Optimising feedback in a multicast system

摘要

The invention concerns the multicasting of data between a source device and a plurality of destination devices. Destination devices receive data from the source device and also an indication of the maximum number of packets to be transmitted and determine the progress of data reception on the basis of the number of packets received or not received. The destination devices then determine whether or not to transmit a feedback of data reception to the source device on the basis of predetermined criteria. Where feedback is transmitted, it includes an indication of the determined progress. The feeback is used by the source device to determine whether to change its the transmission characteristics. The sending of feedback from the destination devices may be ordered according to the progress of each of the devices such that the device with the least progress sends feedback first. Any devices with progress the same as or better than the device with the least progress need not transmit feedback since retransmitted packets will be received in response to the feedback from the device with the least progress. Alternatively destination device feedback may be ordered according to device identifiers.