A method of interleaving time-critical data packets and delay-tolerant data packets on a shared channel emanating from a control port of a switching node permits a strict time requirement for transmission of time-critical data packets to be met. A control circuit of the switching node stores a local time, an indication of a time required to transfer a delay-tolerant data packet waiting to be transferred, a comparator and a selector to control transfer of the time-critical and delay tolerant data packets.