Showing papers by "Alessio Botta published in 2010"

Do you trust your software-based traffic generator?

Abstract: Networking research often relies on synthetic traffic generation in its experimental activities; from generation of realistic workload to active measurements. Often researchers adopt software-based generators because of their flexibility. However, despite the increasing number of features (e.g., replication of complex traffic models), they are still suffering problems that can undermine the correctness of experiments: what is generated is sometimes far from what is requested by the operator. In this article, by analyzing four of the most used packet-level traffic generators in literature, we show how they fail to follow the requested profiles. Moreover, we identify and discuss key concepts affecting their accuracy as well as mechanisms commonly adopted to improve it. This contribution goes toward improving the knowledge researchers and practitioners should have of the tools used in experimental works, and at the same time illustrates some directions for the use and design of software-based traffic generators.

A Markovian Approach to Multipath Data Transfer in Overlay Networks

Abstract: The use of multipath routing in overlay networks is a promising solution to improve performance and availability of Internet applications, without the replacement of the existing TCP/IP infrastructure. In this paper, we propose an approach to distribute data over multiple overlay paths that is able to improve Quality of Service (QoS) metrics, such as the data transfer time, loss, and throughput. By using the Imbedded Markov Chain technique, we demonstrate that the system under analysis, observed at specific instants, possesses the Markov property. We therefore cast the data distribution problem into the Markov Decision Process (MDP) framework, and design a computationally efficient algorithm named Online Policy Iteration (OPI), to solve the optimization problem on the fly. The proposed approach is applied to the problem of multipath data distribution in various wired/wireless network scenarios, with the objective of minimizing the data transfer time as well as the delay and losses. Through both intensive ns-2 simulations with data collected from real heterogeneous networks and experiments over real networks, we show the superior performance of the proposed traffic control mechanism in comparison with two classical schemes, that are Weighted Round Robin and Join the Shortest Queue.

Performance footprints of heavy-users in 3G networks via empirical measurement

Abstract: Cellular technology is widely used for Internet access, also because most operators are now offering Mbit/s data rates at affordable prices. Many studies analyzed the performance of these networks using analytical or simulation approaches. However, due to lack of data from operational environments, very little is known about the performance of real cellular networks. In this paper, we assess the performance of the 3G network of one of the major European telecom operators, using several recent traffic traces of TCP connections to port 80 and 8080. After presenting performance statistics related to all the network users, we focus on heavy users. To assess their performance and to uncover the related causes, we introduce an investigation approach easily repeatable in the very common situation where only data traces are available, with no other information such as mapping of users to cells, network capacity, or packet payload. Analyzing both “single long-lived connections” and “multiple long-lived connections”, we assess the performance of those users, providing insights on how and why performance can vary significantly over time and among different users.

UANM: a platform for experimenting with available bandwidth estimation tools

Abstract: In the field of network monitoring and measurement, the efficiency and accuracy of the adopted tools is strongly dependent on (i) structural and dynamic characteristics of the network scenario under measure and (ii) on manual fine tuning of the involved parameters. This is, for example, the case of the end-to-end available bandwidth estimation, in which the constraints of the measurement stage vary according to the use of the final results. In this work we present UANM (Unified Architecture for Network Measurement), a novel measurement infrastructure for an automatic management of measurement stages, tailored to the end-to-end available bandwidth estimation tools. We describe in details its architecture, illustrating the features we introduced to mitigate the problems affecting available bandwidth estimation in heterogeneous scenarios. Moreover, to provide evidences of UANM benefits, we present an experimental validation in three selected scenarios deployed over a real network testbed: (i) we show how UANM is able to alleviate the interferences among concurrent measures; (ii) we quantify the overhead introduced by the use of UANM; (iii) we illustrate how UANM is capable to provide more accurate results thanks to the knowledge of the network environment.

Integration of 3G connectivity in PlanetLab Europe: a step of an evolutionary path towards heterogeneous large scale network testbeds

Abstract: Distributed research testbeds play a fundamental role in the evaluation of disruptive innovations for the Future Internet. In recent years, the main research funding agencies have promoted several initiatives aimed at designing and building open, large scale, realistic experimental facilities that could be used to evaluate innovative networking architectures, paradigms and services. In this paper, after discussing the main challenges in building such infrastructures, we present how, by leveraging the concept of federation, we managed to introduce a first degree of heterogeneity into PlanetLab Europe, a European testbed federated with PlanetLab, by providing UMTS connectivity to PlanetLab Europe nodes. Our contribution is just a first step of an evolutionary path whose further developments will lead to next generation large-scale heterogeneous testbeds for supporting experimentally-driven research on the Network of the Future (Preliminary results within the same framework of this work have been recently published in Canonico et al. (2007) and Botta et al. (2008)).