Path Computation Algorithms Research Articles

Exploring Path Computation Techniques in Software-Defined Networking: A Review and Performance Evaluation of Centralized, Distributed, and Hybrid Approaches

Software-Defined Networking (SDN) is a networking paradigm that allows network administrators to dynamically manage network traffic flows and optimize network performance. One of the key benefits of SDN is the ability to compute and direct traffic along efficient paths through the network. In recent years, researchers have proposed various SDN-based path computation techniques to improve network performance and reduce congestion.
 This review paper provides a comprehensive overview of SDN-based path computation techniques, including both centralized and distributed approaches. We discuss the advantages and limitations of each approach and provide a critical analysis of the existing literature. In particular, we focus on recent advances in SDN-based path computation techniques, including Dynamic Shortest Path (DSP), Distributed Flow-Aware Path Computation (DFAPC), and Hybrid Path Computation (HPC).
 We evaluate three SDN-based path computation algorithms: centralized, distributed, and hybrid, focusing on optimal path determination for network nodes. Test scenarios with random graph simulations are used to compare their performance. The centralized algorithm employs global network knowledge, the distributed algorithm relies on local information, and the hybrid approach combines both. Experimental results demonstrate the hybrid algorithm's superiority in minimizing path costs, striking a balance between optimization and efficiency. The centralized algorithm ranks second, while the distributed algorithm incurs higher costs due to limited local knowledge. This research offers insights into efficient path computation and informs future SDN advancements.
 We also discuss the challenges associated with implementing SDN-based path computation techniques, including scalability, security, and interoperability. Furthermore, we highlight the potential applications of SDN-based path computation techniques in various domains, including data center networks, wireless networks, and the Internet of Things (IoT).
 Finally, we conclude that SDN-based path computation techniques have the potential to significantly improvement in-order to improve network performance and reduce congestion. However, further research is needed to evaluate the effectiveness of these techniques under different network conditions and traffic patterns. With the rapid growth of SDN technology, we expect to see continued development and refinement of SDN-based path computation techniques in the future.

Indoor Path-Planning Algorithm for UAV-Based Contact Inspection.

Nowadays, unmanned aerial vehicles (UAVs) are extensively used for multiple purposes, such as infrastructure inspections or surveillance. This paper presents a real-time path planning algorithm in indoor environments designed to perform contact inspection tasks using UAVs. The only input used by this algorithm is the point cloud of the building where the UAV is going to navigate. The algorithm is divided into two main parts. The first one is the pre-processing algorithm that processes the point cloud, segmenting it into rooms and discretizing each room. The second part is the path planning algorithm that has to be executed in real time. In this way, all the computational load is in the first step, which is pre-processed, making the path calculation algorithm faster. The method has been tested in different buildings, measuring the execution time for different paths calculations. As can be seen in the results section, the developed algorithm is able to calculate a new path in 8–9 milliseconds. The developed algorithm fulfils the execution time restrictions, and it has proven to be reliable for route calculation.

Path Computation for Dynamic Provisioning in Multi-Technology Multi-Layer Transport Networks

Service providers employ different transport technologies such as PDH, SDH/SONET, OTN, DWDM, Ethernet, MPLS-TP to support different types of traffic and service requirements. A typical transport network element supports adaptation of multiple technologies and multiple layers of those technologies to carry the input traffic. Further, transport networks are deployed such that they follow different topologies like linear, ring, mesh, protected linear, dual homing etc. in different layers. Dynamic service provisioning requires the use of on-line algorithms that automatically compute the path to be taken to satisfy the given service request. Path computation algorithms can be implemented in Path Computation Element (PCE) which can be invoked from Transport SDN controller to automate service provisioning. This paper studies automated path computation for service requests considering the above factors where, a new mechanism for building an auxiliary graph that models each layer as a node within each network element and creates adaptation edges between them and also supports creation of special edges to represent different types of topologies, is proposed. Logical links that represent multiplexing or adaptation are also created in the auxiliary graph. An initial weight assignment scheme for non-adaptation edges that consider both link distance and link capacity is introduced along with three dynamic weight assignment functions that consider the current link utilization. Path computation algorithms considering adaptation and topologies are proposed over the auxiliary graph structure. The performance of the algorithms is evaluated and it is found that the weighted number of requests accepted is higher and the weighted capacity provisioned is lesser for one of the dynamic weight function and certain combination of values proposed as part of the weight assignment. It is found that the proposed approach results in better overall network utilization (improvement of up to 30 Gbps for a scenario with 50,000 service requests) and fragmentation compared to the traditional layered path computation approach for a representative large-scale service provider transport network (Network 1) with 2955 network elements, 5753 physical links and 480 hub nodes. It is also found that the proposed approach results in better overall network utilization (3–4 times lesser utilization for a scenario up to 50,000 service requests) and fragmentation compared to the traditional layered path computation approach for another representative large-scale service provider transport network (Network 2) generated randomly with 2040 network elements and more than 7000 physical links.

