engine/swarm/)]([https://docs.docker.com/engine/swarm/](https://docs.docker.com/engine/swarm/)), accessed on 25 December 2020)) should be used to increase resources reliability and elasticity. As Figure 2 illustrates, there are three blocks in the communication flow of the architecture: (i) Arrival Delay (AD): time interval between arrivals of requests; (ii) Distribution Delay (DD): time interval for distributing jobs; and (iii) Processing Delay (PD): processing time of the requests by the nodes. Recent advances in the invention and fabrication of new lines of mobile devices help ease people's daily activities with a tremendous number of mobile apps, which feature a huge amount of stream-like data transactions through limited connection bandwidths and mobile computing resources.