## 8 Discussion of Results, Conclusions and Future Work  
In this paper a decentralized communications infrastructure based on peer-to-peer overlay technology for control and monitoring of smart microgrids has been proposed. It has been shown that the peer-to-peer paradigm can be applied to build up the communications layer of microgrids, with a set of potential improvements in terms of robustness, efficiency, scalability and flexibility. A novel scheme of locality-routing algorithm (LRA) based on a DHT-Chord overlay has been developed. The presented experimental results show that the number of lookup messages and, consequently, the lookup latency network, are lower with the proposed LRA scheme than with other DHT-flooding techniques. The network overhead is reduced by reducing the amount of lookup messages. Besides, both DHT-flooding lookups algorithms and LRA algorithm have been integrated into a fully decentralized communication architecture to provide optimal control and monitoring of smarts microgrids. The architecture design has been optimized by embedding the additional application layer with the P2P layer. The results show that the performance of each one of architectures depends strongly of the used lookup algorithm as well as the placement of the communication layers in the architecture. Finally, the embedded model has been tested by using relevant network performance parameters such as latency, network usage and bandwidth. The experimental evaluation shows that the proposed P2P architecture are useful for demanding environments where strict network specifications are required, and also that the communication performance meets the network requirements of smart microgrids. Despite the advantages of the proposed solution, there are some limitations that can be pointed out and will guide our future research work:  
* The clusters in the proposed algorithm have been organized around a specific type of DER, such as critical loads, distributed generators, etc. In order to add flexibility to the algorithm, it would be interesting to study the clusters' classification from other features different that the nature of the DER. * The proposed algorithm creates one overlay layer on top of the physical network. However multiple overlays layers could be created to provide other microgrid services. For example, in a second layer, multicast services could be provided. These services could very useful in the microgrid context. For example, when a set of real-time control signal needs to be distributed to a large set of participants. This issue could be carried out by means of tunnels [91] which can give  
Figure 17: Average bandwidth utilization (inbound and outbound) per peer on a network of \(N=25\) peers. multicast services access to the end peers. Overlay multicast can also be perceived as topic-based publish/subscribe [92]. * The proposed solutions have a certain security degree due to redundant link and self-reconfiguration [19] have been implemented. However, the system is sensitive to malicious attacks such as Sybil or Eclipse [93; 94]. Thus additional security procedures should be studied and implemented to reduce the sensitivity to malicious attacks. * The IEC 61850 standard has been widely used in smart substations and it has been also proposed to smart microgrids. It defines priority Generic Object Oriented Substation Events (GOOSE) messages and switching Ethernet for fast and reliable transmissions among DERs. The objective is to improve the transmission efficiency and guarantee that the transmission time of each message is lower than 4 ms [95; 96; 97]. The protocol stack should implement this communication mechanism. * The proposed solutions have been validated by means of experimental results that have been carried out by means of virtual machines. The achieved results take into account most of the system physical limitations. Therefore, it can be concluded that the proposed solutions are an interesting approach to the problem of communications in smart microgrids.