Two-Phase Virtual Network Function Selection and Chaining Algorithm Based on Deep Learning in SDN/NFV-Enabled Networks

With the advances of Software-Defined Networks (SDN) and Network Function Virtualization (NFV), Service Function Chain (SFC) has been becoming a popular paradigm to carry and complete network services. Such new computing and networking paradigm enables Virtual Network Functions (VNFs) to be placed in software entities/virtual machines over a network of physical equipments in elastic and flexible way with low capital and operation expenses. VNFs are chained together to steer traffic as needed. However, most of the existing traffic steering and routing path computation algorithms for SFC are complex, unscalable, and low time-efficiency. In this paper, we study the VNF Selection and Chaining Problem (VNF-SCP) in SDN/NFV-enabled networks. We formulate VNF-SCP as a Binary Integer Programming (BIP) model in order to compute routing path for each SFC Request (SFCR) with the minimum end-to-end delay. Then, a novel Deep Learning-based Two-Phase Algorithm (DL-TPA) is introduced, where VNF selection network and VNF chaining network are designed to achieve intelligent and efficient VNF selection and chaining for SFCRs. Performance evaluation shows that DL-TPA can achieve high prediction accuracy and time efficiency of routing path computation, and the overall network performance can be improved significantly.

Efficient Recovery Path Computation for Fast Reroute in Large-Scale Software-Defined Networks

With an increasing demand for resilience in software-defined networks (SDN), it becomes critical to minimize service recovery delay upon route failures. Fast reroute (FRR) mechanisms are widely used in IP and MPLS networks by computing the recovery path before a failure occurs. The centralized control plane in SDN can potentially enhance path computation, so that FRR path computation can better scale in SDN than in traditional networks. However, the traditional FRR path computation algorithms could lead to a poor performance in large-scale SDN. The problem can become more severe for a highly dynamic network, which often sees dozens of failures or configuration changes in any single day. We propose a new algorithm that exploits pruned searching to quickly compute recovery paths for all-pair switches/hosts upon a link failure. For applications requiring stringent path robustness levels, we also extend this algorithm to quickly find the shortest guaranteed-cost path, which ensures that the recovery path used upon on-path link failures has the minimum cost. Compared with traditional solutions, our evaluations show that our algorithm is about 8 ~ 81 times faster than the practical implementation, 1.93 ~ 3.11 times faster than the state-of-the-art solution. Our results also show that the shortest guaranteed-cost path can reduce the cost of the recovery path significantly. Moreover, we design a prototype to show how to deploy our algorithm in an OpenFlow network.

The Development of an Algorithm of Evacuation Plans in Emergencies for Client-Server Architecture

A sufficient number of public notification systems in the case of emergencies at nuclear power plants have been developed and implemented. However, most of them have some drawbacks related to system performance, the ability to direct the public to evacuation points, promptness in warning. Mostly, they do not use the capabilities of state- of-the-art technologies — mobile applications for smartphones, which allow elimination of these drawbacks. This research is aimed at the design and development of the public notification system using an algorithm for making effective plans of evacuation in emergencies based on the client- server architecture. In addition to the server and client parts, the package also uses Google Maps services for dealing with an interactive map. A special characteristic of this software solution is an innovative approach to the calculation and transfer of the evacuation plan to the victim. The following three parameters are the most important in finding an effective way for each victim: distance to the shelter; time to cover an estimated distance; movement speed. Such an algorithm makes it possible to calculate an adequate route of evacuation separately for each victim, adjusting the distance depending on the speed of movement and fullness of shelters. The efficiency of the developed algorithm for the distribution of potential victims in shelters and evacuation points is presented in AnyLogic models. The paper presents the analysis of using the evacuation model for short path and using the developed path calculation algorithm. The simulated situations have shown the possibility of saving a larger number of people. The developed information system effectively deals with the models built in the AnyLogic program.

