# Routing Protocols for Low Power and Lossy Networks in Internet of Things Applications
## 6 Conclusions  
The creation of the 6 LoWPAN working group by IETF allowed the development of a solution to provide the use of IPv6 over low power devices. This contribution boosted the emergence of IoT applications. However, since the definition of LLNs, the routing in the networks with low power devices is considered a significant challenge. Seeing the importance of studying appropriate routing solutions, IETF created the RoLL working group. Initial conclusions of a study developed by the new working group showed that the existent IETF standard routing protocols were unable to provide the routing requirement of LLNs. Thus, RoLL began the development of a new routing solution considering the specificities identified by the group for different LLN applications.  
Although the RoLL working group has defined RPL as the standard routing protocol for LLNs, several works have shown that the solution presents severe limitations and drawbacks. Thus, various new solutions studied in the course of this document have emerged in recent years trying to mitigate the existent routing issues. The currently-proposed enhancements are designed, in general, to solve problems related to P2P and mobility support, multicast data forwarding, energy efficiency, and QoS improvement. However, it is important to note that these new routing solutions are for the IoT/LLN network, as they are not limited to RPL enhancements. LOADng and its advances have emerged as a potential solution, especially for P2P communication, though it is much less studied than RPL in the recent literature.  
The comprehensive analyses and discussions about the studied routing strategies have allowed the identification of the evolution of state-of-the-art solutions. However, it is also possible to point out various limitations of current proposals, which shows that they are still unable to fulfill the IoT routing requirements feasibly. Finally, several research directions and guidelines were presented for consideration in the design of new proposals.  
[PERSON] collected and performed a deep analysis and reviewed the related literature on the topic, wrote the first draft of the document, performed the comparison study, and identified some open research issues. [PERSON] supervised all of the study, consolidated the comparison analysis and open issues, and reviewed the structure and the first draft. [PERSON], [PERSON], and [PERSON] reviewed the text carefully, verified the comparison study, and reviewed the identified open issues. [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] contributed equally to the scope definition, motivation, and focus of the paper.  
This work has been supported by the Brazilian National Council for Research and Development (CNPq) via Grant Nos. 201155/2015-0 and 309335/2017-5, by the National Funding from the FCT (Fundacao para a Ciencia e a Tecnologia) through the UID/EEA/500008/2019 Project, by the Government of the Russian Federation, Grant 08-08, by RNP with resources from MCTIC, Grant No. 01250.075413/2018-04, under the Radiocommunication Reference Center (Centro de Referencia em Radiocomunicacoes (CRR)) project of the National Institute of Telecommunications (Instituto Nacional de Telecomunicacoes (Inatel)), Brazil, and by the International Scientific Partnership Program ISPP at King Saud University through ISPP #0129.  
The authors declare no conflict of interest.