Explicit Control Protocol Research Articles

Achieving Fast Convergence and High Efficiency using Differential Explicit Feedback in Data Center

Since most flows are short-lived in data center networks, fast convergence becomes very important to help the short flows effectively utilize high bandwidth. Though current explicit feedback-based transport control protocols (TCPs) provide fast convergence via fine-grained congestion information from customized switches, they unavoidably incur large traffic overhead for widely existing small packets in data center applications, resulting in suboptimal network efficiency. To solve this issue, we propose a datacenter TCP based on <b>D</b>ifferential <b>E</b>xplicit <b>C</b>ongestion <b>N</b>otification, called DECN, to achieve fast convergence without any traffic overhead. Specifically, DECN feeds rate difference between the target and current rate back to the source by using multiple consecutive packets. Besides, we propose an enhanced version DECN* which obtains the optimal number of consecutive packets according to the packet loss rate. The experimental results of NS2 simulation and testbed implementation show that DECN and its enhanced version DECN* achieve comparable fast convergence as XCP without incurring any extra feedback overhead. Compared with the state-of-the-art explicit feedback-based TCPs, they reduce the flow completion time by up to 34&#x0025; in typical data center applications.

Implicit versus explicit vector management strategies in models for vector-borne disease epidemiology.

Throughout the vector-borne disease modeling literature, there exist two general frameworks for incorporating vector management strategies (e.g. area-wide adulticide spraying and larval source reduction campaigns) into vector population models, namely, the "implicit" and "explicit" control frameworks. The more simplistic "implicit" framework facilitates derivation of mathematically rigorous results on disease suppression and optimal control, but the biological connection of these results to real-world "explicit" control actions that could guide specific management actions is vague at best. Here, we formally define a biological and mathematical relationship between implicit and explicit control, and we provide mathematical expressions relating the strength of implicit control to management-relevant properties of explicit control for four common intervention strategies. These expressions allow the optimal control and basic reproduction number analyses typically utilized in implicit control modeling to be interpreted directly in terms of real-world actions and real-world monetary costs. Our methods reveal that only certain sub-classes of explicit control protocols are able to be represented as implicit controls, and that implicit control is a meaningful approximation of explicit control only when resonance-like synergistic effects between multiple explicit controls have negligible effects on population reduction. When non-negligible synergy exists, implicit control results, despite their mathematical tidiness, fail to provide accurate predictions regarding vector control and disease spread. Collectively, these elements build an effective bridge between analytically interesting and mathematically tractable implicit control and the challenging, action-oriented explicit control.

3CP: Coordinated Congestion Control Protocol for Named-Data Networking

Congestion control has a vital role in the prosperity of any network. Thus, designing an effective mechanism for congestion control of the NDN is an active research area. In NDN, congestion control and interest forwarding mechanisms are usually considered an integrated plane for the network traffic management. In this paper, we propose to decouple the forwarding and congestion control planes. We offer a novel architecture for the NDN router in which congestion control and forwarding modules cooperate for interest flow management and congestion control. Based on this framework, we introduce a new explicit feedback-based congestion control protocol (3CP) for managing the consumers’ sending rate in an NDN environment that multi-source and multi-path content delivery is intrinsically supported. 3CP employs a new per-packet feedback computation to inform consumers from the available resource of paths toward repositories. Also, it provides feedback to the forwarding mechanism of a router for adjusting the sending rate of interest packets to each interface. By interest flow management, 3CP controls the traffic of data packets in the network. As a significant achievement, 3CP prevents multi-path flows from acquiring more network resources and could manage fair resource allocation to the flows in each path, whereas the consumers obtain the same throughput. The packet-level simulation was conducted by an NDN simulator, and the results confirmed that 3CP outperforms the existing multi-source/multi-path congestion control mechanisms in NDN.

