Optical Circuit Switching Research Articles

Adoption of fuzzy fractional order theory under Reco-Mo algorithm in data analysis of optical circuit switches

In order to analyze the optimization value of Reco-Mo based on fuzzy fractional order theory for data analysis of optical circuit switches, first, the co-flow scheduling strategy is expounded. According to the Burkhofvon-Neumann (BvN) matrix decomposition algorithm, the co-flow scheduling algorithm is described. Then, the fuzzy fractional order theory is combined with the co-flow scheduling algorithm, and the Reco-Mo algorithm is proposed. Finally, E-FWO algorithm and E-SCFE algorithm are introduced to carry out comparative analysis in real production environment. The results show that when the number of co-flows is 30, 50, 70, 90 and 110, the co-flow completion time of Reco-Mo algorithm is less than that of E-FWO algorithm and E-SCFE algorithm. At 70, 90, and 110, the accuracy of Reco-Mo algorithm is significantly higher than that of E-FWO and E-SCFE algorithms. When the density of Reco-Mo algorithm is 0.1, the completion time of co-flow is 38.46% and 37.25% lower than that of E-FWO algorithm and E-SCFE algorithm. At 1.0 and 1.3, the accuracy of Reco-Mo algorithm is significantly higher than that of E-FWO and E-SCFE. The completion time of Reco-Mo algorithm under different data transmission volumes (0.5, 1.0, 1.5, 2.0, 2.5 GB) is less than that of E-FWO and E-SCFE. At 1.5, 2.0, and 2.5 GB, the accuracy of Reco-Mo algorithm is significantly higher than that of E-FWO and E-SCFE. When the co-flow arrival time interval is 100 ms, the Reco-Mo algorithm reduces the completion time by 50.34% and 51.97% respectively compared with E-FWO and E-SCFE algorithms. At 100, 200, and 300 ms, the accuracy of Reco-Mo algorithm is significantly higher than that of E-FWO and E-SCFE. In conclusion, compared with E-FWO and E-SCFE algorithms, Reco-Mo algorithm has always maintained its dominant position in terms of co-flow completion time and accuracy under different parameters of co-flow quantity, co-flow density, co-flow transmission data volume, and co-flow arrival interval, which provides a theoretical basis for the application of mathematical algorithm in data processing of optical circuit switches in data centers in the future.

The Construction of High-Performance Optoelectronic Interconnection Network and the Realization of Cloud Computing for Traffic Data Recognition

Due to the problems of congestion, insufficient scalability, and high cost in the network core layer link, the network interconnection architecture needs to be optimized. The photoelectric interconnection technology has attracted the attention of many researchers with its high bandwidth, low latency, and low power consumption. In this study, after fully considering the requirements of optoelectronic switching on network node degree and processing delay and corresponding to different transmission characteristics of circuit switching and optical circuit switching, an optoelectronic interconnection architecture supporting heterogeneous network topology, namely THtop, is proposed. According to the optical circuit switching/circuit switching characteristics of the Internet, the corresponding topology structure is designed respectively in this architecture to enhance the system integration and reduce the cost. At the same time, in order to meet the requirements of wavelength and number of hops of optical circuit switching, distributed control is designed in THtop, and the design method of heterogeneous optical switching unit is introduced in the switching equipment, so that the optical switching node can further reduce the cost while playing its role. The use of high-speed optoelectronic networks will cause a large amount of traffic on the channel. In this study, the traffic identification is analyzed on the proposed THtop architecture. The Map Reduce framework in cloud computing is used as the identification model, and the K-means algorithm is taken as the identification algorithm. According to its characteristics, the W_K-means algorithm is proposed for the type identification of traffic. The results show that under the OpenNet Internet simulation environment, when the traffic is set to a certain level, more than 90% of the non-blocking network switching can be realized under the THtop architecture, and the completion time of the mouse flow and elephant flow can be significantly improved. Therefore, under the Map Reduce model, the proposed W_K -means algorithm can quickly identify different traffic types.

