Date Added: Nov 2012
End-to-end reliability in Delay Tolerant Networks (DTNs) is challenging and complicated because of high delay and absence of stable end-to-end path in the intermittently connected mobile environment. Some existing acknowledgement mechanisms use active forwarding to provide the end-to-end reliability, while incurring excessive retransmissions or replications. The other passive mechanisms aim to reduce the storage overhead but may suffer a large delay. To improve the storage delay tradeoff, the authors propose a Congestion Level based end-to-end ACKnowledgement (CL-ACK) mechanism, which adaptively adjusts the spread manner of ACK packets according to the ratio of drops over replications.