A comprehensive survey on Segment Routing Traffic Engineering

Traffic Engineering(TE)enables management of traffic in a manner that optimizes utilization of network resources in an efficient and balanced manner.However,existing TE solutions face issues relating to scalability and complexity.In recent years,Segment Routing(SR)has emerged as a promising source routing paradigm.As one of the most important applications of SR,Segment Routing Traffic Engineering(SR-TE),which enables a headend to steer traffic along specific paths represented as ordered lists of instructions called segment lists,has the capability to overcome the above challenges due to its flexibility and scalability.In this paper,we conduct a comprehensive survey on SR-TE.A thorough review of SR-TE architecture is provided in the first place,reviewing the core components and implementation of SR-TE such as SR Policy,Flexible Algorithm and SR-native algorithm.Strengths of SR-TE are also discussed,as well as its major challenges.Next,we dwell on the recent SR-TE researches on routing optimization with various intents,e.g.,optimization on link utilization,throughput,QoE(Quality of Experience)and energy consumption.Afterwards,node management for SR-TE are investigated,including SR node deployment and candidate node selection.Finally,we discuss the existing challenges of current research activities and propose several research directions worth of future exploration.

Traffic Engineering in Dynamic Hybrid Segment Routing Networks

The emergence of Segment Routing(SR)provides a novel routing paradigm that uses a routing technique called source packet routing.In SR architecture,the paths that the packets choose to route on are indicated at the ingress router.Compared with shortest-path-based routing in traditional distributed routing protocols,SR can realize a flexible routing by implementing an arbitrary flow splitting at the ingress router.Despite the advantages of SR,it may be difficult to update the existing IP network to a full SR deployed network,for economical and technical reasons.Updating partial of the traditional IP network to the SR network,thus forming a hybrid SR network,is a preferable choice.For the traffic is dynamically changing in a daily time,in this paper,we propose a Weight Adjustment algorithm WASAR to optimize routing in a dynamic hybrid SR network.WASAR algorithm can be divided into three steps:firstly,representative Traffic Matrices(TMs)and the expected TM are obtained from the historical TMs through ultrascalable spectral clustering algorithm.Secondly,given the network topology,the initial network weight setting and the expected TM,we can realize the link weight optimization and SR node deployment optimization through a Deep Reinforcement Learning(DRL)algorithm.Thirdly,we optimize the flow splitting ratios of SR nodes in a centralized online manner under dynamic traffic demands,in order to improve the network performance.In the evaluation,we exploit historical TMs to test the performance of the obtained routing configuration in WASAR.The extensive experimental results validate that our proposed WASAR algorithm has superior performance in reducing Maximum Link Utilization(MLU)under the dynamic traffic.

Traffic Engineering Based on Deep Reinforcement Learning in Hybrid IP/SR Network

Segment Routing(SR)is a new routing paradigm based on source routing and provide traffic engineering(TE)capabilities in IP network.By extending interior gateway protocol(IGP),SR can be easily applied to IP network.However,upgrading current IP network to a full SR one can be costly and difficult.Hybrid IP/SR network will last for some time.Aiming at the low flexibility problem of static TE policies in the current SR networks,this paper proposes a Deep Reinforcement Learning(DRL)based TE scheme.The proposed scheme employs multi-path transmission and use DRL to dynamically adjust the traffic splitting ratio among different paths based on the network traffic distribution.As a result,the network congestion can be mitigated and the performance of the network is improved.Simulation results show that our proposed scheme can improve the throughput of the network by up to 9%than existing schemes.

Research of MPLS traffic engineering over differentiated services

An approach to traffic engineering that uses differentiated services (DS) andmulti-protocol label switching (MPLS) to provide quantitative network quality of service (QoS)guarantees over an IP network was proposed. The traffic associated with assured forwarding (AF)Per-Hop behavior (PHB) in differentiated services enabled IP network was modeled. Furthermore, theeffect of such traffic on network resources with die objective of developing efficient trafficengineering methodologies was analyzed and the optimization problem relating to traffic engineeringin DS networks with an MPLS core was formulated. The service received by TCP and UDP flows when theyshare either a link or a MPLS traffic trunk was also compared and found that in order to benefitfrom traffic engineering, MPLS trunks should be implemented end-end (first router to last router).If some part of the network is MPLS trunk-unaware, the benefits are reduced or eliminated.