Data Processing Platform of Cloud Computing and Its Performance Analysis Based on Photoelectric Hybrid Interconnection Architecture

Data processing platform is the core support platform of cloud computing. The use of electric interconnection architecture will increase the complexity of network topology, while optical interconnection architecture is ideal, so cloud computing platform based on optical interconnection has become a research hotspot. The distributed optical interconnection architecture of cloud computing data processing platform is focused on. Combining the hybrid mechanism of optical circuit switching and electric packet switching, it can meet a variety of traffic requirements. Meanwhile, it improves the switching mechanism, communication strategy, and router structure. Moreover, considering that the hybrid optoelectronic interconnection architecture can improve the network delay and throughput, but there is still a problem of network consumption. Combined with the network characteristics of the data processing platform (wireless mesh structure) of cloud computing, the network topology algorithm is studied, and the relationship between the topology and the maximum number of allocable channels is analyzed. Furthermore, the equation of topological reliability calculation is defined, and the optimization model of topological design is proposed, according to which the data processing platform of cloud computing is further optimized under the photoelectric hybrid interconnection architecture. During the experiment, before topology optimization, by changing the message length, it is found that adding optical circuit switching can help achieving large capacity and new type of transmission, and can effectively reduce the time delay. After topology optimization structure is adopted, the photoelectric hybrid-data processing platform of cloud computing without topology optimization is compared. It is found that under different reliability constraints, the throughput and end-to-end delay of the network are significantly improved, which proves that the data processing platform of cloud computing based on the photoelectric hybrid interconnection architecture is a feasible cloud computing platform.

Online job scheduling for distributed machine learning in optical circuit switch networks

Networking has become a well-known performance bottleneck for distributed machine learning (DML). Although lots of works have focused on accelerating the communication process of DML, they ignore the impact of the physical network on the DML performance. Concurrently, optical circuit switches (OCSes) are increasingly applied in data centers and clusters, which can fundamentally improve DML performance. It is worth noting that the non-negligible OCS reconfiguration delay makes OCS scheduling algorithms have a great impact on the upper application performance. However, existing OCS scheduling solutions are not suitable for DML jobs due to the iterative nature of DML jobs and their interleaving characteristics of communication and computation stages. Therefore, in this paper, we study the online multi-job scheduling for DML in OCS networks. Firstly, we propose heaviest-load-first (HLF), a heuristic algorithm for intra-job scheduling, which is based on the fact that the completion time of flows on the heaviest load port has a significant impact on the job completion time. Furthermore, we present Shortest Weighted Remaining Time First (SWRTF) algorithm for inter-job scheduling. In SWRTF, an available DML job is scheduled when the served job moves from communication stage to the computation stage, which significantly improves the circuit utilization. Based on large-scale simulations, we demonstrate HLF can significantly reduce the iteration communication time by up to 64.97% compared to the state-of-the-art circuit scheduler Sunflow. Besides, SWRTF can save up to 42.9%, 54.2%, 27.2% of Weighted-Job-Completion-Time (WJCT) compared to Shortest-Job-First, Baraat and Weighted-First inter-job scheduling algorithms, respectively.

Asynchronous Optical Traffic Offloading of Hybrid Optical/Electrical Data Center Networks

In recent years, hybrid optical/electrical data center network has been considered a promising interconnection technology for large-scale data centers, since it can efficiently provide sufficient bandwidth. A key issue in hybrid optical/electrical data center networks is finding a way to offload burst traffic through optical circuit switches (OCSs), such that the burst traffic can be offloaded timely while the system operation overhead is low. This article extends the idea of Mahout to propose a local-push asynchronous optical traffic offloading strategy, in which each ToR switch offloads the traffic via the OCSs if its queue length is larger than a preset threshold, and transfers the traffic back to electrical packet switches (EPSs) when the backlog is empty. To seek a proper threshold, we develop a fluid-flow model to analyze the performance of the proposed traffic offloading strategy, from which we demonstrate that there is a trade-off between the mean delay of the traffic and the system operation overhead in a typical data center network. Based on such a trade-off, we provide a rule to select the buffer threshold. We show via simulation that the proposed optical traffic offloading strategy with the threshold selection rule outperforms C-through.

