  The Industrial Internet of Things (IIoT) refers to the use of interconnected
smart devices, sensors, and other technologies to create a network of
intelligent systems that can monitor and manage industrial processes. 6TiSCH
(IPv6 over the Time Slotted Channel Hopping mode of IEEE 802.15.4e) as an
enabling technology facilitates low-power and low-latency communication between
IoT devices in industrial environments. The Routing Protocol for Low power and
lossy networks (RPL), which is used as the de-facto routing protocol for 6TiSCH
networks is observed to suffer from several limitations, especially during
congestion in the network. Therefore, there is an immediate need for some
modifications to the RPL to deal with this problem. Under traffic load which
keeps on changing continuously at different instants of time, the proposed
mechanism aims at finding the appropriate parent for a node that can forward
the packet to the destination through the least congested path with minimal
packet loss. This facilitates congestion management under dynamic traffic
loads. For this, a new metric for routing using the concept of exponential
weighting has been proposed, which takes the number of packets present in the
queue of the node into account when choosing the parent at a particular
instance of time. Additionally, the paper proposes a parent selection and
swapping mechanism for congested networks. Performance evaluations are carried
out in order to validate the proposed work. The results show an improvement in
the performance of RPL under heavy and dynamic traffic loads.
