Fig. 1: Concept of the proposed optical switching and control system.

a Nanosecond optical switching and control system exploiting label control mechanism, Optical Flow Control protocol and clock distribution mechanism. In the proposed system, N racks are grouped into one cluster and each rack hosts H servers. Each top of rack (ToR) consists of one Ethernet switch and two network interface controllers (NICs). The field programming gate array (FPGA)-based ToR₁ and FPGA-based switch controller are zoomed to show the detailed functional components. Data channels carrying the optical packets from the ToRs are cross-connected by the optical switch, and the label channels are used to connect the ToRs to the switch controllers. IPG inter-packet gap, ACK acknowledgment, NACK negative acknowledgment. b Signals exchange between switch controller and ToRs. At system initialization state, the timestamps are exchanged between the switch controller and ToRs to automatically measure the fiber delay and distribute the time of switch controller to connected ToRs to implement the synchronous slotted mechanism. Afterwards, the label request and response packets are exchanged to implement the label control mechanism and Optical Flow Control protocol at each time slot. The clock is also continuously distributed by the label response signals to the ToRs to synchronize the network clock. The label control mechanism, Optical Flow Control protocol and clock distribution mechanism are employed on the label channels with less resource occupied.