• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.539-544
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• 2011

In this paper, a parameter optimization method of RIO-DC (RED (Random Early Detection) with In and Out-De-Coupled Queues) scheme for Assured Service (AS) in Differentiated Services (DiffServ) is proposed. In order to optimize QoS (Quality of Service) performance of the RIO-DC policy for AS in terms of maximum tolerable latency, link utilization, fairness, etc., we should design router nodes with proper RIO-DC operating parameter values. Therefore, we propose a RIO-DC configuration method and the admission control criterion, considering the allocated bandwidth to each subclass and the corresponding buffer size, to increase throughput for In-profile traffic and link utilization. Simulation results show that RIO-DC with the proposed parameter values guarantees QoS performance comparable with the RIO scheme and it improves fairness between AS flows remarkably.

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.764-775
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• 2003

Previous works for the assured service in the Diffserv network have no sufficient consideration on the fairness of bandwidth share based on RTTs and the target rates of TCP flows. In this paper, in order to solve these problems, we propose a TRA3CM(Target rate and RTT Aware 3 Color Marking) mechanism. The TRA3CM mechanism provides three color marking and fair transmission rates among aggregate flows by considering RTT and target rate simultaneously. In case of higher target rate than bottleneck bandwidth, the TRA3CM mechanism is able to mitigate the RTT effect and provides fair transmission rates. In the results of comparing the performance among existing mechanisms and the TRA3CM, the TRA3CM mechanism was able to mitigate the RTT effect better than the former. The TRA3CM is shown to provide good performance for transmission rates proportional to various target rates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.613-627
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• 2004

In this paper, we propose an Aggregate Fairness Maker (ARM) required for an Edge router to improve fairness of throughput among the flows of Assured Service in DiffServ with different round trip time (RTT) and we propose a user flow Three Color Marker (uf-TCM) as a flow marker that marks packets from the flow as green, yellow, or red. A yellow packet is the packet that consumes loss token in uf-TCM as well as that is demoted green packet in AM due to disobey the aggregate traffic profile. The proposed AFH promotes yellow packet to green packet or demotes green packet to yellow packet through the fair method without per-flow management, and it improves the feirness of throughput among the flows as well as link utilization. A yellow packet and a red packet have the same drop precedence at Core Router in our scheme. So we can use the RIO buffer management scheme. We evaluated the performance of our proposed AFM and the REDP Marker that was proposed to improve fairness without per-flow management. Simulation results show that, compared with the REDP marker, proposed AFM can improve performance of throughput fairness among the flows with different RTT and link utilization under the over-provisioning, exact-provisioning, and under-provisioning network environments at Multiple DiffServ domains as well as at Single DiffServ domain.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1351-1354
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• 2001

본 논문에서는 Differentiated Services (DiffServ) 망의 edge 라우터에 적용되는 3 단계 트래픽 제어기 (3 phased traffic conditioner : 3PTC)를 제안하였다. 제안된 3PTC 는 TCP 트래픽의 예약된 대역폭 (reserved rate) 의 차이, UDP/TCP의 상호작용, RTT 및 집합된 트래픽을 구성하는 작은 트래픽 수에 의한 영향을 최소화함으로써, DiffServ 망에서 제공하는 Assured Services 사용자들에게 공정한 대역폭을 보장해 줄 수 있다. 3PTC 는 토큰버킷 단계, 확률결정 단계, 그리고 버퍼관리 단계로 이루어져 있다.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3320-3331
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• 1999

In this paper, we explore two ways to improve the bandwidth assurance performance of Assured Service(AS). It is well known that AS fails to meet the bandwidth assurance target for large-profile TCP flows competing with many small-profile flows. This flows after the back-offs induced by packet drops. Thus currently proposed solution to this problem naturally focus on modifying TCP's behavior to counter the unfairness in the TCP dynamics. Unfortunately, these proposals lack practicability in terms of the required changes in the incumbent Internet infrastructure. Admitting this difficulty, we instead look to not yet deployed Diff-Serv mechanisms for practical solutions. In particular, we investigate the role of RIO, RED with IN(in-profile) and OUT(out-profile), queue management scheme in the assurance failure for As. Specifically, we identify the inadequacy of RIO that aggravates the bandwidth assurance failure. Then we alleviates the bandwidth assurance failure problem by separately controlling the out-of-profile packet queue length. Through extensive simulations we demonstrate that RI+O extends the regime where AS consistently provides the bandwidth assurance.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.133-135
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• 2003