Proposal of cross‐layer bandwidth assignment with buffer size indication for TCP flow control

AbstractIn this paper, we propose, verify, and evaluate a method combining cross‐layer method and bandwidth allocation to overcome the difficulty of flow control in a network with large bandwidth delay product. When the bandwidth delay product is large, there are problems with the convergence time, efficiency and stability of bandwidth utilization, and fairness among traffics of different round‐trip time. As a result of examining the conventional methods, we propose a novel method that can be realized as a functional addition to the existing transmission control protocol (TCP) flow control with improvement in utilization efficiency, fairness, stability, and convergence time. The method is compared with TCP Reno, FAST TCP, CUBIC, Explicit Congestion Notification, and eXplicit Control Protocol by simulation, and is confirmed as having good characteristics.

Robust Lyapunov–Krasovskii based design for explicit control protocol against heterogeneous delays

TCP has been extensively credited for the stability of the Internet. However, as the product of bandwidth and latency increases, TCP becomes inefficient and prone to instability. The explicit control protocol (XCP) is a promising congestion control protocol that outperforms TCP in terms of efficiency, fairness, convergence speed, persistent queue length and packet loss rate. However, XCP is not globally stable in the presence of heterogeneous delays. When the ratio of maximum to average transmission latency is sufficiently large, XCP will become instability. In this paper, according to the robust control theory, with the help of a recently developed Lyapunov–Krasovskii functional, an improved version of XCP, named R-XCP, is proposed to solve the weakness of XCP under heterogeneous delays, which adjusts parameter $$\alpha $$ from an initial value of 0.4 to a reasonable value for improving system robustness. And then, the synthesis problem is reduced to a convex optimization scheme expressed in terms of linear matrix inequalities. Extensive simulations have shown that R-XCP significantly decreases the volatilities of the aggregate traffic rate and control time interval, and indeed achieves this stability goal. Compared with previous work, R-XCP has a better balance between robustness and responsiveness, and the computational complexity declines significantly at the same time. Besides, R-XCP makes the system less sensitive to flows, which contribute little traffic but maliciously report their transmission delays.

The Stability-Featured Dynamic Multi-Path Routing

Stability-featured dynamic multi-path routing (SDMR) based on the existing Traffic engineering eXplicit Control Protocol (TeXCP) is proposed and evaluated for traffic engineering in terrestrial networks. SDMR abandons the sophisticated stability maintenance mechanisms of TeXCP, whose load balancing scheme is also modified in the proposed mechanism. SDMR is proved to be able to converge to a unique equilibria state, which has been corroborated by the simulations.

XCP-Winf and RCP-Winf: Improving Explicit Wireless Congestion Control

Congestion control in wireless networks is strongly dependent on the dynamics and instability of wireless links. Therefore, it is very difficult to accurately evaluate the characteristics of the wireless links. It is known that TCP experiences serious performance degradation problems in wireless networks. Moreover, congestion control mechanisms that rely on network interaction and network parameters, such as XCP and RCP, do not evaluate accurately the capacity and available link bandwidth in wireless networks. In this paper we propose new explicit flow control protocols for wireless mesh networks, based on XCP and RCP. We name these protocols XCP-Winf and RCP-Winf. They rely on the MAC layer information gathered by a new method to accurately estimate the available bandwidth and the path capacity over a wireless network path. The estimation is performed in real time and without the need to intrusively inject packets in the network. These new congestion control mechanisms are evaluated in different scenarios in wireless mesh and ad hoc networks and compared against several new approaches for wireless congestion control. It is shown that both XCP-Winf and RCP-Winf outperform the evaluated approaches, showing its stable behavior and better channel utilization.

