Constraint-based Routing Research Articles

A Constraint-Based Routing and Charging Methodology for Battery Electric Vehicles With Deep Reinforcement Learning

Electric vehicle route planning (EVRP) is generated from the collaborative operation of smart grids and intelligent transportation systems. It has become an essential issue for the widespread use of battery electric vehicles. However, the existed EVRP solutions are of either high computational complexity or low efficiency for large-scale problems. Towards such issues, we propose an efficient Deep Reinforcement Learning based methodology for constraint-based routing while simultaneously considering electric vehicles’ charging policies. We design a two-layer model to find near-optimal solutions and handle the broad range of problem instances according to the rewards and the preset feasibility rules. The first layer is to approximate a sequence of consecutive actions in reality and correspondingly produce a minimum time-consuming feasible route without re-training for each new problem instance. The second layer is to generate a charging scheme along the previously generated feasible path. The proposed methodology is independent of the road network topology and the electric vehicles’ types. Besides, the convergence of value function in the presented model for EVRP is studied. The experiment shows that our methodology outperforms the traditional ones in computation time with comparable solution quality. Moreover, the obtained model can be directly applied to treat other problem instances on various road networks without re-training procedures.

Links Utilization in MPLS Networks Operating with Traffic Engineering Signal Protocols

Multiprotocol Label Switching (MPLS) is a technology that ensures efficient transmission with high speed and lower delays. Traffic Engineering (TE) signal protocols are usually used for active management of the MPLS networks for efficient utilization of resources. This paper presents performance investigation of MPLS TE signal protocols to get a guideline to utilize transmission links efficiently. Comparison is made between two TE signal protocols, namely Resource Reservation Protocol (RSVP) and Constraint-based Routing Label Distribution Protocol (CR-LDP). Simulation results are presented for three MPLS networks having different topologies which are implemented in OPNET (version 14.5) environment to support different applications in the absence and presence of quality of service (QoS) algorithms. The results reveal that MPLS network with CR-LDP TE signal protocol has better performance in the term of link utilization. The RSVP reserves certain paths for transmission while the CR-LDP utilizes almost all of the available links.

A novel stateful PCE-cloud based control architecture of optical networks for cloud services

The next-generation optical network is a service oriented network, which could be delivered by utilizing the generalized multi-protocol label switching (GMPLS) based control plane to realize lots of intelligent features such as rapid provisioning, automated protection and restoration (P&R), efficient resource allocation, and support for different quality of service (QoS) requirements. In this paper, we propose a novel stateful PCE-cloud (SPC) based architecture of GMPLS optical networks for cloud services. The cloud computing technologies (e.g. virtualization and parallel computing) are applied to the construction of SPC for improving the reliability and maximizing resource utilization. The functions of SPC and GMPLS based control plane are expanded according to the features of cloud services for different QoS requirements. The architecture and detailed description of the components of SPC are provided. Different potential cooperation relationships between public stateful PCE cloud (PSPC) and region stateful PCE cloud (RSPC) are investigated. Moreover, we present the policy-enabled and constraint-based routing scheme base on the cooperation of PSPC and RSPC. Simulation results for verifying the performance of routing and control plane reliability are analyzed.

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.

A Cross-Layer Optimization and Design approach under QoS constraints for green IP over WDM networks

Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demands. It is important and valuable to find a way to save power for such networking systems. In this paper, we propose a Cross-Layer Optimization and Design (CLOD) approach to improve the energy efficiency of Internet Protocol (IP) over Wavelength Division Multiplexing (WDM) backbone networks under QoS constraints. CLOD makes use of the skew spatial distribution (i.e. 80–20 law) of traffic demands to construct the virtual topology of IP layer with a consideration of the cross-layer resource constraints. Also, CLOD takes advantage of the constraint-based routing to satisfy the QoS constraints in terms of allowed maximum hop count and allowed maximum link utilization. Taking into account the connection between base network design and network operation, CLOD dimensions the base network by using pattern of network operation and optimizes network power consumption by reconfiguring network to adapt traffic variation and the available resources. Simulation results indicate that CLOD can save power significantly and achieve near energy-proportional networks. In addition, an analysis on trade-off performance between the hop count and power consumption is given.

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.

