• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1542-1550
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• 2015

Delayed ACK is an algorithm implemented to decrease the number of ACK transmissions by delaying an ACK transmission and by waiting for additional ACK instead of transmitting the ACK immediately. By using Delayed ACK in TCP, the congestion of network and the overhead of handling ACKs can be reduced. Waiting time of Delayed ACK is defined as the Delayed ACK timeout, and it is fixed in Window OS basically. However, the fixed value of Delayed ACK timeout is not suitable for dynamic network circumstance, and it may cause unnecessary delay. This paper proposes a regulating Delayed ACK timeout algorithm to reduce the aforementioned unnecessary delay caused by the lengthy default value of the Delayed ACK timeout. We confirm that TCP transmission performance in dynamic network circumstance can be improved using the proposed algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1654-1662
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• 2006

An ad hoc network is multi-hop network composed of radio links. and the transmission quality of a radio link is more unstable than that of a wired circuit. Packet loss thus occurs frequently in an ad hoc network, and the consequent connection failure results in a severe deterioration of TCP performance. TCP performance also deteriorates because of the collision of data packets and ACK packets in the radio channel. In this paper we study to improve the performance of the Mobile Ad-hoc network by using Delayed ACK algorithm with our proposed ODA(Ordering-Delayed ACK) method. The proposed ODA algorithm increases the number of the data packets orderly at the receiver side which is going to be applied for the Mobile Ad-hoc network. We accomplished a computer simulation using NS-2. From the simulation results, we find the proposed ODA algorithm obviously enlarge the channel capacity and improve the network performance at the situation of multi-hop of ad-hoc network than the existing Delayed ACK algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.271-273
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• 2000

본 논문에서는 TCP 수신자가 지연 ACK 옵션(Delayed ACK Option)을 사용할 경우에 TCP 송신자에게 발생하는 성능 저하요인들을 분석하고 다음과 같은 해결책을 제시하였다. 먼저, 느린 시작 구간(Slow Start phase) 처음에 생기는 ACK 타임아웃은 큰 초기 윈도우(large initial window)또는 1-bit 마킹 기법을 통해 해결할 수 있다. 그리고, 느린 시작 구간과 혼잡 회피 구간(Congestion Avoidance phase)에서 혼잡 윈도우(cwnd)가 천천히 증가하는 문제는 적절히 바이트 카운팅 기법을 사용함으로써 해결할 수 있다. 마지막으로, 송신자가 버스트(burst)한 데이터를 네트웍에 발생시키는 문제는 트래픽을 평활(pacing)함으로써 해결할 수 있다. 또한 본 연구에서는 분석적 모델링을 통하여 TCP가 보내는 평균 전송률을 구하였으며 이 결과는 TCP에 친화한 전송률 기반 전송방법(TCP Friendly Rate Based Control)에 응용될 수 있을 것이다. 그리고 시뮬레이션을 통해서 제시한 방법의 성능이 향상됨을 확인하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.272-275
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• 2008

종단에서 네트워크 용량에 대한 정보는 사용자뿐 아니라 전송 계층 프로토콜 상에서 전송량 등을 조절하기 위한 중요한 용도로 활용된다. 이러한 네트워크 용량(또는 대역폭)을 종단에서 측정하기 위해 활용되는 방법 중 하나가 바로 패킷 페어 기법이다. 패킷 페어 기법은 계산이 간단하고 빠른 측정이 가능하다는 장점이 있으나, 각 프로빙 패킷에 대한 즉각적인 응답 패킷을 필요로 하기 때문에 지연 ACK 방식이 존재하는 TCP 상에서는 적용하기 어렵다는 단점이 있다. 본 논문에서는 이러한 지연 ACK의 효과를 그대로 유지하면서 네트워크 용량의 추정이 가능한 지연 패킷 페어 기법을 제안한다. 시뮬레이션 결과를 통해 제안된 지연 패킷 페어 기법이 기존 방식의 정확성, 빠른 측정 시간 등의 장점을 보존하면서 지연 ACK의 사용 여부에 관계없이 정확히 동작할 수 있음을 보였다.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.230-234
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• 2007

Generally, huge amounts of data traffic are generated by using broadcasting method to deliver sensing data to a sink node reliably so that it makes a severe network saturation problem resulting in unreliable data transfer. In order to handle this problem, a new congestion control protocol is required for supporting reliable data transfer, minimal use of energy and network resources at the same time in wireless sensor networks. In this paper, it proposes a Protocol to guarantee both a reliable transfer in data accuracy and minimum consumption of energy waste by using Hop-by-Hop sequence number and DSbACK(Delayed and Selective ACK Buffer Condition) scheme. In addition, it proves that reliability and energy efficiency are enhanced by the proposed method with the simulation results performed on TinyOS platform which is a component based built-in OS announced by UC Berkely with the performance comparison of other existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1309-1316
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• 2016

This paper suggests adjusting TCP for smartphones that often have small size data transmission tendency. Usage of smartphones has been risen dramatically in recent years, including frequent usage of real-time map search, public transportation search, online games, and SNS. Because the small size data transmission ends before the phase of the TCP congestion avoidance, this paper suggests an algorithm that increases the transmission speed ahead of the traffic congestion event. The algorithm reduces unnecessary delay by data size-driven adjustment of the Linux Quick ACK and Nagle's algorithm. Therefore, TCP is improved to maintain a high transmission rate steadily in small data transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.442-445
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• 2006

In Wireless Sensor Networks(WSNs), a sensor node broadcasts an acquisited data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In this paper, we proposes a reliable congestion protocol, ratted HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1B
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• pp.39-46
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• 2005

As the multimedia application traffic takes more portion in the internet traffic, it is necessary to control the network congestion through the congestion control protocol. In addition, the QoS-enabled networks such as DiffServ become an indispensable technology when running the multimedia applications. However, the previously proposed end-to-end congestion control algorithms take the round trip time to react the network congestion. Thus, as the RTT becomes larger, the reaction against the congestion gets delayed further, while the network congestion gets worse. In addition the performance of end-to-end congestion control algorithm is degraded if the QoS-enabled network runs the congestion control mechanism in the network level without any coordination between them. In this paper, we propose the early rate adaptation protocol for the DiffServ network which effectively linke the congestion control algorithm at the host and the congestion mechanism in the network together. By taking advantage of early congestion notification from the network it is possible to react the network congestion more quickly and effectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1055-1059
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• 2006

In Wireless Sensor Networks(WSNs), a sensor node broadcasts the acquisited sensing data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In his paper, we proposes a reliable congestion protocol, called HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

• Journal of Communications and Networks
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• v.4 no.2
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• pp.148-157
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• 2002

This paper investigates schemes to improve TCP performance in multipath forwarding networks. In multipath routing, packets to the same destination are sent to multiple next-hops in either packet-level or flow-level forwarding mode. Effective bandwidth is increased since we can utilize unused capacity of multiple paths to the destination. In packet-level multipath forwarding networks, TCP performance may not be enhanced due to frequent out-of-order segment arrivals at the receiver because of different delays among paths. To overcome this problem, we propose simple TCP modifications. At the sender, the fast retransmission threshold is adjusted taking the number of paths into consideration. At the receiver, the delayed acknowledgment scheme is modified such that an acknowledgment for an out-of-order segment arrival is delayed in the same way for the in-order one. The number of unnecessary retransmissions and congestion window reductions is diminished, which is verified by extensive simulations. In flow-level multipath forwarding networks, hashing is used at routers to select outgoing link of a packet. Here, we show by simulations that TCP performance is increased in proportion to the number of paths regardless of delay differences.