Section: New Results

Experimenting with Fog Infrastructures

To this day, the Internet of Things (IoT) continues its explosive growth. Nevertheless, with the exceptional evolution of traffic demand, existing infrastructures are struggling to resist. In this context, Fog computing is shaping the future of IoT applications. Fog computing provides computing, storage and communication resources at the edge of the network, near the physical world. This section describes two independent contributions on how to study and develop FOG infrastructures. These contributions take place in the context of the Inria/Orange Labs joint laboratory.

• Despite its several advantages, Fog computing raises new challenges which slow its adoption down. In particular, there are currently few practical solutions allowing to exploit such infrastructure and to evaluate potential strategies. In [42], we propose a prototype orchestration architecture building on both Grid5000 and Fit-IoT lab (SILECS). This experimental testbed allows to realistically and rigorously evaluate orchestration strategies. In [20], we propose FITOR, an orchestration system for IoT applications in the Fog environment, which extends the actor-model based Calvin framework to cope with Fog environments while offering efficient orchestration mechanisms. In order to optimize the provisioning of Fog-Enabled IoT applications, FITOR relies on O-FSP, an optimized fog service provisioning strategy which aims to minimize the provisioning cost of IoT applications, while meeting their requirements. Based on extensive experiments, the results obtained show that O-FSP optimizes the placement of IoT applications and outperforms the related strategies in terms of i) provisioning cost ii) resource usage and iii) acceptance rate.

• End devices nearing the physical world can have interesting properties such as short delays, responsiveness, optimized communications and privacy. However, these end devices have low stability and are prone to failures. There is consequently a need for failure management protocols for IoT applications in the Fog. The design of such solutions is complex due to the specificities of the environment, i.e., (i) dynamic infrastructure where entities join and leave without synchronization, (ii) high heterogeneity in terms of functions, communication models, network, processing and storage capabilities, and, (iii) cyber-physical interactions which introduce non-deterministic and physical world's space and time dependent events. In [29], [37], we present a fault tolerance approach taking into account these three characteristics of the Fog-IoT environment. Fault tolerance is achieved by saving the state of the application in an uncoordinated way. When a failure is detected, notifications are propagated to limit the impact of failures and dynamically reconfig-ure the application. Data stored during the state saving process are used for recovery, taking into account consistency with respect to the physical world. The approach was validated through practical experiments on a smart home platform.