• 정보처리학회논문지C
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• 제9C권4호
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• pp.513-522
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• 2002

기존의 end-to-end 방식에서는 네트워크 내부에서 혼잡(congestion)이 발생했을 경우 각 전송자가 즉시 알아 낼 수 없기 때문에 일정시간 동안 수신된 패킷(packet)의 순서에 대한 정보로 흔잡이 발생했는지에 대해 추론하는 것이다. 이와 같은 방법은 RTT(Round Trip Time)가 커지면 혼잡이 발생할 경우 전송자가 전송 양을 줄인다 해도 이미 전송된 패킷들로 인하여 흔잡이 가중되며 전체적인 TCP 동기화 (TCP Global synchronization) 현상을 피할 수 없게 된다. 반면 네트워크 내부에서 직접적으로 정보를 얻거나 처리를 해 줄 수 있다면 혼잡 발생과 동시에 처리가 가능함으로 기존 방식보다 처리율이 향상될 것이다. 본 논문에서는 액티브 라우터의(Active Network) 피드백 메커니즘을 이용하여 네트워크 내부 정보를 각 전송자가 이용할 수 있도록 하기 위해 라우터와의 통신을 이용하였으며, 코어 라우터의 큐 모듈은 RED(Random Early Detection)를 응용하여 ACC의 누락 메커니즘을 개선하였다. ACC를 확장한 메커니즘인 EACC(Enhanced Active Congestion Control)를 제시하고 모의실험을 통해 기존의 혼잡제어나 ACC(Active Congestion Control)보다 성능이 향상됨을 보여준다.

• 한국정보과학회논문지:정보통신
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• 제31권3호
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• pp.269-279
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• 2004

인터넷의 안정성에 가장 큰 영향을 미치는 요소는 종단간에 이루어지는 TCP 혼잡제어이다. 현재 인터넷의 주요 TCP 버전인 Reno가 사용하는 수동적인 혼잡제어 방법은 네트워크의 혼잡을 심화시키는 원인이 된다. 이러한 Reno의 문제점을 개선하기 위해 제안된 Vegas는 Reno에 비해 우수한 성능을 가짐이 증명되었음에도 불구하고 두 가지 심각한 불공정성 문제를 가지고 있기 때문에 범용적으로 사용되지 못하고 있다. 본 논문에서는 이러한 Vegas의 문제점을 보완하기 위해서 기존의 Vegas 혼잡제어 알고리즘을 개선한 새로운 TCP PowerVegas 혼잡제어 알고리즘을 제안한다. rtt(round trip time)만을 기반으로 네트워크의 혼잡을 제어하는 기존의 Vegas에 비해서 제안한 PowerVegas는 rtt와 패킷 손실 정보를 유기적으로 결합시킨 새로운 기법으로 경쟁력 있는 혼잡제어를 수행한다. 그러므로 기존의 Vegas에서 발생했던 불공정성 문제를 모두 효과적으로 개선할 수 있다. 제안한 알고리즘의 성능을 검증하기 위해 동일한 시뮬레이션 환경에서 PowerVegas와 Reno 및 Vegas를 비교하는 실험을 수행하였다. 실험 결과를 통해서 제안한 PowerVegas가 기존 Reno의 혼잡제어 방법에 비해 우수한 성능을 보일 뿐만 아니라, Vegas의 불공정성 문제도 크게 개선되었음을 확인할 수 있었다.

• 한국통신학회논문지
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• 제27권4C호
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• pp.333-341
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• 2002

