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Due to the emergence of high-bitrate application, the cross stratum optimization (CSO) using the path computation element (PCE) has recently stimulated the interest by network operators. With large-scale growth and high complexity of optical transport networks, especially deploying with data centers, how to realize CSO more effectively, accurately and practically will become the research focus. Based on our previous works about the CSO, this paper presents a CSO-oriented software defined multi-domain and multi-layer optical transport networks (SDMOTN) architecture deploying with data centers. The proposed architecture can enable joint optimization of optical networks and application stratum resources, and enhance the service accommodation and the data center responsiveness to end-to-end service demands. Moreover, a novel dynamic global load balancing strategy (DGLB) with dynamic resource rating method for CSO is presented based on the proposed architecture. The overall feasibility and efficiency of the SDMOTN architecture with DGLB strategy are experimentally demonstrated and quantitatively compared with four strategies by experiments on our optical as a service (OaaS) testbed with 1000 virtual nodes. [ABSTRACT FROM AUTHOR]

In response to the need for high bandwidth and power efficient data center interconnection networks, different interconnects have been proposed based on the optical technology used: micro-electromechanical system (MEMS), optical cross connects (OXCs), arrayed waveguide grating routers (AWGRs) and semiconductor optical amplifier (SOAs). MEMS switches are based on mature technology, have low insertion loss and cross-talk, and are data rate independent. They are also the most scalable and the cheapest class of optical switches. However, the reconfiguration time of these switches is of the order of tens of milliseconds while fast optical switches have switching time in the range of a few nanoseconds. Fast optical switches can be based on AWGRs in conjunction with tunable wavelength converters or tunable lasers or they are based on SOAs in broadcast-and-select architecture. In this paper, we propose an optical interconnect architecture for the large scale data centers. The proposed interconnect: Hybrid Optical Switch Architecture (HOSA) is a hybrid design that features slow and fast optical switches. The hybrid design leverages strengths of both types of optical switches. To reduce complexity, we employ a single stage core topology that can be easily scaled up (in capacity) and scaled out (in the number of racks) without requiring major re-cabling and network reconfiguration. We investigate the scalability of the HOSA and show that by using a single stage core topology, it can be scaled to a hundreds of thousands of servers. We also investigate a trade-off between cost and power consumption of our design by comparing it with other well-known interconnects by using analytical modelling. We demonstrate power efficiency as compared to other conventional interconnects on account of upfront CAPEX but the additional CAPEX incurred in deploying our solution instead of traditional architecture is mitigated to some extent by reduced OPEX, due to its greater energy efficiency. We evaluate the performance of the system using network-level simulation by considering diverse workload communication patterns and system design parameters. Our results show low latency and high throughput with different workload communication patterns. [ABSTRACT FROM AUTHOR]

Inter-datacenter networks (Inter-DCNs) and Intra-datacenter networks (Intra-DCNs) are entirely different in communication scales, architecture topologies and sizes, and characteristics of traffic flows. An Inter-DCN is built upon the existing Internet backbone with a fixed mesh topology and is hence difficult to accommodate any physical update or change without significant human intervention. Several core nodes of the backbone network are connecting to Intra-DCNs forming the so-called datacenter (DC) nodes. Different Inter-DCN or Intra-DCN architectures imply different network constructions overhead. An optimized combination of Inter-DCN and Intra-DCN architecture is expected to minimize the construction complexity and cost of DCNs while maintaining efficient network performance. However, research work in this important area has received little attention. In this paper, we study the construction of integrated Inter- and Intra- datacenter networks (integrated-DCN). Specifically, by taking advantages of different optical switching technologies and embedding the new control technology of software defined networking (SDN) in the control plane of integrated-DCN, novel cost-effective DCN architecture will be developed. For the proposed integrated architecture, the important characteristic of traffic asymmetry is investigated and accommodated by developing asymmetric network configuration based on SDN-assisted traffic monitoring/prediction, and the issue of network survivability/availability is explored and addressed by taking into consideration of the unique feature of DCN traffic. [ABSTRACT FROM AUTHOR]