C-share

Integrating optical circuit switches in data-centers is an on-going research challenge. In recent years, state-of-the-art solutions introduce hybrid packet/circuit architectures for different optical circuit switch technologies, control techniques, and traffic re-routing methods. These solutions are based on separated packet and circuit planes that cannot utilize an optical circuit with flows that do not arrive from or delivered to switches directly connected to the circuit's end-points. Moreover, current SDN-based elephant flow re-routing methods require a forwarding rule for each flow, which raises scalability issues. In this paper, we present C-Share - a scalable SDN-based circuit sharing solution for data center networks. C-Share inherently enables elephant flows to share optical circuits by exploiting a flat top-of-rack tier network topology. C-Share is based on a scalable and decoupled SDN-based elephant flow re-routing method comprised of elephant flow detection, tagging and identification, which is utilized by using a prevalent network sampling method (e.g., sFlow). C-Share requires only a single OpenFlow rule for each optical circuit, and therefore significantly reduces the required OpenFlow rule entry footprint and setup rule rate. It also mitigates the OpenFlow outbound latency for subsequent elephant flows. We implement a proof-of-concept system for C-Share based on Mininet, and test the scalability of C-Share by using an event-driven simulation. Our results show a consistent increase in the mice/elephant flow separation in the network, which, in turn, improves both network throughput and flow completion time.

Large-scale silicon photonics switch based on 45-nm CMOS technology

In optical networks for telecom and datacom, an unprecedented energy efficient system is demanded since the amount of data traffic is rapidly increasing while a significant improvement of the energy efficiency in electronics devices such as switch ASICs is no longer expected. To overcome the energy constraints, introduction of energy-efficient optical circuit switching (OCS) to the conventional electrical packet switching network is considered. The energy consumption of the OCS is almost independent of the bandwidth because the transparent optical path with no optical-to-electrical/electrical-to-optical signal conversion supports an ultrawide bandwidth of highly multiplexed optical signals. In the OCS, high-speed and large-port-count optical switches are essential. We have been working on optical switches based on CMOS-compatible silicon photonics that offer fast switching, compactness, low power consumption, and low cost. By using our 45-nm CMOS process, we have recently demonstrated a low loss 32 × 32 silicon photonics switch and its performance improvements of wide operation bandwidth, polarization-independent operation, and so forth. In this paper, we review the recent progress of our silicon photonics switches. We discuss the importance of the silicon photonics switches for a sustainable optical network with a comparison of other switching technologies and explain comprehensively how our numerous achievements are advanced and related to each other.

A Dynamically-Reconfigurable Burst-Mode Link Using a Nanosecond Photonic Switch

Fast optical circuit switching has significant potential to solve scaling issues with traditional packet-switch-based networks and improve bandwidth and power efficiency in datacenter and high-performance computing applications. One difficultly in utilizing a fast optical switch is that the optical signal must be rapidly reacquired after each switching event so as to not significantly impact the overall throughput of the system. Here we present a system-level integration of a nanosecond-scale $2\times 2$ silicon photonic switch with a 25-Gbps burst-mode receiver that can lock in 31 ns. A novel FPGA-based control plane was used to generate test data, control the silicon photonic switch and burst-mode receiver, and measure bit errors at 12.5 and 20 Gbps. Error-free links (BER $ ) with system-level reconfiguration times below 60 ns (at 20 Gbps) and 90 ns (at 12.5 Gbps) including bit- and frame-synchronization are demonstrated.

