The Mobile IPv6 handover process consists of three major stages: movement detection, duplicate address detection and binding signaling. Most of the research efforts for optimizing the handover process focuses on minimizing the delays caused by the first two stages. The delay introduced by binding signaling is largely ignored since the correspondent node is assumed to be stationary. However, this delay can be significant when two communicating nodes are both mobile and may roam across different networks simultaneously. Mobile IPv6 requires that the binding signaling exchanged between the mobile node and the correspondent node to be authenticated using a procedure called return routability test. The signaling involved in the return routability procedure is mandated to be redirected through the home agents to the most up-to-date addresses of the communicating nodes. This may result in a longer handover duration if the mobile and correspondent nodes are both far from their home agent. In this paper, we present our recommendation on the use of direct signaling without the need to have any redirection from a network element. We also present an analysis of the cost involved in utilizing direct and indirect signaling mechanisms.
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