Data centers provide a volume of computation and storage resources for cloud-based services, and generate very huge traffic in data center networks. Usually, data centers are connected by ultra-long-haul WDM optical transport networks due to its advantages, such as high bandwidth, low latency, and low energy consumption. However, since the rigid bandwidth and coarse granularity, it shows inefficient spectrum utilization and inflexible accommodation of various types of traffic. Based on OFDM, a novel architecture named flexible grid optical network has been proposed, and becomes a promising technology in data center interconnections. In flexible grid optical networks, the assignment and management of spectrum resources are more flexible, and agile spectrum control and management strategies are needed. In this paper, we introduce the concept of Spectrum Engineering, which could be used to maximize spectral efficiency in flexible grid optical networks. Spectrum Defragmentation, as one of the most important aspect in Spectrum Engineering, is demonstrated by OpenFlow in flexible grid optical networks. Experimental results are reported and verify the feasibility of Spectrum Engineering. [ABSTRACT FROM AUTHOR]

With the rapid development of cloud computing, optical inter-datacenter (inter-DC) networks have attracted intensive research attentions. Meanwhile, recent advances on the flexible-grid elastic optical networks (EONs) have demonstrated agile spectrum management in the optical layer. Therefore, we expect EONs to become a promising underlying infrastructure for optical inter-DC networks. In this paper, we investigate offline and online routing and spectrum assignment (RSA) problems for anycast requests in elastic optical inter-DC networks. For the offline problem, we formulate an integer linear programming (ILP) model and propose several heuristics based on single-DC destination selection. The optimal solutions for small-scale problems are obtained by solving the ILP, and we compare them with those from the heuristics for measuring the optimization gaps. For the online problem, we design several heuristics to consider the computing and bandwidth resources jointly for efficient service provisioning, including an algorithm that uses multi-DC destination selection. Our simulation results demonstrate that the anycast algorithm with multi-DC destination selection can fully utilize the bandwidth resources in the elastic optical inter-DC network, make computing resources become the bottleneck, and reduce the bandwidth blocking probability of anycast requests effectively. [ABSTRACT FROM AUTHOR]

As is well known, elastic optical network is quite attractive due to its great spectral efficiency and flexibility, which can allocate appropriate size spectrum based on efficient modulation modes such as Orthogonal Frequency Division Multiplexing (OFDM) modulation, etc. These characters are able to better meet the needs of the intra-data-center optical interconnection. To properly analyze and operate elastic optical networks with highly dynamic traffic of the intra-data-center, considering the continuity constraint and the contiguity constraint, efficient methods are required for the on-line routing and spectrum allocation (RSA) issue. In this paper, we propose two methods (AFD and CSL) for assessing the status (spectrum fragmentation) of the network, and present two algorithms (BSPR and HSR) which use the proposed assessment value to perform on-line RSA applied to intra-data-center networks which adopt the Software-Defined Network (SDN) control mode. Simulation results reveal that the proposed approaches allow solving the on-line RSA problem more efficiently with lower blocking probability of the networks. [ABSTRACT FROM AUTHOR]

Abstract: Valiant load balancing (VLB) network has been proposed as a capacity-efficient solution to handle highly dynamic traffic in future backbone networks. In this paper, we study the availability of VLB networks that are overlaid over an optical infrastructure. The main challenges in such a context arise from the unique routing and protection scheme that goes beyond the definition of conventional connection-level service availability as well as the logical link failure correlation that prohibits the use of traditional analytical methods. We propose a network-level availability model to compute the probability that a VLB network is congestion-free under all traffic patterns. Numerical results show that with a proper truncation level, our calculation on availability can be accelerated significantly by generating tight lower and upper bounds. Our main finding is that physical link sharing in a two-layer setting degrades the network availability drastically by several orders of magnitude due to the full mesh requirement for VLB networks, and may remove the capacity efficiency advantage of VLB networks. [Copyright &y& Elsevier]