Robustness and Scalability Improvements for Distance Vector Routing in Large WMNs

IEEE 802.11s enables rapid deployment of Wireless Mesh Networks (WMNs) to supply basic wireless connectivity for client hardware. Application of distance vector based routing protocols proved advantageous in WMNs for efficiency, i.e., low overhead. However, it remains unclear, if plain distance vector routing protocols allow for adequate robustness against outages in large installations. Particularly, the required time for routing re-convergence may be too long, as in practice, the count-to-infinity phenomenon needs to be dealt with. This paper proposes Spare Forwarding Entries (SFEs), resulting in a proactive mechanism improving robustness against outages when compared to the reactive behavior of distance vector protocols. It works as an extension of distance vector operation, i.e., efficiency can be preserved. We integrate SFE into the well-known Babel routing protocol and also propose measures to increase scalability. Simulation studies indicate that SFEs improve robustness against node outages significantly. In certain scenarios, the Packet Delivery Ratio (PDR) was doubled with our mechanisms in place. Further modifications let Babel-based WMNs scale up to 300 nodes. Moreover, convergence times and overhead are significantly smaller.