• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.1
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• pp.73-82
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• 2004

As a new service category to better support TCP traffic in ATM networks, the Guaranteed Frame Rate (GFR) service category aims to support minimum cell rate guarantee, fairly distribute available bandwidth while keeping the simplicity of Unspecified Bit Rate (UBR). In this paper, we proposed a buffer management scheme which uses the per-VC accounting of single FWO queue and capable of supporting both GFR.1 and GFR.2 conformance definition. The proposed buffer management deal with GFR.1 and GFR.2 conformance definitions differentially by controlling the number of CLP=0 cell and CLP=1 cell which are occupying buffer space. The simulation results show that our proposed scheme satisfies the requirements of GFR services as well as improves total fairness index and each conformance definition fairness index.

• Electronics and Telecommunications Trends
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• v.10 no.4 s.38
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• pp.37-55
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• 1995

고속 표준 프로토콜인 FC를 기반으로 한 Gigabit LAN 기술은 다양한 응용과 함께 Giga bps급의 높은 대역폭과 적은 전달지연을 갖는 고속 통신망으로서 매우 적합하다. 본 논문에서는 Gigabit 통신에 적합한 고속 표준 프로토콜인 FC의 표준화 내용과 프로토콜을 살펴보고, FC 기반의 LAN 기술을 위한 호스트 접속 기술 및 현재 연구/개발중인 Gigabit LAN을 구성하기 위한 요소시스템인 GIGAways 스위치 그리고 internetworking을 위한 FC-ATM Transport에 대하여 기술하였다.

• Electronics and Telecommunications Trends
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• v.16 no.5 s.71
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• pp.33-45
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• 2001

원활한 인터넷 서비스를 제공하기 위해서는 인터넷 트래픽을 효율적으로 관리할 수 있어야 하며, 이를 위해 가장 먼저 해야 할 것은 인터넷 트래픽을 측정하는 것이다. 인터넷 트래픽의 측정은 수동적인 측정과 능동적인 측정으로 분류된다. 수동적인 측정은 라우터나 ATM 스위치를 통해 흘러 다니는 트래픽 종류와 트래픽 양을 측정하여 측정네트워크의 트래픽 특성을 파악하는 것이고, 능동적인 측정은 측정네트워크 종단에 위치한 두 호스트 사이에 측정패킷을 투입하여 측정네트워크의 상태를 파악하는 것이다. 본 고는 현재 알려진 인터넷 트래픽 측정 방법과 현재 구현된 측정 시스템을 소개한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.490-492
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• 2001

본 논문은 ATM 멀티캐스트 스위치를 위한 새로운 복사망을 제안하였다. Lee의 복사망과 그 이후 제안된 복사망에서 문제가 된 오버플로우와 충돌 문제를 해결하기 위해 다중경로와 다중출력을 갖는 B-tree 네트워크를 사용하였다. 또한 높은 부하에도 충돌을 줄이고 복사망의 성능을 높이기 위해 B-Tree 네트워크의 각 SE에 출력 및 공유 버퍼 성격을 지닌 크로스포인트 버퍼를 추가한 IBBT 네트워크를 제안하였다. 제안된 복사망은 Lee의 복사망의 특성을 유지하며, 이 IBBT 네트워크를 복사망의 BBN에 적용하고, 셀 분할 알고리즘을 사용하여 복사망의 성능을 향상 시켰다.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.100-110
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• 2001

In this paper, we investigated several buffer management schemes for the design of shared-memory type ATM switches, which can enhance the utilization of switch resources and can support quality-of-service (QoS) functionalities. Our results show that dynamic threshold (DT) scheme demonstrate a moderate degree of robustness close to pushout(PO) scheme, which is known to be impractical in the perspective of hardware implementation, under various traffic conditions such as traffic loads, burstyness of incoming traffic, and load non-uniformity across output ports. Next, we considered buffer management strategies to support QoS functions, which utilize parameter values obtained via connection admission control (CAC) procedures to set tile threshold values. Through simulations, we showed that the buffer management schemes adopted behave well in the sense that they can protect regulated traffic from unregulated cell traffic in allocating buffer space. In particular, it was observed that dynamic partitioning is superior in terms of QoS support than virtual partitioning.

