Optical switching

A network node comprising an optical input, an optical output, at least one queue that can be accessed randomly in time, and a processing system, wherein the node is configured:

• to receive a data packet at the optical input;
• to determine whether to process the data packet as a guaranteed-service packet or as a statistically-multiplexed packet;
• if the data packet is to be processed as a guaranteed-service packet, to send the data packet from the optical output within a predetermined maximum time of receiving the data packet;
• if the data packet is to be processed as a statistically-multiplexed packet, to add the data packet to the queue;
• and
• for two outbound guaranteed-service packets, to determine a plurality of statistically-multiplexed packets whose lengths are such that each of the plurality of statistically-multiplexed packets would fit in a gap between the two guaranteed-service packets, to use a selection process to select a statistically-multiplexed packet from said plurality of statistically-multiplexed packets, and to send the selected statistically-multiplexed packet from the optical output, between the two guaranteed-service packets.