Towards Comparable Network Simulations

Simulations have been a valuable and much used tool in networking research for decades. New protocols are evaluated by simulations. Often, competing designs are judged by their respective performance in simulations. Despite this great importance the state-of-the-art in network simulations is nevertheless still low. A recent survey showed that most publications in a top conference did not even give enough details to repeat the simulations. In this paper we go beyond repeatability and ask: Are different simulations comparable? We study various implementations of the IEEE 802.11 media access layer in ns-2 and OMNeT++ and report some dramatic differences. These findings indicate that two protocols cannot be compared meaningfully unless they are compared in the very same simulation environment. We claim that this problem limits the value of the respective publications because readers are forced to re-implement the work that is described in the paper rather than building on its results. Facing the additional problem that not all authors will agree on one simulator, we address ways of making different simulators comparable

Processing MODIS Data for Fire Detection in Australia

The aim of this work was to use remote sensing data from the MODIS instrument of the Terra satellite to detect bush fires in Australia. This included preprocessing the demodulator output, bit synchronization and reassembly of data packets. IMAPP was used to do the geolocation and data calibration. The fire detection used a combination of fixed threshold techniques with difference tests and background comparisons. The results were projected in a rectangular latidue/longitude map to remedy the bow tie effect. Algorithms were implemented in C and Matlab. It proved to be possible to detect fires in the available data. The results were compared with fire detection done done by NASA and fire detections based on other sensors and found to be very similar.Das Ziel dieser Arbeit war die Nutzung von Fernerkundungsdaten des MODIS Instruments an Bord des Satelliten Terra zur Erkennung von Buschfeuern in Australien. Das schloss die Vorverarbeitung der Daten vom Demodulator, die Bitsynchronisation und die Umpacketierung der Daten ein. IMAPP wurde genutzt um die Daten zu kalibrieren und zu geolokalisieren. Die Feuererkennung bedient sich einer Kombination von absoluten Schwellwerttests, Differenztests und Vergleichen mit dem Hintergrund. Die Ergebnisse wurden in eine rechteckige Laengen/Breitengradkarte projiziert um dem BowTie Effekt entgegenzuwirken. Die benutzten Algrorithmen wurden in C und Matlab implementiert. Es zeigte sich, dass es moeglich ist in den verfuegbaren Daten Feuer zu erkennen. Die Ergebnisse wurden mit Feuererkennungen der NASA und Feuererkennung die auf anderen Sensoren basieren verglichen und fuer sehr aehnlich befunden

Public Key Kryptografie mit GNU Privacy Guard

Vortrag ueber das Warum und Wie der Kryptografie mit oeffentlichen Schluesseln am Beispiel von GNU Privacy Guar

Using linearization for global consistency in ssr

Novel routing algorithms such as scalable source routing (SSR) and virtual ring routing (VRR) need to set up and maintain a virtual ring structure among all the nodes in the network. The iterative successor pointer rewiring protocol (ISPRP) is one way to bootstrap such a network. Like its VRR-analogon, ISPRP requires one of the nodes to flood the network to guarantee consistency. Recent results on self-stabilizing algorithms now suggest a new approach to bootstrap the virtual rings of SSR and VRR. This so-called linearization method does not require any flooding at all. Moreover, it has been shown that linearization with shortcut neighbors has on average polylogarithmic convergence time, only.

The IGOR File System for Efficient Data Distribution in the GRID

Many GRID applications such as drug discovery in the pharmaceutical industry or simulations in meteorology and generally in the earth sciences rely on large data bases. Historically, these data bases are flat files on the order of several hundred megabytes each. Today, sites often need to download dozens or hundreds of such files before they can start a simulation or analysis run, even if the respective application accesses only small fractions of the respective files. The IGOR file system (which has been developed within the EU FP6 SIMDAT project), addresses the need for an easy and efficient way to access large files across the Internet. IGOR-FS is especially suited for (potentially globally) distributed sites that read or modify only small portions of the files. IGOR-FS provides fine grained versioning and backup capabilities; and it is built on strong cryptography to protect confidential data both in the network and on the local sites storage systems.

Measuring large overlay networks - the overnet example

Abstract Peer-to-peer overlay networks have grown significantly in size and sophistication over the last years. Meanwhile, distributed hash tables (DHT) provide efficient means to create global scale overlay networks on top of which various applications can be built. Although filesharing still is the most prominent example, other applications are well conceivable. In order to rationally design such applications, it is important to know (and understand) the properties of the overlay networks as seen from the respective application. This paper reports the results from a two week measurement of the entire Overnet network, the currently most widely deployed DHT-based overlay. We describe both, the design choices that made that measurement feasible and the results from the measurement itself. Besides the basic determination of network size, node availability and node distribution, we found unexpected results for the overlay latency distribution. 1 Description of Overnet and Kademli

Securing the Scalable Source Routing Protocol

The Scalable Source Routing (SSR) protocol combines overlay-like routing in a virtual network structure with source routing in the physical network to a single cross-layer architecture. Thereby, it can provide indirect routing in networks that lack a well-crafted structure. SSR is well suited for mobile ad hoc networks, sensor-actuator networks, and especially for mesh networks. Moreover, SSR directly provides the routing semantics of a structured routing overlay, making it an efficient basis for the scalable implementation of fully decentralized applications. In this paper we analyze SSR with regard to security: We show where SSR is prone to attacks, and we describe protocol modifications that make SSR robust in the presence of malicious nodes. The core idea is to introduce cryptographic certificates that allow nodes to discover forged protocol messages. We evaluate our proposed modifications by means of simulations, and thus demonstrate that they are both effective and efficient