Route or Flood? Reliable and Efficient Support for Downward Traffic in RPL

Abstract

Modern protocols for wireless sensor networks efficiently support multi-hop upward traffic from many sensors to a collection point, a key functionality enabling monitoring applications. However, the ever-evolving scenarios involving low-power wireless devices increasingly require support also for downward traffic, e.g., enabling a controller to issue actuation commands based on the monitored data. The IETF Routing Protocol for Low-power and Lossy Networks (RPL) is among the few tackling both traffic patterns. Unfortunately, its support for downward traffic is significantly unreliable and inefficient compared to its upward counterpart. We tackle this problem by extending RPL with mechanisms inspired by opposed, yet complementary, principles. At one extreme, we retain the route-based operation of RPL and devise techniques allowed by the standard but commonly neglected by popular implementations. At the other extreme, we rely on flooding as the main networking primitive. Inspired by these principles, we define three base mechanisms, integrate them in a popular RPL implementation, analyze their individual and combined performance, and elicit the resulting tradeoffs in scalability, reliability, and energy consumption. The evaluation relies on simulation, using both real-world topologies from a smart city scenario and synthetic grid ones, as well as on testbed experiments validating our findings from simulation. Results show that the combination of all three mechanisms into a novel protocol, T-RPL (i) yields high reliability, close to the one of flooding, (ii) with a low energy consumption, similar to route-based approaches, and (iii) improves remarkably the scalability of RPL with respect to downward traffic.

6TiSCH++ with Bluetooth 5 and Concurrent Transmissions

“…In this case, while DAO's are still sent upwards over the layer-3 RPL links, 6PP again returns centrally computed DAO-ACKs as CT floods from the coordinator. By broadcasting DAO-ACKs in this fashion (as also demonstrated in [23]), 6PP reliably establishes RPL downward routes more quickly than a hop-by-hop approach.…”

“…However, this work did not target a 6TiSCH implementation (which would not have been possible on the employed legacy hardware [22] used in initial editions of the competition). More recently, and particularly relevant to this paper, Istomin et al [23] have examined the use of CT to carry downward RPL traffic in asynchronous CSMA/CA IEEE 802.15.4 networks, while retaining routing-based transmission for upward traffic; thus successfully building on the strengths of both approaches. Furthermore, the authors of [24] demonstrate the applicability of BT 5 CT as a mechanism for single-hop cooperative transmissions and multi-hop timesynchronization alongside a secondary optimized transmission schedule, drawing on similar reasoning to the arguments presented in this paper.…”

“…the mesh. Finally, building on the similar approach taken in [23], 6PP disseminates RPL DAO-ACK messages over CT floods. This allows 6PP to reliably and rapidly establish the downward routes, which is a well-known challenge in wireless mesh networks [16].…”

Residual Energy and Expected Transmission count based routing protocol for Industrial Internet of Things

“…RPL creates a tree topology called Directed Acyclic Graph (DAG) which is used to collect data from the nodes. In RPL the upward routing is used to collect the data from the nodes and downward routing is used to maintain routes to the nodes in the network [7,8]. For each sink node, the DAG is divided into one or more Destination Oriented Acyclic Graph (DODAG) and each DODAG node selects the node closer to the root as parent, based on the routing metric [2,8,9].…”

Prioritized Shortest Path Computation Mechanism (PSPCM) for wireless sensor networks

“…Request for Comments (RFC) 6550 describes RPL as a low power consumption distance-vector proactive routing protocol for resource-constrained devices that form the building block for IoT [ 10 ]. RPL sets up a self-organized, self-healing, self-sustained, and loop-free routing graph known as Distance Oriented Directed Acyclic Graph (DODAG) [ 11 , 12 ].…”