Coordinated computation and setup of multi-layer paths via inter-layer PCE communication: standards, interoperability and deployment

The IETF Path Computation Element (PCE) framework is a prime example of a softwaredefined network virtualisation artifact, originally envisaged about a decade ago for constraintbased routing in the conventional best-effort Internet. Over the years, however, it evolved into the ultimate tool for multi-technology, multidomain, multi-layer, and multi-vendor networking. Carriers have already started to implement PCE-based solutions in their combined Internet IP/MPLS and Wavelength Switched Optical Networks (WSONs). However, significant development and testing is still needed to elevate the PCE concepts from theory to practice. This paper addresses standards, interoperability and deployment of coordinated computation and setup of multi-layer paths from a practical perspective and presents its first implementation in a multi-vendor, interoperable PCE testbed. In our testbed, we try to push the limits of multivendor interoperability, which current research mostly neglects, and thereby identify missing links in the current research and standards necessary to implement and deploy inter-operable multi-layer systems. We point to the key areas that the research and industrial communities will need to address in making the proposed solutions practical, which in turn will drive the upcoming efforts in software-defined networking with inter-operable PCE-based architectures.

A new high performance approach: merging optimal multicast sessions for supporting multisource routing

Each single source multicast session (SSMS) transmits packets from a source node s i to a group of destination nodes t i , i=1,2,?,n. An SSMS's path can be established with a routing algorithm, which constructs multicast path between source and destinations. Also, for each SSMS, the routing algorithm must be performed once. When the number of SSMS increases to N?2, the routing algorithm must be separately performed N?2 times because the number of source nodes increase to N?2 (for each SSMS the routing algorithm must be performed once). This causes that time of computation and bandwidth consumption to grow. To remove this problem, in this paper, we will present a new approach for merging different SSMSs to make a new multicast session, which is performed only with one execution of a routing algorithm. The new approach, merging different sessions together, is based on the optimal resource allocation and Constraint Based Routing (CBR). We will show that as compared to other available routing algorithms, it improves time of computation and bandwidth consumption and increases data rate and network efficiency. The new approach uses CBR and merges more than one single source multicast session (SSMS) problem to one multisource multicast session (MSMS) problem. By solving one MSMS problem instead of solving more than one SSMS, we can obtain an optimal solution that is more efficient than optimal solutions of SSMS problems.

The Efficiency of Constraint Based Routing in MPLS Networks

The paper presents the simulation results and evaluates the efficiency of constraint base routing algorithms used in MPLS network from the point of their usability in Next Generation Networks. The efficiency of constraint based routing is evaluated according following criteria: optimal path selection, routing priority of traffic flows selected for constraint routing and bandwidth allocation by MAM or RDM bandwidth constraints models.

Distributed multicast multichannel paths

Supporting multimedia applications in QoS-aware multicast deployment has become an important research dimension in recent years. Future communication networks will face an increase in traffic driven by multimedia applications with stringent requirements in the following important functions: (1) nodes and links used distributing, (2) packets duplication distributing, (3) QoS supporting, (4) multichannel routing. For improving these four functions, in this paper we propose a new polynomial time algorithm, named Nodes Links Distributed-Multicast Multichannel Routing (NLD-MMR), based on the Constraint-Based Routing (CBR) and Linear Programming (LP). The new algorithm by constructing Distributed Multicast Multichannel Paths (DMMCP) can distribute or compact both paths and traffic. Our simulation study shows that the proposed algorithm, as compared to other available algorithms, performs well and constructs a new generation of optimal paths with the best cost and efficiency.

Reducing the effects of routing inaccuracy by means of prediction and an innovative link-state cost

The routing inaccuracy problem is one of the major issues impeding the evolution and deployment of Constraint-Based Routing (CBR) techniques. This paper proposes a promising CBR strategy that combines the strengths of prediction with an innovative link-state cost. The latter explicitly integrates a two-bit counter predictor, with a novel metric that stands for the degree of inaccuracy (seen by the source node) of the state information associated with the links along a path. In our routing model, Link-State Advertisements (LSAs) are only distributed upon topological changes in the network, i.e., the state and availability of network resources along a path are predicted from the source rather than updated through conventional LSAs. As a proof-of-concept, we apply our routing strategy in the context of circuit-switched networks. We show that our approach considerably reduces the impact of routing inaccuracy on the blocking probability, while eliminating the typical LSAs caused by the traffic dynamics in CBR protocols.

