RPL routing protocol

For a long time, sensors were simply used to quantify and monitor a physical value locally: a CO ₂ sensor in a factory, a temperature sensor in the home, a brightness sensor for urban lighting, and so on. The advent of the Internet and research into wireless technologies enabled these sensors to be equipped with connectivity, giving rise to wireless sensor networks. The widespread use of these sensors has led to the creation of a host of new applications: monitoring household energy consumption, managing urban traffic lights or intelligent lighting systems for local authorities. More broadly, wireless sensor networks can be seen as a subset of the wider concept of the Internet of Things. The Internet of Things aims to provide connectivity to a heterogeneous set of everyday objects (washing machine, electricity meter, lighting or clothing, for example) using wired or wireless communications.

Because of the low power (energy, processing) of the objects to be connected to the Internet, it has often been considered impossible to connect them to traditional Internet architecture, leading to the development of proprietary, non-interoperable solutions (ZigBee, LON, KNX, etc.). The IETF (Internet Engineering Task Force), the organization in charge of standardizing Internet protocols, therefore set up several working groups to specify interoperable protocols for networks made up of highly constrained devices or LLNs (Low Power and Lossy Networks).

The 6LoWPAN (The IPv6 in Low-Power Wireless Personal Area Networks) working group defined how to transport IPv6 datagrams over low-speed, low-power links, and how to form and maintain an IPv6 (Internet Protocol version 6) subnet. The ROLL working group has defined the RPL routing protocol, which enables the construction of a routing topology on constrained networks. Note that RPL should not be pronounced as a three-letter acronym, but as the English word "riple" meaning undulation. The CORE group is developing a simplified version of HTTP that requires fewer resources while retaining compatibility with HTTP. Finally, the ACE group is concerned with security in constrained environments. These four working groups play a key role in defining an open, interoperable Internet of Things.

In this article, we'll focus on the RPL routing protocol, presenting the different mechanisms implemented in RPL.

A glossary of key terms is included at the end of the article.