An Evaluation of Routing Algorithms in Traffic Engineering and Quality of Service Provision of Network on Chips

Nowadays the number of cores that are integrated into NoC (Network on Chip) systems is steadily increasing, and real application traffic, running in such multi-core environments requires more and more bandwidth. In that sense, NoC architectures should be properly designed so as to provide efficient traffic engineering, as well as QoS support. Routing algorithm choice in conjunction with other parameters, such as network size and topology, traffic features (time and spatial distribution), as well as packet injection rate, packet size, and buffering capability, are all equivalently critical for designing a robust NoC architecture, on the grounds of traffic engineering and QoS provision. In this paper, a thorough numerical investigation is achieved by taking into consideration the criticality of selecting the proper routing algorithm, in conjunction with all the other aforementioned parameters. This is done via implementation of four routing evaluation traffic scenarios varying each parameter either individually, or as a set, thus exhausting all possible combinations, and making compact decisions on proper routing algorithm selection in NoC architectures. It has been shown that the simplicity of a deterministic routing algorithm such as XY, seems to be a reasonable choice, not only for random traffic patterns but also for non-uniform distributed traffic patterns, in terms of delay and throughput for 2D mesh NoC systems.

Segment routing for traffic engineering and effective recovery in low-earth orbit satellite constellations

Low-Earth Orbit Satellite Constellations(LEO-SCs)provide global,high-speed,and low latency Internet access services,which bridges the digital divide in the remote areas.As inter-satellite links are not supported in initial deployment(i.e.the Starlink),the communication between satellites is based on ground stations with radio frequency signals.Due to the rapid movement of satellites,this hybrid topology of LEO-SCs and ground stations is time-varying,which imposes a major challenge to uninterrupted service provisioning and network management.In this paper,we focus on solving two notable problems in such a ground station-assisted LEO-SC topology,i.e.,traffic engineering and fast reroute,to guarantee that the packets are forwarded in a balanced and uninterrupted manner.Specifically,we employ segment routing to support the arbitrary path routing in LEO-SCs.To solve the traffic engineering problem,we proposed two source routings with traffic splitting algorithms,Delay-Bounded Traffic Splitting(DBTS)and DBTS+,where DBTS equally splits a flow and DBTS+favors shorter paths.Simu-lation results show that DBTS+can achieve about 30%lower maximum satellite load at the cost of about 10%more delay.To guarantee the fast recovery of failures,two fast reroute mechanisms,Loop-Free Alternate(LFA)and LFA+,are studied,where LFA pre-computes an alternate next-hop as a backup while LFA+finds a 2-segment backup path.We show that LFA+can increase the percentage of protection coverage by about 15%.

Traffic Engineering for Proactive Failure Recovery of IP Networks

As a promising approach to improve network reliability, proactive failure recovery （PFR） re-routes failure affected traffic to backup paths without waiting for the completion of IP routing convergence. However the failure affected traffic may cause congestion if it is not carefully allocated over the backup paths according to their available capacity. A post failure traffic engineering （PostTE） scheme is proposed to balance the load in the PFR scheme. Loop-free backup paths are prepared in advance to cover all the potential single-link failures. The failure affected load is locally allocated to the backup paths through solving a linear programming （LP） problem. Most of the time, the maximum link utilization （MLU） of the network is minimized under both the failure and failure-free cases. For the tested education networks, the LP problem can be solved within milliseconds.

Dynamic response mechanism and precursor characteristics of gneiss rockburst under different initial burial depths

To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.