Load Control for Overloaded MPLS/DiffServ Networks during SLA Negotiation

In end-to-end QoS provisioning some bandwidth portions on the link may be reserved for certain traffic classes (and for particular set of users) so the congestion problem of concurrent flows (traversing the network simultaneously) can appear. It means that in overloaded and poorly connected MPLS/DS networks the CR (Constraint-based Routing) becomes insufficient technique. If traffic engineering is supported with ap-propriate traffic load control the congestion possibility can be predicted before the utilization of guaranteed service. In that sense the initial (proactive) routing can be pre-computed much earlier, possible during SLA (Service Level Agreement) negotiation. In the paper a load simulation technique for load balancing control purpose is proposed. It could be a very good solution for congestion avoidance and for better load-balancing purpose where links are running close to capacity. To be acceptable for real application such complicated load control technique needs very effective algorithm. Proposed algorithm was tested on the network with maximum M core routers on the path and detail results are given for N=3 service classes. Further improve-ment through heuristic approach is made and results are discussed. Some heuristic options show significant complexity savings that is appropriate for load control in huge networks.

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.

Real-time traffic routing over a multilayered satellite architecture

In this paper, we present a constraint-based routing strategy for real-time traffic over a multilayered hierarchical satellite architecture. Both quality (Bit-Error Rate BER) on free-space optical and radio Inter-Satellite Links (ISLs) and bandwidth availability on satellite links are taken into account when setting up routes for high-priority for real-time traffic such as Voice over IP (VoIP). We propose to have a separate queue for real-time traffic to protect it from being swamped by bursty best-effort traffic. Packets from several real-time flows are aggregated onto the same Label Switched Path (LSP) based on destination and priority, and are shielded from each other by a proportional dropping policy, where packets from flows exceeding their Committed Information Rate (CIR) have high dropping probability during congestion. The performance of our prioritised load balancing routing algorithm on a multilayered satellite network is simulated and analysed.

Genetic algorithm for pareto optimum-based route selection

A quality of service (QoS) or constraint-based routing selection needs to find a path subject to multiple constraints through a network. The problem of finding such a path is known as the multi-constrained path (MCP) problem, and has been proven to be NP-complete that cannot be exactly solved in a polynomial time. The NPC problem is converted into a multiobjective optimization problem with constraints to be solved with a genetic algorithm. Based on the Pareto optimum, a constrained routing computation method is proposed to generate a set of nondominated optimal routes with the genetic algorithm mechanism. The convergence and time complexity of the novel algorithm is analyzed. Experimental results show that multiobjective evolution is highly responsive and competent for the Pareto optimum-based route selection. When this method is applied to a MPLS and metropolitan-area network, it will be capable of optimizing the transmission performance.

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

Ant algorithm for amplifier spontaneous emission (ASE)-aware routing

In this paper, we propose and demonstrate an Ant-based constraint-based routing for transparent optical networks based on ASE noise accumulation along the lightpath. Our proposed algorithm selects the route based on the minimum ASE noise, leading to lower blocking probability. The numerical results show that the proposed algorithm outperforms the traditional shortest path routing algorithm. The results show that these ASE have a significant impact on transparent networks. Careful gain choice, low noise figure are strongly desired for the accomplishment of efficient, cost-effective, high capacity WDM transparent optical networks.

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.

Demand assigned capacity management (DACM) in IP over optical (IPO) networks

The demand assigned capacity management (DACM) problem in IP over optical (IPO) network aims at devising efficient replenishment schedules from the optical domain conditioned upon traffic evolution processes in the IP domain. A replenishment schedule specifies the location, sizing, and sequencing of link capacity expansions to support the growth of Internet traffic demand in the IP network subject to economic considerations. A major distinction in the approach presented in this paper is the focus of attention on the economics of excess bandwidth in the IP domain, which can be viewed as an inventory system that is endowed with fixed and variable costs and depletes with increase in IP traffic demand requiring replenishment from the optical domain. We develop mathematical models to address the DACM problem in IPO networks based on a class of inventory management replenishment methods. We apply the technique to IPO networks that implement capacity adaptive routing in the IP domain and networks without capacity adaptive routing. We analyze the performance characteristics under both scenarios, in terms of minimizing cumulative replenishment cost over an interval of time. For the non-capacity adaptive routing scenario, we consider a shortest path approach in the IP domain, specifically OSPF. For the capacity adaptive scenario, we use an online constraint-based routing scheme. This study represents an application of integrated traffic engineering which concerns collaborative decision making targeted towards network performance improvement that takes into consideration traffic demands, control capabilities, and network assets at different levels in the network hierarchy.

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.