Electronic architectures of optical slot switching nodes

An optical slot switching node network called POADM (packet optical add-drop multiplexers) has formerly been proposed as a flexible solution for metropolitan ring networks to carry data traffic with a sub-wavelength switching granularity and with a good energy efficiency, which is enabled by optical transparency. In this paper, we propose several architectures for the electronic side of optical slot switching nodes. Those architectures increase the flexibility with which a client, attached to a node, can access the transport medium, through the addition of electronic switches, working either at client frame granularity or at slot granularity (a slot encapsulates several client frames); such electronic switches can be located at either transmitter, receiver, or both sides of a node, thereby decreasing traffic latency, at the expense of increased node cost and/or energy consumption. This paper focuses on the latency aspect only. We assess and compare the latency of these node architectures with simulations; some results are also backed analytically. The utilization of an (electronic) slot switch enables load balancing across the transport channels, while the node architecture with an (electronic) client frame switch additionally permits flow aggregation, resulting in lower queuing delay. The lowest queuing delay is achieved by the architecture embedding client frame switches at both transmitter (Tx) and receiver (Rx) sides, while the absence of electrical switches leads to the worst performance, but presents the advantage of lower cost and consumption with respect to the other architectures. The utilization of client frame switches at Tx or Rx presents intermediate performances.