Silicon Non-Blocking 4 × 4 Optical Switch Chip Integrated With Both Thermal and Electro-Optic Tuners

We experimentally demonstrate an integrated strictly non-blocking silicon 4 × 4 optical switch chip that can be operated in both thermo-optic (TO) and electro-optic (EO) switching modes. It is based on the double-layer network (DLN) architecture and consists of twelve 2 × 2 Mach-Zehnder interferometer (MZI) switch elements. TO phase shifters based on TiN microheaters and EO phase shifters based on p-i-n diodes are embedded in both waveguide arms of the MZI elements. The power consumption for TO and EO switching is 34 mW/π and 7 mW/π, respectively. The on-chip insertion losses are 1.74 ± 0.59 dB and 3.79 dB ± 1.32 dB for TO and EO switching, respectively. Due to the merits of the DLN architecture and the optimized performance of the switch elements, the chip possesses low crosstalk of -29.1 dB and -19.4 dB for TO and EO switching, respectively. Quadrature phase-shift keying (QPSK) optical signals with a data rate of 64 Gb/s are transmitted through the switch with no observable deteriorations. Such an optical switch is a promising candidate for both optical circuit switching and optical packet switching for a variety of applications.

RSS: a relay-based schedule scheme for optical data center network

The ever-increasing communication requirements have led to the introduction of optical circuit switch (OCS) to data center, which is capable of providing more flexible bandwidth allocation compared to the electrical packet switching. However, the challenge still arises due to non-negligible reconfiguration delay of commercially available MEMS-based optical circuit switching technology, even though it provides high bandwidth with low per-bit cost and power. Additionally, existing scheduling schemes amortize long switch delay by means of reconfiguring OCS every a few 100 s of milliseconds, not only causing the degradation of the latency performance, but also incurring the low utilization of optical links. In this paper, we propose an OCS-based scheduling scheme called relay-based schedule scheme (RSS), which can leverage idle optical paths to forward traffic from remote nodes only with straightforward software modifications on controller. We evaluate the performance of the proposed scheme via OMNET++ simulator, and the results demonstrate that our proposal delivers significant benefits, including reducing the average mice flow FCTs (flow complete time) by up to 80% and reducing the end-to-end packet delay by 50% compared to non-RSS schemes.

Decoupled scheduling in Store-and-Forward OCS networks

By introducing storage into Optical Circuit Switched (OCS) networks and storing delay-tolerant requests until off-peak hours, the networks can have better performance. Since scheduling a data transfer in SnF networks has to deal with the spatial and temporal arrangement of the request, it is much more complicated than the routing-alone problem. In our prior research, we proposed TS-MLG, a holistic approach to solve this problem, but the computational and spatial complexity of the approach is high, limiting its use in large scale networks. In this paper, we propose a decoupled solution and specific algorithms for both sub-problems. The solutions can reduce spatial and computational complexity from O(N2*L2) to O(N*L) with marginal sacrifice on network performance, in which N and L are respectively the number of network nodes and state changes in the network. Simulation results show that in a moderate sized network with frequent state changes, the computing time of request scheduling can be reduced by 600 times. We conclude that the decoupled SnF scheduling has the potential of analyzing SnF in large networks with frequent state changes.

A Brief Review on the Methods that Improve Optical Burst Switching Network Performance

Abstract In this tutorial, we give an introduction to optical burst switching (OBS) networks and compare different methods that have been given to improve performance of these networks. OBS is an alternative to optical circuit switching and optical packet switching by separating data from control packets and sending them in a different wavelength. OBS networks suffer from an issue based on their bufferless nature, burst contentions. In these networks, when two data bursts are competing on the same wavelength, one of them is dropped and it leads to a significant reduction on the performance of the network. A lot of researches have been done to solve this problem. Some of them are addressed in this paper.

TIO: A VLC-enabled hybrid data center network architecture

To satisfy the ever-increasing bandwidth demand of modern data centers, researchers have proposed hybrid Data Center Networks (DCNs), which employ high-bandwidth Optical Circuit Switches (OCSs) to compensate for Electrical Packet Switches (EPS). Existing designs, such as Helios and c-Through, mainly focus on reconfiguring optical devices to meet the estimated traffic requirements. However, these designs face two major challenges in their OCS-based networks, namely, the complex control mechanism and cabling problems. To solve these challenges, we propose TIO, a hybrid DCN that employs Visible Light Communication (VLC) instead of wired OCS design to connect racks. TIO integrates the wireless VLC-based Jellyfish and wired EPS-based Fat Tree seamlessly and combines the opposite and complementary characteristics, including wireless VLC direct connection and wired electrical packet switching, random graph, and Clos topology properties. To further exploit the merits of TIO, we design a hybrid routing scheme and congestion-aware flow scheduling method. Comprehensive evaluations indicate that TIO outperforms the Jellyfish and Fat Tree in both topology properties and network performance, and the flow scheduling method also evidently improves performance.