본 논문은 CDMA 이동전화 기지국에서 처리되는 이동전화 Traffic을 과학적이고 체계적으로 분석하여 BTS(Base Station Transceiver Subsystem)와 중계기의 통화량을 정확하게 예측함으로써 무선망 엔지니어링을 효과적으로 수행할 수 있는 기틀을 마련한 연구이다. 중계기는 BTS와 물리적으로 직접 연결되어 원격 중계 역할을 담당하는 단순한 기능을 가지고 있고, 중계기에 유입되는 Traffic을 계산 할 수 없는 구조를 가지고 있다. 기지국 Traffic은 BTS와 중계기 Traffic이 혼합된 통계 데이터를 의미한다. BTS와 중계기의 Traffic을 구분하기 위해서 기지국과 이동국 사이의 통화거리 분포 측정이 가능하도록 제안된 RTD(Round Trip Delay)를 활용하여 Traffic을 분석하고자 하였다. BTS를 기준으로 BTS와 이동국이 직접 통화하는 경우보다, BTS에서 일정거리에 있는 중계기를 통해서 이동국과 통화로를 구성하는 경우에 상당한 호(call) 지연이 발생하교 BTS와 중계기 사이의 이격 거리에 따라 시간지연이 커지는 현상에 착안하였다. 이러한 근거를 바탕으로 중계기에 임의의 Time Delay를 설치 실험한 결과 Traffic 구분이 불가능하던 중계기 Traffic이 일정한 시간 지연상태로 BTS에 유입되어 99.78%가 구분되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2405-2423
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• 2012

In a traditional Single Sign-On (SSO) scheme, the user and the Service Providers (SPs) have given their trust to the Identity Provider (IdP) or Authentication Service Provider (ASP) for the authentication and correct assertion. However, we still need a better solution for the local/native true SSO to gain user confidence, whereby the trusted entity must play the role of the ASP between distinct SPs. This technical gap has been filled by Trusted Computing (TC), where the remote attestation approach introduced by the Trusted Computing Group (TCG) is to attest whether the remote platform integrity is indeed trusted or not. In this paper, we demonstrate a Trustworthy Mutual Attestation (TMutualA) protocol as a proof of concept implementation for a local true SSO using the Integrity Measurement Architecture (IMA) with the Trusted Platform Module (TPM). In our proposed protocol, firstly, the user and SP platform integrity are checked (i.e., hardware and software integrity state verification) before allowing access to a protected resource sited at the SP and releasing a user authentication token to the SP. We evaluated the performance of the proposed TMutualA protocol, in particular, the client and server attestation time and the round trip of the mutual attestation time.

• 제어로봇시스템학회논문지
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• 제11권4호
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• pp.385-391
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• 2005

As the Internet real-time multimedia applications increases, the bandwidth available to TCP connections is oppressed by the UDP traffic, result in the performance of overall system is extremely deteriorated. Therefore, developing a new transmission protocol is necessary. The TCP-friendly algorithm is an example satisfying this necessity. The TCP-Friendly Rate Control (TFRC) is an UDP-based protocol that controls the transmission rate that is based on the available round trip time (RTT) and the packet loss rate (PLR). In the data transmission processing, transmission rate is determined based on the conditions of the previous transmission period. If the one-step ahead predicted values of the control factors are available, the performance will be improved significantly. This paper proposes a prediction model of transmission rate control factors that will be used in the transmission rate control, which improves the performance of the networks. The model developed through this research is predicting one-step ahead variables of RTT and PLR. A multiplayer perceptron neural network is used as the prediction model and Levenberg-Marquardt algorithm is used for the training. The values of RTT and PLR were collected using TFRC protocol in the real system. The obtained prediction model is validated using new data set and the results show that the obtained model predicts the factors accurately.

• Industrial Engineering and Management Systems
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• 제13권2호
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• pp.221-230
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• 2014

With the progress and prosperity of commerce and industry, time and money increasingly form an equal partnership. Using air carriers to shorten the round-trip time has become an important choice for many people in the tourism process. Faced with increasing competition within the aviation service environment, airline evaluation criteria and the requirements of customers are gradually dominating the evaluation mechanism for air transport service quality. Over the past few years, attention on the transport quality of service has been primarily focused more on land-based transport, and less on the relevant evaluation criteria of airlines. Many studies have shown that quality of service will directly affect customer satisfaction, resulting in the fact that good quality aviation services have become increasingly important. Therefore, in practical industrial operations with limited resources, there is an urgent need to delve into the assessment guidelines that have an impact on customers when they choose an airline, which can be used as a basis for improving customer satisfaction. Through a literature review and a reliability and validity analysis, this study summarized 19 evaluation criteria, using the purposive sampling method and the decision laboratory method (DEMATEL). In addition, this study viewed the causal relationship between the evaluation criteria and the degree of association as a continuing project for airlines. This study selected appropriate empirical samples from two domestic airlines. The conclusions may provide recommendations for all airlines.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4015-4033
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• 2015

