Constraint-based Routing Algorithm Research Articles

Path Selection Analysis in MPLS Network Based on QoS

Abstract. Multi-Protocol Label Switching (MPLS) has been proposed as a new approach for integrating layer 3 routing with the layer 2 switching. It integrates the label swapping paradigm of layer 2 (e.g. ATM and Frame Relay) with the routing of layer 3 (e.g. IP and IPX). In the MPLS networks, constraint-based routing computes routes that are subject to constraints such as bandwidth and administrative policy. Because constraint based routing considers more than network topology in computing routes, it may find a longer but lightly loaded path better than the heavily loaded shortest path. In this paper we propose a new constraint based routing algorithm for MPLS networks. The proposed algorithm which is a modification of Wang-Crowcroft algorithm, uses both bandwidth and delay constraints. It means that the reservable bandwidth of all of the links along computed path must be equal to or greater than the bandwidth constraint value and the delay of the path must be less than or equal to the delay constraint value. In the proposed algorithm, the best path is selected based on proposed algorithm. Simulation results show that in comparison with the other methods, the proposed algorithm has a better performance.

Class-Based Constraint-Based Routing with Implemented Fuzzy Logic in MPLS-TE Networks

The paper deals with constraint-based routing (CBR) in MPLS-TE networks and proposes a new CBR algorithm based on fuzzy logic called Fuzzy Class-Based Algorithm (FCBA). Multiprotocol label switching with traffic engineering (MPLS-TE) networks represent a popular mechanism to effectively use resources of service providers’ core networks. The paths can be either built by administrators (explicit routing) or built by using existing routing algorithms which mostly decide based on the shortest paths towards the destination which might not be sufficient in nowadays’ multimedia networks. To address this problem various CBR algorithms have emerged which take into consideration various aspects important to existing traffic like QoS parameters or administrative policies. FCBA makes routing decisions based on traffic classes and by using fuzzy logic we can assign normalized values to various constraints based on the traffic class’ preferences (e.g., low delay paths for voice traffic) and network administrator’s preferences (e.g., avoiding congested links). The paper provides comparison of FCBA with existing CBR approaches based on their ability to provide QoS parameters loss. The simulations show that FCBA provides the best results for the highest priority traffic where it uses lower priority traffic to efficiently utilize the network.

An Efficient Hierarchical Tree Alternative Path (HTAP) and Prims Algorithm Based QOS Routing Approach for MPLS Networks with Enhanced Bandwidth Constraints

Multi- Protocol Label Switching (MPLS) technology helps the progress of numerous features in the Internet, such as routing performance, speed, and traffic engineering. MPLS which may gives mechanisms in IP backbones for over routing using Label Switched Paths (LSPs), summarizing the IP packet in an MPLS packet. This research work concentrates on a new constraint based routing algorithm for MPLS networks. The proposed research work utilizes both bandwidth and delay constraints. Hierarchical Tree Alternative Path (HTAP) Algorithm is utilized in this research work for balancing traffic loads through underutilized paths in order to reduce network congestion. It means that the delay of the path which is figured by the algorithm is less than or equal to the delay constraint value and the remaining bandwidth of all the links all along with the computed path must be equal to or greater than the bandwidth constraint value. In the proposed algorithm best path is computed based on avoiding vital links to reduce call blocking rate, deleting the paths which are not satisfying the bandwidth and delay constraints to reduce complexity of the algorithm and using the prims algorithm is used for shortest path algorithm to reduce path length by finding the shortest path. The proposed algorithm also compares two different topologies to study the performance of the proposed algorithm.

Assessment of a constraint-based routing algorithm for translucent 10Gbits/s DWDM networks considering fiber nonlinearities

We present a constraint-based routing (CBR) approach for real-time operation considering both linear as well as nonlinear signal quality degrading effects in a heterogeneous network infrastructure. Different novel routing algorithms are assessed regarding their blocking probabilities. Furthermore, regenerator pools are placed at a limited number of nodes selected by a heuristic algorithm taking into account the physical impairments. It is shown that CBR together with intelligent regenerator placement can decrease the blocking probability significantly.

On Achieveing Bandwidth-Aware LSP//spl lambda/SP Multiplexing/Separation in Multi-layer Networks

We present a new traffic engineering (TE) model which is based on QoS rerouting and uses hybrid resilience to improve the recovery performance of multi-layer networks where an MPLS network is layered above an MPlambdaS network. We formulate the rerouting of the LSPs/lambdaSPs as a multi-constrained problem and use its polynomial reduction to find a heuristic solution that can be implemented by standardized constraint-based routing algorithms. This heuristic solution uses a cost-based routing optimization to achieve different network configurations which multiplex/separate bandwidth-aware LSPs/lambdaSPs on the network links. We formulate the resilience upon failure as a multi-objective problem consisting of finding a resilience strategy that minimizes recovery operation time and maximizes the LSP/lambdaSP restorability. A solution to this problem is proposed where a hybrid resilience framework is used to achieve restoration in the MPLS layer to complement path switching in the MPlambdaS layer. We evaluate the performance of the TE model when rerouting the tunnels carrying the traffic offered to a 23- and 31-node networks. Simulation reveals that the hybrid resilience model performs better than classical recovery mechanisms. In terms of restorability, quality of rerouting paths and rerouting stability

Benefits of the use of impairment constraint routing in optical networks

In transparent optical networks, the optical signal accumulates the effects of all physical impairments present along the path it traverses. The conventional selection of signal paths based on e.g. shortest path routing without considering the signal quality and its association with the physical impairments does not always provide the optimum solution in terms of network performance such as blocking and resource utilization. This paper proposes an impairment constraint based routing algorithm to achieve an optimal combination of physical and networking performance taking into account all physical linear impairments including noise, chromatic and polarization mode dispersion, crosstalk and filter concatenation effects in an integrated approach. The performance of a typical metropolitan area network is examined and the improvement achieved when using the proposed approach compared to the conventional shortest path routing is demonstrated.

