Bandwidth estimation techniques seek to provide an accurate estimation of available bandwidth such that network applications can adjust their behavior accordingly. However, most current techniques were designed for wired networks and produce relatively inaccurate results and long convergence times on wireless networks where capacity can vary dramatically. This paper presents a new wireless bandwidth estimation tool, WBest, designed for fast, non-intrusive, accurate estimation of available bandwidth in IEEE 802.11 networks. WBest is a two-stage algorithm: 1) a packet pair technique estimates the effective capacity over a flow path where the last hop is a wireless LAN (WLAN); and 2) a packet train technique estimates achievable throughput to infer the available bandwidth. WBest parameters are optimized given the tradeoffs of accuracy, intrusiveness and convergence time. The advantage of WBest stems from avoiding a search algorithm to detect the available bandwidth by statistically detecting the available fraction of the effective capacity to mitigate estimation delay and the impact of random wireless channel errors. WBest is implemented and evaluated on an 802.11 wireless testbed. Comparisons with other available bandwidth estimation tools shows WBest to have higher accuracy, lower intrusiveness and faster convergence times. Thus, WBest demonstrates the potential for improving the performance of applications that need bandwidth estimation, such as multimedia streaming, on wireless networks.

/pdf/wbest-a-bandwidth-estimation-tool-for-ieee-802-11-wireless-47fiyve49y.pdf

WBest: A bandwidth estimation tool for IEEE 802.11 wireless networks

Network management is becoming increasingly challenging with the relentless growth in network size, traffic volume, and the diversity in QoS requirements. Traditionally, the concept of predefined Service Level Agreements (SLAs) has been utilized to establish QoS parameters. However, most state-of-the-art technologies in this area are both proprietary and inflexible. To this end, Software Defined Networking (SDN) has the potential to make network management tasks flexible, scalable, and an open platform to encourage innovation. In this paper, we present the design of PolicyCop, an open, flexible, and vendor agnostic QoS policy management framework targeted towards OpenFlow based SDN. PolicyCop provides an interface for specifying QoS SLAs and then exploits the control plane's API to enforce them. PolicyCop also monitors the network and autonomically readjusts network parameters to meet customer SLAs. We present experimental results to demonstrate PolicyCop's effectiveness in ensuring throughput, latency, and reliability guarantees.

PolicyCop: An Autonomic QoS Policy Enforcement Framework for Software Defined Networks

Enterprises want their in-cloud services to leverage the performance and security benefits that middleboxes offer in traditional deployments. Such virtualized deployments create new opportunities (e.g., flexible scaling) as well as new challenges (e.g., dynamics, multiplexing) for middlebox management tasks such as service composition and provisioning. Unfortunately, enterprises lack systematic tools to efficiently compose and provision in-the-cloud middleboxes and thus fall short of achieving the benefits that cloud-based deployments can offer. To this end, we present the design and implementation of Stratos, an orchestration layer for virtual middleboxes. Stratos provides efficient and correct composition in the presence of dynamic scaling via software-defined networking mechanisms. It ensures efficient and scalable provisioning by combining middlebox-specific traffic engineering, placement, and horizontal scaling strategies. We demonstrate the effectiveness of Stratos using an experimental prototype testbed and large-scale simulations.

Stratos: A Network-Aware Orchestration Layer for Middleboxes in the Cloud

This paper addresses the problem of choosing the best streaming policy for distortion optimal multipath video delivery, under network bandwidth and playback delay constraints. The streaming policy consists in a joint selection of the network path and of the video packets to be transmitted, along with their sending time. A simple streaming model is introduced, which takes into account the video packet importance, and the dependencies between packets. A careful timing analysis allows to compute the quality perceived by the receiver for a constrained playback delay, as a function of the streaming policy. We derive an optimization problem based on a video abstraction model, under the assumption that the server knows, or can predict accurately the state of the network. A detailed analysis of constrained multipath streaming systems provides helpful insights to design an efficient branch and bound algorithm that finds the optimal streaming strategy. This solution allows to bound the performance of any scheduling strategy, but the complexity of the algorithm becomes rapidly intractable. We therefore propose a fast heuristic-based algorithm, built on load-balancing principles. It allows to reach close to optimal performance with a polynomial time complexity. The algorithm is then adapted to live streaming scenarios, where the server has only a partial knowledge of the packet stream, and the channel bandwidth. Extensive simulations show that the proposed algorithm only induces a negligible distortion penalty compared to the optimal strategy, even when the optimization horizon is limited, or the rate estimation is not perfect. Simulation results also demonstrate that the proposed scheduling solution performs better than common scheduling algorithms, and therefore represents a very efficient low-complexity multipath streaming algorithm, for both stored and live video services

