Generic-II routing and wavelength assignment algorithm for a wavelength-routed WDM network

In this paper, we have developed a Generic routing and wavelength assignment algorithm (Generic RWA-II) which is used for the calculation of blocking probability of network. A simple mathematical model has also been proposed for the optimization and minimization of blocking probability. The implementation of the proposed model and algorithm has less complexity and the computation used in this model is quite efficient. This paper suggests an optimum path and assigns wavelength to that path, as a solution to routing and wavelength assignment problem to have least blocking probability. This model can be implemented on different network topologies. Further, the model is also used to evaluate the blocking performance of a 6-node simple network topology and hence used to improve its performance on the basis of blocking probability.     

Survivable routing and wavelength assignment algorithm for multiple link failures in wavelength-routed all-optical WDM networks

In this paper, we have investigated the problem of enhancing multiple-fault restorability in the path protected wavelength-routed all-optical WDM networks. The system architecture considered is circuit-switched with dynamic arrival of session requests. We have proposed a mechanism, which is used to combat multiple link failures. A survivable routing and wavelength assignment algorithm has been proposed which is very efficient for the networks having multiple failures. This algorithm deals with the optical networks with multiple faults and is effective for the varying load applied to nodes. This algorithm works well for the load applied to the nodes varying from low to high.     

Fault-tolerant routing and wavelength assignment algorithm for multiple link failures in wavelength-routed all-optical WDM networks

In this paper, we investigate the problem of enhancing multiple-fault restorability in the path protected wavelength-routed all-optical WDM networks. The system architecture considered is circuit-switched with dynamic arrival of session requests. We propose a mechanism, which is used to combat multiple link failures. A routing and wavelength assignment algorithm has been proposed with the name of fault-tolerant routing and wavelength assignment algorithm. The comparison of this algorithm has also been made with the best-fit and first-fit algorithms. This algorithm deals with the optical networks with multiple faults and is effective for the varying load applied to nodes. This algorithm works well for the load applied to the nodes varying from low to high.     

Routing and wavelength assignment in wavelength-routed all-optical WDM networks

In this paper, low-complexity mathematical model has been developed which is used for the calculation of the blocking probability of network and this model does not require any simulation statistics. The implementation of the model proposed has less complexity and the computation used in this model is quite efficient. The routing algorithm has also been proposed in this paper depending upon the proposed model, which is very efficient in calculation and minimization of the blocking probability. This algorithm suggests an optimum path as a solution to routing problem. The wavelength assignment technique has also been suggested in this paper to minimize the blocking probability. The proposed model and algorithms can be implemented on different network topologies. Furthermore, the model, routing algorithm and wavelength assignment technique is also used to evaluate the blocking performance of NSFNet and EUPAN Network topology and hence used to improve its performance on the basis of the blocking probability.     

Blocking in wavelength-routed all-optical WDM network with wavelength conversion

The blocking probability in wavelength-routed all optical networks is very important measure of performance of the network, which can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper, we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for wavelength-convertible networks. The model can be used to evaluate the blocking performance of any network topology also it can be useful to improve its blocking performance of the given network topology. The blocking probability variation of the network for a particular load (per link) has been studied based on the load variation and total number of wavelengths used in the network. This model gives good results for high load (per link).     

Blocking in wavelength-routed all-optical WDM network with or without wavelength conversion

The blocking probability in wavelength-routed all-optical networks is a very important measure of performance of the network. This blocking probability can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for both wavelength convertible networks as well as for wavelength non-convertible networks. The model is can be used to evaluate the blocking performance of any network topology also it can be useful to improve its performance of the given network topology.     

Blocking in wavelength-routed all-optical WDM networks

In this paper, we have developed a low complexity mathematical model which is used for the calculation of blocking probability of network and this model does not require any simulation statistics. The implementation of the model proposed has less complexity and the computation used in this model is quite efficient. This paper suggests an optimum path as a solution to routing problem and the appropriate number of wavelengths have also been suggested which should be free in a network to have the least blocking probability. This model can be implemented on different network topologies. Further, the model is also used to evaluate the blocking performance of NSFNet topology and hence used to improve its performance on the basis of blocking probability.     

