Maximizing Primary Capacities in Survivable Networks

One of the major challenges for optical network operators is related to realizing profitable networks that preserve the overall satisfaction of their end customers. This necessitates ensuring a controlled network resource usage while decreasing connection blocking probability. However, optical networks are witnessing the introduction of an increasing number of new services, each having different requirements. As such, the evolution towards resource efficient connection setup management strategies that provide differentiated call-blocking probability becomes inevitable. Building on the previous observation, we propose in this paper a novel connection setup management strategy. This latter aims to differentiate the blocking probability among different classes of lightpath requests, while avoiding the starvation of the lower class lightpaths. The main idea behind our proposal is to privilige higher class lightpaths via preemption and to protect the lower class lightpaths through rerouting. In this manner, the proposed strategy serves the double objective of minimizing the overall connection blocking probability and of realizing quality of service (QoS) differentiation. The previous claim is asserted through our simulation results that gauge the main benefits behind our proposed connection setup strategy. The simulation results drawn from the National Science Foundation Network (NSFNET) and the European Optical Network (EON) show that the proposed strategy achieves both differentiated and low blocking probabilities.

In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection. The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables, so that the route for a connection request can be determined promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability. The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm very attractive for both the optical circuit switching networks and future optical burst switching networks

Group replica caching scheme for optical grid networks

The number of users and data packets has increased in 4G cellular networks. Therefore, 4G cellular network providers suffer from the network capacity problem. In order to solve this problem, femtocell concept is suggested. It can reduce the coverage hole and enhance the QoS. However, only small number of femtocells experience the large amount of loads. To solve this problem, Mobility Load Balancing (MLB) algorithm is suggested, which is a kind of load balancing algorithm. To distribute the traffic load, MLB algorithm modifies the handover region. If the handover region is reduced by MLB algorithm, some cell edge users are compulsively handed over to neighbor femtocell. In this paper, we analyze the relation between MLB performing period and performance indicators. For example throughput and blocking probability is reduced, if period is decreased. On the contrast, if period is increased, the number of handover frequency is decreased. Using this relation, we suggest the adaptive periodic MLB algorithm. This algorithm includes the advantage of both long period and short period MLB algorithm, such as high throughput, the small number of handover frequency, and low blocking probability.

A reliability analysis of Double-Ring topologies with Dual Attachment using p-cycles for optical metro networks

Resiliency to link failures in optical networks is becoming increasingly important due to the increasing data rate in the fiber. Path protection schemes attempt to guarantee a backup path for a connection upon a failure in the network, thereby reducing the recovery time for a connection. In this paper, we develop a failure dependent path protection scheme that dynamically assigns a primary path and backup paths, one for each failure that would affect the primary path. A connection established on the primary path will be re-established on its backup path only if a failure in the network affects the connection. We evaluate the performance of our developed protocol and compare with an alternative approach based on sub-graph routing that achieves high network utilization and low blocking probability at the cost of re-establishing connections even if the failure in the network does not affect the primary path of the connection. We observe that up to a factor of eight reduction in the number of reconfiguration scenarios is achieved with less than 10% reduction in effective network utilization and less than 3% reduction in fairness metrics for tolerating any single link failure in NSFNET and ARPA-2 networks. The failure dependent protection approach developed in this paper is also applicable to any general failure scenarios that are modeled as shared risk link group failures.

Protection Techniques using Resource Delayed Release for SDN-based OTN over WDM Networks

One of the most important performance measurements in wavelength-division multiplexing (WDM) networks is the call blocking probability. In this paper, we present an approximate analytical method to evaluate the blocking probabilities in survivable WDM networks with dynamically arriving connection requests. Our approach utilizes the wavelength independence whereby WDM network can be regarded as an aggregation of disjoint single wavelength sub-networks with a common physical topology. In each single wavelength sub-network, we derive the calculation of the blocking probability from an exact analysis. We assume dedicated protection with fixed routing and either first-fit or random wavelength assignment. Simulation results demonstrate the accuracy of the proposed method.