The future mobile networks consist of hyper-dense heterogeneous and small cell networks of same or different radio access technologies (RAT). Integrating mobile networks of different RATs to provide seamless and smooth mobility service will be the target of future mobile converged network. Generally, handover from high-speed networks to low-speed networks faces many challenges from application perspective, such as abrupt bandwidth variation, packet loss, round trip time variation, connection disruption, and transmission blackout. Existing inter-RAT handover solutions cannot solve all the problems at the same time. Based on the high-layer convergence sublayer design, a new receiver-aided soft inter-RAT handover is proposed. This soft handover scheme takes advantage of multihoming ability of multi-mode mobile station (MS) to smooth handover procedure. In addition, handover procedure is seamless and applicable to frequent handover scenarios. The simulation results conducted in UMTS-WiMAX converged network scenario show that: in case of TCP traffics for handover from WiMAX to UMTS, not only handover latency and packet loss are eliminated completely, but also abrupt bandwidth/wireless RTT variation is smoothed. These delightful features make this soft handover scheme be a reasonable candidate of mobility management for future mobile converged networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.133-151
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• 2019

In order to achieve faster content distribution speed and stronger fault tolerance, a P2P peer can connect to multiple peers in parallel and receive chunks of the data simultaneously. A critical issue in this environment is selecting a set of nodes participating in swarming sessions. Previous related researches only focus on performance metrics, such as downloading time or the round-trip time, but in this paper, we consider a new performance metric which is closely related to the network and propose a peer selection algorithm that produces the set of peers generating optimal worst link stress. We prove that the optimal algorithm is practicable and has the advantages with the experiments on PlanetLab. The algorithm optimizes the congestion level of the bottleneck link. It means the algorithm can maximize the affordable throughput. Second, the network load is well balanced. A balanced network improves the utilization of resources and leads to the fast content distribution. We also notice that if every client follows our algorithm in selecting peers, the probability is high that all sessions could benefit. We expect that the algorithm in this paper can be used complementary to existing methods to derive new and valuable insights in peer-to-peer networking.

• 한국멀티미디어학회논문지
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• 제24권5호
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• pp.676-683
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• 2021

Wi-Fi Round-trip timing (RTT) based location estimation technology estimates the distance between the user and the AP based on the transmission and reception time of the signal. This is because reception instability and signal distortion are greater than that of a Received Signal Strength Indicator (RSSI) based fingerprint in an indoor NLOS environment, resulting in a large position error due to multipath fading. To solve this problem, in this paper, we propose an end-to-end based WiFi Trilateration Net (WTN) that combines neural network-based RTT correction and trilateral positioning network, respectively. The proposed WTN is composed of an RNN-based correction network to improve the RTT distance accuracy and a neural network-based trilateral positioning network for real-time positioning implemented in an end-to-end structure. The proposed network improves learning efficiency by changing the trilateral positioning algorithm, which cannot be learned through differentiation due to mathematical operations, to a neural network. In addition, in order to increase the stability of the TOA based RTT, a correction network is applied in the scanning step to collect reliable distance estimation values from each RTT AP.

• ETRI Journal
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• 제44권6호
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• pp.1020-1033
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• 2022

In this paper, we propose novel disaggregated memory module (dMM) architecture and memory access control schemes to solve the collision and contention problems of memory disaggregation, reducing the average memory access time to less than 1 ㎲. In the schemes, the distributed scheduler in each dMM determines the order of memory read/write access based on delay-sensitive priority requests in the disaggregated memory access frame (dMAF). We used the memory-intensive first (MIF) algorithm and priority-based MIF (p-MIF) algorithm that prioritize delay-sensitive and/or memory-intensive (MI) traffic over CPU-intensive (CI) traffic. We evaluated the performance of the proposed schemes through simulation using OPNET and hardware implementation. Our results showed that when the offered load was below 0.7 and the payload of dMAF was 256 bytes, the average round trip time (RTT) was the lowest, ~0.676 ㎲. The dMM scheduling algorithms, MIF and p-MIF, achieved delay less than 1 ㎲ for all MI traffic with less than 10% of transmission overhead.