Xiahe Liu

Efficient resource allocation for all-optical multicasting over spectrum-sliced elastic optical networks

Recently, optical orthogonal frequency-division multiplexing technology has attracted intensive research interest because spectrum-sliced elastic optical networks (EONs) can be constructed based on it. In this paper, we investigate how to serve multicast requests over EONs with multicast-capable routing, modulation level, and spectrum assignment (RMSA). Both EON planning with static multicast traffic and EON provisioning with dynamic traffic are studied. For static EON planning, we formulate two integer linear programming (ILP) models, i.e., the joint ILP and the separate ILP. The joint ILP optimizes all multicast requests together, while the separate ILP optimizes one request each time in a sequential way. We also propose a highly efficient heuristic that is based on an adaptive genetic algorithm (GA) with minimum solution revisits. The simulation results indicate that the ILPs and the GA provide more efficient EON planning than the existing multicast-capable RMSA algorithms that use the shortest path tree (SPT) and the minimal spanning tree (MST). The results also show that the GA obtains more efficient EON planning results than the separate ILP with much less running time, as it can optimize all multicast requests together in a highly efficient manner. For the dynamic EON provisioning, we demonstrate that the GA is also applicable, and it achieves lower request blocking probabilities than the benchmark algorithms using SPTand MST.

Joint defragmentation of optical spectrum and IT resources in elastic optical datacenter interconnections

With its agile spectrum management in the optical layer, the flexible-grid elastic optical network can become a promising physical infrastructure to efficiently support the highly dynamic traffic in future datacenter interconnections (DCIs). While the resulting elastic optical DCIs (EO-DCIs) need to serve requests that not only require bandwidth resources on fiber links but also require multidimensional IT resources in the DCs, multidimensional resource fragmentation can occur during dynamic network operations and deteriorate the network performance. To address this issue, this paper investigates the problem of joint defragmentation (DF) for the spectrum and IT resources in EO-DCIs. Specifically, we reoptimize the allocations of multidimensional resources jointly with complexity-controlled network reconfigurations. For the DFoperation, we first study the request selection process and propose a joint selection strategy that can perform the spectrum- and IT-oriented selections adaptively according to the network status. Then, we formulate a mixed integer linear programming model and design several heuristics to tackle the problem of network reconfiguration in the joint DF. The proposed algorithms are evaluated with extensive simulations. Simulation results demonstrate that the proposed joint DF algorithms can significantly reduce the blocking probability in EO-DCIs by consolidating the spectrum and IT resource usages effectively.

Design integrated RSA for multicast in elastic optical networks with a layered approach

In this paper, we incorporate a layered approach to design integrated multicast-capable routing and spectrum assignment (MC-RSA) algorithms for achieving efficient all-optical multicasting in spectrum-sliced elastic optical networks (EONs), which are based on the optical orthogonal frequency-division multiplexing (O-OFDM) technology. For each multicast request, the proposed algorithms decompose the physical topology into several layered auxiliary graphs according to the network spectrum utilization. Then, based on the requests bandwidth requirement, we select a proper layer and calculate a multicast light-tree within it. With these procedures, the routing and spectrum assignment (RSA) for each multicast request is done in an integrated way. We evaluate the proposed algorithms in simulations of static network planning and dynamic network provisioning. The simulation results demonstrate that compared to the existing MC-RSA algorithms, our approaches achieve more efficient network planning in terms of spectrum utilization, and provide lower blocking probabilities in network provisioning.

On the Spectrum-Efficient Overlay Multicast in Elastic Optical Networks Built with Multicast-Incapable Switches

We study overlay multicast (OL-M) in multicast-incapable elastic optical networks (EONs), and propose a spectrum-efficient OL-M scheme that relies on the spectrum-flexible member-only relay, i.e., OL-M-SFMOR. Our simulation results indicate that OL-M-SFMOR achieves significant improvements on the spectrum-efficiency of multicast in EONs, when compared with other multicast schemes, even including the all-optical multicast schemes in multicast-capable EONs.

