• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.383-386
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• 2001

This paper presents a novel multicast architecture for shared multibuffer ATM switch, which is tailored for throughput enhancement in multicast environments. The address queues for multicast cells are separated from those for unicast cells to arbitrate multicast cells independently from unicast cells. Three read cycles are carried out during each cell slot and multicast cells have chances to be read from shared buffer memory(SBM) in the third read cycle provided that the shared memory is not accessed to read a unicast cell. In this architecture, maximum two cells are queued at each fabric output port per time slot and output mask choose only one cell. Extensive simulations are carried out and it shows that the proposed architecture has enhanced throughput comparing with other multicast schemes in shared multibuffer switch architecture.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.68-75
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• 1998

The Asynchronous Transfer Mode(ATM) networks are being adopted as backbones over various parts of Internet. Also, TCP is one of the most widespread transport protocols, nowadays. It can be used with ATM. But, TCP shows poor end-to-end performance on ATM networks. Effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as congested link transmits cells from corrupted packets. This paper examines the behavior of TCP over ATM-UBR using EPD switch in a broadband environment. With a threshold close to the buffer size, the buffer can be used more efficiently, but more drops and retransmission occurs. If the threshold is much less than buffer size, efficient is not good, but few drops can happen. Therefore, decision of the threshold is important.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1922-1931
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• 1999

A multicast traffic’s feature is the function of providing a point to multipoints cell transmission, which is emerging from the main function of ATM switch. However, when a conventional point-to-point switch executes a multicast function, the excess load is occurred because unicast cell as well as multicast cell passed the copy network. Additionally, due to the excess load, multicast cells collide with other cells in a switch. Thus a deadlock that losses cells raises, extremely diminishes the performance of switch. An input queued switch also has a defect of the HOL (Head of Line) blocking that less lessens the performance of the switch. In the proposed multicast switch, we use shared memory switch to reduce HOL blocking and deadlock. In order to decrease switch’s complexity and cell's processing time, to improve a throughput, we utilize the method that routes a cell on a separated paths by traffic pattern and the scheduling algorithm that processes a maximum 2N cell at once in the control part. Besides, when cells is congested at an output port, a cell loss probability increases. Thus we use the Output Memory (OM) to reduce the cell loss probability. And we make use of the method that stores the assigned memory (UM, MM) with a cell by a traffic pattern and clears the cell of the Output memory after a fixed saving time to improve the memory utilization rate. The performance of the proposed switch is executed and compared with the conventional policy under the burst traffic condition through both the analysis based on Markov chain and simulation.

• The Transactions of the Korea Information Processing Society
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• v.6 no.6
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• pp.1581-1589
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• 1999

In B-ISDN(Broadband Integrated Services Digital Networks), the efficient implementation of multicast function is very important since the demand for distributed type of service such as VOD(Video On Demand) system is expected to grow. In this paper, the multicast performance characteristics of fully-interconnected switch fabric used for our research is the proper architecture for a small-sized switch element, and it uses bit addressing method for addressing scheme and thus it is easy to implement multicast function without adding a function block. To incorporate the bursty nature of traffic in ATM networks, we used IBP(Interrupted Bernoulli Process) model as an input traffic model. We presented and analyzed the simulation results in terms of the multicast operation of the switch. Based. on this study, it its analyzed that congestion avoidance may be feasible if we use a proper traffic control scheme by finding an overload point due to multicast.

• The Journal of the Acoustical Society of Korea
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• v.18 no.6
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• pp.65-70
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• 1999

In ATM network there exist several traffics according to QoS, such as CBR, rt-VBR, nrt-VBR, UBR, and ABR. Many studies have done at the traffic management of ABR which uses the unused network bandwidth. Many flow control mechanisms have proposed to use efficiently the unused bandwidth. In TMWG(Traffic Management Working Group) of ATM Forum, there exist rate-based, credit-based, and mixture of them to manage flow control of ABR traffic. Among these, rate-based mechanisms adopted as standard because it is flexible and also makes it possible to implement ATM switch with low price and high capacity. In this paper, we study the switch that uses EFCI, ER and VS/VD(Virtual Source/Virtual Destination) with rate-based mechanism. Instead of using queue threshold, we propose a new algorithm which uses bandwidth threshold of input stage of switch, and manages efficiently ABR traffic with EPRCA algorithm.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.65-72
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• 2002

