Performance Improvements of OSPF MANET Extensions: A Cross Layer Approach

The IETF OSPF working group has recently considered extensions to Open Shortest Path First (OSPF) routing protocol for efficient operation over mobile ad hoc networks (MANET). Although these extensions greatly improve the scalability of OSPF in MANET environment, they only explore options that are available at the network layer, and assume generic broadcast radios such as IEEE 802.11 devices operating in ad hoc mode. These extensions have not considered cross layer integration to allow OSPF be more adaptive to dynamic changing wireless channel. In this paper, we investigate the benefits and tradeoffs of cross layer integration and optimization to further enhance the performance of OSPF. Our studies are carried out in simulation, emulation, and an 802.11 testbed. The performance results show that the cross layer signalling mechanisms could greatly improve the responsiveness of OSPF: i) they drastically reduced the packet losses due to link breakages, ii) the end-to-end latency was reduced by more than 60% in our experiments since the link congestion was also considered in route selection calculations, and finally iii) the delivery ratio improved linearly with traffic load.