Routing, Modulation And Spectrum Assignment Algorithm Research Articles

A routing modulation and spectrum assignment algorithm for semi-filterless elastic optical networks

Development of 5G/F5G technology leads to massive applications accessing to backbone networks, which requires the backbone networks to be upgraded. Semi-filterless elastic optical network (semi-FEON) is a suitable technology to cheaply and gradually upgrade backbone networks. In semi-FEON, routing, modulation and spectrum assignment (RMSA) problem is one of the key issues. In this paper, we study the dynamic RMSA problem in semi-FEON and propose an RMSA algorithm. The algorithm includes three innovations: a K-shortest-subnet-paths (KSSP) algorithm is designed to search candidate paths in semi-FEON, a load-balancing-least-resources (LBLR) policy is introduced to re-sort the candidate paths, and a maximum-occupied-neighbors (MON) rule is proposed to assign spectrum resources to connection requests in semi-FEON. Simulation results show that the proposed KSSP-LBLR-MON algorithm outperforms the existing works in term of bandwidth blocking probability. Concretely, the improvement ratio is greater than 59.98% and 66.64% in German-Net and Henan-Net, respectively.

A Single–Multi-Path Combinatorial RMSA Algorithm with Least Resource Consumption in Semi-Filterless Optical Networks

Filterless optical networks (FONs) have become a cost-effective solution for optical network deployment due to their low-cost characteristics. However, eliminating active switching elements causes signals to propagate over unintended links, wasting spectral resources. Therefore, semi-filterless optical networks (Semi-FONs) have become a more cost-effective solution. This paper mainly studies the routing, modulation, and spectrum assignment (RMSA) problem in semi-filterless optical networks. It proposes a single–multi-path combination (LR-SMPC) RMSA algorithm with the least resource consumption. The algorithm first obtains the K shortest paths that satisfy the conditions according to the K short path (KSP) algorithm and re-orders the paths according to the resource consumption path re-ordering strategy, selecting the three paths that consume the least resources as the set of candidate paths. Then, based on the single–multi-path combination scheme of the set of candidate paths, the resource consumption of each scheme and the maximum number of available spectrum blocks for each path is calculated, from which the single path or multi-path with the least resource consumption is selected to serve the request. We perform simulation experiments on two network topologies using Poisson traffic models and compare them with existing single-path algorithms (S-P), fixed spectrum assignment granularity algorithms (g = 1), and adaptation spectrum assignment algorithms (g adaptation) to evaluate the performance of the proposed algorithm. The simulation results show that the proposed algorithm exhibits better performance in terms of both blocking rate and spectrum utilization.

A RMSA algorithm for semi-filterless optical networks based on minimum resource consumption and spectrum fragmentation

Semi-filterless optical networks (semi-FONs), a novel passive wide area network (WAN) solution, have attracted considerable attention. This paper investigates the dynamic routing, modulation and spectrum assignment (RMSA) problem in semi-FONs, where requests may propagate on unnecessary links due to the broadcast characteristics of semi-FONs, resulting in wastage of spectrum resources. Moreover, the dynamically setup and torn down of requests can lead to significant spectrum fragments. To address these issues, this paper studies semi-FONs based on two metrics: resource consumption M and fragmentation degree N. Resource consumption M refers to reducing spectrum wastage caused by broadcasting and establishing requests using minimal resources, while fragmentation degree N refers to the situation where the remaining available resources after establishing a request are more concentrated. Based on these metrics, we propose the Minimum Resource Consumption and Fragmentation Degree (Min-RCF) algorithm. We conduct simulation experiments on the German-Net and China’s Henan-Net network topologies, and the results demonstrate that the proposed Min-RCF algorithm achieves lower blocking probability and spectrum waste rate than the compared algorithms.

