Automated Deployment and Customization of Routing Overlays on PlanetLab

International audiencePlanetLab testbed is widely used to evaluate protocols and applications under realistic Internet conditions, but this realism comes at the cost of uncontrolled topology and traffic behavior. The use of overlay networks on PlanetLab can solve this problem by giving more control to the experimenter. However, manually creating such overlays is far from simple, and existing solutions are either not available for all PlanetLab nodes, or lack support for low level overlays. Deployment and customization of overlay architectures are also poorly supported. In this paper we present a flexible solution to support overlay networks on Plan-etLab, providing deployment automation, tunneling, routing, and traffic shaping capabilities. By building our solution into NEPI, a general framework for network experimentation, which automates design, deployment, and management of experiments, we simplify the complexity of building overlays on PlanetLab, and foster reusability and extensibility though NEPI's modular structure

On the Uplink Performance of TCP in Multi-rate 802.11 WLANs

Part 7: TCPInternational audienceIEEE 802.11 defines several physical layer data rates to provide more robust communication by falling back to a lower rate in the presence of high noise levels. The choice of the current rate can be automatized; e.g., Auto-Rate Fallback (ARF) is a well-known mechanism in which the sender adapts its transmission rate in response to link noise using up/down thresholds. ARF has been criticized for not being able to distinguish MAC collisions from channel noise. It has however been shown that, in the absence of noise and in the face of collisions, ARF does not play a significant role for TCP’s downlink performance. The interactions of ARF, DCF and uplink TCP have not yet been deeply investigated. In this paper, we demonstrate our findings on the impact of rate fallback caused by collisions in ARF on the uplink performance of various TCP variants using simulations

Code-Transparent Discrete Event Simulation for Time-Accurate Wireless Prototyping

Exhaustive testing of wireless communication protocols on prototypical hardware is costly and time-consuming. An alternative approach is network simulation, which, however, often strongly abstracts from the actual hardware. Especially in the wireless domain, such abstractions often lead to inaccurate simulation results. Therefore, we propose a code-transparent discrete event simulator that enables a direct simulation of existing code for wireless prototypes. With a focus on lower layers of the communication stack, we enable a parametrization of the simulation timings based on real-world measurements to increase the simulation accuracy. Our evaluation shows that we achieve close results for throughput (deviation below 3 % for UDP) and latency (corrected deviation about 13 %) compared to real-world setups, while providing the benefits of code-transparent simulation, i.e., to flexibly simulate large topologies with existing prototype code. Moreover, we demonstrate that our approach finds implementation defects in existing hardware prototype software, which are otherwise difficult to track down in real deployments.QC 20170629</p