Number Of Active Flows Research Articles

Adaptive Flow-Level Resource Allocation for Wireless Mesh Networks

In this paper, we study how to achieve network utility maximization (NUM) in flow-level wireless networks, which can be characterized by the random arrivals and departures of flow-level traffic in such networks. Existing work in this area has mainly concentrated on finding the stability region in such networks while achieving the NUM objective. In this paper, we propose a fully distributed adaptive CSMA based flow-level cross-layer resource allocation algorithm (FLRA), which achieves the NUM goal while satisfying desired delay requirement via optimized link scheduling at the MAC layer and optimal flow-level admission control at the transport layer. Detailed algorithm design is presented. We analyze the convergence property of FLRA and its optimality in terms of network utility while meeting desired delay requirement. We further reveal the relationship among maximum network utility, desired delay, and number of active flows when a network reaches stability. We conduct extensive simulations and the results validate the effectiveness of our analytical results.

Joint route selection and resource allocation in multihop wireless networks based on a game theoretic approach

In this work we aim to design simple, distributed self-configuring solutions for the problem of route selection and channel and power allocation in multihop autonomous wireless systems using a game theoretic perspective. We propose and compare three games with different levels of complexity: a potential flow game where players need complete network knowledge, a local flow game requiring full information of the flow and a low complexity cooperative link game which works with partial information of the flow. All these games have been designed to always assure the convergence to a stable point in order to be implemented as distributed algorithms. To evaluate their quality, we also obtain the best achievable performance in the system using mathematical optimization. The system is modeled with the physical interference model and two different definitions of the network utility are considered: the number of active flows and the aggregated capacity in bps. Results show that the proposed games approach the centralized solution, and specially, that the simpler cooperative link game provides a performance close to that of the flow games.

Active flows in diagnostic of troubleshooting on backbone links

In this paper, we propose a novel approach to finding and predicting anomalous network states based on a flow monitoring mechanism. We assume that number of active flows can show a real network state. Moreover, the dependence between flow number and link utilisation allows us to derive an equation for the confidence interval on high-loaded network links. Experiments have been conducted that confirmed the basic position of the model and identified the anomaly network states. A software package based on this model has been created that allows the prevention of DDoS attacks. For successful operation of this software the number of active flows that single IP address can generate has been analysed.

On the Scalable Fairness and Efficient Active Queue Management of RED

Internet routers generally see packets from a fast flow more often than a slow flow. This suggests that network fairness may be improved without per-flow information. In this paper, we propose a scheme using Most Recently Used List (MRUL)-a list storing statistics of limited active flows that sorted in most recently seen first mode-to improve the fairness of RED. Based on the list, our proposed scheme jointly considers the identification and punish of the fast and unresponsive fast flows, and the protection of slow flows. Its performance improvements are demonstrated with extensive simulations. Different from the previous proposals, the complexity of our proposed scheme is proportional to the size of the MRUL list but not coupled with the queue buffer size or the number of active flows, so it is scalable and suitable for various routers. In addition, another issue we address in this paper is queue management in RED. Specifically, we replace the linear packet dropping function in RED by a judicially designed nonlinear quadratic function, while original RED remains unchanged. We call this new scheme Nonlinear RED, or NLRED. The underlying idea is that, with the proposed nonlinear packet dropping function, packet dropping becomes gentler than RED at light traffic load but more aggressive at heavy load. As a result, at light traffic load, NLRED encourages the router to operate in a range of average queue sizes rather than a fixed one. When the load is heavy and the average queue size approaches the pre-determined maximum threshold (i.e. the queue size may soon get out of control), NLRED allows more aggressive packet dropping to back off from it. Simulations demonstrate that NLRED achieves a higher and more stable throughput than RED and REM. Since NLRED is fully compatible with RED, we can easily upgrade/replace the existing RED implementations by NLRED.