A Multi-objective QoS Mechanism for Web Applications: Improved EFXCP

The research of QoS is concerned with multiple QoS requirements (multi-QR): queue delay, delay jitter and guaranteed throughput etc. As different QoS requirements have different attributes, it is hard to ensure multi-QR in one QoS mechanism. A common method to ensure multi-QR is normalizing multi-QR into one value range by a utility function and then finding the optimal solution of the utility function. However, although multi-QR are considered in such QoS mechanisms, in fact, no concrete QoS requirement can been strictly ensured, which may be embarrassing because web application usually requires one or more concrete QoS requirements to be satisfied strictly. Therefore, it is significant to design a real multi-objective QoS mechanism to satisfy different QoS requirements of various web applications. Our previous works proposed an efficient and fair explicit congestion control protocol (EFXCP) which can achieve excellent performance in terms of high link utilization, low queue delay, low delay jitter, etc. Because different web applications have different throughput requirements, to further satisfy throughput requirements of web applications, we extend EFXCP in this paper to implement an improved EFXCP (IEFXCP). Firstly, ToS field in IP header is utilized to classify different web applications, and then the relative fair bandwidth allocation is proposed between different types of web applications to preferentially ensure throughput requirements of high prior web applications. Therefore, IEFXCP can simultaneously satisfy multi-QR: queue delay, delay jitter and guaranteed throughput. The performance of IEFXCP is validated by extensive NS2 simulations over a wide range of network scenarios, the results show that IEFXCP is a real multi-objective QoS mechanism. DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.4009

Using Fuzzy Logic Control to Provide Intelligent Traffic Management Service for High-Speed Networks

In view of the fast-growing Internet traffic, this paper propose a distributed traffic management framework, in which routers are deployed with intelligent data rate controllers to tackle the traffic mass. Unlike other explicit traffic control protocols that have to estimate network parameters (e.g., link latency, bottleneck bandwidth, packet loss rate, or the number of flows) in order to compute the allowed source sending rate, our fuzzy-logic-based controller can measure the router queue size directly; hence it avoids various potential performance problems arising from parameter estimations while reducing much consumption of computation and memory resources in routers. As a network parameter, the queue size can be accurately monitored and used to proactively decide if action should be taken to regulate the source sending rate, thus increasing the resilience of the network to traffic congestion. The communication QoS (Quality of Service) is assured by the good performances of our scheme such as max-min fairness, low queueing delay and good robustness to network dynamics. Simulation results and comparisons have verified the effectiveness and showed that our new traffic management scheme can achieve better performances than the existing protocols that rely on the estimation of network parameters.

Improving the efficiency and fairness of eXplicit Control Protocol in multi-bottleneck networks

The Transmission Control Protocol (TCP) has been extensively credited for the stability of the Internet. However, as the product of bandwidth and latency increases, TCP becomes inefficient and prone to instability. The eXplicit Control Protocol (XCP) is a novel and promising congestion control protocol that outperforms TCP in terms of efficiency, fairness, convergence speed, persistent queue length and packet loss rate. However, the XCP equilibrium solves a constrained max–min fairness problem instead of a standard max–min fairness problem. The additional constraint under XCP leads to inefficiency and unfairness for the topologies that have multiple bottleneck links.In this paper, according to classical control theory, we propose an XCP bandwidth compensation algorithm on basis of the proportional integral controller (PI-XCP), which reconfigures the available bandwidth variable from the fixed hardware determined physical link capacity value to a configuration value that can be dynamically changed. Through a reasonable online compensation, PI-XCP gets efficient and fair bandwidth allocation in a multi-bottleneck network. Extensive simulations have shown that PI-XCP indeed achieves this goal. Simulations also have shown that PI-XCP preserves good properties of XCP, including fast convergence, negligible queue length and zero packet loss rate. Compared with iXCP, an enhancement to address the XCP equilibrium problem, PI-XCP decreases the computational complexity significantly, and achieves more effective control in highly dynamic situations, especially in the presence of short-lived flows.

A Pilot Survey of Mercury in Drugs, Cosmetics and Household Products Using Reliable Analytical Methods

The concentration of mercury (Hg) was accurately determined in more than 228 drugs, cosmetics and household products manufactured in a variety of countries. Some drugs were found to contain up to 4424 ppb Hg, and some skin creams contained up to 2769 ppm Hg. Hg in skin creams was found to be almost 100% elemental Hg (Hg0), a volatile species of Hg. Hg0 can enter the human body through inhalation and skin absorption, potentially resulting in the serious consequence of mercury poisoning. The mercury can also volatilize, contaminating the surrounding air. Other people, for example, infants and children, who are close to or contacting the skin of the person using the cosmetics, can also absorb the mercury. Total mercury (THg) was determined by combustion/trap/CVAFS. Methyl mercury (MeHg) and inorganic mercury (Hg2+) were determined by the ethylation based method. The emission of Hg0 was determined by evaporation/trap/CVAFS. All analyses were performed in accordance with explicit quality assurance and quality control protocols and procedures.