<p>Recently, an upsurge of interest has been observed in providing multimedia on-demand (MoD) services to mobile users over wireless networks. Nevertheless, due to the rapidly varying nature of mobile networks and the scarcity of radio resources, the commercial implementation is still limited. This paper presents an efficient group-based multimedia-on-demand (GMoD) service model over multicast-enabled wireless infrastructures, where users requesting the same content are grouped and served simultaneously with a single multicast stream. The grouping is fulfilled through a process named "batching". An analytical model is derived to analyse a timeout-based hatching scheme with respect to the tradeoff between user blocking probability and reneging probability. Based on the deduced analytical model, an optimal timeout-based hatching scheme is proposed to dynamically identify the optimal tradeoff point that maximizes the system satisfaction ratio given a particular system status. The proposed scheme is evaluated by means of simulation and compared with two basic hatching schemes (timeout-based, size-based), and two hybrid ones (combined-for-profit, combined-for-loss). The simulation results demonstrate the proposed approach can ensure significant gains in terms of user satisfaction ratio, with low reneging and blocking probabilities.</p>

Vertically stacked optical banyan (VSOB) networks are attractive for serving as optical switching systems due to the desirable properties (such as the small depth and self-routing capability) of banyan network structures. Although banyan-type networks result in severe blocking and crosstalk, both these problems can be minimized by using sufficient number of banyan planes in the VSOB network structure. The number of banyan planes is minimum for rearrangeably nonblocking and maximum for strictly nonblocking structure. Both results are available for VSOB networks when there exist no internal link-failures. Since the issue of link-failure is unavoidable, we intend to find the minimum number of planes required to make a VSOB network nonblocking when some links are broken or failed in the structure. This paper presents the approximate number of planes required to make a VSOB networks rearrangeably nonblocking allowing link-failures. We also show an interesting behavior of the blocking probability of a faulty VSOB networks that the blocking probability may not always increase monotonously with the increase of link-failures; blocking probability decreases for certain range of link-failures, and then increases again. We believe that such fluctuating behavior of blocking probability with the increase of link failure probability deserves special attention in switch design.  Keywords: Banyan networks; Blocking probability; Switching networks; Vertical stacking; Link-failures. © 2009 JSR Publications. ISSN: 2070-0237(Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i1.1070

A resource-efficient provisioning framework (RPF) is proposed in this paper for optical networks providing dedicated path protection (DPP) and shared path protection (SPP) services. The framework reduces resource consumption by considering spare capacity reservation of DPP and SPP cooperatively while provides 100% survivability guarantee and maintains the recovery time for both protection types against the predominant single link failures. To tackle the service provisioning problem under the framework, an integer linear programming (ILP) formulation is presented to find the optimal routing solution for a given set of traffic demands. The objective is to minimize total capacities consumed by working and backup paths of all demands. Then, heuristics are developed for on-line routing under dynamic change of traffic. Numerical results show that compared with traditional provisioning framework (TPF), the RPF has the following advantages: (1) Over 10% capacity savings are achieved for static service provisioning; (2) blocking probability of both protection types is greatly reduced; (3) lower resource over build is achieved; and (4) average backup-path hop distance of shared-path-protected flows is reduced. Finally, network survivability in face of double link failures is discussed under the framework.