Integrating Coflow and Circuit Scheduling for Optical Networks

There are more and more structured traffic flows (a.k.a coflow) in today's data center networks. Completing a coflow is extremely important for various applications, e.g., MapReduce. To reduce the coflow completion time or CCT, one may increase the link capacity by applying advanced optical circuit switches in data center networks. Due to special features of optical circuit switches, both traffic scheduling and circuit scheduling will influence the CCT. However, previous solutions have some significant limitations: they consider either coflow scheduling, or circuit scheduling for only one optical circuit switch, which are both insufficient. In this paper, we study the integrated coflow and circuit scheduling (GCCS) problem with the objective to minimize the CCT, and prove its NP-hardness. We present an integrated algorithm which includes two steps, coflow scheduling and circuit scheduling, respectively. We also analyze that the proposed algorithm can achieve the approximation ratio O(h) in most practical situations, where h is the maximum number of ports among all lightpaths. Through large-scale simulations, we demonstrate that the integrated solution can significantly reduce the CCT by about 43-70 percent compared with the state-of-the-art coflow scheduler for optical networks.

Wormhole optical network: a new architecture to solve long diameter problem in exascale computer

The exascale computer will be built in the near future thanks to rapid innovations in semiconductor logic, memory, architectures, interconnections and other essential technologies. It is difficult to design an interconnection network that combines high performance with low power consumption. Therefore, building an interconnection network with high cost performance plays a critical role in building such a large scale system. Currently, torus-interconnected network like 6D-Torus possesses suitable properties for the petascale computer. However, the diameter within the torus-interconnected network is too long to achieve efficient global communication in the exascale computer. In addition, a direct connection method is not adaptive to the diverse characteristics of traffic. Here, we propose an architecture called Wormhole Optical Network (WON) for the exascale computer which is based on optical circuit switching. WON was designed to fully integrate into the electrical network of 6D-Torus. WON allows for the use of three novel technologies, namely the dynamic topology with optical links, algorithm of cross dimension order routing, and strategy of flow control for deadlock-free. We evaluated WON using both a prototype system and a simulator for the exascale computer. Our analysis shows that compared to the traditional electrical architecture, WON architecture reduced the time of data communication by 14–29% on exascale, a result obtained for a wide selection of diverse applications. Through enabling an SDN controller to adjust topology, WON maintains high utilization of optical links for inter-process communication from diverse applications. Further, we quantified WON’s flexibility of job deployment for mitigating hotspot traffic. We show that WON reduced latency by 20–35% in the large-range deployment and improved throughput by 30% in the long-distance deployment.

An optical packet metro architecture for Fixed Mobile Convergence in the cloud era

The present paper addresses future network architectures considered for Fixed Mobile Convergence, where users can access resources transparently either through fixed access technologies or through the mobile RAN. Optical technologies rely on Wavelength Division Multiplexing (WDM) to meet continuously growing bandwidth demands. However, although in the core network optical circuit switching may efficiently support huge traffic aggregates, closer to the access, in future Metropolitan Area Networks (MAN), it is necessary to provide a finer granularity, and a dynamical bandwidth control, to very heterogeneous traffic demands. This is supported by Optical Packet Switching (OPS) relying on WDM slotted Add/Drop Multiplexing (WSADM). A flow-based transfer mode, compatible with SDN control is first specified, and applied to bi-directional MAN rings. This mode is shown to provide several methods for supporting both local and global repair in case of failure. Mathematical models are derived to assess optical packet insertion performance and are used to illustrate how WSADM rings can support MAN performance requirements. Lastly the impact of locating the IP edge, and Data Centres closer to the users than in legacy architectures, within the MAN is addressed.

