Link Peek: A Link Outage Resilient IP Packet Forwarding Mechanism for 6LoWPAN/RPL Based Low-Power and Lossy Networks (LLNs)

Packets traversing through a multi-hop Low-power and Lossy Network (LLN) experience various link outage conditions in transit that can lead to packet loss at an intermediate relay node. Motivated by the problem of providing high Packet Delivery Ratio (PDR) in the LLNs running RPL(Routing Protocol for Low-power and Lossy Networks) routing protocol, we implemented a lightweight add-on functionality to the network layer's packet forwarding mechanism, Link Peek, in which the forwarding node iteratively retransmits the packet to its alternate/next best parent belonging to the same RPL DODAG(Destination Oriented Directed A cyclic Graph) instance whenever IEEE 802.15.4 MAC layer retransmission count set by our mechanism for the current best parent is exceeded. With this simple reactive and successive retry mechanism, our experimentation has shown significant performance gain in terms of achieving high PDRs, even at higher data rates, over the LLNs under different operating environments. We implemented Link Peek over the Contiki RPL protocol stack. We describe the implementation details and discuss various tunable parameters that affect the network performance. The Cooja simulation and real-world physical test bed experimentation with link outage environment showed PDRs > 99.40% with Link Peek as against the PDRs of 76-90% obtained using the native network stack implementation. Through the experimental results we demonstrate the effectiveness of our approach in supporting higher data rates even in node mobility scenarios.