The weaknesses of the Internet led to the creation of a new network paradigm – network virtualization. Virtualization is a very successful technique for sharing and reusing resources, which results in higher efficiency. Despite its advantages, including flexibility in network architecture, virtualization imposes many challenges, such as physical resource allocation to virtual devices. An efficient allocation strategy for these resources can ensure good Quality of Service (QoS) in virtual networks, whether in node or link failure events. This paper presents a conflict-free rerouting scheme with efficient additional capacity usage for link and node failure resilience in a virtual network using switches. Combining an IP Fast Rerouting approach and flow-splitting strategy, this scheme provides short reaction time, stable performance and low complexity because the rerouting calculation and configuration are performed in advance. We show that rerouting by traffic splitting based on the entering arc and destination is sufficient to address all link-failure situations in the network, assuming that the network is two-link connected. After modelling the dimensioning problem as an Integer Linear Programme, we demonstrate through practical implementation of our rerouting scheme on different networks that the scheme can substantially minimize the additional capacity draw on the substrate network. A solution using multiple virtual planes is also provided to solve several conflict problems in the case of simultaneous multiple link failures.

Solving an integrated production and transportation problem (IPTP) is a very challenging task in semiconductor manufacturing with turnkey service. A wafer fabricator needs to coordinate with outsourcing factories in the processes including circuit probing testing, integrated circuit assembly, and final testing for buyers. The jobs are clustered by their product types, and they must be processed by groups of outsourcing factories in various stages in the manufacturing process. Furthermore, the job production cost depends on various product types and different outsourcing factories. Since the IPTP involves constraints on job clusters, job-cluster dependent production cost, factory setup cost, process capabilities, and transportation cost with multiple vehicles, it is very difficult to solve when the problem size becomes large. Therefore, heuristic tools may be necessary to solve the problem. In this paper, we first formulate the IPTP as a mixed integer linear programming problem to minimize the total production and transportation cost. An efficient genetic algorithm (GA) is proposed next to tackle the problem when it becomes too complicated. The objectives are to minimize total costs, where the costs include production cost and transportation cost, under the environment with backup capacities and multiple vehicles, and to determine an appropriate production and distribution plan. The results demonstrate that the proposed GA model is an effective and accurate tool.

The widespread deployment of wireless telecommunication networks and growing Internet traffic globally leads to a substantial increase in signal traffic demands in fiber optic networks. This demand surge places significant pressure on the survivability of optical networks, specifically when faced with fiber cable failures that prevent failed optical fibers from satisfying connection requests. To address this challenge, in this paper, we consider integrated planning of regenerator installation, optical connection routing, and wavelength assignment (RWA) for wavelength division multiplexing (WDM) optical networks under link failures. To the best of our knowledge, we are the first to consider such an integrated problem. We minimize the number of backup regenerators required to fulfill all connection requests under all potential link failures while accounting for the wavelength and routing constraints. We formulate the problem as an integer program, while its size exponentially increases with the network size by nature. To solve large-scale instances for practical uses in the industry, we propose efficient algorithms to generate near-optimal solutions that are practically implementable. We perform extensive numerical experiments to demonstrate the effectiveness of our approach in solving real-world instances provided by our industry partners. The results show that our approach can efficiently obtain high-quality solutions while ensuring a minimal increase in backup regenerators as the network grows. Our solutions also offer valuable insights into planning a cost-effective and reliable fiber optic network for network operators.

Protected working capacity envelope concept has been proposed to simplify network management and operation in survivable WDM networks. Dynamic lightpath provisioning within working capacity envelope is only required to perform shortest path routing algorithm. Based on PWCE concept, we propose an efficient approximation approach, called Lagrangean relaxation with binary exponential reduction heuristics (LBER), aimed, to resolve the routing and capacity assignment (RCA) problem in survivable WDM networks to protect any single link failure. The task is first formulated as a mixed integer non-linear optimization problem in which the bottleneck link blocking probability for call setup is to be minimized. By sequentially solving a series of Lagrangean relaxation problems, the range of uncertainty of target blocking probability is reduced by half between the solutions of two adjacent problems such that the near optimal solution can be obtained in short time. We conduct a performance study on the proposed algorithms under different parameter settings. We further draw comparisons between LBER and a minimum working hop heuristic approach via experiments over two well known benchmark networks. Numerical results demonstrate that LBER outperforms minimum working hop approach for networks with both uniform and non-uniform demand distributions.