Experimenting with bandwidth-variable routing and signaling on a large-scale ASON test-bed

Bandwidth-variable (BV) optical networks have been proposed as a novel technology to provide spectrum-efficient transportation. In order to study the performance of the BV optical networks, we propose a BV extension to RSVP-TE signaling protocol and implement it with different routing schemes on our large-scale ASON test-bed. Results show that the adaptive routing (AR) combined with forward reservation RSVP-TE signaling (AR+RSVP-fBV) scheme has lower routing blocking probability; however, since its signaling blocking probability is higher than the fixed routing (FR) combined with backward reservation RSVP-TE signaling (FR+RSVP-bBV) scheme, it has no significant advantage in the overall blocking performance, especially in a highly dynamic network scenario. The introduction of spectrum conversion cannot improve the overall blocking performance significantly due to its higher signaling blocking probability, and worse yet, it increases setup delay.     

Exact performance analytical model for spectrum allocation in flexible grid optical networks

Dynamic flexible grid optical networks have gained much attention because of the advantages of high spectrum efficiency and flexibility, while the performance analysis will be more complex compared with fixed grid optical networks. An analytical Markov model is first presented in the paper, which can exactly describe the stochastic characteristics of the spectrum allocation in flexible grid optical networks considering both random-fit and first-fit resource assignment policies. We focus on the effect of spectrum contiguous constraint which has not been systematically studied in respect of mathematical modeling, and three major properties of the model are presented and analyzed. The model can expose key performance features and act as the foundation of modeling the Routing and Spectrum Assignment (RSA) problem with diverse topologies. Two heuristic algorithms are also proposed to make it more tractable. Finally, several key parameters, such as blocking probability, resource utilization rate and fragmentation rate are presented and computed, and the corresponding Monte Carlo simulation results match closely with analytical results, which prove the correctness of this mathematical model.     

ACO-based routing and spectrum allocation in flexible bandwidth networks

Optical networks with flexible bandwidth provisioning are a very promising networking architecture. It enables efficient resource utilization and supports heterogeneous bandwidth demands. In this paper, we focus on the dynamic routing and spectrum allocation (RSA) problem which emerges in such networks and propose a novel dynamic RSA algorithm by means of ant colony optimization (ACO). In our proposed algorithm, ants are launched to modify the routing table according to the length and the spectrum fragmentation information along the path. A simulation study is performed considering five algorithms in terms of blocking probability: WDM-based RWA approach, KSP-based RSA approach, Slot-based RSA algorithm, and our proposed ACO-based RSA approach. We then compare the deterioration degree of blocking probability by adding more types of line rate. Simulation results indicate that our proposed ACO-based RSA approach achieves lower blocking probability, complexity, and higher adaptability to more line rates mixture.     

Dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes

The wavelength selective switch-based reconfigurable optical add/drop multiplexers is a promising switching equipment for future reconfigurable wavelength-division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment problem. In an asymmetric switching scenario, using the classic Dijkstra’s algorithm can lead to invalid paths traversing unconnected ports of an asymmetric node. To solve this problem, we propose both link-state (LS) and distance vector (DV) schemes for dynamic lightpath provisioning in optical WDM mesh networks with asymmetric nodes. The proposed LS schemes include the asymmetric switching-aware (ASA) Dijkstra’s algorithm, the $K$ -shortest path-based algorithm, and the entire path searching (EPS) algorithm. Simulation results show that the ASA-Dijkstra’s algorithm will bring notable improvement of the blocking performance with low computational complexity, while the EPS algorithm has much higher complexity and is not suitable to be employed in large-scale networks. On the other hand, our proposed DV solution, i.e., the information diffusion-based routing (IDBR), can achieve the lowest blocking probability with the lowest computational complexity. Moreover, IDBR does not require the distribution of local asymmetric switching information like the LS schemes, thus having a high level of topology confidentiality.     

An efficient hybrid protection scheme with shared/dedicated backup paths on elastic optical networks

Fast recovery and minimum utilization of resources are the two main criteria for determining the protection scheme quality. We address the problem of providing a hybrid protection approach on elastic optical networks under contiguity and continuity of available spectrum constraints. Two main hypotheses are used in this paper for backup paths computation. In the first case, it is assumed that backup paths resources are dedicated. In the second case, the assumption is that backup paths resources are available shared resources. The objective of the study is to minimize spectrum utilization to reduce blocking probability on a network. For this purpose, an efficient survivable Hybrid Protection Lightpath (HybPL) algorithm is proposed for providing shared or dedicated backup path protection based on the efficient energy calculation and resource availability. Traditional First-Fit and Best-Fit schemes are employed to search and assign the available spectrum resources. The simulation results show that HybPL presents better performance in terms of blocking probability, compared with the Minimum Resources Utilization Dedicated Protection (MRU-DP) algorithm which offers better performance than the Dedicated Protection (DP) algorithm.     

