Group replica caching scheme for optical grid networks

In optical grid networks, data files for job execution are replicated at multiple sites in order to distribute loads and achieve high performance computing. Those replicas are downloaded in parallel in order to reduce downloading time. Furthermore, each replica is downloaded with multiple wavelengths. Although parallel and multi-wavelength downloading reduce downloading time, they raise blocking probability of file downloading. This is because they use a lot of wavelength resources and thus often generate bottleneck links. To resolve this problem, this paper proposes a parallel and multi-wavelength downloading scheme for optical grid networks. The proposed scheme provides replica selection, route selection, and wavelength selection for parallel and multi-wavelength downloading. In the proposed scheme, clients dynamically select combinations of a replica, a route, and a wavelength in such a way that they suppress the generation of bottleneck links. Through simulation experiments, we show that the proposed scheme efficiently improves blocking probability of parallel and multi-wavelength downloading.

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

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.

Minimum link and boundary distance spectrum assignment algorithm based on adaptive modulation scheme in semi-filterless optical networks

Achieving low blocking probability and connection restorability in the presence of a link failure is a major goal of network designers. Typically fault tolerant schemes try to maintain low blocking probability by maximizing the amount of primary capacity in the network. In this chapter, we assume the total capacity on each link is fixed, and then it is allocated into primary or backup capacity. The distribution of primary capacity affects blocking probability for dynamic traffic. This can be seen by simulating dynamic traffic with different ways to distribute capacities in a network. A Hamiltonian p-cycle is a capacity optimal way of allocating primary and backup capacity. However, different Hamiltonian p-cycle may deliver different blocking probability for dynamic traffic. In general, more evenly distributing the backup and primary capacity lowers the blocking probability. This chapter provides upper bounds on how much primary capacity a network can provide if it uses a link based protection strategy to guarantee survivability for one or more link failures. Using integer linear programs we show that requiring preconfiguring carries a cost in terms of capacity if the solution is structured as a set of cycles.

In order to find out the tradeoff between recovery time and resource overhead when a link failure occurs, we propose a software-defined based fast restoration scheme for elastic optical datacenter networks, called precomputation based restoration path (P-RP). By extending the controller functionality and OpenFlow protocol in software defined networking (SDN) technology, we establish a novel elastic optical inter-datacenter network architecture which can quickly and accurately converge the network state information with a global view for failure recovery. Based on this architecture, the P-RP performs path computation and bandwidth resource selection for restoration before a failure occurs. The experimental results demonstrate that the proposed scheme can achieve fast recovery with low blocking probability while maintaining high spectrum efficiency. Compared with existing restoration schemes, average recovery time is improved by up to 28%.

Service differentiation-based spectrum defragmentation in mixed grid optical networks

On-demand reservation strategy is proposed for optical network resource scheduling. The proposed approach introduces time window reservation on grid integrated with wavelength-routed optical network, according to the application request with anticipant time range and rate. The time window deploys variable size, when time-window is not suitable for current application requirement, the resource scheduler can negotiate the next time window allocation with the switch. Time-window resource reservation approach loans dividing time multiplexing mechanism. Considering with multiple parallel lightpaths' monopolization, the proposed reservation approach improves network resource request service rate and makes the application having the QoS-aware ability.

Extending the researches on wavelength switched optical networks (WSON), efficient integration of the novel optical packet switching network and wavelength switching-based optical circuit switching network technologies which offers both best-effort packet delivery and QoS guaranteed lightpath services has been being studied. In addition, researches on the optical-layer transparent data processing, such as all-optical wavelength multicasting, all-optical 3R regeneration, etc, are conducted simultaneously. It is believed that future innovative optical network services (INSes) would be built on these novel future-proof technologies, and foster colorful applications in the new generation networks. Before the wide applications of INS in different fields, there would be a foreseeable strong requirement for INS firstly posed by pioneer grid applications, e.g., e-science, e-government, and e-banking, etc, which would require the high-performance underlying networks. Our research here is motivated to glue the optical networks and grid applications by integrating lightpath, geographically distributed INS systems and grid resources (e.g., computers, storages, instruments, etc.), and finally offering an easy-to-use high performance networked grid computing environment-optical grid network (OGN) to user applications. In this paper, we introduce our research activities of a distributed optical grid network infrastructure (OGNI), and the creation of the future easy-to-use INS based on OGNI. The proposals have been validated through fieldtrial experiments over a developed WSON testbed.