Blocking probability calculation in wavelength-routed all-optical networks

In this paper we have proposed a mathematical model to reduce the blocking probability of the WDM optical network. The mathematical model proposed has a closed-form expression and does not require simulated statistics, it has low implementation complexity and the computation is quite efficient. This model suggests us to choose the best path and appropriate number of free wavelengths in the network. We can go for the compromise between the path length and number of free wavelength. The model is also used to evaluate the blocking performance of NSFNet topology and hence used to improve its performance.     

Distributed control based routing and wavelength assignment strategy for WDM optical networks

Wavelength-division-multiplexing (WDM) is emerging as the dominant technology for the next generation optical networks. The control strategy can be either centralized or distributed. In centralized control, there is a central controller to keep track of the state of the network. It is also responsible for selecting the path for data transmission. Most of the work done in this field is based on centralized control. For large networks, distributed control is preferred over centralized control because of low control overhead. Distributed control strategy requires exchange of control messages among nodes. The distributed control generally results in the possibility of resource reservation conflicts among simultaneous path establishments and poor resource utilization. In this paper, we have proposed one distributed control based routing and wavelength assignment strategy that avoids the problem of resource reservation conflicts along with the efficient utilization of resources.     

Wavelength assignment algorithms for WDM optical networks

In this paper, we have proposed an efficient wavelength assignment algorithm for dynamic provisioning of lightpath. This proposed algorithm is based on most-used wavelength assignment algorithm. We have also suggested a mathematical model for WDM optical networks for minimization of blocking probability. The results of proposed algorithm and suggested model are then compared with the conventional wavelength assignment algorithms such as first-fit, best-fit, random and most-used wavelength assignment algorithms. These proposed approaches are very effective for the minimization of blocking probability of optical WDM networks.     

Routing and wavelength assignment algorithms for multiclass WDM optical networks

In this paper dynamic routing and wavelength assignment strategies have been proposed for multiclass WDM optical networks. Multiclass optical networks provide multiple classes of services to the subscriber according to the requirement, which in turn increase operational profitability. Each class of service could be characterized by parameters like number of wavelengths, expected call holding time and average arrival rate of request. The proposed strategies have been analyzed and compared with existing strategies on the basis of blocking probabilities for multiclass traffic scenarios. Simulation results on different network topologies demonstrate that the performance of proposed strategies “Fixed shortest/alternate shortest path routing with wavelength reservation (FSASWR)” and “Fixed alternate shortest path routing with least priority wavelength assignment (FASPL)” are much better as compared to existing strategies. Proposed strategies minimize blocking probability of the multiclass network using limited number of wavelengths.     

Routing and wavelength assignment in WDM networks with dynamic link weight assignment

We consider the routing and wavelength assignment problem on wavelength division multiplexing networks without wavelength conversion. When the physical network and required connections are given, routing and wavelength assignment (RWA) is the problem to select a suitable path and wavelength among the many possible choices for each connection such that no two paths using the same wavelength pass through the same link. In wavelength division multiplexing (WDM) optical networks, there is need to maximize the number of connections established and to minimize the blocking probability using limited resources. In this paper, we have proposed three dynamic link weight assignment strategies that change the link weight according to the traffic. The performance of the existing trend and the proposed strategies is shown in terms of blocking probability. The simulation results show that all the proposed strategies perform better than the existing trend.     

WDM全光网络中一种分布式路由及波长分配协议

在全光网络中,光信号在全光域内传输,避免了光-电转换带来的延迟,因此全光网支持高数据率传输并提供巨大的网络容量。WDM(波分多路复用)技术的采用使得高速光传输线路与低速终端处理设备之间能够相互兼容。探讨了WDM全光网中的路由及波长分配问题,提出了一种用于WDM网络中的分布式路由及波长分配协议,具有开销小、阻塞率低以及良好的可扩展性,是一种比较实用的RWA协议。     

自相似业务下WDM光网的动态阻塞性能

研究了在自相似业务下,WDM光网的动态路由和波长分配问题以阻塞率为判据,通过大量的数字仿真试验分析了WDM光网在不同路由策略下,相对于自相似业务的Hurst参量和标准偏差参量的动态性能此外,对在泊松业务和自相似业务下的WDM光网的动态性能做了比较。     

A method of segment protection based on p-cycle for dynamic multicast with limited-range wavelength converter in WDM network