Performance Analysis of an Adaptive Link Status Update Scheme Based on Link-Usage Statistics for QoS Routing

In the global Internet, a constraint-based routing algorithm performs the function of selecting a routing path while satisfying some given constraints rather than selecting the shortest path based on physical topology. It is necessary for constraint-based routing to disseminate and update link state information. The triggering policy of link state updates significantly affects the volume of update traffic and the quality of services (QoS). In this letter, we propose an adaptive triggering policy based on link-usage statistics in order to reduce the volume of link state update traffic without deterioration of QoS. Also, we evaluate the performance of the proposed policy via simulations.

On surviving dual-link failures in path protected optical WDM mesh networks

In this paper, we investigate the problem of enhancing dual-failure restorability in path protected mesh-restorable optical Wavelength Division Multiplexed (WDM) networks. Recent studies have demonstrated the need to survive simultaneous dual-link failures and have also provided solutions for handling such failures. A key finding of these early efforts is that designs providing complete (i.e. 100%) protection from all dual-failures need almost triple the spare capacity compared to a system that protects against all single-link failures. However, it has also been shown that systems designed for 100% single-link failure protection can provide reasonable protection from dual-link failures [M. Clouqueur, W. Grover, Mesh-restorable networks with 74 enhanced dual-failure restorability properties, in: Proc. SPIE OPTICOMM, Boston, MA, 2002, pp. 1–12]. Thus, the motivation for this work is to develop a hybrid mechanism that provides maximum (close to 100%) dual-failure restorability with minimum additional spare capacity. The system architecture considered is circuit-switched with dynamic arrival of sessions requests. We propose an adaptive mechanism, which we term active protection, that builds upon a proactive path protection model (that provides complete single-failure restorability), and adds dynamic segment-based restoration to combat dual-link failures. The objective is to optimize network survivability to dual-link failures while minimizing additional spare capacity needs. We also propose a heuristic constraint-based routing algorithm, which we term best-fit, that aids backup multiplexing among additional spare paths towards this goal. Our findings indicate that the proposed active protection scheme achieves close to complete (100%) dual-failure restorability with only a maximum of 3% wavelength-links needing two backups, even at high loads. Moreover, at moderate to high loads, our scheme attains close to 16% improvement over the base model that provides complete single-failure restorability. Also, the best-fit routing algorithm is found to significantly assist backup multiplexing, with around 15%–20% improvement over first-fit at all loads. The segment-based restoration algorithm reiterates the importance of utilizing wavelength converters in protection and is seen to provide around 15%–20% improvement over link restoration especially at moderate to high loads.

Enhanced pool sharing: a constraint-based routing algorithm for shared mesh restoration networks [Invited

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). We investigate the availability performance of networks with shared mesh restoration and demonstrate that these networks cannot provide highly available protection services. A major factor in the poor performance of shared mesh restoration is that the resources at backup links are shared among demands. If multiple service-affecting failures occur in the network a multitude of these demands will rush to utilize the spare resources on backup links. These resources are not adequate to serve all of these demands simultaneously. We propose a heuristic routing algorithm that attempts to improve the availability performance of shared mesh restoration. We measure the likelihood that a backup link will not be available to restore a newly arrived demand if or when more than one failure occurs in the network. We adjust the backup bandwidth on that link if the measured likelihood exceeds a preset threshold. As a typical representative, we show that the downtime improves by 7%, 11%, and 18% when the total backup bandwidth in the network is increased by 5%, 10%, and 20%, respectively. These values are obtained through a series of fitting experiments.

Constraint-based routing in the internet: Basic principles and recent research

Novel routing paradigms based on policies, quality of service (QoS) requirements, and packet content have been proposed for the Internet over the last decade. Constraint-based routing algorithms select a routing path satisfying constraints that are either administrative-oriented (policy routing) or service-oriented (QoS routing). The routes, in addition to satisfying constraints, are selected to reduce costs, balance network load, or increase security. In this article, we discuss several constraint-based routing approaches and explain their requirements, complexity, and recent research proposals. In addition, we illustrate how these approaches can be integrated with Internet label switching and QoS architectures. We also discuss examples of application-level routing techniques used in today's Internet.

Integrated Routing Algorithms for Provisioning “Sub-Wavelength” Connections in IP-Over-WDM Networks

This work focuses on developing and implementing comprehensive unified constraint-based routing algorithms within the generalized multi-protocol label switching framework (GMPLS) to provision “sub-wavelength” circuits (low-rate traffic streams). Constraint-based routing is further augmented in this work by dynamically routing both an active and another alternate link/node-disjoint backup path at the same time in order to provision a given connection request. This new integrated approach combines both IP routing and optical resource allocation to setup end-to-end connections.