PCE algorithm for traffic grooming and QoS in multi-layer/multi-domain IP over WDM networks

Message sequencing and channel assignment are two important issues that need to be addressed when scheduling variable-length messages in a wavelength division multiplexing (WDM) network. Channel assignment addresses the problem of choosing an appropriate data channel via which a message is transmitted to a node. This problem has been addressed extensively in the literature. On the other hand, message sequencing which addresses the order in which messages are sent, has rarely been addressed. In this paper, we propose a set of scheduling techniques for single-hop WDM passive star networks, which address both the sequencing aspect and the assignment aspect of the problem. In particular, we develop two priority schemes for sequencing messages in a WDM network in order to increase the overall performance of the network. We evaluate the proposed algorithms, using analytical modeling and extensive discrete event simulations, by comparing their performance with state-of-the-art scheduling algorithms that only address the assignment problem. We find that significant improvement in performance can be achieved using our scheduling algorithms where message sequencing and channel assignment are simultaneously taken into consideration. This suggests that, when scheduling messages in WDM networks, one has to consider message sequencing, as well as channel assignment. As a result, we anticipate that this research will open new directions into the problem of on-line scheduling in WDM networks.

Inter-domain path provision under a wavelength continuity constraint (WCC), including path computation and resource reservation procedures, is a major challenge in multi-domain wavelength division multiplexing (WDM) optical networks, because of the requirement for confidentiality between the domains. Based on the hierarchical path computation element (PCE) architecture, this work proposed a path establishment scheme under a WCC to provide a fast inter-domain path establishment solution and decrease the influence of the WCC. The hierarchical PCE architecture consists of a single parent PCE serving as the arbitrator and multiple child PCEs responsible for the child domains. By cooperation between the parent PCE and the child PCEs, both inter-domain path computation and inter-domain wavelength reservation can be processed in parallel to accelerate and optimize WCC lightpath provisioning and thus to reduce the blocking probability. The effectiveness of this solution has been evaluated through simulations. The simulation results show that the proposed solution can achieve lower computation and reservation delays and thus lead to lower blocking probabilities on the multi-domain WCC paths.

In this paper, we investigate the problem of survivable grooming for anycasting over wavelength division multiplexing (WDM) networks. Anycasting is a communication paradigm in which a source node sends data to any one out of multiple candidate destinations. In WDM networks, the standard anycasting problem involves the establishment of a connection from the source to any one destination with the objective of minimizing the resources used. In order to provide survivability, the problem can be extended to find both a connection to a primary destination and a connection to a backup destination. The connections, which may require an amount of bandwidth that may be less than the bandwidth of an entire wavelength, can be groomed with other connections in the WDM network. We propose an auxiliary graph approach to solving the survivable grooming problem for anycasting in WDM networks, and we propose three different protection approaches for providing different degrees of survivability against link failures and destination failures. The effectiveness of the proposed schemes is verified through simulation.

To utilize the wavelength resources of Internet protocol (IP) over wavelength division multiplexing (WDM) optical networks, a multi-constrained multicast traffic grooming algorithm is proposed in this paper. This algorithm can achieve multicast traffic grooming in IP over WDM optical networks under multi-constraints, including the number of optical transceivers, wavelength conversion capability and wavelength splitting capability. We simulated the traffic grooming algorithm using the topology of GEANT. Emulation results show that our algorithm has a lower blocking proportion compared with the multi-hop traffic grooming algorithm, which can achieve multicast traffic grooming more effectively.

With the rising popularity of multicasting services in meshed wavelength division multiplexing (WDM) networks, protecting dynamic sub-wavelength granularity multicast requests against network failures becomes an important issue in network operation process. This paper investigates survivable dynamic multicast traffic grooming problem in WDM networks, and a connection-level segment shared protection (CL-SSP) algorithm is proposed to protect multicast requests against single link failure in dynamic traffic grooming process. Specifically, to improve network resource sharing in traffic grooming process, a lightpath-fragmentation (LPF) method is adopted to fragment primary/backup lightpaths into segments upon setup in the physical layer routing process. Extensive numerical simulations are carried out to study the blocking performance of CL-SSP scheme in different cases. Influences of LPF method on CL-SSP blocking performance are also evaluated.

In Wavelength Division Multiplexing (WDM) networks, providing survivability during routing along with maintaining load balancing is a daunting task. In this paper, we propose an Ant based survivable routing and load balancing technique in WDM networks which discovers survivable and load balanced feasible paths. Ant agents are launched in the network to gather essential information such as available bandwidth, route length and number of free wavelengths. A combined feasibility value is generated from these factors for each path. While transmitting data to the destination, the source selects the path with high feasible value and low load as primary path, and other paths as backup paths. During congestion and failures, data transmission is redirected through the backup paths. Thus, our technique provides survivability and load balancing at hand efficiently. Simulation results show that our technique reduces packet drops efficiently by detecting and controlling the congestion.