RMSA algorithms resilient to multiple node failures in dynamic EONs

In Elastic Optical Networks (EONs), the way different service demands are supported in the network is ruled by the Routing, Modulation and Spectrum Assignment (RMSA) algorithm, which decides how the spectrum resources of the optical network are assigned to each service demand. In a dynamic EON, demand requests arrive randomly one at a time and the accepted demands last in the network for a random time duration. So, one important goal of the RMSA algorithm is the efficient use of the spectrum resources to maximize the acceptance probability of future demand requests. On the other hand, multiple failure events are becoming a concern to network operators as such events are becoming more frequent in time. In this work, we consider the case of multiple node failure events caused by malicious attacks against network nodes. In order to obtain RMSA algorithms resilient to such events, a path disaster availability metric was recently proposed which takes into account the probability of each path not being disrupted by an attack. This metric was proposed in the offline variant of the RMSA problem where all demands are assumed to be known at the beginning. Here, we exploit the use of the path disaster availability metric in the RMSA of dynamic EONs. In particular, we propose RMSA algorithms combining the path disaster availability metric with spectrum usage metrics in a dynamic way based on the network load level. The aim is that the efficient use of the resources is relaxed for improved resilience to multiple node failures when the EON is lightly loaded, while it becomes the most important goal when the EON becomes heavily loaded. We present simulation results considering a mix of unicast and anycast services in 3 well-known topologies. The results show that the RMSA algorithms combining the path disaster availability metric with spectrum usage metrics are the best trade-off between spectrum usage efficiency and resilience to multiple node failures.

Temporal and Spectral 2D Fragmentation-Aware RMSA Algorithm for Advance Reservation Requests in EONs

In this paper, we explore the problem of routing, modulation and spectrum assignment (RMSA) for advance reservation (AR) requests in elastic optical networks (EONs), with the objective to further reduce the blocking probability and improve the spectrum utilization. On the one hand, we propose a minimum resource consumption routing policy (MRC) for leaving more free resources for future requests. On the other hand, we introduce a two-dimensional (2D) path resource model, in which each AR request can be transformed into a rectangle block whose length and width are related to request bandwidth and request duration respectively. Therefore, the spectrum assignment problem of AR requests is simplified to the two-dimensional rectangle packing problem. Furthermore, we design several factors to evaluate the two-dimensional fragmentation caused by a rectangle packing operation, where we consider the fragmentation situation in the rectangle block neighborhood for the first time. Based on these factors, we propose a two-dimensional fragmentation-aware spectrum assignment strategy (2D-FA). Through the combination of MRC and 2D-FA, we propose a novel RMSA algorithm named MRC-2D-FA for dynamically provisioning AR requests in EONs. Simulation results show that MRC-2D-FA can achieve lower bandwidth blocking probability and higher spectrum utilization compared with several well-performed benchmark algorithms.

RMSA algorithm for malleable-reservation requests in elastic optical networks

Abstract Elastic optical networking is a promising technology for the next generation of optical core networks and the routing, modulation and spectrum assignment (RMSA) problem is one of its key issues. The RMSA problems for immediately reservation (IR) and advance reservation (AR) requests have been widely researched. Malleable reservation (MR) requests are another kind of important traffics in elastic optical networks (EONs). However, the RMSA problem for MR requests has not been well considered. In this paper, we investigate the RMSA problem for MR requests in EONs and propose an algorithm named Min-RRD. The algorithm assigns frequency-time blocks with the minimum sum of three indexes, namely number of used resources ( R used ), number of impacted resources ( R impacted ) and distance to corner ( D corner ), to MR requests. Simulation results show that the proposed algorithm has a lower blocking probability and a smaller delay than the existing algorithm. Hence, it is a well-performed RMSA algorithm.

