The present invention provides a method of transmitting data in a network of interconnectable end-user nodes comprising a source node, a recipient node and a plurality of further nodes, wherein each of the end-user nodes is executing an instance of a communication client application. The invention also provides corresponding method of receiving data, and corresponding computer programs and user terminals. The method of transmitting data comprises: comprising: the communication client of the source node receiving a command to transmit the data to the recipient node; the source node selecting from the plurality of further nodes at least one storage node to store the data from the source node before being retrieved by the recipient node; transmitting the data from the source node to the at least one storage node; and the source node providing a network identity for each of the at least one storage nodes to the recipient node.