Traffic Pattern Adaptive Hybrid Electrical and Optical Switching Network for HPC System

As the performance requirements and scale of high-performance computing (HPC) systems grow rapidly, systems with such a large number of computing nodes present significant challenges in network architecture design because their peak performance is increasingly limited by communication rather than computation. Moreover, certain HPC application always shows some specific communication patterns, and different topologies have various performances with these patterns. To implement a traffic pattern adaptive HPC system, we propose a topology reconfigurable hybrid network architecture based on optical circuit switching (OCS), which could be adjusted into different classical topologies. And an algorithm of topology calculating and a permutation matrix-based optical switch configuration mechanism are proposed to construct network. We discuss network performances with limited OCS switches occupation, and results show that traffic pattern adaptive network improves the performance of latency and throughput to a large extent.

Simultaneous Wavelength and Format Conversions Based on the Polarization-Insensitive FWM in Free-Space Optical Communication Network

Free-space optical (FSO) network is an effective way to enhance the interoperability and improve the resource utilization of the FSO communication systems. Since the structure is relatively simple and the nodes are not so many, wavelength conversion-based optical circuit switching (WC-OCS) is an appropriate candidate for the FSO network to solve the blocking problem. Meanwhile, format conversion to lower the data rate is also necessary in case the atmospheric channel deteriorates. In this paper, we construct a 3-node FSO network and experimentally investigate the feasibility of simultaneous WC-OCS and format conversion based on straight-lined single-pump four-wave mixing (FWM) process. The biterror-ratio (BER) results of the on-off key, binary phase-shift keying (BPSK), and quadrature phase-shift keying (QPSK) signals show that comparing to the corresponding back-to-back (B2B) transmission at the reference BER level of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> , power penalties caused by WC-OCS are less than 1-dB for all the three formats. In the format conversion experiment from QPSK to BPSK, the power penalties, comparing to the original BPSK signal after B2B and WCOCS transmission, are also less than 1 dB at the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> reference BER level. Consequently the feasibility and practicability of the FWM-based optical signal processing at FSO network nodes are experimentally validated.

OMUX: Optical Multicast and Unicast-capable interconnection network for data centers

Exponential growth of traffic and bandwidth demands in current data center networks requires low-latency high-throughput interconnection networks, considering power consumption. By considering growth of both multicast and unicast applications, power efficient communication becomes one of the main design challenges in today's data center networks. Addressing these demands, optical networks suggest several benefits as well as circumventing most disadvantages of electrical networks. In this paper, we propose an all-optical scalable architecture, named as OMUX, for communicating intra-data centers. This architecture utilizes passive optical devices and enables optical circuit switching without any switch configuration or path reservation. In addition, it is customized for both unicast and multicast transmissions. It can replace aggregation and core switches in the network, to reduce power consumptions. Simulation results verify its lower latency, higher throughput, and reduced power consumption, compared to conventional electrical or alternative optical solutions.

Improving Performance of Optical Networks by a Probable Approach

Abstract Optical Burst Switching (OBS) networks are new emerging techniques that alternate Optical Circuit Switching (OCS) and Optical Packet Switching (OPS) techniques. The high bandwidth of fiber links in these networks, besides WDM (Wavelength Division Multiplexing) helps the Internet to handle the heavy traffic. OBS networks have an important issue that needs to be tackled. These networks are bufferless in their nature, so when two bursts are trying to reserve one wavelength one of them is dropped. This drop can be assumed as an indicator of congestion; as a result, the sending rate will be decreased, despite the fact that the network may not be congested. So, wired protocols like TCP (Transmission Control Protocol) cannot work to their high potential in OBS networks. In this paper, we propose a new scheme based on a probable approach that can distinguish burst drops caused by contentions from burst drops caused by contention, so we can improve the performance of the network. Extensive simulative studies show that the proposed algorithm outperforms TCP Vegas in terms of throughput and packet delivery count.