• Title/Summary/Keyword: TCP downlink

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Novel Uplink Congestion Control Method for TCP Throughput Enhancement (TCP 성능 향상을 위한 새로운 상향링크 혼잡 제어 기법)

  • Sohn, Kyungho;Kim, Han-Seok;Kwak, Dongho;Roy, Abhishek;Kim, Dongsook;Kim, Young Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.42 no.1
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    • pp.153-156
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    • 2017
  • In this paper, we propose a novel uplink congestion control scheme, which enhances downlink TCP throughput by improving response time of TCP acknowledgements without TCP modification. Through the experimental results, it is manifested that the proposed scheme is able to achieve better downlink TCP throughput.

TCP Uplink Station-Level Fairness Support in IEEE 802.11 Networks (IEEE 802.11 네트워크에서 TCP 업링크 스테이션 간 공평성 지원)

  • Jun, Kyoog-Koo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.6B
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    • pp.553-558
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    • 2009
  • There have been various research efforts to support the fairness between uplink and downlink of TCP streams in IEEE 802.11 networks. Existing methods, which have been effective for the fairness, however could not provide the solution for the unfairness caused by the situation in which a station which is having multiple TCP uplink streams monopolizes the uplink bandwidth. This paper proposes a method that AP allocates token buckets for each uplink TCP station. The proposed method is also able to support the fairness between the uplink and downlink. To remedy the underutilization which may happen under token bucket-based schemes, it allows the movement of redundant tokens among the token buckets. By controlling the token movements, it can balance the fairness and the utilization. Simulation results show that the proposed method is able to support the fairness of the TCP uplink stations, as well as the fairness between the uplink and downlink.

Performance Evaluation of Uplink ACK Packets Transmission IEEE 802.16e WiMAX Systems (IEEE 802.16e WiMAX 시스템에서 업링크 ACK 패킷 전송 성능평가)

  • Jun, Kyung-Koo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.9A
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    • pp.790-795
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    • 2011
  • The need for broadband wireless data networks such as IEEE 802.16e WiMAX systems increases as a variety of wireless information devices like smart phones are adopted rapidly in everyday life. Since most of mobile applications employ TCP as their transport layer protocol, the performance improvement of TCP in WiMAX systems is crucial. This paper proposes an efficient method to transmit uplink piggyback ACK packets by exploiting the uplink packet buffering which happens because of the resource allocation scheme of the WiMAX systems. The proposed method can support not only the ACK filtering but also the merging of the piggyback ACK packets. As a result, the bandwidth reduction in the piggyback ACK packet transmission leads to the improvement of the downlink throughput. The simulation results show that the bandwidth for the ACK packets reduces more than 90%, and the downlink throughput increases at least 30%.

TCP Acknowledgement Compression for Fairness Among Uplink TCP Flows in IEEE 802.11n WLANs (IEEE 802.11n 무선랜에서 상향링크 TCP 플로우간 형평상 향상을 위한 TCP ACK 압축기법)

  • Kim, Minho;Park, Eun-Chan;Kim, Woongsup
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.7
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    • pp.653-660
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    • 2013
  • This paper deals with the problem of unfairness among uplink TCP (Transmission Control Protocol) flows associated with frame aggregation employed in IEEE 802.11n WLANs (Wireless Local Area Networks). When multiple stations have uplink TCP flows and transmit TCP data packets to an AP (Access Point), the AP has to compete for channel access with stations for the transmission of TCP ACK (acknowledgement) packets to the stations. Due to this contention-based channel access, TCP ACKs tend to be accumulated in the AP's downlink buffer. We show that the frame aggregation in the MAC (Medium Access Control) layer increases TCP ACK losses in the AP and leads to the serious unfair operation of TCP congestion control. To resolve this problem, we propose the TAC (TCP ACK Compression) mechanism operating at the top of the AP's interface queue. By exploiting the properties of cumulative TCP ACK and frame aggregation, TAC serves only the representative TCP ACK without serving redundant TCP ACKs. Therefore, TAC reduces queue occupancy and prevents ACK losses due to buffer overflow, which significantly contributes to fairness among uplink TCP flows. Also, TAC enhances the channel efficiency by not transmitting unnecessary TCP ACKs. The simulation results show that TAC tightly assures fairness under various network conditions while increasing the aggregate throughput, compared to the existing schemes.

Analytical Modeling of TCP Dynamics in Infrastructure-Based IEEE 802.11 WLANs

  • Yu, Jeong-Gyun;Choi, Sung-Hyun;Qiao, Daji
    • Journal of Communications and Networks
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    • v.11 no.5
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    • pp.518-528
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    • 2009
  • IEEE 802.11 wireless local area network (WLAN) has become the prevailing solution for wireless Internet access while transport control protocol (TCP) is the dominant transport-layer protocol in the Internet. It is known that, in an infrastructure-based WLAN with multiple stations carrying long-lived TCP flows, the number of TCP stations that are actively contending to access the wireless channel remains very small. Hence, the aggregate TCP throughput is basically independent of the total number of TCP stations. This phenomenon is due to the closed-loop nature of TCP flow control and the bottleneck downlink (i.e., access point-to-station) transmissions in infrastructure-based WLANs. In this paper, we develop a comprehensive analytical model to study TCP dynamics in infrastructure-based 802.11 WLANs. We calculate the average number of active TCP stations and the aggregate TCP throughput using our model for given total number of TCP stations and the maximum TCP receive window size. We find out that the default minimum contention window sizes specified in the standards (i.e., 31 and 15 for 802.11b and 802.11a, respectively) are not optimal in terms of TCP throughput maximization. Via ns-2 simulation, we verify the correctness of our analytical model and study the effects of some of the simplifying assumptions employed in the model. Simulation results show that our model is reasonably accurate, particularly when the wireline delay is small and/or the packet loss rate is low.