We present a novel strategy for the operation of a mixed fixed/flexible grid optical network which would be useful for the gradual migration from a fixed to a flexible mode of operation. Routing and spectrum allocation (RSA) in co-existing fixed/flexible grid optical networks with a multi-path sub-band virtual concatenation (VCAT) technique is considered. An integer linear programming (ILP) model and efficient heuristic algorithms based on k-shortest path (KSP) and spectrum window planes (SWPs) are proposed for the RSA optimization which minimizes the maximum number of frequency slots (FSs) used in the fiber link. Simulation studies are presented to show the efficiency of the proposed approaches.

Traffic grooming, i.e. the aggregation of multiple traffic streams on one channel or wavelength, has often been considered in the context of reducing blocking and improving capacity utilization. More recently, traffic grooming has also been advocated in the context of energy-aware routing. In this paper we study energy-efficient path selection under the scheduled traffic model in IP-over-WDM optical networks. We show that there is indeed a strong relation between traffic grooming and energy efficiency, but also that it sometimes pays off not to groom. We propose an energy-aware routing algorithm that is based on traffic grooming, but which has the flexibility to deviate from it where needed. Our approach can be applied to networks with and without wavelength conversion. Simulations show that our energy-aware routing algorithm both brings significant energy savings as well as a lower blocking probability in comparison to a shortest paths based routing algorithm and a traffic grooming algorithm.

With the emergence of cloud services based on data centers, demands for bandwidth-intensive applications have increased dramatically, and application services have transferred to a more diversified direction. Management as well as capacity of the backbone network needs further development to catch up with rapidly evolved application demands. Optical network virtualization can facilitate the sharing of physical infrastructure among multiple network applications. Virtual Network Embedding (VNE), the main implementation of network virtualization, determines how to map a virtual network request onto physical substrate. To expand the network capacity, flexible-grid elastic optical networks have been considered as a promising supporting technology for the future infrastructure of the next-generation Internet. However, due to the expense of key enabling equipment for flexible grid optical networks, the brown-field migration from a fixed grid to a flexible grid gave birth to the co-existing fixed/flexible grid. Based on the co-existing fixed/flexible grid optical networks, we investigate the problem of Virtual Optical Network (VON) provisioning, and present a flexible-grid-aware virtual network embedding algorithm to map the virtual networks onto the substrate network. In addition, the performance of the algorithm was evaluated under four different network scenarios. Simulation results show that the proposed algorithm can achieve better performance in all four scenarios.

In optical grid networks, the main challenge is to account for not only network parameters, but also for resource availability. Anycast routing has previously been proposed as an effective solution to provide job scheduling services in optical grids, offering a generic interface to access grid resources and services. The main weakness of this approach is its limited scalability, especially in a multi-domain scenario. This paper proposes a novel anycast proxy architecture, which extends the anycast principle to a multi-domain scenario. The main purpose of the architecture is to perform aggregation of resource and network states, and as such improve computational scalability and reduce control plane traffic. Furthermore, the architecture has the desirable properties of allowing Grid domains to maintain their autonomy and hide internal configuration details from other domains. Finally, we propose an impairment-aware anycast routing algorithm that incorporates the main physical layer characteristics of large-scale optical networks into its path computation process. By integrating the proposed routing scheme into the introduced architecture we demonstrate significant network performance improvements.

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.