Cache Consistency in Mobile Ad-hoc Networks with SSUM

This paper proposes the Smart Server Update Mechanism for Maintaining Cache Consistency in Mobile Environments, the server autonomously sends data updates to the Cache Nodes (CN), meaning that it has to keep track of which CNs cache which data items. This can be done using a simple table in which an entry consists of the id of a data item (or query) and the address of the CN that caches the data. A node that desires a data item sends its request to its nearest Query Directory (QD). If this QD finds the query in its cache, it forwards the request to the CN caching the item, which, in turn, sends the item to the requesting node (RN). Otherwise, it forwards it to its nearest QD, which has not received the request yet. If the request traverses all QDs without being found, a miss occurs and it gets forwarded to the server which sends the data item to the RN. In the latter case, after the RN receives the confirmation from the last traversed QD that it has cached the query, it becomes a CN for this data item and associates the address of this QD with the item and then sends a Server Cache Update Packet (SCUP) to the server, which, in turn, adds the CNs address to the data item in its memory. This setup allows the server to send updates to the CNs directly whenever the data items are updated.