• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.144-154
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• 1996

Proposed numerous algorithms for the policing function have mainly focused on their performances. Besides their performance evaluation, however, the VLSI-implementation of these algorithms is worth consideration as well. Although, no algorithms for the policing function have been standardized up to now, ITU-T I.371 suggests two examples of algorithms, the Virtual Scheduling Algorithm (VSA) and the Continuous State Leaky Bucket algorithm. In this paper, we suggest the architecture of a policing device implementing the VSA among various algorithms for the peak cell rate policing and discuss some issues on the implementation. We also present how to select the policing modes of the two devices used to realize various policing schemes and show the experimental results obtained under four different peak cell rate values to confirm that the device performs the policing function satisfactorily. We exploit the priority encoder to run the algorithm in parallel instead of sequentially, which reduces the operation time to a great extent.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.11
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• pp.106-115
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• 1996

In this paper, the method using virtual scheduling suggested algorithm (VSSA) is suggested by considering cell delay variation and token rate of leaky bucket. This method is compared with virtual scheduling algorithm (VSA) and virtual scheduling algorithm with no tolerance excessive peak cell rate. As a result, the research shows that the usage parameter control using vSSA makes quality of service better than the usage parameter control using vSA or VSANT does because the suggested method reduces the violated cell probability of conformed peak cell rate and intentionally excessive peak cell rate.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.261-264
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• 2000

When there ate several classes of customers demanding service times with different distributions at some stations of a queueing network, the stability problem becomes suddenly complicated compared with the single class case. Recently many researchers had tried to find some kind of stability conditions for multiclass queueing networks, but did not get significant results except in very limited 2-station cases. In this study, we try to develop some dynamic control techniques which can guarantee the stability under the nominal traffic condition. Our approach includes the randomization method and the leaky bucket control scheme. Also, we mention other possibilities such as the discrete-review approach and the generalized round-robin technique. Both theoretical and experimental results will be presented.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.126-129
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• 1998

In order to control the flow of traffics in ATM networks and optimize the usage of network resources, an efficient control mechanism is necessary to cope with congestion and prevent the degradation of network performance caused by congestion. This paper proposes a new UPC(Usage Parameter Control) mechanism that varies the token generation rate and the buffer threshold of leaky bucket by using a Neural Network controller observing input buffers and token pools, thus achieving the improvement of performance. Simulation results show that the proposed adaptive algorithm uses of network resources efficiently and satisfies QoS for the various kinds of traffics.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.23-31
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• 1996

This paper proposes a new UPC(usage parameter control) mechanism that varies the token generation rate of leaky bucket by observing virtual buffer, thus achieving an improvement of performance. An acceptance of a call in B-ISDN is determined by call admission control. A UPC that polices the agreed traffic parameters of a call and takes appropriate actions to prevent congestion in networks. The cell loss probability of conventional UPC is far from that of ideal UPC. The proposed mechanism has a better policing ability and response time for nonconforming call. The proposed mechanism uses ON-OFF model as input traffic. The results of simulation show the efficiency of the proposed mechanism.

• ETRI Journal
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• v.22 no.3
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• pp.1-9
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• 2000

Self-Clocked Fair Queueing (SCFQ) algorithm has been considered as an attractive packet scheduling algorithm because of its implementation simplicity, but it has unbounded delay property in some input traffic conditions. In this paper, we propose a Rate Proportional SCFQ (RP-SCFQ) algorithm which is a rate proportional version of SCFQ. If any fair queueing algorithm can be categorized into the rate proportional class and input is constrained by a leaky bucket, its delay is bounded and the same as that of Weighted Fair Queueing (WFQ) which is known as an optimal fair queueing algorithm. RP-SCFQ calculates the timestamps of packets arriving during the transmission of a packet using the current value of system potential updated at every packet departing instant and uses a starting potential when it updates the system potential. By doing so, RP-SCFQ can have the rate proportional property. RP-SCFQ is appropriate for high-speed packet-switched networks since its implementation complexity is low while it guarantees the bounded delay even in the worst-case input traffic conditions.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.248-250
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• 2000