In the optical multicast network, node and link failures have very important influence on the network survivability which may lead to multiple destinations cannot receive data. Based on the wavelength layered-graph method, a method of efficiency-score based on heuristic algorithm of pre-configured cycle (p-Cycle) based-segment protection (ESHS) for dynamic multicast with limited-range wavelength conversion was presented in this paper. By finding the multicast tree segment protection, the total available p-Cycles are constructed for the multicast. Then we calculate each p-Cycle efficiency-score, the highest efficient-score p-Cycle is selected as the multicast route protection p-Cycle. The simulation results show that the ESHS can get higher performance than the existing ESHT algorithm, in terms of multicast request blocking probability and wavelength utilization.     

Provisioning for restorable WDM optical networks

Restoration is a very critical issue in WDM optical networks. Provisioning also plays a great role in the networks because it deals with resource allocation. In this paper, we have presented two provisioning strategies for restorable networks: unity link weight strategy and varying link weight strategy. The strategies are implemented for critical applications which require 100% degree of survivability. The simulation is done using different proportionate of resources for working and restoration lightpaths. The simulated results show that the performance of the unity link weight strategy is much better than the varying link weight strategy in terms of resource requirement and blocking probability.     

Delay-constrained anycast routing problem in WDM networks with wavelength conversions

Anycast routing and wavelength assignment problem has been intensively studied in wavelength-division multiplexing (WDM) networks, however, real-time application where packets have explicit expiration deadlines is not taken into consideration. In a WDM network, each link is associated with limited wavelengths available for channel connections. Data transmission over one wavelength to another requires wavelength conversion, which causes a long delay of message transmission. When the network and the set of anycast routing requests are given, the delay-constrained wavelength conversions anycast routing (DWCAR) problem is to find a set of light-paths, one for each source, for anycasting message to one member of the anycast destination group. The objective is to find a minimum number of wavelength conversions with the constraint that the sum of delays along every path must not exceed a given delay-bound. In this paper, we present a Tabu-search based delay-constrained anycast routing algorithm (TSDA) to solve this NP-complete problem, and compare it to a simple K shortest path based anycast algorithm (KSPA). Simulation results show TSDA achieves an average 40–50% improvement in required wavelength conversions.     

Restoration approach in WDM optical networks

Critical applications require proactive-based survivability strategy which provides 100% degree of survivability, low blocking probability and very low restoration time. In this paper, we have proposed an efficient proactive restoration approach for WDM optical network that efficiently utilizes the resources and reduces blocking probability as compared to existing proactive restoration approach. It gives priority to primary lightpath as compared to backup lightpath because primary lightpath should not share resources with other lightpaths in critical applications but backup lightpaths can share the resources, i.e. backup multiplexing.     

Static and dynamic routing and wavelength assignment algorithms for future transport networks

In this paper, two static and three dynamic routing algorithms have been proposed and compared to some of the existing algorithms on the basis of blocking probability. The two proposed static routing and wavelength assignment (RWA) algorithms reduce the blocking probability to maximize the utilization of network. For dynamic algorithms, first a model with no weights assignments is presented and then three algorithms are proposed and analysed with weight assignment resulting in reduction of blocking probability. All these algorithms are analysed and compared with four wavelength assignment schemes which are first-fit, random, most used and least used. It is shown that our proposed static algorithms give the best performance for first-fit wavelength assignment and most used wavelength assignment strategies with reduced complexity. For least used wavelength assignment and random wavelength assignment, 1 fixed and 2 alternate routing algorithm gives the lowest blocking probability. For dynamic routing, it has been shown that our proposed algorithm “less weight to maximum empty and nearest” gives the least blocking probability as compared to the other dynamic routing algorithms for random, most used and least used wavelength assignment strategies.     

有业务量疏导能力的WDM网格网阻塞性能分析

提出一个新分析模型来计算有业务量疏导能力的波分复用(WDM)网格网的呼叫阻塞概率,WDM网络中的业务量疏导定义为复用、解复用和交换低速率业务量到高容量光路的行为.该模型首先把原始网络分解为单个子系统,然后再对这些子系统进行独立分析,最后对这些子系统的结果进行适当组合得到整个网络的解.同时,模型考虑了链路负载和链路阻塞事件之间的相关性.仿真结果表明该模型给出的结果较准确.