Elastic optical network for fragmented bandwidth allocation with limited slicers

Study and Analysis of Routing and Spectrum Allocation (RSA) and Routing, Modulation and Spectrum Allocation (RMSA) Algorithms in Elastic Optical Networks (EONs)

This paper focuses on the Routing and Spectrum Allocation (RSA) problem in Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) Elastic Optical Networks (EON) with consideration of transmission impairments. A majority of the literature in EON is based on improving the spectral efficiency and efficient utilization of available spectral resources. However, transmission impairments such as pass-band filter narrowing effect, shot noise and amplified spontaneous emission (ASE) beat noise products due to coherent detection and cross-talk in cross-connect (XC) etc. limit the unconstrained allocation of spectral resources. Thus, these transmission impairments may eventually become a barrier to the continuous resource allocation in EON. In this paper, we introduce a novel RSA technique with the transmission impairments in the coherent optical transport network, which we formulate as Transmission Impairments Aware RSA (TIA-RSA) problem. First, an optimal integer linear programming (ILP) for RSA is presented which minimizes delay-bandwidth product. Thereafter, a heuristic algorithm for large networks is also proposed. Our results indicate that the proposed heuristic algorithm yields close to optimal solution for low running times. We further propose an architecture for optical XC for EON.

Flexgrid technology is now considered to be a promising solution for future high-speed network design. In this context, we need a tutorial that covers the key aspects of elastic optical networks. This tutorial paper starts with a brief introduction of the elastic optical network and its unique characteristics. The paper then moves to the architecture of the elastic optical network and its operation principle. To complete the discussion of network architecture, this paper focuses on the different node architectures, and compares their performance in terms of scalability and flexibility. Thereafter, this paper reviews and classifies routing and spectrum allocation (RSA) approaches including their pros and cons. Furthermore, various aspects, namely, fragmentation, modulation, quality-of-transmission, traffic grooming, survivability, energy saving, and networking cost related to RSA, are presented. Finally, the paper explores the experimental demonstrations that have tested the functionality of the elastic optical network, and follows that with the research challenges and open issues posed by flexible networks.

Elastic optical network (EON) is considered as the platform for future optical transport networks. Routing and spectrum allocation (RSA) has a significant bearing on EON. Currently, researches tend to presume that RSA supports discrete or continuous rates. However, the approach of applying continues rates inevitably places a high burden on the management and implementation of EON. Contrastingly, discrete rates are static and could be misaligned with the demands of customers. We propose an EON that advertise continuous (any) rates, while in reality admitting a limited set of quantized levels. This approach redesigns the marketing strategy of EON services. We show how to quantize and map the continuous advertised rates into a limited set of quantized levels optimally, and with minimal effect. We use simulation to evaluate the different parameters impacting the continuous model and confirm the feasibility of the proposed model.

With the growing popularity of 5G mobile communications, cloud and fog computing, 4K video streaming, etc., population distribution and migration have increasing influence on traffic distribution in metro elastic optical networks (EONs). Traffic distribution is further diversified according to people's tendency to use network services in different places at different times. We use the term "tidal traffic" to represent traffic distribution with strong disequilibrium in the time and space dimensions. Note that tidal traffic can potentially result in low bandwidth utilization and weak service capability, as network resources are not allocated properly. To address this problem, in this study, we first analyze traffic characteristics of access networks and metro networks, and mathematically formulate an onion tidal traffic model (OTTM) in EONs. Second, based on the traditional routing and spectrum allocation (RSA) algorithm, which provides end-to-end connection by allocating frequency slot resources in EONs, we propose two algorithms to enhance bandwidth efficiency based on the OTTM model. We call them pre-detour RSA (PD-RSA) and pre-detour k-shortest paths RSA (PDK-RSA). Next, we analyze the shortcomings of a benchmark algorithm named min-hop k-shortest paths RSA (MHK-RSA) under tidal traffic, and compare PD-RSA and PDK-RSA with MHK-RSA via simulation. Simulation results show that PD-RSA and PDK-RSA can effectively reduce at least 26% and 18% of blocking probability, respectively, compared to MHK-RSA with the same time complexity.