본 논문은 망에 대한 유연성과 망의 성능의 효율성을 개선하기 위해서 기존의 회선 교환 위성 망에서 데이터 트래픽을 다루는 시스템을 제안하고 성능을 분석한다. 제안한 시스템은 각 연결의 용량 변경 요구를 동적으로 허락하기 때문에, 그 연결 자체의 초기화 설정 및 연결을 해제하는 다른 별도의 알고리즘이 필요 없어 기존의 회선 교환 위성 망보다 효율적이다. 또, 서비스 질을 결정적으로 보장함으로 망의 유연성 및 신뢰성을 높인다. 트래픽 소스는 Dual Leaky Bucket에 의해 일정하게 조정된 트래픽을 사용하며, 이러한 트래픽을 이용하여 제안한 시스템의 성능을 수학적으로 분석하였고, 이를 시뮬레이션을 통해 검증하였다. 이러한 분석 결과는 앞으로 회선 교환 시스템에서 프로토콜의 설계 및 구현 시 유용하게 사용될 수 있을 것으로 사료된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1091-1094
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• 2000

본 논문은 위성 망에서 데이터 Traffic을 다루는 System을 제안하고, 성능을 분석한다. Traffic Source는 듀얼 리키 버켓(DLB : Dual Leaky Bucket)에 의해 일정하게 조정된 Traffic을 사용하며, 이러한 Traffic을 이용하여 제안한 시스템의 성능을 수학적으로 분석하고, 이를 시뮬레이션을 통해 검증한다. 제안한 시스템은 각 연결의 용량 변경 요구를 동적으로 허락하기 때문에 그 연결 자체의 초기화 설정 및 연결을 해제하는 다른 별도의 알고리즘이 필요 없어 기존의 회선 교환 시스템보다 효율적이다. 또한, 서비스 질을 결정적으로 보장함으로 망의 유연성 및 신뢰성을 높인다. 이러한 분석 결과는 앞으로 회선 교환 System에서 Protocol의 설계 및 구현 시 유용하게 사용될 수 있을 것으로 생각된다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.142-144
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• 2005

Distributed Denial of Service는 네트워크나 개인 호스트를 위협하는 대표적인 공격 트래픽이다. DDoS 공격은 특정한 패턴을 가지고 있지 않기 때문에 탐지가 어려울 뿐 아니라, TNF2K와 같은 간단한 tool로 공격이 가능하여 그 심각성은 실로 크다. 이러한 DDoS를 탐지하기 위한 메카니즘이나 알고리즘은 많이 개발되었다. 하지만 DDoS의 근원지를 판별하고 대응하는 것이 아닌, 단지 방어 지정에서 전체 threshold를 낮추거나 leaky bucket처럼 수용 능력 이상의 패킷을 폐기하는 방법으로 네트워크나 개인 호스트를 보호한다. 무분별하게 전체 트래픽을 줄이는 것은 네트워크의 resource를 고갈 시키지는 않지만, 정상적인 clients가 공격당하고 있는 호스트에 연결을 할 수가 없다. 이를 위해 여러 단계의 테스트를 통해 합법적인 검증 IP table을 만들고, 검증 IP table에 있는 source IP를 제외한 나머지 트래픽을 차단한다면, DDoS 공격에 대해서 대응을 하면서 정상적인 Clients의 연결을 보호 할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.833-841
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• 1997

In this paper, the hybrid LB-TJW(Leaky Bucket-Triggered Jumping Window) algorithm for multimedia traffic control is proposed and its performance is evaluated and analyzed. Its architecture is composed of the peak bit rate controller and the average bit rate controller. Generally, the cell which violates the peak bit rate is discraded in LBalgorithm, and the average bit rate of JW or TJW algorithm is better than that of LB algorithm. However, the hybrid LB-TJW algorithm passes it though the network if the cell does not violate the peak bit rate. If the cell violates the peak bit rate, the hybrid LB-TJW algorithm passes it to the average bit rate controller which perforithm to monitor the average bit rate of input traffic. The TJW algorithm monitors the cell that violates the average bit rate. If the cell does not violate the average bit rare, the LB-TJW algorithm passes it through the network. As simulation results, the cell loss rate and the buffer size of the LB-TJW algorithm is reduced to half as much as those of LB algortihm.