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  • Ryosuke Minami, Shotaro Ishikura, Miki Yamamoto
    IEICE Communications Express
    2023年 12 巻 12 号 624-627
    発行日: 2023/12/01
    公開日: 2023/12/01
    ジャーナル フリー

    BBR has been proposed as congestion-based congestion control by Google. It was originally designed to operate around optimal operating point where maximum throughput is obtained without incurring increase of roundtrip delay. In this paper, with simple analysis and detailed simulation results, we show that BBR increases its delivery rate even though BBR flows sharing the same bottleneck link fully utilize available bandwidth. From simple analysis results, we propose a new BBR delivery rate calculation algorithm which regulates delivery rate moderately, BMR. Our simulation results show that our proposed BMR operates around the optimal operating point.

  • Yu NAKAYAMA, Kaoru SEZAKI
    IEICE Transactions on Communications
    2017年 E100.B 巻 2 号 313-322
    発行日: 2017/02/01
    公開日: 2017/02/01
    [早期公開] 公開日: 2016/08/22
    ジャーナル 認証あり

    In recent years, the reduced cost and increased capacity of memory have resulted in a growing number of buffers in switches and routers. Consequently, today's networks suffer from

    bufferbloat
    , a term that refers to excess frame buffering resulting in high latency, high jitter, and low throughput. Although ring aggregation is an efficient topology for forwarding traffic from multiple, widely deployed user nodes to a core network, a fairness scheme is needed to achieve throughput fairness and avoid
    bufferbloat
    , because frames are forwarded along ring nodes. N Rate N+1 Color Marking (NRN+1CM) was proposed to achieve per-flow fairness in ring aggregation networks. The key idea of NRN+1CM is to assign a color that indicates the dropping priority of a frame according to the flow-input rate. When congestion occurs, frames are selectively discarded based on their color and the frame-dropping threshold. Through the notification process for the frame-dropping threshold, frames are discarded at upstream nodes in advance, avoiding the accumulation of a queuing delay. The performance of NRN+1CM was analyzed theoretically and evaluated with computer simulations. However, its ability to avoid
    bufferbloat
    has not yet been proven mathematically. This paper uses an M(n)/M/1/K queue model to demonstrate how
    bufferbloat
    is avoided with NRN+1CM's frame-dropping threshold-notification process. The M(n)/M/1/K queue is an M/M/1/K queuing system with balking. The state probabilities and average queue size of each ring node were calculated with the model, proving that the average queue size is suppressed in several frames, but not in the most congested queue. Computer simulation results confirm the validity of the queue model. Consequently, it was logically deducted from the proposed M(n)/M/1/K model that
    bufferbloat
    is successfully avoided with NRN+1CM independent of the network conditions including the number of nodes, buffer sizes, and the number and types of flows.

  • Zhicheng Zhao, Weihua Cao
    Journal of Advanced Computational Intelligence and Intelligent Informatics
    2023年 27 巻 3 号 346-351
    発行日: 2023/05/20
    公開日: 2023/05/20
    ジャーナル オープンアクセス

    Traditional congestion-control algorithms based on packet loss are more favorable for short round-trip time (RTT) flows. However, when the flow occupies the bottleneck bandwidth, the effect of bottleneck bandwidth and round-trip propagation time (BBR) congestion-control algorithm is on contrary. A short RTT flow may become “starved” after multiple iterations, which leads to a significant fairness problem in the BBR. This study analyzed the convergence using the BBR algorithm principle and the effect of RTT on fairness. Thereafter, we proposed an improved algorithm termed BBR-f, constructed an inverse proportional function of RTT, and added a gain function to the congestion window (CWND) gain. A simulation experiment using the ns-3 network simulator platform shows that the algorithm can optimize fairness and improve bottleneck-linked bandwidth utilization. Finally, the Jain fair index was used to evaluate its effectiveness, and a comparison experiment with traditional algorithms was performed to verify the efficiency of the proposed method.