Recent advances in physical layer optics have made slicing of optical bands into multiple subbands with different bandwidths possible. Due to this development, spectrum allocation has become easier in elastic optical networks (EONs). More specifically, owing to the slicing technology, the defragmentation problem in EONs can be addressed easily, i.e., more demands can be fit into empty spectrum slots by breaking the demands as needed using the slicing technology. This paper proposes a spectrum allocation scheme considering the slicing process at any nodes, e.g., source node and intermediate nodes, in EONs. Slicing-and-stitching technology is applied to break the contiguous-spectrum constraint in an EON so that spectrum fragmentation is reduced. While slicing a demand from one node to another, the following questions must be answered: (1) Which parts of the spectrum band should be sliced? (2) In which node(s) along the path of a demand should the slicings be done to reduce the bandwidth blocking rate? To answer the above questions, we formulate a mixed-integer linear programming (MILP) model that jointly addresses the above questions as well as minimizes the total number of slicers in a network. To measure the performance of the MILP, we used the bandwidth blocking ratio (BBR) of the network as a performance metric. Our results from the MILP show that introducing slicing at every node in the network improves the BBR by as much as 68% compared to a conventional case where slicing a demand is allowed only at the source node.

Bounds for two static optimization problems on routing and spectrum allocation of anycasting

On solving the capacitated routing and spectrum allocation problem for flexgrid optical networks

This work investigates the immediate reservation (IR), advance reservation (AR), malleable reservation (MR) service provisioning in elastic optical networks (EONs).We design request scheduling and/or routing and spectrum allocation (RSA) algorithms for the IR/AR/MR request, respectively. Simulation results show that the proposed IR/AR/MR service provisioning package can reduce request blocking probability effectively.

Elastic optical networks (EONs) can make service accommodation more flexible and precise by employing efficient routing and spectrum allocation (RSA) algorithms. In order to improve the efficiency of RSA algorithms, the advanced-reservation technique was introduced into designing RSA algorithms. However, few of these advanced-reservation-based RSA algorithms were focused on the unavailable spectrum resources in EONs. In this paper, we propose an Advanced-Reservation-based Invalid-Spectrum-Aware (AR-ISA) resource allocation algorithm to improve the networking performance and the resource alignment of EONs. By employing a new index, Invalid Spectrum Rate (ISR), to record the proportion of unavailable spectrum resources in EONs, the proposed AR-ISA algorithm set a network load threshold to trigger the postponement of an arriving service. Compared with the traditional slack-based AR mechanism, the proposed algorithm has more concerns about the current spectrum usage of the path designated by the service than the conflicts between AR services and other existing services. To further increase the networking performance, the proposed algorithm adopts defragmentation to increase the number of available spectrum resources when postponing a service. Theoretical analysis and simulation results show that the proposed AR-ISA algorithm has obvious effectiveness in reducing the service blocking rate and increasing the spectrum alignment rate.

Fragmentation assessment based on-line routing and spectrum allocation for intra-data-center networks with centralized control

In this paper, we compare performance of fixed-grid Wavelength Division Multiplexing (WDM) and Elastic Optical Networks (EONs) in dynamic provisioning of many-to-many (m2m) flows. Currently, with a growth of services relying on many-to-many communication paradigm such as distributed computing, inter-Data Center communication, content delivery networking or other requiring high-bandwidth in group communication, it is vital to deliver new solutions facilitating these demanding transmissions. Therefore, the authors investigate provisioning of m2m traffic in high-performance optical networks. This work focuses on dynamic Routing and Wavelength Assignment (RWA) problem in WDM networks as well as Routing and Spectrum Allocation (RSA) problem in EONs for m2m flows using replicated communication through auxiliary rendezvous servers.

O consumo energético nas redes de núcleo atualmente é impactado pelas aplicações de Bulk Data Transfer (BDT) entre os principais Centros de Dados (CDs) da Internet. Isso ocorre porque essas aplicações consomem a maior parte dos recursos disponíveis e o fazem por longos períodos de tempo. Devido ao aumento do tráfego na rede, que ocorre a cada ano, um dos principais desafios para os provedores de serviço em nuvem é a eficiência energética. Para servir à crescente demanda, o paradigma das Redes Ópticas Elásticas (EON) têm sido proposto com o objetivo de atender requisições com maior flexibilidade, aproveitando melhor o espectro de frequência. Este artigo propõe a solução Energy Efficient Aware-BDT in EON (EEABE), um algoritmo de Roteamento e Alocação de Espectro (RSA) ciente de eficiência energética para realizar BDT inter-CD (ICD), que é capaz de escalonar requisições BDT e implementar a técnica de sleep mode para reduzir o consumo energético dos elementos comutadores na rede óptica.

Penalty-method based impairment-aware performance of Elastic Optical Networks with spectrum conversion

In this work, novel metaheuristic algorithms are proposed to address the network coding (NC)-based routing and spectrum allocation (RSA) problem in elastic optical networks, aiming to increase the level of security against eavesdropping attacks for the network's confidential connections. A modified simulated annealing, a genetic algorithm, as well as a combination of the two techniques are examined in terms of confidentiality and spectrum utilization. Performance results demonstrate that using metaheuristic techniques can improve the performance of NC-based RSA algorithms and thus can be utilized in real-world network scenarios.