In the sending of data in a network from a sending node to a receiving node via a relay node, the receiving node sends a notification arranged to notify both the sending node and receiving node of receipt of data at the receiving node. Notifications acknowledge that the data has been correctly received over each individual stage of transmission, and further acknowledge to the sending node that data has been correctly transmitted over the whole transmission path and received at the receiving node. The burden on the network of sending acknowledgments is reduced while notifications of data transmission over single stages and over the whole transmission path are provided.