Abstract: Flow control of data packets through a packet switching network to reduce congestion is controlled by an adaptive preferential permit packet (APP) processing from an orginating data terminal through each packet switch node of the network to a destination data terminal. APP requires less buffer storage capacity at each switch node, and enables data packets to enter the network only when there is a permit packet indication that the data packets are likely to reach, and be accepted by, their destination. The permit packet is sent node to node (16-19, 25, 28) prior to a transmission of a bulk of data packets. Each node is equipped to queue buffer (12-15, 21-24) a permit packet on a preferential basis ahead of data packets. The node discards the permit packet if the number of packets awaiting transmission from that node exceeds a prescribed threshold. This is throttling process, since the originating port times out and resends a permit packet if a permit-return packet is not received within a predetermined time.