In this paper, we implement a high-speed swatch tilth the function for label integration to enhance the expansion of networks using the label space of routers efficiently on MPLS over ATM networks. We propose an appropriate hardware structure to support the VC-merge function and differentiated services simultaneously. In this paper, we use the adaptive congestion control method such as EPD algorithm in carte that there is a possibility of network congestion in output buffers of each core LSR. In addition, we justify the validity of the proposed VC-merge method through simulation and comparison to conventional Non VC-merge methods. The proposed VC-merge capable switch is modeled in VHDL. synthesized, and fabricated using the SAMSUNG 0.5um SOG process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1631-1642
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• 1999

In this paper, we propose a new fault tolerant ATM Switch and a new adaptive self-routing scheme used to make the switch to be fault tolerant. It can provide more multiple paths than the related previous switches between an input/output pair of a switch by adding extra links between switching elements in the same stage and extending the self-routing scheme of the Banyan network. Our routing scheme is as simple as that of the banyan network, which is based on the topological relationships among the switching elements (SE’s) that render a packet to the same destination with the regular self-routing. These topological properties of the Banyan network are discovered in this paper. We present an algebraic proof to show the correctness of this scheme, and an analytic reliability analysis to provide quantitative comparisons with other switches, which shows that the new switch is more cost effective than the Banyan network and other augmented MIN’s in terms of the reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1323-1333
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• 1997

In this paper, we propose an efficient architecture for a high-speed cell concentrator/distributor(HCCD) in an ATM(Asynchronous Transfer Mode) switch and by analyzeing the simulation results evaluate the performance of the proposed architecuture. The proposed HCCD distributes cells from a switch link to local processors, or concentrates cells from local processor s to a switch link. This design is to guarntee a high throughput for the IPC (inter-processor communication) link in a distributed ATM switching system. The HCCD is designed in a moudlar architecture to provide the extensibility and the flexibility. The main characteristics of the HCCD are 1) Adaption of a local CPU in HCCD for improving flexibility of the system, 2) A cell-baced statistical multiplexing function for efficient multiplexing, 3) A cell distribution function based on VPI(Virtual Path Identifier), 4) A bypassing capability for IPC between processor attached to the same HCCD, 5) A multicasting capability for point-to-multipoint communication, 6) A VPI table updating function for the efficient management of links, 7) A self-testing function for detecting system fault.

• The Journal of the Korea Contents Association
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• v.2 no.2
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• pp.73-84
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• 2002

In this paper, we propose a enhanced ERICA switch algorithm using the buffer management scheme which can reduce the queue length, support the efficiency link utilization and the fair share. It has three different buffer thresholds which are low threshold, congestion notification threshold and high threshold. According to the each buffer threshold status, switch announced congestion notification to the source differently. So, sources could know the congestion more quickly and fast remover from network congestion. As a experimental results, it is proved that proposed algorithm is the more efficient than ERICA. Especially, proposed switch algorithm provides congestion control mechanism to make the best use of with keeping fairness and reduce queue length.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.252-254
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• 1998

유선에서 이용하는 능력으로 무선으로도멀티미디어 서비스를 이용하고자 연구된덧이 무선 ATM이다. 무선 ATM에서 핸드오프는 망 레벨과 무선 A레벨의 무선 핸드오프로 구분할 수 있다. 망 레벨의 핸드오프에서 CX의 선택은 빠르고 매끄러운 핸드오프를 지원해 주는데 중요한 역할을 한다. 망 관리에는 하나의 연결서버가 망의 연결관리를 해주는 중앙 집중 연결관리(Centralized Connection Management Scheme)와 각노드에서 연결을 관리하는 분산된 연결관리(Distributed Connection Management Scheme)로 나뉜다. 여기서 문제점은 중앙집중 연결관리에서는 전달지연시간(Propagation delay), 분산된, 연결관리에서는 시스템 오버헤드가 발생한다는 것이다. 이러한 중앙집중 연결관리의 지연시간과 분산된 연결관리의 오버헤드를 감소시키기 Distributed 위해 탐색알고리즘을 제안한다.