In this paper, we compare performance of fixed-grid Wavelength Division Multiplexing (WDM) and Elastic Optical Networks (EONs) in dynamic provisioning of many-to-many (m2m) flows. Currently, with a growth of services relying on many-to-many communication paradigm such as distributed computing, inter-Data Center communication, content delivery networking or other requiring high-bandwidth in group communication, it is vital to deliver new solutions facilitating these demanding transmissions. Therefore, the authors investigate provisioning of m2m traffic in high-performance optical networks. This work focuses on dynamic Routing and Wavelength Assignment (RWA) problem in WDM networks as well as Routing and Spectrum Allocation (RSA) problem in EONs for m2m flows using replicated communication through auxiliary rendezvous servers.

We study the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages in WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their time constraints.

Provisioning multicast QoS for WDM-based optical wireless networks

WDM Network Issues: QOT Impairments, Dynamic Bandwidth Allocation, Modeling and Monitoring Schemes based on ML

This paper proposes the optimal design of lightpath Routing and Wavelength Assignment (RWA) problem in Wavelength Division Multiplexing (WDM) networks without wavelength conversion. We formulate RWA as a mixed Integer Linear Programming (ILP) problem where the objective is to minimize the cost of wavelength assignment to the fiber links in the network. The Lagrangean relaxation technique and the optimization-based heuristics are used to solve this problem. Two sets of computational experiments are performed to test the algorithms for the maximum carried traffic and minimum wavelength requirements in three different network topologies (GTE, ARPA, OCT network). Based on solution quality to the computational experiments, the error gaps between the upper bound and the lower bound are close enough that the near optimal solutions could be obtained. On the other hand, we also show that the solution quality degrade gracefully under more and more heavy traffic network environment. By assessing solution quality and the computational time, we propose the efficient and effective optimization-based algorithms based on the Lagrangean relaxation method for the RWA problem in the WDM networks without wavelength conversion.

This paper presents a comprehensive investigation of a wide range of protection strategies against all single link failures in all-optical wavelength division multiplexing (WDM) networks based on mesh and multi-ring architectures. In the mesh architecture, three protection strategies namely, minimal cost, single link basis and disjoint path protection strategies are investigated. In the multi-ring architecture, the distribution and non-distribution traffic multi-ring design strategies are extensively examined. Although, the concepts of mesh and multi-ring designs have previously been perceived to be fundamentally different, in this paper, we shall explain and show that these two architectures can be systematically related and viewed as a unified concept. This new way of looking at the fully survivable network design helps us to understand clearly the mechanisms and performance of each protection strategy. In addition, this approach allows us to see the trend of fiber-cost requirements that increase step-by-step from the most complicated mesh protection to the simplest multi-ring protection architectures. To minimize the system cost of 100% protection WDM networks, mathematical models based on the integer linear programming (ILP) are derived as the tool for achieving optimal path placement, wavelength assignment and ring selection simultaneously. Apart from the mathematical model, the main contributions of this paper are the analysis and comparison in aspects of the spare capacity requirement and ease of operation and practical feasibility amongst these protection strategies. However, the emphasis will be on the multi-ring protection schemes. In addition, the influence of the number of multiplexed wavelengths per fiber to design outcomes and the benefit of having wavelength conversion capability in WDM network environment are also studied. Copyright © 2004 AEI.

In wavelength division multiplexing (WDM) networks, failures may imply severe loss of data due to the high transmission rates, leading to the need for employment of protective mechanisms. Transparency and switching in all-optical networks cause physical impairment, which can significantly degrade signal quality. If the signal quality along a path is below acceptable values, this path cannot be used for incoming requests in the establishment of lightpaths. Therefore, quality must be checked by the routing and wavelength assignment algorithm. The present article introduces two novel algorithms for shared path protection in WDM networks that take into consideration the Polarization Mode Dispersion, Amplifier Spontaneous Emission, and homowavelength cross-talk physical impairments during path selection. The efficiency of these algorithms is compared to that of their impairment-unaware counterparts.

As multicast applications become widely popular, supporting multicast in all-optical wavelength division multiplexing (WDM) networks becomes an important problem. In this paper, we study multicast routing in sparse splitting WDM networks, in which only a small percentage of nodes are capable of light splitting. Specifically, an efficient sparse splitting constrained multicast routing algorithm called MCNFH is proposed and evaluated by simulations. The results show that the proposed algorithm has better performance in terms of wavelength channel cost and the maximum number of wavelengths per link than existing algorithms.

Dynamic multicast traffic grooming in wavelength division multiplexing (WDM) networks was analyzed to minimize networkwide costs and to increase the network resource utilization. A network model was developed for dynamic multicast traffic grooming with resource constraints and an algorithm that can provide quality of service (QoS) was proposed. The QoS is measured by the maximum number of lightpaths passing between the source and the destinations. The blocking probability of the algorithm was assessed in simulations. The results show that a higher QoS requirement results in higher blocking probability, and when the QoS requirement is low, changes in the QoS requirements have only small effects on the blocking probability.