Technique for Estimating the Number of Active Flows in High-Speed Networks

The online collection of coarse-grained traffic information, such as the total number of flows, is gaining in importance due to a wide range of applications, such as congestion control and network security. In this paper, we focus on an active queue management scheme called SRED since it estimates the number of active flows and uses the quantity to indicate the level of congestion. However, SRED has several limitations, such as instability in estimating the number of active flows and underestimation of active flows in the presence of non-responsive traffic. We present a Markov model to examine the capability of SRED in estimating the number of flows. We show how the SRED cache hit rate can be used to quantify the number of active flows. We then propose a modified SRED scheme, called hash-based two-level caching (HaTCh), which uses hashing and a two-level caching mechanism to accurately estimate the number of active flows under various workloads. Simulation results indicate that the proposed scheme provides a more accurate estimation of the number of active flows than SRED, stabilizes the estimation with respect to workload fluctuations, and prevents performance degradation by efficiently isolating non-responsive flows.

Random early detection with flow number estimation and queue length feedback control

We evaluate effects of parameters in queue management on performance using 2k factorial designs. Among these systematic and environmental parameters, number of flows and Pmax are two dominant factors affecting RED performance. Then, we propose a novel active queue management scheme, NRED, employing flow number estimation and queue length feedback control, which are motivated from Bloom filter and control theory, respectively. By estimation of number of active flows, NRED is more scalable than FRED which employs per-active-flow accounting. Furthermore, fluctuation of queue length under NRED is smaller than BLUE, REM, SRED and DRED. Especially, NRED can stabilize queue length very fast even when a lot of flows suddenly crowd into the network. NRED is suitable to be deployed in today's networks where hot spot frequently occurs.

A Method of Bandwidth Dimensioning and Management Using Flow Statistics

We develop a method of dimensioning and manag- ing the bandwidth of a link on which TCP flows from access links are aggregated. To do this, we extend the application of the processor-sharing queue model to TCP performance evaluation by using flow statistics. To handle various factors that affect actual TCP behavior besides the access-link bandwidth, such as round-trip time, window-size, and other bottlenecks, we extend the model by replacing the access-link bandwidth with the actual file-transfer speed of a flow under a low utilization of the aggregation link. We only use the number of active flows and the link utilization to estimate the file-transfer speed. Unlike previous studies, the extended model based on the actual transfer speed does not require any assumptions/predeterminations about file- size, packet-size, and round-trip times, etc. Using the extended model, we predict the TCP performance when the link utilization increases. We also show a method of dimensioning the bandwidth needed to maintain TCP performance. We show the effectiveness of our method through simulation analysis. I. INTRODUCTION

Performance sensitivity and fairness of ECN-aware ‘modified TCP’

The paper discusses how explicit congestion notification (ECN) can be used to devise an Internet congestion control mechanism that is more rapidly reactive and allows best-effort flows to rapidly adjust to fluctuations in available capacity. Our ECN-mod protocol involves simple modifications to TCP behavior and leverages more aggressive marking-based router feedback. Simulations show that ECN-mod is better than TCP NewReno for both persistent sources and Web-style intermittent traffic sources, and makes the link utilization significantly less sensitive to the variation in the number of active flows. Simulations also show that, while ECN-mod flows obtain a larger portion of the available capacity than conventional best-effort traffic, they do not starve or significantly penalize such TCP-based flows.

Efficient fair queuing using deficit round-robin

Fair queuing is a technique that allows each flow passing through a network device to have a fair share of network resources. Previous schemes for fair queuing that achieved nearly perfect fairness were expensive to implement; specifically, the work required to process a packet in these schemes was O(log(n)), where n is the number of active flows. This is expensive at high speeds. On the other hand, cheaper approximations of fair queuing reported in the literature exhibit unfair behavior. In this paper, we describe a new approximation of fair queuing, that we call deficit round-robin. Our scheme achieves nearly perfect fairness in terms of throughput, requires only O(1) work to process a packet, and is simple enough to implement in hardware. Deficit round-robin is also applicable to other scheduling problems where servicing cannot be broken up into smaller units (such as load balancing) and to distributed queues.