Fragmentation-aware service provisioning for advance reservation multicast in SD-EONs.

In this paper, we study the service provisioning schemes for dynamic advance reservation (AR) multicast requests in elastic optical networks (EONs). We first propose several algorithms that can handle the service scheduling and routing and spectrum assignment (RSA) of AR multicast requests jointly, including an integrated two-dimensional fragmentation-aware RSA (2D-FMA) that can alleviate the 2D fragmentation caused by light-tree provisioning. Then, we leverage the idea of software-defined EONs (SD-EONs) that utilizes OpenFlow (OF) in the control plane to demonstrate and evaluate the proposed algorithms. Specifically, we build an SD-EON control plane testbed, implement the algorithms in it, and perform control plane experiments on dynamic AR multicast provisioning. The results indicate that 2D-FMA achieves the best blocking performance and provides the shortest average setup delay.

Impairment- and Splitting-Aware Cloud-Ready Multicast Provisioning in Elastic Optical Networks

It is known that multicast provisioning is important for supporting cloud-based applications, and as the traffics from these applications are increasing quickly, we may rely on optical networks to realize high-throughput multicast. Meanwhile, the flexible-grid elastic optical networks (EONs) achieve agile access to the massive bandwidth in optical fibers, and hence can provision variable bandwidths to adapt to the dynamic demands from the cloud-based applications. In this paper, we consider all-optical multicast in EONs in a practical manner and focus on designing impairment- and splitting-aware multicast provisioning schemes. We first study the procedure of adaptive modulation selection for a light-tree, and point out that the multicast scheme in EONs is fundamentally different from that in the fixed-grid wavelength-division multiplexing networks. Then, we formulate the problem of impairment- and splitting-aware routing, modulation and spectrum assignment (ISa-RMSA) for all-optical multicast in EONs and analyze its hardness. Next, we analyze the advantages brought by the flexibility of routing structures and discuss the ISa-RMSA schemes based on light-trees and light-forests. This paper suggests that for ISa-RMSA, the light-forest-based approach can use less bandwidth than the light-tree-based one, while still satisfying the quality of transmission requirement. Therefore, we establish the minimum light-forest problem for optimizing a light-forest in ISa-RMSA. Finally, we design several time-efficient ISa-RMSA algorithms, and prove that one of them can solve the minimum light-forest problem with a fixed approximation ratio.

Joint Spectrum and IT Resource Allocation for Efficient VNF Service Chaining in Inter-Datacenter Elastic Optical Networks

We study how to allocate spectrum and IT resources jointly for realizing efficient virtual network function (VNF) service chaining in inter-datacenter elastic optical networks. We first formulate an integer linear programming model to solve the problem exactly, and then a longest common subsequence-based heuristic is proposed. The simulation results indicate that the proposed algorithms can reuse the deployed VNFs efficiently and arrange the spectrum utilization in a much more load-balanced manner.

Joint Defragmentation of Spectrum and Computing Resources in Inter-Datacenter Networks over Elastic Optical Infrastructure

In this paper, we consider to apply a joint defrag-mentation (DF) of spectrum and computing resources in the inter-datacenter (inter-DC) networks built over elastic optical infrastructure based on the optical orthogonal frequency-division multiplexing (O-OFDM) technology. We propose joint DF algorithms that consist of a request selection strategy to select active requests for reconfiguring and an anycast-based DF routing and spectrum assignment (DF-RSA) to reconfigure the selected requests. For the joint DF, two request selection strategies and three anycast-based DF-RSA schemes are designed, and their combinations are evaluated with simulations. The simulation results show that by considering the usages of spectrum and computing resources jointly, the proposed algorithms can improve the blocking performance of the inter-DC network significantly with controlled numbers of DF operations.

Spectrum- and Energy-Efficient Multicasting over Multicast-Incapable EONs with Member-Only Flexible Relay

We propose to enable multicast in elastic optical networks that only have multicast-incapable nodes by using member-only flexible relay. Compared with the traditional overlay multicast, the proposed scheme can be spectrum- and energy-efficient.