• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.88-91
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• 2000

In this paper we approach the problem of congestion control for TCP traffic over ATM-UBR networks by focusing on the fact that to get best performance. We study how to efficiently support TCP traffic in the subnet ATM model, when ATM is only a single link in the whole path. We show that when UBR connection. We analyze the ATM-UBR network service using the BSD 4.3 Reno, Tahoe TCP. However we found the fact that the characteristic of fast recovery algorithm makes a serious degradation of performance in multiple cell loss drop situation. We propose new fast recovery algorithm to solve the problem.

• Proceedings of the KAIS Fall Conference
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• 2006.11a
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• pp.180-185
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• 2006

자기 유사성(self-similarity)은 다양한 네트워크 환경에서 공통적으로 발생하는 현상인 것으로 정체 제어에서 자기 유사성 트래픽의 장거리 상관 구조를 활용할 가능성과 MTS(Multiple Time Scale) 정체 제어의 프레임워크를 발전시켜, 이 프레임워크가 전송 율 기반 피드백 제어의 성능을 향상시키는 데 시뮬레이션을 통해 트래픽 조건으로 다음과 같이 연구한다. 자기유사성 트래픽 조건에서 3가지 단계로 구성한다. 먼저 TCP의 모듈 형 확장에서 Tahoe, Reno, Vegas등 다양한 버전의 TCP에 적용되는 간단한 인터페이스를 통한 함수 호출을 정의하고, 이것이 성능을 크게 향상시는 것을 입증한다. 두 번째로, 광대역 WAN에서 지연-대역폭의 곱이 높을 경우 더욱 심각해지는 사후 제어의 불확실성 차이를 해소함으로써 MTS TCP가 기반 피드백 제어에 사전성을 부여한다는 것을 입증한다. 세번째는 트래픽 제어의 3가지 차원인, 즉 추적 능력, 연결 지속 기간, 공정성이 성능에 미치는 영향 등을 비교 분석하여 입증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3753-3771
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• 2016

Increasingly, numerous and various Internet-capable devices are connected in end user networks, such as a home network. Most devices use the combination of TCP and 802.11 DCF as a system platform, but whereas some devices such as a streaming video persistently generate traffic, others such as a motion sensor do so only intermittently with lots of pauses. This study addresses the issue of performance in this heterogeneous traffic wireless LAN environment from the perspective of fairness. First, instantaneous fairness is introduced as a notion to indicate how immediately and how closely a user obtains its fair share, and a new time-based metric is defined as an index. Second, extensive simulation experiments have been made with TCP Reno, Vegas, and Westwood to determine how each TCP congestion control corresponds to the instantaneous fairness. Overall, TCP Vegas yields the best instantaneous fairness because it keeps the queue length shorter than the other TCPs. In the simulations, about 60% of a fair share of the effective user bandwidth is immediately usable in any circumstance. Finally, we introduce two simple strategies for adjusting TCP congestion controls to enhance instantaneous fairness and validate them through simulation experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.264-270
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• 2006

In this paper we verified that the window based TCP performance of throughput can be improved by the traffic connection efficiency. and have studied the performance of traffic congestion control that is controlling transmission rate. In wireless network, the bidirectional node is run by estimating the usage rate of link of error control idle and the throughput is shown by transmitting segments. The throughput rate shows almost no delay due to the bidirectional traffic connection efficiency up to the allowable point as increasing the transport rate by the critical value, depending on the size of end-to-end node queue of the increase of transport rate. This paper reports the performance improvement as the number of feedback connection traffic congestion control increases because of the increase of the number of asynchronous transport TCP connections.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.125-132
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• 2007

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 1% packet loss rate, it outperforms 3% by TCP New Jersey and 5% by TCP Wes1wood. In 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it outperforms other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

• Journal of Information Processing Systems
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• v.12 no.1
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• pp.73-82
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• 2016

