• 한국멀티미디어학회논문지
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• 제18권2호
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• pp.189-198
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• 2015

Despite the fact that traffic engineering techniques have been comprehensively utilized in the past to enhance the performance of communication networks, the distinctive characteristics of Software Defined Networking (SDN) demand new traffic engineering techniques for better traffic control and management. Considering the behavior of traffic, large flows normally carry out transfers of large blocks of data and are naturally packet latency insensitive. However, small flows are often latency-sensitive. Without intelligent traffic engineering, these small flows may be blocked in the same queue behind megabytes of file transfer traffic. So it is very important to identify large flows for different applications. In the scope of this paper, we present an approach to detect large flows in real-time without even a short delay. After the detection of large flows, the next problem is how to control these large flows effectively and prevent network jam. In order to address this issue, we propose an approach in which when the controller is enabled, the large flow is mitigated the moment it hits the predefined threshold value in the control application. This real-time detection, marking, and controlling of large flows will assure an optimize usage of an overall network.

• Journal of information and communication convergence engineering
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• 제5권3호
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• pp.239-244
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• 2007

In the telematics system, a reasonable path search time should be guaranteed from a great number of user's queries, even though the optimal path with minimized travel time might be continuously changed by the traffic flows. Thus, the path search method should consider traffic flows of the roads and the search time as well. However, the existing path search methods are not able to cope efficiently with the change of the traffic flows and to search rapidly paths simultaneously. This paper proposes a new path search method for fast computation. It also reflects the traffic flows efficiently. Especially, in order to simplify the computation of variable heuristic values, it employs a simplification method for estimating values of traffic-adaptable heuristics. The experiments are carried out with the $A^*$ algorithm and the proposed method in terms of the execution time, the number of node accesses and the accuracy. The results obtained from the experiments show that the method achieves very fast execution time and the reasonable accuracy as well.

• Journal of Information Processing Systems
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• 제6권3호
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• pp.307-322
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• 2010

Traffic classification is an essential task for network management. Many researchers have paid attention to initial sub-flow features based classifiers for traffic classification. However, the existing classifiers cannot classify traffic effectively in mobile IP networks. The classifiers depend on initial sub-flows, but they cannot always capture the sub-flows at a point of attachment for a variety of elements because of seamless mobility. Thus the ideal classifier should be capable of traffic classification based on not only initial sub-flows but also various types of sub-flows. In this paper, we propose a classifiable sub-flow selection method to realize the ideal classifier. The experimental results are so far promising for this research direction, even though they are derived from a reduced set of general applications and under relatively simplifying assumptions. Altogether, the significant contribution is indicating the feasibility of the ideal classifier by selecting not only initial sub-flows but also transition sub-flows.

• Management Science and Financial Engineering
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• 제15권1호
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• pp.51-69
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• 2009

A network model and a Genetic Algorithm (GA) is proposed to solve the simultaneous estimation of the trip distribution and traffic assignment from traffic counts in the congested networks in a logit-based Stochastic User Equilibrium (SUE). The model is formulated as a problem of minimizing a non-linear objective function with the linear constraints. In the model, the flow-conservation constraints are utilized to restrict the solution space and to force the link flows become consistent to the traffic counts. The objective of the model is to minimize the discrepancies between two sets of link flows. One is the set of link flows satisfying the constraints of flow-conservation, trip production from origin, trip attraction to destination and traffic counts at observed links. The other is the set of link flows those are estimated through the trip distribution and traffic assignment using the path flow estimator in the logit-based SUE. In the proposed GA, a chromosome is defined as a real vector representing a set of Origin-Destination Matrix (ODM), link flows and route-choice dispersion coefficient. Each chromosome is evaluated by the corresponding discrepancies. The population of the chromosome is evolved by the concurrent simplex crossover and random mutation. To maintain the feasibility of solutions, a bounded vector shipment technique is used during the crossover and mutation.