Research on optical code assignment algorithm based on PCE domain

Abstract In the multi-granularity optical switching system with optical-code granularity, the wavelength and optical code resource reservation table is established in the PCE domain according to the PCEP common standard, which effectively solves the problem of reserved optical-code conflict in the resource reservation request process, and reasonably allocates utilize the optical code resources in the optical network. At the same time, based on the principle of multi-granularity optical code switching, the exchange path computation algorithm of multi-granularity switching system refined to optical-code packet granularity is studied, and a new routing and optical-code assignment (ROCA) scheme is given. An optical-code fragment minimization allocation algorithm is proposed, which adaptively routes resources according to service segmentation and optical-code polling, rationally utilizes optical-code resources in wavelengths, and effectively reducing optical-code fragments and improving used wavelengths. Furthermore, the blocking rate of the network is reduced. Compared with the First-Fit algorithm, this algorithm reduces the blocking rate of the network and improves the throughput of the network.

SDN-Based End-to-End Fragment-Aware Routing for Elastic Data Flows in LEO Satellite-Terrestrial Network

The wide coverage of satellite networks and the large bandwidth of terrestrial networks have led to an increasing research on the integration of the two networks (ISTN) for complementary advantages. However, most researches on routing mainly focus on the internal routing of the satellite network. Due to the point-to-area coverage of the channel characteristics between the satellites and the ground stations, the heterogeneity of ISTN has increased, which makes that the routing algorithm of the traditional satellite networks cannot be applied to the end-to-end routing of ISTN. Meanwhile, the data flows with elastic quality of service attribute make the routing pre-assign and resource allocation in ISTN much more complicated, which has been rarely researched before. In this paper, we first describe the unified network architecture based on software-defined network and model the data flow. Then, based on the considerations of latency, capacity, wavelength fragmentation, and load balancing, a heuristic service-oriented path computation algorithm for elastic data flows is proposed for the complex heterogeneity of the ISTN. The simulation shows that, the end-to-end routing mechanism can reduce the blocking rate of the ISTN, and our proposed algorithm greatly reduces the wavelength fragmentation and bandwidth consumption, and has a better performance on load balancing, with a slight disadvantage in latency when the network load is high.

Match Field based Algorithm Selection Approach in Hybrid SDN and PCE Based Optical Networks

The evolving internet-based services demand high-speed data transmission in conjunction with scalability. The next generation optical network has to exploit artificial intelligence and cognitive techniques to cope with the emerging requirements. This work proposes a novel way to solve the dynamic provisioning problem in optical network. The provisioning in optical network involves the computation of routes and the reservation of wavelenghs (Routing and Wavelength assignment -RWA). This is an extensively studied multi-objective optimization problem and its complexity is known to be NP-Complete. As the exact algorithms incurs more running time, the heuristic based approaches have been widely preferred to solve this problem. Recently the software-defined networking has impacted the way the optical pipes are configured and monitored. This work proposes the dynamic selection of path computation algorithms in response to the changing service requirements and network scenarios. A software-defined controller mechanism with a novel packet matching feature was proposed to dynamically match the traffic demands with the appropriate algorithm. A software-defined controller with Path Computation Element-PCE was created in the ONOS tool. A simulation study was performed with the case study of dynamic path establishment in ONOS-Open Network Operating System based software defined controller environment. A java based NOX controller was configured with a parent path computation element. The child path computation elements were configured with different path computation algorithms under the control of the parent path computation element. The use case of dynamic bulk path creation was considered. The algorithm selection method is compared with the existing single algorithm based method and the results are analyzed.

Algorithmic and Complexity Aspects of Path Computation in Multi-Layer Networks

Carrier-grade networks comprise several layers where different protocols coexist. Nowadays, most of these networks have different control planes to manage routing on different layers, leading to a suboptimal use of the network resources and to additional operational costs. However, some routers are able to encapsulate, decapsulate, and convert protocols, and act as a liaison between these layers. A unified control plane would be useful to optimize the use of the network resources and to automate the routing configurations. Software-defined networking-based architectures offer an opportunity to design such a control plane. One of the most important problems to deal with in this design is the path computation process. Classical path computation algorithms cannot resolve the problem, as they do not take into account encapsulations and conversions of protocols. In this paper, we propose algorithms to solve this problem and study several cases. If there is no bandwidth constraint, we propose a polynomial algorithm that computes the optimal path. We also give lower and upper bounds on the optimal path length. On the other hand, we show that the problem is $\mathsf {NP}$ -hard if there is a bandwidth constraint (or other quality-of-service parameters), even if there is only two protocols and in a symmetric graph. We study the complexity and the scalability of our algorithms and evaluate their performances on real and random topologies. The results show that they are faster than the previous ones proposed in the literature. These algorithms can also have important applications in automatic tunneling.

