Yue-Cai Huang

Torus-Topology Data Center Network Based on Optical Packet/Agile Circuit Switching with Intelligent Flow Management

We review our work on an intra-data center (DC) network based on co-deployment of optical packet switching (OPS) and optical circuit switching (OCS), conducted within the framework of a five-year-long national R&D program in Japan (~March 2016). For the starter, preceding works relevant to optical switching technologies in intra-DC networks are briefly reviewed. Next, we present the architecture of our torus-topology OPS and agile OCS intra-DC network, together with a new flow management concept, where instantaneous optical path on-demand, so-called Express Path is established. Then, our hybrid optoelectronic packet router (HOPR), which handles 100 Gbps (25 Gbps × 4-wavelength) optical packets and its enabling device and sub-system technologies are presented. The HOPR aims at a high energy-efficiency of 0.09 [W/Gbps] and low-latency of 100 ns regime. Next, we provide the contention resolution strategies in the OPS and agile OCS network and present the performance analysis with the simulation results. It is followed by the discussions on the power consumption of intra-DC networks. We compare the power consumption and the throughput of a conventional fat-tree topology with the N-dimensional torus topology. Finally, for further power saving, we propose a new scheme, which shuts off HOPR buffers according to the server operation status.

A torus datacenter network based on OPS/OCS/VOCS enabled by smart flow management

We present an energy-efficient, low-latency, torus-topology intra-data center network with the deployment of 100-Gb/s hybrid optoelectronic routers, where OPS, OCS and virtual OCS are all supported on a single hardware platform enabled by smart flow management.

Torus data center network with smart flow control enabled by hybrid optoelectronic routers [Invited]

A torus-topology photonic data center network with smart flow control is presented, where optical packet switching (OPS), optical circuit switching (OCS), and virtual OCS (VOCS) schemes are all enabled on a unified hardware platform via the combination of hybrid optoelectronic routers (HOPR) and a centralized network controller. An upgraded HOPR is being developed with the goal of handling 100 Gbps optical packets with a high energy efficiency of 90 mW/Gbps and low latency of less than 100 ns. The architecture of HOPR and its enabling technologies are reviewed, including a label processor, optical switch, and optoelectronic shared buffer. We also explain the concept and operation mechanisms of both the data and control planes in the hybrid OPS/OCS/VOCS torus network. The performance of these three transmission modes is evaluated by numerical simulations for a network composed of 4096 HOPRs.

Optical packet and path switching intra-data center network: Enabling technologies and network performance with intelligent flow control

We review recent development of energy-efficient, low-latency intra-data center network, emphasizing on intelligent flow control capability, which simultaneously supports both OPS and OCS on-demand on a 100-Gbps (25-Gbps × 4-wavelength) platform consisting of hybrid optoelectronic packet routers.

OPS/agile-OCS data center network with flow management

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

Bypassing Route Strategy for Optical Circuits in OPS-Based Data Center Networks

In optical packet switching (OPS)-based data center networks (DCNs), it is preferred to set up temporal optical circuit switching (OCS) paths for large-data transmission that requires high reliability. However, inappropriate OCS path selection could severely affect the original OPS traffic. This is because an OCS path may break the network topology and cause OPS packet circulations. We propose to maintain bypassing routes for every link of the OCS path when it is established. Then, the OPS packets can bypass the OCS links by being deflected to the bypassing routes. Therefore, this method facilitates the coexistence of OCS in OPS-based DCNs. Numerical simulations demonstrate the benefit achieved by our proposal compared with non-bypassing-route scenarios.

Novel virtual OCS in OPS data center networks

This paper proposes a novel virtual optical circuit switching (VOCS) scheme for data center networks where short flows are transmitted via optical packet switching (OPS), while long flows with reliability requirement are transmitted via VOCS. VOCS preserves the advantage of optical circuit switching (OCS) for reliable communication, while it overcomes the disadvantage of OCS in terms of low link utilization. In the VOCS/OPS scheme, idle periods of the virtual circuits can be used by OPS, which thus enhances the overall performance. Simulations on a 6-dimensional torus topology data center network with 4096(=46) nodes are conducted with the following observations: (1) OPS is almost not affected with the introduction of quite a large number (i.e., 3800) of virtual circuits. (2) VOCS has much less impact on the performance of OPS, compared to OCS. (3) The VOCS flow length has little impact on the overall performance. Index Terms—data center network; optical packet switching; virtual optical circuit switching; flow management.

Bypassing routes strategy for optical circuits in OPS-based data center networks

In OPS-based data center networks, setting up temporal OCS paths for high-reliability-required large data transmissions is preferred. However, inappropriate OCS path selection could severely affect the original OPS traffic, which is because OCS path may break the network topology and cause OPS packet circulations. We propose to hold bypassing routes for every link of the OCS path when it is established. Then, the OPS packets could bypass the OCS links by being deflected to the bypassing routes. Therefore, this method facilitates the coexistence of OCS in OPS-based data center networks. Simulations demonstrate the benefit achieved by our proposal compared to no-bypassing-route scenarios.

OPS/OCS Intra-Data Center Network with Intelligent Flow Control

We review recent development of energy-efficient, low-latency intra-data center network which simultaneously supports OPS and OCS with inteligent flow control on a single platform of 100-Gbps hybrid optoelectronic packet routers.