• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.7
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• pp.22-29
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• 2002

The Gauranteed Frame Rate service category was proposed by the ATM Forum as an enhancement to the UBR service. This service aims to support minimum cell rate gaurantee for each virtual connection and allow any excess bandwidth in the network to be shared among the contending VCs in a fair manner. We propose a new buffer management algorithm for GFR service through FIFO queuing discipline. Proposed scheme can provide minimum bandwidth guarantee for GFR VCs as well as improve the fairness among the competing GFR VCs on a single FIFO queue. From simulation results, we demonstrate the proposed scheme fulfills the requirement of GFR service as well as improves the TCP throughput.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.892-895
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• 2002

We propose new buffer management scheme for GFR service through FIFO queuing discipline. Proposed scheme can provide minimum bandwidth guarantees for GFR VCs as well as improve the fairness among the competing GFR VCs on a single FIFO queue. From simulation results, we demonstrate the proposed scheme fulfills the requirements of GFR service as well as improves the TCP throughput.

• Journal of KIISE:Information Networking
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• v.27 no.3
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• pp.315-322
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• 2000

네트워크에서 QoS를 보장하기 위해 최근에 제안되는 패킷 스케줄링 알고리즘은 대부분 우선 순위에 입각한 패킷 전송 서비스를 한다. 이러한 우선 순위를 유지하기 위한 큐의 관리에는 많은 비용이 들므로 QoS를 보장하는 네트워크에서 우선 순위 큐의 관리 비용을 줄이는 노력이 필요하다. 패킷 스케줄링 알고리즘 중 RPO+(Rotate Priority Queue)는 우선 순위 FIFO(First in first out)큐를 사용하여 주기 적으로 재명명되는 패킷 스케줄링 알고리즘이다. FIFO 큐에 패킷들을 근사 정렬하여 패킷의 우선 순위를 유지하므로 계산 복잡도를 줄이지만, 패킷 우선 순위를 유지하기 위해 2배(2P)의 큐를 필요로 한다.[1] 본 논문에서는 필요한 큐의 개수를 P개의 큐로 제한하여 큐에 대한 관리 비용을 줄였으며 엔터프라이즈 환경에서 애플리케이션이 요구하는 서비스 특성에 따라 클래스로 구분하여 적합한 패킷 스케줄링 서비스를 제공하는 알고리즘을 제시한다. 본 기법은 추가적인 오버플로우 큐를 관리하고 패킷 어드미션 컨트롤러를 통해 패킷 전송 지연 시간을 제한함으로 다양한 애플리케이션의 네트워크 QoS 요구를 보장하고 패킷 전손 효율을 높였다.

• Journal of Korean Society of Transportation
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• v.19 no.3
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• pp.101-113
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• 2001

Since late 1970s. one of the principal research areas in transportation problem is dynamic traffic assignment (DTA). Although many models have been developed regarding DTA, yet they have some limits of describing real traffic patterns. This reason comes from the fact that DTA model has the time varying constraints such as state equation, flow propagation constraint, first in first out(FIFO) rule and queuing evolution. Thus, DTA model should be designed to satisfy these constraints as well as dynamic route choice condition, dynamic user equilibrium. In this respect, link-based DTA models have difficulty in satisfying such constraints because they have to satisfy the constraints for each link, while path-based DTA models may easily satisfy them. In this paper we develop a path-based DTA model. The model includes point queue theory to describe the queue evolution and simulation loading method for depicting traffic patterns in more detail. From a numerical test, the model shows promising results.

• Journal of the Korean Operations Research and Management Science Society
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• v.20 no.2
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• pp.1-10
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• 1995

In this study, a threshold policy is considered for the M/M/2 queueing system with server vacations. The probability generating function for the number of customers present in the system is derived using an embedded Markov chain approach. Then, assuming a linear cost structure, an efficient procedure to find an optimal threshold policy is presented. The Laplace-Stieltjes transofrm for th waiting time of an arbitrary customer under a "FIFO" discipline is also derived.o derived.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.517-526
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• 2001

In order to reduce the increasing packet loss rates caused by an exponential increase in network traffic, the IETF(Internet Engineering Task Force) is considering the deployment of active queue management techniques such as RED(Random Early Detection). While active queue management in routers and gateways can potentially reduce total packet loss rates in the Internet, this paper has demonstrated the inherent weakness of current techniques and shows that they are ineffective in preventing high loss rates. The inherent problem with these queue management algorithms is that they all use queue lengths as the indicator of the severity of congestion. In this paper, in order to solve this problem, a new active queue management algorithm called MRED(Modified Random Early Detection) is proposed. MRED computes the packet drop probability based on our heuristic method rather than the simple method used in RED. Using simulation, MRED is shown to perform better than existing queue management schemes. To analyze the performance, we also measure throughput of traffics under the FIFO control, and compared the performance with that of this MRED system.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.70-78
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• 2006

This paper has addressed the scheme to design single rate Rate Adaptive Shaper (srRAS) proposed in RFC2963. srRAS is the shaper used in conjugation with downstream single rate Three Color Marker (srTCM) described in RFC269. it is tail-drop First Input First Out (FIFO) queue that is drained at a variable rate. srTCM meters IP packet streams from srRAS and marks its packets to be either green, yellow, or red. This shaper has been proposed to use at the ingress of differentiated services networks providing AF PHB. And then srRAS can reduce the burstiness of the upstream traffic of srTCM. This paper addresses algorithm, architecture of srRAS, and the scheme to implement srRAS using Field-Programmable Gate Arrays (FPGA) and the related technology.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.337-342
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• 2012

This paper presents performance evaluation of real-time mechanisms for real-time embedded linux. First, we presents process for implementing open-source real-time embedded linux namely RTAI and Xenomai. These are real-time extensions to linux kernel and we implemented real-time embedded linux over the latest linux kernel. Measurements of executions of real-time mechanisms for each distribution are performed to give a quantitative comparison. Performance evaluations are conducted in kernel space about repeatability of periodic task, response time of Semaphore, FIFO, Mailbox and Message queue in terms of inter-task communication for each distribution. These rules can be helpful for deciding which real-time linux extension should be used with respect to the requirements of the real-time applications.

• Journal of the Korean Statistical Society
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• v.28 no.1
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• pp.125-133
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• 1999

We consider a FIFO single-server queueing model in which both the arrival and service processes are modulated by the amount of work in the system. The arrival process is a non-homogeneous Poisson process(NHPP) modulated by work, that is, with an intensity that depends on the work in the system. Each customer brings a job consisting of an exponentially distributed amount of work to be processed. The server processes the work at various service rates which also depend on the work in the system. Under the stability conditions obtained by Browne and Sigman(1992) we derive the exact stationary distribution of the work W(t) and the first exit probability that the work level b is exceeded before the work level a is reached, starting from x$\in$[a, b].

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.47
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• pp.125-138
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• 1998

In this paper, we investigate the effect of re-entrance to the same work station in a job shop with multiple identical machines. System A is defined as the system in which re-entrance is not permitted, and system B is defined as the system in which re-entrance is permitted. By the analytical result of the queueing network, we find that the two systems have the same queue length distributions and utilizations under FIFO dispatching rule when all parameters are same. Simulation models are developed for various comparisons between the two systems, and simulation experiments are conducted for the combinations of five dispatching rules, two average workloads and two due date allowances. Five performance measures are selected for the comparison. The simulation results show that permitting re-entrance affects for some combinations of system environments.