A Resource-Periodic-Arrangement Strategy for RMSA Problem in Elastic Optical Networks

Elastic optical networks (EONs), which can flexibly assign spectrum resources to connection requests, have become the most promising technology for the next generation of optical core networks. Routing, modulation and spectrum assignment (RMSA) problem is one of the key issues in elastic optical networks. In the RMSA problem, spectrum resources in links are generally divided into frequency slices and connection requests with different capacities can use different numbers of frequency slices to transfer their data; however, this may lead to misalignment of idle frequency slices in links and then result in the increase of blocking probability of connection requests. In this article, we propose a resource-periodic-arrangement (RPA) strategy. The strategy partitions frequency slices into periodically arranged standard frequency blocks and each connection request exactly uses one or more standard frequency blocks. The RPA strategy can effectively reduce the misalignment of frequency slices. Furthermore, an RPA-based RMSA algorithm is designed, in which an enhanced-most-used policy is adopted to choose standard frequency blocks to connection requests. Simulation results show that the RPA-based RMSA algorithm can distinctly reduce blocking probability of connection requests, comparing with existing algorithms.

A pre-split multi-flow RMSA algorithm in elastic optical networks

Abstract Elastic optical networking is a promising technology for the next generation optical networks, due to its flexibility of spectrum provisioning. Routing, modulation and spectrum assignment (RMSA) problem is one of the key issues in Elastic optical networks. In the problem, constraints of spectrum continuity and spectrum contiguity must be met, which limits the use of spectrum resources. Multi-flow measure, which splits a connection request into multiple flows if the connection request cannot be served as a whole, can relax the spectrum contiguity constraint. The existing multi-flow RMSA algorithms are post-split. In this paper, we propose a pre-split multi-flow RMSA algorithm, in which three innovative measures are adopted, namely partitioning frequency slices into standard blocks, pre-splitting connection requests into flows exactly using the standard blocks, and searching for available standard blocks for the flows with a proposed modified-most-used rule. The measures can make both the occupied and idle frequency slices aligned, so they are expected to lower the blocking probability of connection requests. Simulation results show that the proposed algorithm can get a better performance in term of blocking probability, comparing with three benchmarks.

A RMSA algorithm for elastic optical network with a tradeoff between consumed resources and distance to boundary

Abstract Elastic optical network (EON) has been a promising technology for the next generation of core transport networks, because it can support flexible spectrum assignment. Routing, modulation and spectrum assignment (RMSA) is one of the key issues in EON. In this paper, two indexes are considered during the spectrum assignment process, number of consumed resources R and distance to boundary I. Minimizing R means using the least resources to establish a connection while minimizing I implies that remainder idle resources are more lumped after a connection is established. Both of them can reduce blocking probability of network. However, optimizations of R and I are sometimes contradictory, so we propose three policies to make a tradeoff between them, which are R : I , I : R and R + I . The R : I policy takes R as the primary objective while the I : R policy sets I as the chief one; the R + I policy takes a linear combination α R + ( 1 - α ) I as the optimizing objective. Simulations are taken on the NSF-Net and UBN topologies, which show that the R + I policy can get the best performance in most cases. We further compare the R + I policy with two existing well-performed algorithms, the First-Last-Fit algorithm and the Block-Assignment algorithm. Simulation results reveal that blocking probability of the R + I policy is far less than that of the comparative objects.

Dynamic time and spectrum fragmentation-aware service provisioning in elastic optical networks with multi-path routing

Abstract In this paper, we propose a multi-path fragmentation-aware routing, modulation and spectrum assignment algorithm (RMSA) for advance reservation (AR) and immediate reservation (IR) requests in elastic optical networks. Immediate reservation requests should be provided with service immediately, while advance reservation requests have specific starting times and holding times. As lightpaths are set up and torn down, fragmentation may occur in both spectrum and time domains. To decrease the two-dimensional fragmentation and to solve the problem of resource scarcity, we propose splitting requests into different parts and transferring these parts along one or more paths utilizing sliceable bandwidth variable transponders. We first introduce a model to solve the problem and propose a two-dimensional fragmentation occurrence measurement in spectrum and time domains. Then we propose a multi-path fragmentation-aware RMSA algorithm (MPFA). Simulation results show that MPFA can achieve better performance than existing algorithms in terms of blocking probability and spectrum utilization.