On-Line Path Computation and Function Placement in SDNs

We consider service requests that arrive in an online fashion in Software-Defined Networks (SDNs) with network function virtualization (NFV). Each request is a flow with a high-level specification of routing and processing (by network functions) requirements. Each network function can be performed by a specified subset of servers in the system. The algorithm needs to decide whether to reject the request, or accept it and with a specific routing and processing assignment, under given capacity constraints (solving the path computation and function placement problems). Each served request is assumed to “pay” a pre-specified benefit and the goal is to maximize the total benefit accrued. In this paper we first formalize the problem, and propose a new service model that allows us to cope with requests with unknown duration without preemption. The new service model augments the traditional accept/reject schemes with a new possible response of “stand by.” We also present a new expressive model to describe requests abstractly using a “plan” represented by a directed graph. Our algorithmic result is an online algorithm for path computation and function placement that guarantees, in each time step, throughput of at least a logarithmic fraction of a (very permissive) upper bound on the maximal possible benefit.

Accurate and fast path computation on large urban road networks: A general approach.

Accurate and fast path computation is essential for applications such as onboard navigation systems and traffic network routing. While a number of heuristic algorithms have been developed in the past few years for faster path queries, the accuracy of them are always far below satisfying. In this paper, we first develop an agglomerative graph partitioning method for generating high balanced traverse distance partitions, and we constitute a three-level graph model based on the graph partition scheme for structuring the urban road network. Then, we propose a new hierarchical path computation algorithm, which benefits from the hierarchical graph model and utilizes a region pruning strategy to significantly reduce the search space without compromising the accuracy. Finally, we present a detailed experimental evaluation on the real urban road network of New York City, and the experimental results demonstrate the effectiveness of the proposed approach to generate optimal fast paths and to facilitate real-time routing applications.

Need of Algorithm Selection in Next Generation Optical Networks

The IP-based data networks and optical networks have been managed independently with layered protocol stack approach. Both of them were over-provisioned to manage any traffic anomalies and failures. The next generation optical network is expected to handle the needs of the emerging applications in a cost-effective way while satisfying the required QoT. In such scenario, the intents of the application layer must be accounted in the path computation. There is no single path computation algorithm exists which behave optimally under varying traffic conditions. Hence the need for the intent-driven automated algorithm selection was identified. The authors have phrased this intent specific lightpath provisioning problem as the path computation algorithm selection problem. An algorithm selection methodology was proposed with the study of the least congested path in ONOS based software defined controller environment. This approach is claimed as an amenable candidate for the next generation software-defined optical network.

A Minimum Path Calculation Algorithm for Protecting the Edge Weight Privacy in Cloud Circumstance

Based on the encryption algorithm, this paper presents an algorithm to calculate a minimum path between nodes, which protects the privacy and security of edge weights. This algorithm carries on the encryption to the edge weight information, and then the encrypted data is outsourced to the cloud platform. Using breadth first theory, cloud server can directly achieve the graph like data encryption from the initial node outward, and calculate the minimum path from the initial node to the other nodes. This aims to calculate the minimum path between any two nodes. The minimum path calculated by the client and cloud server interaction in collaboration. The main calculation can be from the server, the client only decrypt and judges the operation simple. This algorithm can make the low computational capability of the client and also use cloud computing task to calculate the minimum path computation intensive, and to ensure that the intermediate results of calculation of edge weights. The final result of privacy information will not be leaked. Theoretical analysis and simulation experiments show the safety and correctness of the algorithm.

Tracing Seismic Shortest Path Rays in Anisotropic Medium with Rolling Surface

AbstractIt has very important theoretical and practical values to take rolling surface and seismic anisotropy into consideration in seismic forward modeling and inversion. Based on previous researches, the shortest path calculation algorithm is introduced in this paper to calculate seismic travel times in anisotropic media with rolling surface. In the process of model gridding, the whole model is divided into square cells firstly and rolling boundary is regarded as the approximation of units with irregular shapes. Then shortest path calculation is achieved on irregular grids by setting irregular nodes. Sena's group velocity approximation is used to calculate seismic travel times in anisotropic media during ray tracing, and seismic shortest path ray tracing in a complex anisotropic medium with rolling surface is achieved in the end. Theoretical model calculations show that the method in this paper can be reliably applied to complex anisotropic models with higher calculation accuracy.