• ETRI Journal
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• 제5권2호
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• pp.17-28
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• 1983

This paper deals with the problem of optimally controlling traffic flows in urban transportation traffic networks. For this, a nonlinear discrete-time model of urban traffic network is first suggested in order to handle the phenomenon of traffic flows such as oversaturatedness and/or undersaturatedness. Then an optimal control problem is formulated and a hierarchical optimization technique is applied, which is based upon a prediction-type two-level method of Hirvonen and Hakkala.

• 한국경제지리학회지
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• 제10권4호
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• pp.427-443
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• 2007

본 연구의 목적은 현재 서울시를 포함한 수도권 지역에서 가장 높은 수송분담율을 차지하고 있는 지하철망 상 통행흐름의 시 공간적 구조를 밝히고, 그러한 통행흐름과 토지이용의 관계성을 밝히는 것이다. 특히 본 연구에서는 지난 2004년 7월 이후 수도권 대중교통이용자의 대부분이 이용하고 있는 교통카드 통행거래자료 중 매년 주중 하루치의 통행 트랜잭션 데이터베이스에 대하여 데이터마이닝 기법을 적용하여 지난 4년간 수도권 지하철망 상 통행흐름의 위상학적 구조를 비교분석하였다. 또한 하루 중 시간대별 통행흐름의 공간적 특징을 분석하기 위하여 하루를 아침 출근시간대, 낮 시간대, 저녁 퇴근 시간대로 나누어 수도권 지하철망 상의 각 지하철역의 시간대별 출발통행량과 도착통행량을 산출하고, GIS를 이용하여 그 공간적 패턴을 비교한 결과 시간대별로 확연한 차이가 나타남을 확인하였다. 그리고 지하철 통행흐름의 위상학적 구조와 토지이용과의 관계성을 밝히기 위하여 각 지하철역의 시간대별 출발 도착 통행량과 그 지하철역 주변지역의 토지이용상태를 반영하는 지리적 변수들 간의 상관관계분석과 다중회귀분석을 실시하였으며, 분석 결과 시간대별 출발 통행량 및 도착 통행량 관계를 설명하는 선형 대수식을 도출하였다. 함수식의 적합성 판명을 위하여 공선성진단과 이분산성분석을 실시하였다.

• 한국경제지리학회지
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• 제12권4호
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• pp.521-539
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• 2009

본 연구의 목적은 지속가능한 도시교통체계 확립을 위한 방향 모색을 위한 기초 작업으로 서울에서 대기오염 등 다양한 환경문제를 야기하는 도로교통흐름의 시 공간적 특성을 분석하는 것이다. 특히 1990년대 중후반부터 진행되어오고 있는 수도권지역 신도시 개발로 인구분포에 나타나고 있는 변화와 1990년대 후반의 IMF로 경제 사회 기술적 환경이 크게 바뀌면서 산업 구조의 재편과 함께 나타나고 있는 서울시 도로교통흐름과 토지이용의 시 공간적 변화에 초점을 두고 분석하였다. 이를 위하여 1993년부터 서울시 주요지점에 설치한 118개 측정지점에서 실시간 관측한 14년간의 도로교통흐름 자료를 이용하여 서울시 교통흐름의 시간적 변화와 공간적 변화를 분석하였다. 서울시 전체의 연평균일일교통량에 대한 시계열적 분석 결과 서울시 도로교통흐름의 변화추세는 1997년과 2003년 두 시점을 변곡점으로 큰 변화를 보임을 확인하였다. 이러한 변곡점들을 전후한 시점들의 도로교통흐름을 GIS를 적용하여 공간적 구조를 분석해 보면 서울시 교통흐름은 도심의 교통량감소와 시계지점의 교통량 증가, 강남권의 교통량증가, 한강교량을 통한 강남 북 간 교통량 감소 등, 뚜렷한 공간적 변화가 관찰된다. 이러한 현상은 서울시의 토지이용패턴이 크게 변화하였으며, 그에 따라 지역 간 기능적인 연계구 조도 크게 달라졌음을 암시하는 것이므로 본 연구에서는 서울시 도로교통흐름의 공간적 구조에 나타나는 변화가 서울시의 토지이용변화와 어떻게 연관되어 있는가를 밝히기 위하여 먼저 수도권 거주인구분포에 나타나는 변화와의 관계성을 분석 하였다. 분석 결과 서울시 도로교통흐름의 공간구조에 나타나는 변화는 신도시를 비롯한 경기도 지역의 거주 인구의 증가와 서울 도심지역 인구 감소 현상과 밀접히 연관되어 있음을 확인할 수 있었다. 좀 더 구체적으로 서울시 산업구조와 분포에 나타나는 변화와 서울시 도로교통흐름의 공간적 구조에 나타나는 변화를 파악하기 위하여 구별 도로교통량 증감률과 산업별 산업체 수와 종사자수의 증감률, 거주인구증감률을 중심으로 세 개의 선형모형을 구성하고 다중회귀분석을 적용하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권6호
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• pp.575-596
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• 2009

