Photonic-Frame-Based TCP proxy architecture in optically interconnected data center networks

Optical switching is a good candidate for achieving the key requirements of high scalability, low latency and low power consumption in future large-scale data center networks (DCNs). However, circuit-based optical switching has a disadvantage of a long reconfiguration time. Packet-based optical switching also faces challenges such as the complexity of optical header processing and the difficulty of buffering in optical switches to resolve contention. To address these problems, we present a packet-switched optical network architecture design with a photonic frame wrapper that can generate variable-size photonic frames for optically interconnected intra-DCN. The proposed architecture forms hybrid DCN architecture consisting of a flattened optical switch layer for the data path and a conventional electrical switch layer for the control path. The photonic frame wrapper can increase bandwidth utilization by minimizing guard-time insertion in the optical switch domain. We also introduce a photonic frame wrapper with proxy solution to fully exploit the gain of the proposed architecture even in inter-DCN communication with long delays, which is compliant with standard TCP instances at end nodes. In intra-DCN, the average queuing delay is analyzed to find the efficient combinations between the guard time and time-slot length for the variable-sized photonic frame. We also analyzed the bandwidth overhead of guard time, to show it is comparable to that of Ethernet based DCN. In inter-DCN, the proxy solution demonstrates a noticeable TCP performance enhancement compared with the photonic frame wrapper in terms of bandwidth efficiency and end-to-end delay by theoretical and OPNET simulation analyses.