The utility of hello messages for determining link connectivity

Abstract

INTRODUCTIONInfrastructured IEEE 802.11b networks are becoming ubiquitous. These networks offer high bandwidth wireless connectivity well-suited for a variety of traffic types, including multimedia distribution. One drawback of infrastructured networks is the complexity of deploying and configuring these networks. Ad hoc networking protocols do not suffer from this limitation. By using a multihop ad hoc network connectivity is maximized.For quality multimedia sessions, routing paths between nodes in an ad hoc network must be continually monitored. Numerous ad hoc routing protocols [1,3,4,7,12] make use of periodic broadcast messages to determine local connectivity. Also, because of the difficulty of obtaining IEEE 802.11 feedback about link connectivity in real networks, many current protocol implementations utilize hello messages [2,3,6,9,10].The basis of using hello messages to determine connectivity stems from the assumption that reception of a hello message indicates a viable communication channel with the source of the hello. This mechanism works well on wired networks, which experience few packet losses and connectivity changes. However, when used in wireless ad hoc networks the effectiveness decreases due to many factors. Some of the factors that have significant effect are: hello loss settings, hello packet size and 802.11b packet handling.

A Turnover based Adaptive HELLO Protocol for Mobile Ad Hoc and Sensor Networks

“…In [1], authors claim that the usefulness of a HELLO protocol depends on the size of the beacon messages, their transmission rate and the lifetime of deprecated entries of the neighborhood table. While these aspects are important, only a few studies have been performed about them.…”

“…While sensor networks are generally static, some applications involve mobility (e.g., herd health control as targeted by the WASP European project 1 ). Localized routing schemes are a resource-efficient way of achieving communication between two end hosts.…”

“…However, finding the correct frequency is not obvious: if it is too low (i.e., with regards to the speed of hosts), then tables quickly become obsolete. On the contrary, if it is too high, then tables will be up to date but a high part of the available bandwidth will 1 http://wasp-project.org be wasted to the detriment of data traffic. There obviously exists a trade-off between these behaviors, but finding the optimal one is not trivial.…”

Improving the Performance of TCP in the Presence of Interacting UDP Flows in Ad Hoc Networks

“…We have used the Ad hoc On demand Distance Vector (AODV) [15] as the routing protocol in our simulation studies. AODV provides an alternative to mechanism to determine link connectivity by periodically broadcasting Hello messages [16]. As the use of Hello messages has been shown to reduce false link failures, we use these messages in our simulations.…”

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