Facing limited network resources such as bandwidth and processing capability, the Internet will have congestion from time to time. In this paper, we propose a scheme to maximize the total utility offered by the network to the end user during congested times. We believe the only way to achieve our goal is to make the scheme application-aware, that is, to take advantage of the characteristics of the application. To make our scheme scalable, it is designed to be class-based. Traffic from applications with similar characteristics is classified into the same class. We adopted the RED queue management mechanism to adaptively control the traffic belonging to the same class. To achieve the optimal utility, the traffic belonging to different classes should be controlled differently. By adjusting link bandwidth assignments of different classes, the scheme can achieve the goal and adapt to the changes of dynamical incoming traffic. We use the control theoretical approach to analyze our scheme. In this paper, we focus on optimizing the control on two types of traffic flows: TCP and Simple UDP (SUDP, modeling audio or video applications based on UDP). We derive the differential equations to model the dynamics of SUDP traffic flows and drive stability conditions for the system with both SUDP and TCP traffic flows. In our study, we also find analytical results on the TCP traffic stable point are not accurate, so we derived new formulas on the TCP traffic stable point. We verified the proposed scheme with extensive NS2 simulations.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.652-653
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• 2015

This study investigates the effect of real-time traffic information on the traffic flows in Korea. Recently, the development of smartphones has made it easier to use the route guidance service based on real-time traffic information. By the Big Data analysis in the study, it was found that the number of postings on the web community sites increased sharply in 2010 and 2011 when the smartphones spread widely. In the analysis of the traffic speeds by time, the average traffic speeds for morning and evening rush hours on weekdays from 2009 to 2014 of the 142 sections in the 6 national highways in Gyeonggi-do, Korea were used. From the results of the analysis, it was found that the percentage of the number of sections with the improved traffic flows increased greatly in 2012 compared to 2011. The findings of the study indicate the effect of the real-time traffic information on improving traffic flows.

• Journal of Communications and Networks
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• 제3권4호
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• pp.324-333
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• 2001

The Differentiated Services (Diffserv) framework has been proposed by the IETF as a simple service structure that can provide different Quality of Service (QoS) to different classes of packets in IP networks. IP packets are classified into one of a limited number of service classes, and are marked in the packet header for easy classification and differentiated treatments when transferred within a Diffserv domain. The Diffserv framework defines simple and efficient QoS differentiation mechanisms for the Internet. However, the original Diffserv concept does not provide a complete QoS management framework. Since traffic flows in IP networks are unidirectional from one network point to the other and routing paths and traffic demand get dynamically altered, it is important to monitor end-to-end traffic status, as well as traffic status in a single node. This paper suggests a distributed QoS monitoring method that collects the statistical data of each service class in every Diffserv router and calculates edge-to-edge QoS of the aggregated IP flows by combining routing topology and traffic status. A format modeling of edge-to-edge Diffserv flows and algorithms for aggregating edge-to-edge QoS is presented. Also an SNMP-based QoS management prototype system for Diffserv networks is presented, which validates our QoS management framework and demonstrates useful service management functionality.