Active queue management with discrete sliding modes in TCP networks

In this paper, a new active queue management (AQM) algorithm for data traffic control in TCP/IP networks is developed. The algorithm design is based on the principles of discrete sliding-mode control. Unlike majority of earlier studies, the design procedure considers the effects of both non-negligible delay in transferring data and feedback information and unpredictable capacity variations. The switching function is selected to incorporate a delay compensation mechanism, which ensures efficient network operation even for large bandwidthdelay product connections. The proposed algorithm, implemented as a packet marking scheme, is tested in discrete event ns-2 simulator. The results show that the algorithm provides fast convergence to steady state after sudden, unanticipated capacity changes. By generating smaller overshoots, the proposed algorithm also allows for reducing buffer space requirements to avoid packet loss as compared to the benchmark AQM solutions

Flow control in connection-oriented networks: a time-varying sampling period system case study

summary:In this paper congestion control problem in connection-oriented communication network with multiple data sources is addressed. In the considered network the feedback necessary for the flow regulation is provided by means of management units, which are sent by each source once every M data packets. The management units, carrying the information about the current network state, return to their origin round trip time RTT after they were sent. Since the source rate is adjusted only at the instant of the control units arrival, the period between the transfer speed modifications depends on the flow rate RTT earlier, and consequently varies with time. A new, nonlinear algorithm combining the Smith principle with the proportional controller with saturation is proposed. Conditions for data loss elimination and full resource utilisation are formulated and strictly proved with explicit consideration of irregularities in the feedback information availability. Subsequently, the algorithm robustness with respect to imprecise propagation time estimation is demonstrated. Finally, a modified strategy implementing the feed-forward compensation is proposed. The strategy not only eliminates packet loss and guarantees the maximum resource utilisation, but also decreases the influence of the available bandwidth on the queue length. In this way the data transfer delay jitter is reduced, which helps to obtain the desirable Quality of Service (QoS) in the network

Soft variable structure control in time-delay systems with saturating input

summary:In order to achieve a short regulation cycle, time-optimal control has been considered in the past. However, the sensitivity to errors and uncertainties, and implementation difficulties in the practical systems, have incited other research directions to meet this objective. In this paper, soft Variable Structure Control (VSC) is analyzed from the perspective of linear time-delay systems with input constraint. The desired fast convergence under a smoothly varying control signal is obtained. The stability issues originating from the non-negligible delay are addressed explicitly by incorporating a dead-time compensator, applicable to both structurally stable and unstable plants. The properties of the obtained dynamic soft VSC system are demonstrated analytically and compared with the linear and saturating control structures

Sterowanie przepływem danych w połączeniowych sieciach teleinformatycznych

In this paper formal, control-theoretic methods are applied to design an efficient congestion control algorithm for modern connection-oriented data transmission networks. The design is based on the principles of discrete-time sliding-mode control and linear-quadratic optimal control. The asymptotic stability of the closed-loop system with the designed controller implemented is demonstrated, and the conditions for achieving the maximum throughput in the networks are defined.W pracy zaprojektowano nowy algorytm sterowania przepływem danych dla połączeniowych sieci teleinformatycznych. Do tego celu wykorzystano zaawansowane metody teorii sterowania - dyskretne sterowanie ślizgowe oraz dyskretne sterowanie optymalne z kwadratowym wskaźnikiem jakości. Pokazano, że zaproponowany algorytm pozwala wyeliminować ryzyko gubienia danych przy jednoczesnym pełnym wykorzystaniu dostępnego pasma

Flow control in connection-oriented networks: a time-varying sampling period system case study

summary:In this paper congestion control problem in connection-oriented communication network with multiple data sources is addressed. In the considered network the feedback necessary for the flow regulation is provided by means of management units, which are sent by each source once every M data packets. The management units, carrying the information about the current network state, return to their origin round trip time RTT after they were sent. Since the source rate is adjusted only at the instant of the control units arrival, the period between the transfer speed modifications depends on the flow rate RTT earlier, and consequently varies with time. A new, nonlinear algorithm combining the Smith principle with the proportional controller with saturation is proposed. Conditions for data loss elimination and full resource utilisation are formulated and strictly proved with explicit consideration of irregularities in the feedback information availability. Subsequently, the algorithm robustness with respect to imprecise propagation time estimation is demonstrated. Finally, a modified strategy implementing the feed-forward compensation is proposed. The strategy not only eliminates packet loss and guarantees the maximum resource utilisation, but also decreases the influence of the available bandwidth on the queue length. In this way the data transfer delay jitter is reduced, which helps to obtain the desirable Quality of Service (QoS) in the network

Congestion Control in Data Transmission Networks: Sliding Mode and Other Designs

Congestion Control in Data Transmission Networks details the modeling and control of data traffic in communication networks. It shows how various networking phenomena can be represented in a consistent mathematical framework suitable for rigorous formal analysis. The monograph differentiates between fluid-flow continuous-time traffic models, discrete-time processes with constant sampling rates, and sampled-data systems with variable discretization periods. The authors address a number of difficult real-life problems, such as: • optimal control of flows with disparate, time-varying delay; • the existence of source and channel nonlinearities; • the balancing of quality of service and fairness requirements; and • the incorporation of variable rate allocation policies. Appropriate control mechanisms which can handle congestion and guarantee high throughput in various traffic scenarios (with different networking phenomena being considered) are proposed. Systematic design procedures using sound control-theoretic foundations are adopted. Since robustness issues are of major concern in providing efficient data-flow regulation in today’s networks, sliding-mode control is selected as the principal technique to be applied in creating the control solutions. The controller derivation is given extensive analytical treatment and is supported with numerous realistic simulations. A comparison with existing solutions is also provided. The concepts applied are discussed in a number of illustrative examples, and supported by many figures, tables, and graphs walking the reader through the ideas and introducing their relevance in real networks

Continuous Genetic Algorithms as Intelligent Assistance for Resource Distribution in Logistic Systems

This paper addresses the problem of resource distribution control in logistic systems influenced by uncertain demand. The considered class of logistic topologies comprises two types of actors—controlled nodes and external sources—interconnected without any structural restrictions. In this paper, the application of continuous-domain genetic algorithms (GAs) is proposed in order to support the optimization process of resource reflow in the network channels. GAs allow one to perform simulation-based optimization and provide desirable operating conditions in the face of a priori unknown, time-varying demand. The effectiveness of inventory management process governed under an order-up-to policy involves two different objectives—holding costs and service level. Using the network analytical model with the inventory management policy implemented in a centralized way, GAs search a space of candidate solutions to find optimal policy parameters for a given topology. Numerical experiments confirm the analytical assumptions

Ruting niejedyną skuteczną metodą organizacji ruchu w sieciach

In the paper it is proposed different from routing approach to traffic organization in ad-hoc networks, where nodes, instead of searching of optimal paths of relaying based on a topology, take independent decisions based on local only information. As a result, high scalability and robustness with low overhead is achieved.W artykule zaproponowano odmienne od rutowania podejście do organizacji komunikacji w sieciach ad-hoc, w którym węzły sieci, zamiast budować jej obraz celem ustalenia optymalnej ścieżki transmisji, grają ze sobą, podejmując samodzielne decyzje na podstawie dostępnych lokalnie informacji. W rezultacie, przy niewielkim narzucie uzyskuje się wysoką skalowalność i odporność