Excavation compensation theory and supplementary technology system for large deformation disasters

Given the challenges in managing large deformation disasters in energy engineering,traffic tunnel engineering,and slope engineering,the excavation compensation theory has been proposed for large deformation disasters and the supplementary technology system is developed accordingly.This theory is based on the concept that“all destructive behaviors in tunnel engineering originate from excavation.”This paper summarizes the development of the excavation compensation theory in five aspects:the“theory,”“equipment,”“technology,”the design method with large deformation mechanics,and engineering applications.First,the calculation method for compensation force has been developed based on this theory,and a comprehensive large deformation disaster control theory system is formed.Second,a negative Poisson's ratio anchor cable with high preload,large deformation,and super energy absorption characteristics has been independently developed and applied to large deformation disaster control.An intelligent tunnel monitoring and early warning cloud platform system are established for remote monitoring and early warning system of Newton force in landslide geological hazards.Third,the double gradient advance grouting technology,the two-dimensional blasting technology,and the integrated Newton force monitoring--early warning--control technology are developed for different engineering environments.Finally,some applications of this theory in China's energy,traffic tunnels,landslide,and other field projects have been analyzed,which successfully demonstrates the capability of this theory in large deformation disaster control.

Solution to multiple attribute group decision making problems with two decision makers

A kind of multiple attribute group decision making （MAGDM） problem is discussed from the perspective of statistic decision-making. Firstly, on the basis of the stability theory, a new idea is proposed to solve this kind of problem. Secondly, a con- crete method corresponding to this kind of problem is proposed. The main tool of our research is the technique o~ the jackknife method. The main advantage of the new method is that it can identify and determine the reliability degree of the existed decision making information. Finally, a traffic engineering example is given to show the effectiveness of the new method.

Improved STCA Model for Multi-Lane Using Driving Guidance under CVIS

In a multi-lane area,the increasing randomness of lane changes contributes to traffic insecurity and local traffic flow instability.A study on safe lane shifting activity that focuses on threat assessment under real-time knowledge is necessary to enhance smooth vehicle flow.This paper proposed amore comprehensive lane changing guidance rule to investigate the status of surrounding vehicles to accommodate future vehicle-on-road collaborative environments based on these parameters 1)lane change demand and 2)treat assessment function.The collaborative relationships between vehicles are analyzed using a cellular automata model based on their location,velocity,and acceleration.We analyze and examine the relationship between the number of lanes and traffic flow when the road capacity is heavily mined via intelligent lane changing.Our analysis can further provide theoretical guidance for the selection of road expansion mode.Our proposed STCA-L is compared based on the average speed,average flow,lane changing frequency,spatial and temporal pattern of STCA,STCA-I,and STCA-S,and STCA-M under different vehicle densities.The numerical simulation results show that our proposed STCA-L provides themost flexible lane changing guidance in the multi-lanes road.Moreover,the simulated results show that the exponential growth of physical space cannot provide the corresponding increase in the average flow of vehicles.

关于我国高校英文科技期刊国际影响力提升的思考

本文从办刊体制、编辑人员专业水平、期刊评价体制、学术界唯SCI论四个方面对高校英文科技期刊的发展弊端进行了调研,总结出Journal of Traffic and Transportation Engineering (English Edition)(JTTE,交通运输工程学报(英文版))创刊以来所采取的提升期刊国际影响力的措施和方法:在“中国科技期刊卓越行动计划”的支持下,JTTE充分发挥自身优势,依靠长安大学在道路工程、交通运输领域强大的学术影响力,团结作者、学者、编委三方力量,将期刊介绍给全世界,从而提高了期刊的国际显示度;在新媒体背景下,期刊利用跨平台推荐、社交媒体推广等方式宣传期刊内容,加快了期刊内容传播。

Special issue: Management of road and railway traffic and transportation engineering

In recent years,with the development of road and railway transportation industries,a variety of complicated decisionmaking problems have emerged in real-world applications.It is urgent to analyze these problems from the perspective of theoretical and methodological innovations,and provide methods in management,decision-making and application so as to achieve efficient operations of traffic and transportation systems.These problems have

Exploring injury severity of children and adolescents involved in traffic crashes in Greece