In cognitive radio networks (CRNs), the performance of the transmission control protocol (TCP) at the secondary user (SU) severely drops due to the mistrigger of congestion control. A long disruption is caused by the transmission of primary user, leading to the mistrigger. In this paper, we propose a cross-layer approach, called a CR-aware scheme that enhances TCP performance at the SU. The scheme is a sender side addition to the standard TCP (i.e., TCP-NewReno), and utilizes an explicit cross-layer signal delivered from a physical (or link) layer and the signal gives an indication of detecting the primary transmission (i.e., transmission of the primary user). We evaluated our scheme by implementing it onto a software radio platform, the Universal Software Radio Peripheral (USRP), where many parts of lower layer operations (i.e., operations in a link or physical layer) run as user processes. In our implementation, we ran our CR-aware scheme over IEEE 802.15.4. Furthermore, for the purpose of comparison, we implemented a selective ACK-based local recovery scheme that helps TCP isolate congestive loss from a random loss in a wireless section.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1384-1390
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• 2008

The TCP protocol is originally designed for wired network, however it performs very poor in wireless network due to different nature of wireless network from wired networks. In terms of TCP performance improvement in wireless Ad-hoc network, many researches show that small congestion window size of TCP connection can improve TCP performance. We propose a new TCP algorithm to improve TCP performance in wireless Ad-hoc network. The basic idea of our approach is that TCP receiver estimates the optimum window size and then sets congestion window limit of TCP sender to an optimum value by using the advertised window field in TCP ACK packet. From extensive computer simulation, the proposed algorithm shows superior performance than traditional TCP protocols in terms of packet delivery ratio and packet loss.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1713-1715
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• 2007

Measurement of network traffic have shown that the self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting the long-range correlation structure in a self-similar traffic for the congestion control. We have advanced the framework of the multiple time scale congestion control and showed its effectiveness at enhancing performance for the rate-based feedback control. Our contribution is threefold. First, we define a modular extension of the TCP-a function called with a simple interface-that applies to various flavours of the TCP-e.g., Tahoe, Reno, Vegas and show that it significantly improves performance. Second, we show that a multiple time scale TCP endows the underlying feedback control with proactivity by bridging the uncertainty gap associated with reactive controls which is exacerbated by the high delay-bandwidth product in broadband wide area networks. Third, we investigate the influence of the three traffic control dimensions-tracking ability, connection duration, and fairness-on performance.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.385-389
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• 2002

Ad-hoc 무선망은 고정된 유선망을 가지지 않고 이동 노드들로만 구성된 망이다. 여러 가지 이동 노드에 대한 이동 제약이 없고, 유선망이나 기지국 같은 기반 구조를 필요를 하지 않기 때문에 여러 환경에 적용이 가능하다. 그러나 라우터들 사이의 이동성과 다른 연결 요소들의 가변적인 요소는 잠재적으로 속도감 있고 예측 불가능하게 변하는 망을 가져올 수 있다. 이에 따른 패킷의 손실이 무선 네트워크에서 자주 발생하게 된다. 최근 몇 년 동안 Ad-hoc망에서 사용되는 라우팅 프로토콜의 각각에 대한 성능을 분석하는 연구가 있었지만, Ad-hoc 무선망에서 특정한 프로토콜의 TCP 버전별 비교 분석에 대한 연구가 미비한 실정이다. 따라서 본 논문에서는 무선 네트워크가 가지는 단점을 보완하고 트래픽 성능을 향상시키기 위한 한 방편으로, Ad-hoc 라우팅 알고리즘인 DSR 프로토콜을 이용하여 TCP Tahoe, Sack, Reno 버전별로 토폴로지의 크기의 변화와 이동 노드의 이동 속도의 변화에 따라 트래픽의 성능을 모의 실험하여 비교 분석하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.2
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• pp.214-227
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• 2003

Developing an application, it is difficult to catch an exact requirement with the conventional text-based method. It has also problems in verification and analysis at each developing stage. Therefore, if an adjustment is required with an error and change of requirement, a bad effect happen in the whole system. In this case, it also affect adversely on the developing cost and period. Meanwhile, if an analysis or verification is performed, the possibility of an error frequency reduces. Thus, not only is it easier to correct the error but also add an new requirement. This thesis embody a TCP/IP congestion control algorithm with SDL which provides automatically graphic interface, verification and analysis to each developing stage. Using SDL gave a clear representation embodiment in each developing stage and easiness of adjustment due to changing requirements or correcting errors. In addition, the stages of protocol have been certified in a simulation by verification of MSC and the results showed a possibility of developing a better TCP/IP protocol.