A Novel Priority-Based Path Computation Approach for Finding Domain Sequences in PCE-Based Multi-domain Networks

During recent decades new routing paradigms based on policies and quality of service provisioning have been proposed. The aim of these constraint-based path selection algorithms is to satisfy a set of quality of service constraints. This can help to reduce costs and balance network load. Path computation algorithms pose new challenges when extending them to larger inter-domain networks. The process of path computation in these complex cases could be delivered to the external nodes like PCEs. In inter-domain cases, path computation schemes are more prone to blocking due to the long response time of the requests. To address this issue, we propose an algorithm to find the domain sequences in computing the end-to-end path from the source to the destination. The proposed algorithm also increases the number of successful requests while minimizing the blockage in network. The main advantage of the algorithm is to improve the overall network utilization, which can be seen in simulation results.

Global obstacle avoidance and minimum workpiece setups in five-axis machining

The state-of-the-art tool path computation algorithms for five-axis machining consider only the workpiece and clamping device for collision avoidance. However, in a real five-axis machining process, there are many other types of obstacles beyond workpiece and clamps that the tool assembly must avoid, e.g., sensors and other intrusive devices. In such cases, the only solution at present is by means of computer simulation of the machining process after the tool path has been computed. If collision is found, it requires re-computing the tool path and/or changing the setup of the workpiece. This process is then re-iterated until all the collisions are resolved. As a result, the process is time consuming and requires excessive human intervention. In this paper, we present rigorous analyses of the obstacles in five-axis machining and propose efficient numerical algorithms for calculating and representing them. Using our results, the obstacle-free tool orientations can be determined completely at the tool path planning stage, rather than relying on the simulation afterward. In addition, as a direct application of our mathematical modeling, we present a heuristic-based solution to the optimal workpiece setups problem: finding a minimum number of workpiece setups for an arbitrary sculpture part surface so that it can be machined completely on a given five-axis machine without colliding with the obstacles. We use orthogonal table–table five-axis machines as an example and work out a numerical experiment using the proposed solution.

A Hybrid End-to-End QoS Path Computation Algorithm for PCE-Based Multi-Domain Networks

Inter-domain quality of service (QoS) routing is a challenging problem for today's Internet. This problem requires the computation of paths that cross multiple domains and meet different QoS constraints. In addition, the used computation methods must meet the constraints of confidentiality and autonomy imposed by the domains of different operators. Path computation element (PCE)-based architecture offers a promising solution for inter-domain QoS routing. It ensures the computation of end-to-end QoS paths while preserving the confidentiality and the autonomy of the domains. In this paper, we propose a novel hybrid end-to-end QoS path computation algorithm, named HID-MCP, for PCE-based networks. HID-MCP is a hybrid algorithm that combines the advantages of pre-computation and on-demand computation to obtain end-to-end QoS paths. Moreover, it integrates a crankback mechanism for improving path computation results in a single domain or in multiple domains based on the PCE architecture. Detailed analyses are provided to assess the performance of our algorithm in terms of success rate and computational complexity. The simulation results show that our algorithm has an acceptance rate of the requests very close to the optimal solution; precisely, the difference is lower than 1 % in a realistic network. Moreover, HID-MCP has a low computational complexity. Besides, our solution relies on the PCE architecture to overcome the limitations related to inter-domain routing such as domain autonomy and confidentiality.

Experimental assessment of dynamic integrated restoration in GMPLS multi-layer (MPLS-TP/WSON) networks

We present the implementation of the GMPLS control plane functions and path computation algorithm deployed within the CTTC ADRENALINE testbed for the dynamic integrated restoration in multi-layer (MPLS-TP over WSON) networks. The experimental assessment is conducted in terms of the blocking probability, path computation time, restorability and restoration time.

Indoor Navigation and Guidance of an Autonomous Robot Vehicle with Static Obstacle Avoidance and Optimal Path Finding Algorithm

This work, presents an application for static obstacle avoidance and optimal path finding of an autonomous robot vehicle with navigation and control. Angular position and location of the vehicle is measured intermittent by means of an electronic compass sensor and a linear position encoder for the navigation purposes. Vehicle movements and orientation is controlled real time by a stationary computer. Besides navigation a self developed algorithm is integrated to the system for static obstacle avoidance and optimal path finding. An environmental map to detect the static obstacle positions are pre-defined and different maps depended on working area are evaluated by using a suitable computer program. To guide the vehicle to a given target, an optimal path calculation algorithm is applied. During high level control operations are executed by the computer, low level operations are made by a microcontroller to minimize time depended errors. The results and simulations of experimental testing showed the effectiveness of the proposed approach for navigation applications.