From MANET To IETF ROLL Standardization: A Paradigm Shift in WSN Routing Protocols

In large networks, a data source may not reach the intended sink in a single hop, thereby requiring the traffic to be routed via multiple hops. An optimized choice of such routing path is known to significantly increase the performance of said networks. This holds particularly true for wireless sensor networks (WSNs) consisting of a large amount of miniaturized battery-powered wireless networked sensors required to operate for years with no human intervention. There has hence been a growing interest on understanding and optimizing WSN routing and networking protocols in recent years, where the limited and constrained resources have driven research towards primarily reducing energy consumption, memory requirements and complexity of routing functionalities. To this end, early flooding-based and hierarchical protocols have migrated within the past decade to geographic and selforganizing coordinate-based routing solutions. The former have been brought to standardization through the Internet Engineering Task Force (IETF) Mobile Ad-hoc Networks (MANET) working group; the latter are currently finding their way into standardization through the IETF Routing Over Low power and Lossy networks (ROLL) working group. This article thus surveys this paradigm shift for routing in WSNs and, unlike previous milestone surveys, follows a rather chronological organization within the given protocol taxonomy. For each protocol family, we provide a didactic presentation of the basic concept, a discussion on the enhancements and variants on that concept, and a detailed description of the latest state-of-the-art protocols of that family. We believe that this organization sheds some light on the design choices of emerging IETF ROLL protocols and also provides design parameters of interest to the WSN engineer, essentially enabling the design and implementation of more reliable and efficient WSN solutions.