Dual MAC Based Hierarchical Optical Access Network for Hyperscale Data Centers

A dual media access control (DMAC) based hierarchical optical access network (HOAN) is proposed for data center networks, consisting of passive optical distribution modules (PODMs) at passive optical access layer and top-of-cluster (ToC) switches at electronic access layer. A PODM organizes a group of servers into a computing cluster and forms the intra-cluster channel. Each ToC switch connected with several PODMs forms the inter-cluster channel based on time and wavelength division multiplexing (TWDM). A load-sensing dual-mode (LSDM) protocol is presented for the intra-cluster channel to realize distributed low-load competition and high-load polling operation; the inter-cluster channel applies any polling based TWDM protocol to offer flexible bandwidth allocation. Simulations show that the LSDM can reach 0.95 throughputs at high traffic load, less than 32 μs frame latency, 128 μs frame latency on the 99.9th percentile of the simulated results at 25 Gbps with high priority, verifying the LSDM protocol can realize high throughput, low latency, and the measured latency variation. Compared the performances of DMAC based HOAN with those of passive optical cross-connection network (POXN) and passive optical top-of-rack interconnect (POTORI) architecture, when the normalized intra-rack traffic load reaches 0.8, average frame latencies in one computing cluster are 70.4, 184, and 2480 μs at 10 Gbps, and normalized available bandwidths for inter-cluster channels are 1, 0.2, and 0.2, respectively. Furthermore, the DMAC based HOAN is characterized with the scalability capable of organizing up to 320000 servers with only 500 ToC switches.