• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1591-1594
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• 2002

BE(Best-Effort)방식의 인터넷에서 제공되던 Text위주의 서비스 제공 방식이 Multimedia 위주의 서비스로 점차 바뀌어 감에 따라, 기존의 BE(Best-Effort)방식으로는 Multimedia QoS(Quality of Service)를 보장하기가 어려워졌다. 이에 IETF(Internet Engineering Task Force)에서는 변화하는 인터넷 환경에서 QoS 보장을 위해 Diffserv(Differentiated Service)방식을 제안하게 되었다. 본 논문에서는 Content를 제공하는 Linux Web Server에서 패킷을 클래스 분류기준(Classification Method)에 의해 분류하고 Scheduling Algorithm을 적용하여 DSCP(Differentiated Service CodePoint) 값을 Web Server 자체에서 결정하여 경계라우터(Edge Router)로 전송하는 방식을 취하였으며, 이를 토대로 하여 경계라우터의 Traffic 부하를 줄이고, 경계라우터의 코어라우터(Core Router)화를 통해 더욱더 향상된 Differentiated Service를 제공하는 것이 목적이다. 이를 본 논문에서는 ns2 를 통해 IETF에서 제안된 Diffserv방식과 본 논문에서 제안한 방식의 Diffserv 방식과 현재의 BE방식을 비교하여 어느 정도의 성능 향상이 있었는지 비교 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.444-454
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• 2004

To support diverse transmission requirements of multimedia applications, Quality of Service (QoS) should be provided in the Internet, where only the best-effort service is available. In this paper, we describe our recent effort on the implementation and verification of an extendable and flexible QoS allocation and resource management system based on the bandwidth broker model for realizing the IETF differentiated service (DiffServ). Focusing on the bandwidth issue over single administrative domain, the implemented system provides real-time resource reservation and allocation, delayed call admission control, simple QoS negotiation between sewer and users, and simple resource monitoring. The implemented system is verified by evaluating the performance of a resource-intensive application over the real-world testbed network.

• Journal of the Korea Society of Computer and Information
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• v.7 no.4
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• pp.24-32
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• 2002

Recent advances in Telecommunication and Internet have how made it possible to break the space-time barriers and allow physicians to deliver health care to patients at any time and any place, having led to a new branch of computer applications called Telemedicine System. In Telemedcine, Network and I/O performance requirements are generally more important than computing capability. Accordingly, this thesis is aimed at inquiring into how to satisfy QoS guarantee of network to compensate for the defects of the existing best-effort services and suggesting how to solve network bottleneck problem. using DiffServ in Telemedicine service system through Internet.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.35-38
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• 2002

In this paper, the design of explicit rate-based congestion control in high speed communication networks is considered. The goal of congestion control is to achieve high link utilization, low packet loss, low delay, and fairness among the best-effort sources. To deal with the propagation delays associated with the best effort sources, An MPC technique is employed to solve the congestion problem[1] here. However, the problem with this method is that the closed loop performance relies highly on the knowledge of average service rate. This paper focuses on coping with the problem described above by using a CARIMA model for service rate(available rate).

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.181-181
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• 2000

We identified the performance problems of scheduling algorithms such as FCFS, and demonstrated the superiority of WFQ in terms of realtime performance measures. For this purpose, we presented the service scenario and performed the analysis for the delay bound and fairness which are required to support the realtime applications in the Internet.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.155-162
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• 1999

Various applications of video conferencing are required real-time transmission in order to offer service of best effort in internet. Because the bandwidth of internet changes dynamically, appropriated QoS could not be guaranteed To resolve the problem. available bandwidth between sender and receiver is measured. And according to measured bandwidth, the transmission of multimedia data is controlled In this paper, we propose algorithm of efficient transmission for best QoS in internet According to a present status of network, we measure available bandwidth using feedback RTCP information and change a compression rate to reduce a producing CODEC data. And according to the priority that is measured by packet loss for received RTCP information, we abandon frames indicated as lower weight in transmission buffer of sender.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.319-321
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• 2000

현재 인터넷이 제공하는 최선의 서비스(best-effort)를 개선하기 위해서 IETF(Internet Engineering Task Force)의 DiffServ(Differentiated Service)WG에서는 현재의 인터넷 서비스를 보다 차별화된 QoS를 제공할 수 있도록 하는 방안으로서 Differentiated Service를 제안하였다. 본 논문에서는 이러한 Differentiated Service의 개념과 구조를 살펴보고 Differentiated Service에서 트래픽 포워딩을 효율적으로 제공하기 위한 하나의 방법으로서 CBQ를 이용한 패킷 전송 기법을 제안한다. 본 논문에서 제안하고 있는 이러한 방법을 통해 서비스 측면에서 어느 정도까지의 QoS를 보장할 수 있는지를 실험적으로 보이고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.859-866
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• 2003

In this paper, we designed the bandwidth allocation scheme with priority consideration for upstream channel access of EthernetPON. The objective of our scheme is to control the multi services in more effective way according to their CoS(Class of Service) or QoS(Quality of Service). The designed scheme considers transmission priority in the both side of OLT and ONU. In the OLT's view, the Two-step scheduling algorithm is applied with which we can support multiple bandwidth allocation policies simultaneously, i.e. SBA for the time-sensitive, constant rate transmission services and DBA for the best-effort services. This Two-step scheduling algorithm reduces the scheduling complexity by separating the process of transmission start time decision from the process of grant generation. In the ONU's view, the proposed scheme controls 8 priority queues of the 802.1d recommended 8 service classes. Higher priority queue is serviced in prior during the allowed GATE time from OLT. The OPNET modeling and simulation result compares the performance of each bandwidth allocation policy with SBA or DBA only approach.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.754-756
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• 2001

현재 인터넷 사용자의 증가와 더불어 사용자들이 원하는 서비스가 다양해짐에 따라 기존의 Best effort 서비스로는 사용자들이 요구하는 응용 서비스들을 제대로 지원할 수가 없게되었고, 이에 IETF(Internet Engineering Task Force)애서는 사용들의 QoS 제공을 위해 Integrated service model과 Differential service model이 제안되었다. 그러나 소규모 망에서 적용 가능한 Intserv와 대규모 망에서 사용적절한 Diffserv망의 service 방식이 다르기 때문에 End-to-End간에 QoS 제공을 위해서는 이에 대한 망의 연동이 필요하다. 본 논문에서는 두 망간의 연동을 위한 Framework을 제안하였다.