• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12B
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• pp.1052-1062
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• 2004

Recent studies have pointed out that existing high-speed TCP protocols have a severe unfairness and TCP friendliness problem. As the congestion window achieved by a high-speed TCP connection can be quite large, there is a strong possibility that the sender will transmit a large burst of packets. As such, the current congestion control mechanisms of high-speed TCP can lead to bursty traffic flows in hi인 speed networks, with a negative impact on both TCP friendliness and RTT unfairness. The proposed solution to these problems is to evenly space the data sent into the network over an entire round-trip time. Accordingly, the current paper evaluates this approach with a high bandwidth-delay product network and shows that pacing offers better TCP friendliness and fairness without degrading the bandwidth scalability.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.275-284
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• 2010

The current multihome-aware protocols (like stream control transmission protocol (SCTP) or parallel TCP for concurrent multipath data transfer (CMT) are not designed for high-capacity and large-latency networks; they often have performance problems transferring large data files over shared long-distance wide area networks. It has been shown that SCTP-CMT is more sensitive to receive buffer (rbuf) constraints, and this rbuf-blocking problem causes considerable throughput loss when multiple paths are used simultaneously. In this research paper, we demonstrate the weakness of SCTP-CMT rbuf constraints, and we then identify that rbuf-blocking problem in SCTP multihoming is mostly due to its loss-based nature for detecting network congestion. We present a simulation-based performance comparison of FAST TCP versus SCTP in high-speed networks for solving a number of throughput issues. This work proposes an end-to-end transport layer protocol (i.e., FAST TCP multihoming as a reliable, delaybased, multihome-aware, and selective ACK-based transport protocol), which can transfer data between a multihomed source and destination hosts through multiple paths simultaneously. Through extensive ns-2 simulations, we show that FAST TCP multihoming achieves the desired goals under a variety of network conditions. The experimental results and survey presented in this research also provide an insight on design decisions for the future high-speed multihomed transport layer protocols.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.104-113
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• 2009

Recently, high-speed Internet users and broadband network infrastructure are increasing. However, the TCP protocol widely used in the Internet is an appropriate transport only for the legacy Internet, it is inefficient for traffic transport for network environments with large bandwidth-delay product. In order to remedy this problem, there have been many researches about improved congestion control algorithms for broadband networks. In these studies, most of performance evaluation has been done by simulations. In this paper, after we reviewed the proposed high bandwidth transport layer protocols, we implemented a real testbed, measured the performance and analyzed the problems of high-speed transport protocols through the international research network TEIN2 between three nations, Korea, China, and Germany.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.10-17
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• 2015

A satellite communication system is one of viable solutions for Internet applications running in wide areas. However, the performance of TCP can be seriously degraded in the satellite networks due to long round-trip time (RTT) and high bit error rate (BER) over satellite links. Therefore, a performance enhancing proxy(PEP) based TCP splitting connection scheme is used in the satellite link to improve the TCP performance. In this paper, we implement PEP testbed and conduct experiment to evaluate the performance of TCP splitting connection by comparing with high-speed TCP solutions in various environments. In our experimental environment, we consider multiple connections, high packet loss, and limited bandwidth. The experiment results show that PEP improves the TCP throughput than high-speed TCP variants in various environments. However, there is no improvement of the TCP throughput with the limited bandwidth because there is packet loss caused by both the congestion and the channel error.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.3
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• pp.185-190
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• 2022

We propose a high speed data communication method for motor drive systems with fast control cycle in order to collect state variables of motor control without degrading control performance. Ethernet is chosen for communication device, and multi-core DSP architecture is exploited for communication processing load distribution. The communication program including network protocol stack and motor control program are assigned to two separate cores, and data between two cores are exchanged using interrupt-based inter-process communication mechanism, which enables to achieve a high-speed communication performance without degrading the motor control performance. The performance of developed communication method is demonstrated by real experiments using TCP, UDP and Raw Socket protocols in an experimental setup consisting of TI's TMS320F28388D motor control card and MS Windows PC.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.571-580
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• 2005

In fast long-distance networks, TCP's congestion control algorithm has the problem of utilizing bandwidth effectively. Several window-based congestion control protocols for high-speed and large delay networks have been proposed to solve this problem. These protocols deliberate mainly three properties : scalability, TCP-friendliness, and RTT-fairness. These protocols, however, cannot satisfy above three properties at the same time because of the trade-off among them This paper presents a new window-based congestion control algorithm, called EM (Exponential Increase/ Multiplicative Decrease), that simultaneously supports all four properties including fast convergence, which is another important constraint for fast long-distance networks; it can support scalability by increasing congestion window exponentially proportional to the time elapsed since a packet loss; it can support RTT-fairness and TCP-friendliness by considering RTT in its response function; it can support last fair-share convergence by increasing congestion window inversely proportional to the congestion window just before packet loss. We evaluate the performance of EIMD and other algorithms by extensive computer simulations.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3390-3398
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• 1999

To achieve high-speed communication and to improve QoS characteristics, ATM is now being used as underlying transfer mechanism of Internet protocols, or TCP/IP. When TCP uses the ABR service in ATM networks, the ABR service control is important to improve the performance of TCP/IP traffic as long as there is no interaction between ABR rate control and TCP flow control. In such environment, the interoperability of EFCI and ER switches becomes unavoidable in order to more effectively control ABR traffic in ATM network. In this paper, we use the model of mixed EFCI-ER environment and discuss the performance issues, e.g., the fairness of bandwidth allocation, drop rate, throughput by using various ER switch algorithms. Among various ERSwitch algorithms, we present one algorithm that have a less network topology and allocate the fair share of VC bandwidth by simulation results.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3260-3268
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• 1999

As the proliferation of multimedia traffic over High-speed Internet increases, ATM network will be vital to adopt as backbone network over various parts of Internet. In this paper, we investigate the performance of TCP/IP traffic flow over ABR and UBR of ATM service to study for the high throughput and good fairness by simulation technique. Although TCP is run in the transport layer, it is controlled by several methods, e.g, EPD, PPD, RED, EFCI, ER etc, in ATM layer when TCP uses the ABR/UBR service. Therefore, if one cell is discarded in ATM layer, a packet of TCp will be laost. And, also, along with the increasing of the number of VC among switches, the throughput and fairness will be degraded. In order to improve these degradations, we propose the effective parameter control operations of EFCI and ER on ABR service, and also suggest the buffer management methods on UBR service. Finally, through the simulation results, the improved throughput and fairness are shown.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.42-44
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• 2003

As the industry is developed, uses of various electric motor are increasing from general home to various fields of industry, and the kind becomes various daily. For these reasons, it is required to study the remote control and a package management about change of a speed drive system, the supervision of administration appliance by real time, and the collection and process data together using internet prevailed on industry whole. This paper deals with the development of a Web-Based remote control system for permanent magnet synchronous motor drives. The client/server system using TCP/IP protocols and DSP controller for remote control through internet and the Web interface that users can confirm data and state of PMSM(Permanent Magnet Synchronous Motor) is developed. This system is available for driving, braking, variable speed control and monitoring for PMSM in real time through administration program of Web-Based.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1295-1300
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• 2006

In this paper, we have developed RFID systems with integrated tag location data for efficient logistics information systems. These are consist of RFID readers with GPS module and RFID networks to service tag location data. The developed RFID readers can get location informations Of the tags, transfer them high speed by TCP/IP protocols, and operate as web servers. And we presented a simple service network system based on EPC network to service both location and tag data. The proposed system can be applicable to tracebility or finding locations of the products.