TCP Performance improvement over Asymmetric Bandwidth Satellite Network using ACK filtering and Packet scheduling (비대칭 대역폭 위성망에서의 TCP 성능 향상을 위한 단말국 ACK 필터링 및 패킷 스케줄링 기법)

  • Kim, YongSin;Choi, Hoon;Ahn, Jaeyoung;Kim, Younghan
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.4
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    • pp.1-8
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    • 2000
  • A defect of decrease in TCP throughput can be investigated in asymmetric environment of different uplink and downlink bandwidths. Under two-way TCP traffic, the total link utilization is decreased by the successive injection of data packets in buffer. To solve these problems, terminal ACK filtering and packet scheduling mechanisms are introduced in this paper. ACK filtering eliminates the buffered ACK packets and transmits recent ACK packets in the uplink with limited bandwidth. Packet scheduling is the method of preventing 'clustering' and 'ack compression' states which are generated in the two-way TCP traffic. The guarantee of the data traffic in reverse TCP connection and the high throughput in forward TCP connection are investigated by simulation.

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Uplink Congestion Control over Asymmetric Networks using Dynamic Segment Size Control (비대칭 망에서 동적 세그먼트 크기 조정을 통한 상향링크 혼잡제어)

  • Je, Jung-Kwang;Lee, Ji-Hyun;Lim, Kyung-Shik
    • Journal of KIISE:Information Networking
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    • v.34 no.6
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    • pp.466-474
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    • 2007
  • Asymmetric networks that the downlink bandwidth is larger than the uplink bandwidth may cause the degradation of the TCP performance due to the uplink congestion. In order to solve this problem, this paper designs and implements the Dynamic Segment Size Control mechanism which offers a suitable segment size for current networks. The proposed mechanism does not require any changes in customer premises but suppress the number of ACKs using segment reassembly technique to avoid the uplink congestion. The gateway which adapted the Dynamic Segment Size Control mechanism, detects the uplink congestion condition and dynamically measures the bandwidth asymmetric ratio and the packet loss ratio. The gateway reassembles some of segments received from the server into a large segment and transmits it to the client. This reduces the number of corresponding ACKs. In this mechanism, the SACK option is used when occurs the bit error during the transmission. Based on the simulation in the GEO satellite network environment, we analyzed the performance of the Dynamic Segment Size Control mechanism.

On the Performance Evaluation of the Backoff Selection of AP in an IEEE 802.11 WLAN (IEEE 802.11 WLAN에서 AP의 백오프 값에 따른 TCP성능 변화 연구)

  • Park, Sang-Ha;Woo, Hee-Kyoung;Kim, Chong-Kwon
    • Proceedings of the Korea Information Processing Society Conference
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    • 2005.11a
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    • pp.1371-1374
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    • 2005
  • 지금까지 IEEE 802.11 WLAN 에서 많이 연구되어진 주제는 노드들 간의 공평성(fairness)과 처리량(throughput)을 높이는데 중점이 맞추어진 것들이 대부분이었다. 성능을 높이기 위한 AP의 CW값에 관한 연구는 노드들 간에 관한 연구에 비하여 비교적 적은 편이다. 지금은 노드들과 AP가 충돌하게 되면 BEB(Binary Exponential backoff)방식으로 셋팅되어 사용하게 있기 때문에 1:N의 불공평한(unfairness) 상황이 발생한다. AP에서 노드들로 가는 하향링크(downlink) 전송이 많은 상황에서 AP가 다른 노드들과 똑같은 채널 접근확률을 가지는 것은 바람직하지 않기 때문에 AP에게 우선권(priority)을 주어 전체 성능을 높이는 것이 필요하다. 따라서 본 논문에서는 AP의 CW(Contention Window)값이 변화함에 따라 전체 성능에 끼치는 영향과 노드 수의 변화에 따른 AP의 적절한 백오프 CW값을 분석해 보고자 한다.

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Preventing Network Performance Interference with ACK-Separation Queuing Mechanism in a Home Network Gateway using an Asymmetric Link (비대칭 링크를 사용하는 홈 네트워크 게이트웨이에서 네트워크 성능 간섭 현상을 막기 위한 패킷 스케줄링 기법)

  • Hong, Seong-Soo
    • Journal of KIISE:Computing Practices and Letters
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    • v.12 no.1
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    • pp.78-89
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    • 2006
  • In development of network-enabled consumer electronics, much of the time and effort is spent analyzing and solving network performance problems. In this paper, we define an instance of such problems discovered while developing a commercial home network gateway. We then analyze its cause and propose a solution mechanism. Our home network gateway uses art asymmetric link (ADSL) and suffers from an undesirable phenomenon where downlink traffic interferes with upload speed. We call this phenomenon the network performance interference problem. While this problem can easily be confused with receive livelock caused by packet contention at the input queue, we and that this is not the case. By performing extensive experiments and analysis, we reveal that our problem is caused by packet contention at the output queue and certain intrinsic characteristics of TCP. We devise an ACK-separation queuing mechanism for this problem and implement it in the home network gateway Our experiments show that it effectively solves the problem.