본 논문에서는 IEEE 802.11 WLAN $^{[1]}$ 에서 QoS를 제공하기 위해 새로운 MAC­layer 구조를 제안한다. 주요 특징으로는 향후 Core Network의 모델로서 제시되고 있는 DiffServ 구조의 특징들을 WLAN에 적용하는 것을 들 수 있으며, 이를 통해 다양한 종류의 멀티미디어 트래픽에 적용될 End­to­end QoS를 보다 효율적 보장하고자 한다. DiffServ에서 제시되고 있는 Expedited. Assured forwarding과 일반적인 Best­effort traffic에 대한 service 차등화 기법을 WLAN에서 적용하기 위해 기존 MAC layer에서의 DCF, PCF 대신 EDWM(Extended DiffServ in WLAN MAC)이라는 새로운 MAC­layer 구조를 제시한다. 이를 통해 시간지연에 민감한 Expedited forwarding과 대역폭의 보장을 필요로 하는 Assured forwarding의 요구 사항(QoS)을 효율적으로 보장할 수 있다. 이에 더하여 기존의 인프라(infrastructure)인 IEEE 802.11b 환경의 DCF와 이를 통하여 service를 제공받는 일반적인 Best­effort traffic을 위한 backward compatibility 보장 방안을 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.481-483
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• 2004

본 논문에서는 차등 서비스 네트워크(Diffserv network)의 확신 서비스(assured service)에서 발생할 수 있는 TCP와 UDP 플로우 사이의 공명성 문제를 해결하기 위한 TRBD(Target Rate-based Dropping) 기법을 제안한다. 차등 서비스 네트워크의 확신 서비스에서의 공평성 향상에 대한 기존 연구는 마킹 확률을 변경하여 공평성을 향상시키는 연구가 중심이 되어 왔다. 이러한 연구들은 코어노드에서의 큐 관리를 위하여 주로 MRED(Multiple RED)골 이용하기 때문에 TCP 및 UDP, 목표 전송률 등에 대한 고려가 부족하다. 본 논문에서 제안하는 TRBD 기법은 코어노드에서 목표 전송률에 따라 UDP의 폐기 확률을 조정하여 TCP-UDP 공평성 및 목표 전송률을 고려한 공평성을 향상시킬 수 있다. ns 시뮬레이터를 이용한 실험을 통하여 TRBD 기법의 TCP-UDP 공평성 향상을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.461-471
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• 2004

Recently, subscribers have strong desire to get QoS based personalized services in high-speed Internet access. Service providers have been rapidly replacing ADSL, cable broadband access networks with Metro-Ethernet based VDSL. But, it is difficult for Motto-Ethernet based broadband access networks to provide QoS based personalized services, because already deployed network elements cannot distinguish subscribers by specific traffic characteristics. In this paper, when the access network has tree topology, we show that it is possible to provide QoS for each downstream flow with only per flow traffic shaping at the edge node without QoS functions in access networks. In order to show that our suggested scheduling algorithm at the edge node can support the assured service in tree topology access networks, we evaluated its performance by simulation. The suggested scheduling algorithm can shape per-flow traffic based on the maximum bandwidth, and guarantees minimum bandwidth per flow by modifying the DRR scheduler. Simulation results show that congestion and loss in the access network elements are greatly reduced, TCP performance is highly enhanced and loss for assured CBR service flows is reduced by only shaping per-flow traffic at the edge node using our proposed scheduling algorithm.

• Proceedings of the Korea Information Assurance Society Conference
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• 2004.05a
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• pp.43-50
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• 2004

Diffserv Network DSCP(Differentiated Service Code Point)는 8bit로 구성되어 있고, 그 중 6bit만 사용되고, 나머지 2bit는 비워져 있는 상태로 있다. 이 2bit를 사용하여, DF(Default Forwarding), EF(Expedited Forwarding), AF(Assured Forwarding)의 DSCP 에 각각의 Service Class Code Point를 부여해서 사용자의 패킷을 구분하여 서비스하는 DiffServ 같은 경우 상용화가 되었을 때, DiffServ를 서비스하는 망에서 동일한 DiffServ 정책을 설정해서 사용할 수 있는 기법을 제안한다.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.469-481
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• 2004

Previous works for the AF(Assured Forwarding) service in the Diffserv network have no sufficient consideration on the fairness of bandwidth share based on RTTs, the target rates, and the impact of UDP against TCP. In this paper, in order to solve these problems, we propose a FDSA(Fair Differentiated Service Architecture) composed of TRA3CM(Target rate and RTT Aware 3 Color Marking) and TRBD(Target Rate Based Dropping) mechanisms. The TRA3CM and TRBD mechanisms provide three color marking and fair transmission rates among aggregate flows by considering RTT, target rate, and UDP flows simultaneously. In the results of comparing the performance among existing mechanisms and the TRA3CM-TRBD, the TRA3CM-TRBD mechanism was able to mitigate the RTT and UDP effect better than the former. The TRA3CM-TRBD is shown to provide good performance for transmission rates proportional to various target rates.