• Journal of the Korea Computer Industry Society
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• v.3 no.1
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• pp.95-104
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• 2002

This paper presents some studies on the Internet TCP/IP(Transmission Control Protocol-Internet Protocol) traffic over ATM(Asynchronous Transfer Mode) UBR(Unspecified Bit Rate) and ABR(Available Bit Rate) classes of service. Fuzzy logic prediction has been used to improve the efficiency and fairness of traffic throughput. For TCP/IP over UBR, a novel fuzzy logic based cell dropping scheme is presented. This is referred to as fuzzy logic selective cell drop (FSCD). A key feature of the scheme is its ability to accept or drop a new incoming packet dynamically based on the predicted future buffer condition in the switch. This is achieved by using fuzzy logic prediction for the production of a drop factor. Packet dropping decision is then based on this drop factor and a predefined threshold value. Simulation results show that the proposed scheme significantly improves TCP/IP efficiency and fairness. To study TCP/IP over ABR, we applied the fuzzy logic ABR service buffer management scheme from our previous work to both approximate and exact fair rate computation ER(Explicit cell Rate) switch algorithms. We then compared the performance of the fuzzy logic control with conventional schemes. Simulation results show that on zero TCP packet loss, the fuzzy logic control scheme achieves maximum efficiency and perfect fairness with a smaller buffer size. When mixed with VBR traffic, the fuzzy logic control scheme achieves higher efficiency with lower cell loss.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.311-315
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• 2008

The switching fabric used to make high speed switching for packet transfer between input and output interface in recent internet environments. Without making any changes in order to remain ATM switching fabric, the existing structures should split/reassemble a packet to certain size, set aside cross-point buffer and will put loads on the system. In this paper, we proposed a new switch architecture, which has separated data memory plane and switching plane packet data will be stored on the separate memory structure and simultaneously only the part of the memory address pointers can pass the switching fabric. The small mini packets which have address pointer and basic information would be passed through the switching fabric. It is possible to achieve the remarkable switching performance than other switch fabrics with contending variable length packets.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.52-63
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• 1998

In this paper, several improvements to a copy network proposed previously for multicast packet switching are described. The improvements provide a solution to some problems inherent in multicasting. The input fairness problem caused by overf low is solved by a dynamic starting point decider(DSD), which can calculate running sums of copy requests starting from any input port. The starting point is changed adaptively in every time slot based on both the fill level of the input buffers in current time slot and the overflow situations of the previous time slot. Using the fill level of the conventional network. The DSD also provides the function of regulating overall copy requests according to the amount of input traffics. This is an essential function in improving overall throughputs of the copy networks. The throughput of a multicast switch can be improved substantially if partial service of copy request is implemented when overflow occurs. Call-splitting can also be implemented by the DSD in a straightforward manner. The hardware for the DSD is derived with the objective of simple architectures for the high speed operation. Simulation study of the copy network under various traffic conditions is presented to evaluate its performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.9
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• pp.12-19
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• 2002

Guaranteed Frame Rate(GFR) service is intended to efficiently support TCP/IP traffic in ATM networks. The GFR service not only guarantees a minimum service rate at the frame level, but also supports a fair share of available bandwidth. The original GFR proposal outlined two switch implementation scheme : FIFO Queuing and perVC-Queuing. In general, it has been shown that FIFO Queuing is not sufficient to provide rate guarantees and perVC-Queuing with scheduling is needed. In perVC-Queuing implementation, scheduling algorithm plays key rule to provide rate guarantees and to improve fairness. We proposed a new scheduling algorithm for the GFR service. Proposed algorithm can provide minimum service rate guarantee and fair sharing to GFR VCs. Computer simulation results show that proposed scheduling scheme provide a much better performance in TCP Goodput and fairness than previous scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.629-642
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• 1996

ATM switch handles the traffic for a wide range of appliations with different QOS(Quality-of-Service) requirements. In ATM switch, the priority control mechanism is needed to improve effectively the required QOS requirements. In this paper, we propose a priority control mechanism using the cell transfer ratio type and discard threshold in order to archive the cell loss probability requirement and the delay requirement of each service class. The service classes of our concern are the service class with high time priority(class 1) and the service class with high loss priority control mechanism, cells for two kind of service classes are stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the shole range of the buffer and cells for class 1 are allocated up to discard threshold of the buffer. In case cells in the buffer are transmitted, one cell for class 1 is transmitted whenever the maximum K cells for class 2 are transmitted consecutively. We analyze the time delay and the loss probability for each class of traffic using Markov chain. The results show that the characteristics of the mean cell delay about cells for class 1 becomes better and that of the cell loss probability about cells for class 2 becomes better by selecting properly discard threshold of the buffer and the cell transfer ratio according to the condition of input traffic.