Time-optimal processes for interacting spin systems

Reversible adiabatic processes connecting thermal equilibrium states are usually considered to be infinitely slow. Recently, fast reversible adiabatic processes for quantum systems have been discussed. Here we present time-optimal processes for a paradigmatic ensemble of two interacting spin- systems in an external magnetic field, which previously had been employed as working fluid in a quantum refrigerator. These processes are realized by appropriate bang-bang or quasi–bang-bang controls of the external magnetic field. Explicit control protocols including the necessary times for a transition connecting thermal equilibrium states depending on the limiting conditions on the magnetic field strength are presented.

Combining explicit admission control and congestion control for predictable data transfers in grids

To improve the Grid infrastructure’s efficiency, the co-reservation of distributed resources is often required. Therefore, Grid applications need to move large amounts of data between these resources within deterministic time frames. In most cases it is possible to specify the volume and the deadline in advance. This paper proposes an approach for data-movement management and bandwidth reservation in Grid, which provides a high acceptance probability of flows in the network while maintaining efficient network-resource utilization. To achieve this, our proposal combines explicit admission control and high-speed transport protocols to enable an opportunistic sharing of the capacity by flows having heterogeneous bandwidth and delay requirements. We formulate the problem and discuss several objective functions. Then we present different heuristics and evaluate them according to the request’s acceptance rate and the network’s utilization metrics. Our simulations include all the communication and computation overheads which are involved in such data transfers.

ARROW-WTCP: A fast transport protocol based on explicit congestion notification over wired/wireless networks

An explicit congestion notification (ECN)-based distributed transport protocol, ARROW-WTCP (AcceleRate tRansmission towards Optimal Window size TCP for Wireless network), was proposed. The ARROW-WTCP enables feasible deployment of ARROW-TCP from wired to wireless networks by providing a joint design of source and router algorithms. The protocol obtains the actual capacity of the wireless channel by calculating the queue variation in base station (BS) and adjusts the congestion window by using the feedback from its bottleneck link. The simulation results show that the ARROW-WTCP achieves strong stability, max-min fairness in dynamic networks, fast convergence to efficiency without introducing much excess traffic, and almost full link utilization in the steady state. It outperforms the XCP-B (eXplicit Control Protocol Blind), the wireless version of XCP, in terms of stability, fairness, convergence and utilization in wireless networks.

Queue Stability Analysis and Performance Evaluation of a TCP-Compliant Window Management Mechanism

Addressing performance degradations in end-to-end congestion control has been one of the most active research areas in the last decade. A huge number of techniques have been proposed in the past, but some of them miss the challenging target of both minimizing network delay and keeping goodput close to the network capacity (e.g., active queue management (AQM) techniques); others require changes in both network routers and hosts that make them difficult to deploy [e.g., eXplicit Control Protocol (XCP)]. In a previous paper, a novel mechanism, called Active Window Management (AWM), has been proposed by the same authors with the aim of controlling the queue length in network routers, maintaining it almost constant to achieve no loss, while maximizing network utilization. The target of this paper is twofold: 1) carrying out a deep analysis of the AWM algorithm stability to evaluate the impact of some system parameters on the performance of the whole system; 2) demonstrating that AWM can be gradually introduced, maintaining the compatibility with the current Internet. An extensive numerical analysis is proposed to demonstrate that AWM stabilizes the queue around a target value with small oscillations.