Video Packet Selection and Scheduling for Multipath Streaming

We address the problem of joint path selection and source rate allocation in order to optimize the media specific quality of service in streaming of stored video sequences on multipath networks. An optimization problem is proposed in order to minimize the end-to-end distortion, which depends on video sequence dependent parameters, and network properties. An in-depth analysis of the media distortion characteristics allows us to define a low complexity algorithm for an optimal flow rate allocation in multipath network scenarios. In particular, we show that a greedy allocation of rate along paths with increasing error probability leads to an optimal solution. We argue that a network path shall not be chosen for transmission, unless all other available paths with lower error probability have been chosen. Moreover, the chosen paths should be used at their maximum available end-to-end bandwidth. Simulation results show that the optimal flow rate allocation carefully adapts the total streaming rate and the number of chosen paths, to the end-to-end transmission error probability. In many scenarios, the optimal rate allocation provides more than 20% improvement in received video quality, compared to heuristic-based algorithms. This motivates its use in multipath networks, where it optimizes media specific quality of service, and simultaneously saves network resources at the price of a very low computational complexity.

/pdf/media-flow-rate-allocation-in-multipath-networks-2yh3ghg55l.pdf

Media Flow Rate Allocation in Multipath Networks

For estimating the available bandwidth along a network path,a novel active probing methodology COPP(chirp of packet paris)is presented combining self-induced congested principle with packet pair technique.After a sequence of packet pairs with gradually reduced intra-pair spacing was transmitted,COPP process would discover all turning bandwidth.Then every bandwidth was bound with a distinct weight according of the degree of interference of the underlying turning point and its neighbors to yield the final estimate by weighted adding up all turning bandwidth.Based on analysis of inter-packet spacing and one-way delay of single packet in a packet pair,the decision rules for determining whether a packet pair is turning point were shown.We also described the weighting process to obtain different weights for different kinds of turning point and discussed the effect of different thresholds on estimation.Simulation results in several cross traffic conditions indicate that COPP provides accurate estimation with relatively fewer overhead compared to other estimating tools.

Efficient available bandwidth estimation for network paths

This paper proposes COPP,i.e.chirp of packet pairs,a novel active method to yield available bandwidth along network paths.The probes in COPP are composed of several chirps of packet pairs,e.g.several trains of packet pairs where the interval between the first and the second packet within packet pair is gradually decreased.For each chirp of packet pairs traversed the measured path,we find out all turning points in the chirp,and then give them distinct weight in the final available bandwidth calculation according to the degree of experienced distortion.The turning point is such a packet pair that is disturbed more obviously by cross traffic in contrast to its neighbor pairs.Two rules are developed to determine whether a packet pair is a turning point or not.Additionally,COPP can determine its estimate bound dynamically by exploiting the bandwidth requirements of concrete applications if known.We also inspect the selection of the probe packet size in COPP through simulations.Finally,comparisons between COPP and other measurement tools such as Pathload and Spruce show that COPP is an agile and stable technique and can provide relatively higher accurate results with fewer overheads.

Towards Estimating Available Bandwidth on Network Paths with Application Requirements

This paper puts forwards a staged and validated experiment teaching method which organizes many independent experiments logically according to their difficulty and content. With this method, students get expectant experiment effect in the limited time.

Zhao Wen-tao

Papers

Efficient available bandwidth estimation for network paths

Towards Estimating Available Bandwidth on Network Paths with Application Requirements

Study and Practice on Information Security Introduction