IPv6 Multihop Host Configuration for Low-Power Wireless Networks

Abstract

Standard routing protocols for Low power and Lossy Networks are typically designed to optimize bottom-up data flows, by maintaining a cycle-free network topology. The advantage of such topologies is low memory footprint to store routing information (only the parent's address needs to me known by each node). The disadvantage is that other communication patterns, like top-down and bidirectional data flows, are not easily implemented. In this work we propose MHCL: IPv6Multihop Host Configuration for Low-Power Wireless Networks. MHCL employs hierarchical address allocation that explores cycle-free network topologies and aims to enable top-down data communication with low message overhead and memory footprint. We evaluated the performance of MHCL both analytically and through simulations. We implemented MHCL as a subroutine of RPL protocol on Contiki OS and showed that it significantly improves top-down message delivery in RPL, while using a constant amount of memory (i.e., independent of network size) and being efficient in terms of setup time and number of control messages. homes, one can imagine a low-power wireless network connecting the appliances and other electric devices of a home to a gateway, or a border router. While away from home, one might wish to connect to the refrigerator at home to check whether one is out of milk and should buy some on the way home. In order to deliver this request, a message would need to be sent to the IPv6 address of the refrigerator. This message would first be delivered to the home gateway and then be routed downwards through the multihop wireless network connecting the appliances. Each node in this network would act as a router and decide which way to forward the message, so that it reaches the refrigerator.Even though top-down data traffic is typically not the main target of low-power multihop wireless networks, it is enabled by some popular routing protocols in an alternative operating mode, so that routes are optimized for bottom-up traffic, but top-down traffic is still possible. In the RPL protocol, for example, nodes maintain a DAG (Directed Acyclic Graph) topology, in which each node keeps in memory a small list of parent nodes, to which it forwards data upwards to the root. If a node wants to act not just as a source but a destination, it sends a special message upwards through the DAG, and the intermediate nodes (if they operate in the so-called storing mode) add an entry for this destination in the routing table created specifically for downward routing. The size of each such table is potentially O(n), where n is the size of the subtree rooted at the routing node. Given that memory space may be highly constrained in low-power wireless networks, all routes often cannot be stored, and packets must therefore be dropped. This results in high message loss and high memory footprint. In order to reduce the size of the routing table, it would be desirable to aggregate several addresses of closely located destination nodes in a single routing table entry. However, because IPv...