Link failures would result in changes in reachability between members, which consequently leads to changes in membership, called a view change. When a link failure for the nodes is suspected, a group leader constructs a new view where suspected nodes are excluded from the existing view. It then transmits it to the currently connected members. To maintain the frequent changes caused by node mobility, the group membership service for MANETs 1) needs to recognize the reachability status of the nodes as accurate as possible and 2) should reduce the meaningless view changes to avoid the capricious view change.
MANET environments are unstable due to the characteristics of MANETs such as node mobility and lack of infrastructure. If the network situation is unstable, the connection between hosts is repeatedly disconnected and reconnected. This situation brings about the frequent view changes. Furthermore the disconnection of multiple nodes rather than a single node is general in MANETs because the communication with far nodes out of a transmission range is possible, only if an intermediate node between the source and destination nodes exists. Therefore the effciency of group membership service in terms of the number of messages and view changes is influenced by how well the network partition is maintained. In this dissertation, we propose a network partition handling scheme based on the reachability estimation for group membership service.
The reachability guarantees nodes to communicate each other and the reachability status are collected using various schemes. The most widely adopted and simple scheme is to broadcast or send to specific nodes messages of reachability status periodically. The existing message exchange-based scheme generates messages periodically even though the reachability status itself does not change. However, although the proposed reachability estimation scheme does not use periodical messages, it provides more accurate information of reacha...