Analysis of efficient and fair explicit congestion control protocol with feedback delay: Stability and convergence

To overcome the drawbacks of XCP and VCP, we propose an efficient and fair explicit congestion control protocol, EFXCP, for high bandwidth-delay product networks and analyze the stability and convergence attributes of EFXCP. Our simulations showed that EFXCP achieves excellent performance. However, the stability analysis in our previous paper neglected the feedback delay for simplification analysis, which is not consistent with that of present-day networks and make the analysis inaccuracy. To make the analysis more realistic and accurate, to portray the real network, we consider the stability analysis with the feedback delay and present a fluid flow of traffic model of EFXCP. Based on the model, we utilize classical control theory method to further analyze the stability of EFXCP. We also quantitatively define the efficiency and fairness index, and based on these definitions, we qualitatively analyze the efficiency and fairness convergence timings of EFXCP. These conclusions are validated by extensive NS2 simulations.

Evaluation of Router Implementations for Explicit Congestion Control Schemes

Explicit congestion control schemes use router feedback to overcome limitations of the standard mechanisms of the Transmission Control Protocol (TCP). These approaches require additional packet processing in every router and therefore raise the question whether, and how, this can be achieved in high-speed routers. This paper investigates the realization complexity of these router functions of two such schemes, the TCP Quick-Start extension and the Explicit Control Protocol (XCP). Our focus lies on the implementation using a network processor. We show that synchronization issues among parallel processing entities have to be considered, and that this affects the router performance. We develop and compare different synchronization mechanisms for highly parallel packet processing. Our prototype implementation on an Intel IXP network processor allows to quantify the impact on throughput and delay caused by the additional packet processing in the fast path. The measurements reveal that Quick-Start and XCP processing is feasible at multiple Gbit/s line speed, with Quick-Start being simpler to scale. We expect similar results for the implementation of the Rate Control Protocol (RCP), which is another router-assisted congestion control scheme, requiring no elaborate synchronization. Finally, we study the implementation using programmable logic and show the applicability of XCP and in particular Quick-Start even at significantly higher line speeds.

Time-domain sending rate and response function of eXplicit Control Protocol

A response function is usually used to describe the scalability of a protocol for high-speed network. This requires detailed knowledge of the time-domain sending rate. However, studies about the performance of eXplicit Control Protocol (XCP) mainly focus on the steady-state behavior and few address this problem. Under a model with single bottleneck, the time-domain sending rate of XCP is derived in this paper. Simulation results show that this analytic time-domain sending rate is accurate. Combined with a periodic loss model, the response function of XCP is further derived. Unlike response functions of other protocols, the response function of XCP is related to not only the loss event rate, but also the per-flow bandwidth. Simulation results show that it forms an upper bound for the throughput of XCP with given loss event rate and per-flow bandwidth.

Improving XCP to achieve max–min fair bandwidth allocation

TCP is prone to be inefficient and unstable in high-speed and long-latency networks [1]. The eXplicit Control Protocol (XCP) is a new and promising protocol that outperforms TCP in terms of efficiency, stability, queue size, and convergence speed. However, Low et al. recently discovered a weakness of XCP. In a multi-bottleneck environment, XCP may achieve as low as 80% utilization at a bottleneck link and consequently some flows may only receive a small fraction of their max-min fair rates. This paper proposes iXCP, an improved version of XCP. Extensive simulations show that iXCP overcomes the weakness of XCP, and achieves efficient and fair bandwidth utilization in both single- and multi-bottleneck environments. In addition, we prove that iXCP is max-min fair in steady state. This result implies that iXCP is able to fully utilize bottleneck bandwidth. Simulations show that iXCP preserves the good properties of XCP, including negligible queue lengths, near-zero packet loss rates, scalability, and fast convergence. Simulations also show that iXCP overcomes the under-utilization and instability problem of P-XCP [2], and outperforms JetMax [3] in terms of link utilization in the presence of highly dynamic traffic.

Maximization of throughput by effective queue management scheme for high speed network

A new algorithm is proposed to control the congestion in the network based on the minimum drop ratio. Explicit Control Protocol (XCP) is adopted for high speed network, where the queue threshold is assigned to be 85% of the queue size. At the time of congestion, whenever the queue size reaches the threshold value, a new buffer is initialized which is half the queue size. This mechanism thus prevents the drop of packets and hence the drop ratio is minimized and throughput is maximized. Performance of bandwidth utilization, throughput and drop ratio is presented.