  • 内海 哲史
    電子情報通信学会 通信ソサイエティマガジン
    2023年 17 巻 1 号 68-79
    発行日: 2023年
    公開日: 2023/06/01
    ジャーナル フリー
    最近の5 年間で,インターネットにおけるふくそう(輻輳)制御アルゴリズムに関する論文数がV字回復してきている.本稿では,そもそもなぜ,輻輳制御アルゴリズムが必要なのかという観点から,輻輳崩壊,
    Bufferbloat
    といったインターネットにおける輻輳問題について述べる.また,インターネット史上において,代表的な輻輳制御アルゴリズムを紹介し,輻輳制御アルゴリズムの研究領域と研究手法について述べる.更に,輻輳制御アルゴリズムの最近の研究動向と今後の展望について述べる.
  • Yu NAKAYAMA, Ken-Ichi SUZUKI, Jun TERADA, Akihiro OTAKA
    IEICE Transactions on Communications
    2015年 E98.B 巻 12 号 2431-2438
    発行日: 2015/12/01
    公開日: 2015/12/01
    ジャーナル 認証あり
    Ring aggregation networks are widely employed for metro access networks. A layer-2 ring with Ethernet Ring Protection is a popular topology for carrier services. Since frames are forwarded along ring nodes, a fairness scheme is required to achieve throughput fairness. Although per-node fairness algorithms have been developed for the Resilient Packet Ring, the per-node fairness is insufficient if there is bias in a flow distribution. To achieve per-flow fairness, N Rate N+1 Color Marking (NRN+1CM) was proposed. However, NRN+1CM can achieve fairness in case there are sufficient numbers of available bits on a frame header. It cannot be employed if the frame header cannot be overwritten. Therefore, the application range of NRN+1CM is limited. This paper proposes a Signaling based Discard with Flags (SDF) scheme for per-flow fairness. The objective of SDF is to eliminate the drawback of NRN+1CM. The key idea is to attach a flag to frames according to the input rate and to discard them selectively based on the flags and a dropping threshold. The flag is removed before the frame is transmitted to another node. The dropping threshold is cyclically updated by signaling between ring nodes and a master node. The SDF performance was confirmed by employing a theoretical analysis and computer simulations. The performance of SDF was comparable to that of NRN+1CM. It was verified that SDF can achieve per-flow throughput fairness without using a frame header in ring aggregation networks.
  • Yusuke SAKUMOTO, Chisa TAKANO, Masaki AIDA, Masayuki MURATA
    IEICE Transactions on Communications
    2016年 E99.B 巻 2 号 402-411
    発行日: 2016/02/01
    公開日: 2016/02/01
    ジャーナル 認証あり
    Computer networks require sophisticated control mechanisms to realize fair resource allocation among users in conjunction with efficient resource usage. To successfully realize fair resource allocation in a network, someone should control the behavior of each user by considering fairness. To provide efficient resource utilization, someone should control the behavior of all users by considering efficiency. To realize both control goals with different granularities at the same time, a hierarchical network control mechanism that combines microscopic control (i.e., fairness control) and macroscopic control (i.e., efficiency control) is required. In previous works, Aida proposed the concept of chaos-based hierarchical network control. Next, as an application of the chaos-based concept, Aida designed a fundamental framework of hierarchical transmission rate control based on the chaos of coupled relaxation oscillators. To clarify the realization of the chaos-based concept, one should specify the chaos-based hierarchical transmission rate control in enough detail to work in an actual network, and confirm that it works as intended. In this study, we implement the chaos-based hierarchical transmission rate control in a popular network simulator, ns-2, and confirm its operation through our experimentation. Results verify that the chaos-based concept can be successfully realized in TCP/IP networks.
  • Kien NGUYEN, Mirza Golam KIBRIA, Kentaro ISHIZU, Fumihide KOJIMA
    IEICE Transactions on Communications
    2019年 E102.B 巻 9 号 1904-1913
    発行日: 2019/09/01
    公開日: 2019/09/01
    [早期公開] 公開日: 2019/03/18
    ジャーナル 認証あり

    A Multipath TCP (MPTCP) connection uses multiple subflows (i.e., TCP flows), each of which traverses over a wireless link, enabling throughput and resilience enhancements in mobile wireless networks. However, to achieve the benefits, the subflows are necessarily initialized (i.e., must complete TCP handshakes) and sequentially attached to the MPTCP connection. In the standard (MPTCPST), MPTCP initialization raises several problems. First, the TCP handshake of opening subflow is generally associated with a predetermined network. That leads to degraded MPTCP performance when the network does not have the lowest latency among available ones. Second, the first subflow's initialization needs to be successful before the next subflow can commence its attempt to achieve initialization. Therefore, the resilience of multiple paths fails when the first initialization fails. This paper proposes a novel method for MPTCP initialization, namely MPTCPSD (i.e., MPTCP with SYN duplication), which can solve the problems. MPTCPSD duplicates the first SYN and attempts to establish TCP handshakes for all subflows simultaneously, hence inherently improves the loss-resiliency. The subflow that achieves initialization first, is selected as the first subflow, consequently solving the first problem. We have implemented and extensively evaluated MPTCPSD in comparison to MPTCPST. In an emulated network, the evaluation results show that MPTCPSD has better performance that MPTCPST with the scenarios of medium and short flows. Moreover, MPTCPSD outperforms MPTCPST in the case that the opening subflow fails. Moreover, a real network evaluation proves that MPTCPSD efficiently selects the lowest delay network among three ones for the first subflow regardless of the preconfigured default network. Additionally, we propose and implement a security feature for MPTCPSD, that prevents the malicious subflow from being established by a third party.

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