Reliable response delivery in peer-to-peer systems

The unstructured peer-to-peer (P2P) system is the prevalent model in today´s P2P systems. In such systems, a response is sent along the same path that carried the incoming query message. To guarantee the anonymity of the requester, no requester information is included in the query message and each node in the query incoming path only knows its immediate neighbor who sent the query request. This mechanism introduces response loss when any one node or connection in the path fails, which is a general case in the P2P system due to its dynamic nature. We address the response loss problem and present three techniques to alleviate it: redundant response delivery (RRD) scheme as a proactive approach; adaptive response delivery (ARD) scheme as a reactive approach; extended ARD rendered to function in an unstructured P2P system with limited or no flooding based search mechanism. With limited traffic overhead, all three techniques reduce response loss rate by more than 65% and they are all fully distributed.