A master-slave distributed communications network includes a master node, a plurality of slave nodes. Each slave node is configured to store an address of the next node for a message to be routed on an uplink to the master node, and when sending a data packet to the master node it appends the pre-stored address and forwards the data packet to the next node thus lengthening the data packet, as the data packet is progressed from the slave nodes to the master node. For a downlink message, the master node using a pre-stored routing table includes in the data packet the addresses of all the slave nodes on the selected route. As the data packet is progressed from slave node to slave node, the address of each slave node which has forwarded the data packet is deleted thus shortening the overall length of the data packet.