For the purpose of exploring the factors affecting injury severity of children and adolescents involved in traffic crashes in Greece,disaggregate crash data including 13,431 involving children and adolescents from all regions of Greece for the period 2006–2015 were utilized.In order to identify factors affecting injury severity and account for potential unobserved heterogeneity,a series of mixed logit models were utilized.To explore and address potential temporal instability of crash-related risk factors,the likelihood ratio test was applied.Results indicated that night crashes,crashes outside urban areas as well as crashes involving bicycles or powered-two-wheelers are associated with higher injury severity of children and adolescents.Interestingly,crashes involving pedestrians are associated with lower injury severity than head-on collisions and run-off-road collisions with fixed objects.Side and sideswipe crashes also result in lower injury severities.The likelihood ratio test indicated that crash-related factors are instable when comparing the models utilizing data before and after 2010 respectively.This study contributes to the current knowledge in the field,as to the best of our knowledge this is the first study that addresses unobserved heterogeneity when analyzing child and adolescent injury severity.Overall,the findings of this study provide useful insights and could assist in unveiling crash risk factors and prioritize programs and measures to promote road safety of children and adolescents.

Estimation of highway capacity under environmental constraints vs.conventional traffic flow criteria:A case study of Tehran

In this paper,the concept of environmental capacity is developed to identify a convenient maximum traffic volume which will not reduce the life quality of residents.The presented method investigates the idea of traffic capacity under environmental constraints by calculating the maximum number of vehicles allowed on roads based on acceptable levels of air and noise pollutants.In this study,the permissible noise pollution level and permissible levels of CO and NOxpollution are considered for determining environmental capacity.Results show the significant difference between environmental capacity and functional traffic capacity,introduced by the highway capacity manual(HCM)as a conventional method for estimating functional capacity.Thus,maximum allowed pollution is considered a constraint on a vehicle flow rate,which shows the proper traffic flow for selected streets in Tehran,Iran’s capital.The paper concludes that traffic capacity under noise and air pollution constraints is much less(approximately one-fourth and one-eighth for noise and air pollution respectively)than the current highway capacity estimated using HCM guidelines.Therefore,to save the cities like Tehran from noise and air pollution,traffic flows should be limited to the level of environmental capacity by implementing some travel demand management(TDM)policies like road pricing.

Impacts of communication delay on vehicle platoon string stability and its compensation strategy:A review

Based on the four-element model,this paper reviewed the important research progress in vehicle platoon,compared the advantages and disadvantages of different models in each element longitudinally,and summarized the linkage between each element horizontally.The stability criteria are briefly reviewed from three dimensions:local stability,string stability,and traffic flow stability.The impact of communication delay on vehicle platoon is quantitatively summarized from two aspects:the variation of controller gains and the variation of headway time values.Aiming at the inevitable communication delay in vehicle platoon,the compensation strategies are analyzed from five levels.(1)Optimizing the communication network structure.(2)Reconstructing acceleration information.(3)Tuning controller gains.(4)Constructing a multi-branch selection structure.(5)Improving the controller.The results show that,although these compensation strategies can alleviate the negative impact of communication delay to a certain extent,they also have some defects such as difficulty in adapting to complex and various real road conditions,poor accuracy and real-time performance,insufficient security,and limited application scenarios.It is necessary to further improve the accuracy and real-time performance of the device,design an encrypted and scalable network architecture to ensure communication security and adaptability,and conduct further real vehicle testing.

Parking reservation techniques:A review of research topics,considerations,and optimization methods

Growing private vehicle use and a limited supply of parking resources have increased competition for parking spaces.Ineffective searching for parking spaces is a significant barrier to smooth traffic flow.Smart technology-generated parking reservations are regarded as an excellent way to increase parking efficiency and lessen traffic.Although there is increased attention on smart parking research and parking reservation optimization,a scoping review is currently lacking.Therefore,the purpose of this paper is to provide a comprehensive review of the research literature related to parking reservations.Out of the original 438 publications identified in this search,99 were eventually chosen for analysis.The review categorized parking reservations into four research topics:inventory control,allocation decisions,pricing strategies,and performance evaluation.The elements considered in these research themes,modeling techniques,and evaluation criteria are explored in detail.In addition,the challenges and further enhancements of parking reservation optimization are discussed.It is believed that the findings from this study will be beneficial in further research on parking reservations.