Accounting for Shared Regenerators in GMPLS-Controlled Translucent Optical Networks

In translucent optical networks, the usage of sparse opto-electronic regenerators permits to overcome optical signal quality degradations. In dynamic translucent optical networks, where lightpaths are established upon request, regenerators can be effectively time shared. However, the current generalized multiprotocol label switching (GMPLS) protocol suite does not consider how to dynamically reserve and release shared regenerators and how to distribute regenerator availability information to network nodes. In this paper, four Translucent Lightpath Dynamic Provisioning (TLDP) schemes are proposed to establish lightpaths in dynamic distributed translucent optical networks. TLDP schemes differently combine the utilization of specific open shortest path first-traffic engineering (OSPF-TE) or resource reservation protocol-traffic engineering (RSVP-TE) extensions and shared regenerator availability information. Simulation results show that TLDP scheme based on OSPF-TE extensions obtains lower lightpath setup time, but higher control plane load than TLDP schemes based on RSVP-TE extensions. Moreover, schemes based on RSVP-TE extensions or on OSPF-TE extensions obtain the same lowest blocking probability.      

Differential evolution optimization applied to the routing and spectrum allocation problem in flexgrid optical networks

Flexible optical network (FON) architectures are considered a very promising solution where spectrum resources are allocated within flexible frequency grids. Routing and spectrum allocation (RSA) in FON is an NP-complete problem. So far, this problem has been optimally solved for small instances with integer linear programming and has been suboptimally solved for more realistic instances by heuristic strategies. In this paper, we introduce the application of differential evolution (DE) to the off-line RSA problem in flexible optical networks. To the best of our knowledge, our work is the first application of a DE algorithm to the RSA problem. We develop two DE permutation-based algorithms named DE general approach (DE-GC) and DE relative position index (DE-RPI). Comparative studies show that in many cases, DE outperforms many other well-known evolutionary computational approaches. Furthermore, the method typically requires few control parameters. An illustrative example of the application of the DE-based algorithms is presented, and then, different heuristics are compared against the DE-RSA algorithms. Algorithms are evaluated in different test bench optical networks, such as the NSFnet and the European optical network, and for networks up to 40 nodes, such as the USA and Japan networks. Moreover, the DE-based algorithms save up to 37 % of spectrum utilization for the NSFnet and 13 and 15 % for the USA and Japan networks, respectively.     

波分复用光网中的一种新型波长分配算法

目前网络承载业务的趋势是以IP为中心的数据业务,从而促进了以WDM光网络向高速和宽带多波长的应用和普及,为了进一步提高网络的性能并提高资源利用率,出现了光网络控制面技术.路由选择与波长分配问题是WDM光传输网络控制面中非常重要的问题之一.目前实际应用最广泛的波长分配算法是First-Fir(FF)算法.本文基于FF算法,研究动态业务下波分复用光网络在固定选路下的波长分配问题,提出了一种新的波长分配启发式算法——Joint First Fit.计算机仿真试验表明,与常用的FF算法相比,该算法显著的降低了网络呼叫阻塞率,有利于提高网络资源的利用率.     

Routing pre-configuration for fast and scalable path restoration in DWDM networks

In high-speed WDM optical networks, failure recovery is a critical issue as a single element failure in the network will result in the interruption of multiple services. Distributed path restoration is preferable for its high flexibility and efficient resource utilization. However, with the development and maturity of Dense Wavelength Division Multiplexing (DWDM) technology, the resource contention problem arises when simultaneously restoring a large amount of services initiated from many uncoordinated source nodes. This will degrade network performance and result in long service recovery latency. In this paper, we present the Routing Pre-Configuration (RPC) scheme for fast and scalable path restoration in DWDM networks, where pre-failure configuration and post-failure signaling are demonstrated. We compare it with the previous contention resolution approaches and the simulation results prove its improvement in restoration blocking probability and average restoration time.     

大规模异构光网络智能组网技术与实验演示环境(英文)

A novel routing architecture named DREAMSCAPE is presented to solve the problem of path computation in multi-layer, multi-domain and multi-constraints scenarios, which includes Group Engine (GE) and Unit Engine (UE). GE, UE and their cooperation relationship form the main feature of DREAMSCAPE, i.e. Dual Routing Engine (DRE). Based on DRE, two routing schemes are proposed, which are DRE Forward Path Computation (DRE-FPC) and Hierarchical DRE Backward Recursive PCE-based Computation (HDRE-BRPC). In order to ...