Low power and Lossy Networks (LLNs) are a class of network in which both the routers and their interconnect are constrained. RPL routing protocol, which provides a mechanism whereby multipoint-to-point traffic from devices inside the LLN towards a central control point, as well as point-to-multipoint traffic from the central control point to the devices inside the LLN, is supported. Support for point-to-point traffic is also available.
RPL protocol is easy to adopt to network changes and allows to have multiple logical topologies over a single physical topology. Moreover, it provides a loop avoidance and detection mechanism, and it takes into account both link and node properties when choosing paths. However, it assumes other mechanism can be used to provide security.
Nowadays, RPL routing protocol is used in 6LoWPAN and generic LLN networks. There were some successful implementations in TinyOS, and with the deployment of IPv6 it is expected to have more implementations and successful results.