A review of road safety evaluation methods based on driving behavior

Road traffic safety should be evaluated throughout the entire life-cycle of road design,operation,maintenance,and expansion construction.However,traditional methods for evaluating road traffic safety based on traffic accidents and conflict technology are limited by their inability to account for the complex environmental factors involved.To address this issue,a new road safety evaluation method has emerged that is based on driving behavior.Because drivers’behaviors may vary depending on the driving environment and their personal characteristics,evaluating road safety from the perspective of driver behavior has become a popular research topic.This paper analyzes current research trends and mainstream journals in the field of road safety evaluation of driving behavior.Additionally,it reviews the three most commonly used driving behavior data collection methods,and compares the advantages and disadvantages of each.The paper proposes the main application scenarios of road safety evaluation methods based on driving behavior,such as road design,evaluation of the effects of road appurtenances,and intelligent highways.Furthermore,the paper summarizes a driving behavior index system based on vehicle data,driver’s physiological and psychological data,and driver’s subjective questionnaire data.A comprehensive evaluation method based on the fusion of each index system is presented in detail.Finally,the paper points out current research problems and the future development direction of the road safety evaluation method based on driving behavior.

Intelligent Segment Routing: Toward Load Balancing with Limited Control Overheads

Segment routing has been a novel architecture for traffic engineering in recent years.However,segment routing brings control overheads,i.e.,additional packets headers should be inserted.The overheads can greatly reduce the forwarding efficiency for a large network,when segment headers become too long.To achieve the best of two targets,we propose the intelligent routing scheme for traffic engineering(IRTE),which can achieve load balancing with limited control overheads.To achieve optimal performance,we first formulate the problem as a mapping problem that maps different flows to key diversion points.Second,we prove the problem is nondeterministic polynomial(NP)-hard by reducing it to a k-dense subgraph problem.To solve this problem,we develop an ant colony optimization algorithm as improved ant colony optimization(IACO),which is widely used in network optimization problems.We also design the load balancing algorithm with diversion routing(LBA-DR),and analyze its theoretical performance.Finally,we evaluate the IRTE in different real-world topologies,and the results show that the IRTE outperforms traditional algorithms,e.g.,the maximum bandwidth is 24.6% lower than that of traditional algorithms when evaluating on BellCanada topology.

Reviews and prospects of human factors research on curve driving

In order to fully understand the research progress of human factors and traffic safety in curve driving,from the perspective of driver-vehicle-road-environment dynamic traffic system,this paper explored the current research status and development trend of human factors of curve driving,and displayed the development process and structural relationship of human factors research of curve driving by using scientific knowledge map.Through the core collection database of Web of Science,1408 English literatures related to human factors research of curve driving published from 2012 to 2022(as of October 1,2022)were obtained,and the literatures in this field were sorted and analyzed based on the VOSviewer visualization software.The results show that China,Tongji University and Accident Analysis and Prevention are the country,institution and journal with the largest contribution rate in the field of human factors research on curve driving.Co-citation analysis shows that the research contents in this field are divided into 5 clusters:driver’s visual characteristics,risk of collision,vehicle dynamics characteristics,the influence of traffic engineering facilities on driving behavior,selection of driving speed.The co-occurrence analysis of keywords shows that the topics of curve geometry design and vehicle dynamics,driving behavior and risk,driving speed and safety,behavior prediction and intervention measures are the current research hotspots in the research field.It is found that the development trend of traffic safety improvement in curves is to construct a continuous,consistent,multi-level visual reference frame conforming to driving expectation through visual guiding technology,and summarizes the technical concept of linear visual guidance.This study can provide a reference for the study of human factors of curve driving.