Analysis of link break detection using HELLO messages
In this paper, we provide mathematical and experimental proofs that current strategy of declaring a link down in the HELLO protocol, which is widely used for neighborhood discovery in wireless multihop networks, when a specific number of HELLO losses are observed is not a correct strategy. Our mathematical analysis, which involves statistical characterization of error bursts over wireless links by extending Gilbert's bit error model and its validation using HELLO loss data from our wireless mesh testbed, shows that error burst lengths follow geometric distribution, where the probability of additional losses in the burst does not depend on the observed losses. Better alternative is to delete a link when observed mean burst length for the link is longer than the mean route recovery time. Our testbed results show improvement in the throughput when we compared the alternate strategy with default settings of AODV (Ad hoc On-demand Distance Vector) routing protocol using HELLO messaging for neighborhood discovery.
Keywords: HELLO protocol, allowed hello loss, neighborhood discovery, wireless mesh networks, routing protocols, packet error model