Leibniz Supercomputing Center
Leibniz Supercomputing Center
Pohn D.,Leibniz Supercomputing Center
Lecture Notes in Informatics (LNI), Proceedings - Series of the Gesellschaft fur Informatik (GI) | Year: 2015
Federated Identity Management is an effective technology that allows multiple organizations to share resources. Deployments of the protocol Security Assertion Markup Language (SAML) practically require the pre-exchange of aggregated metadata files, making federations to fixed trust boundaries. Dynamic metadata exchange between identity provider and service provider via a trusted third party (TTP) overcomes these barriers. In this paper, we contrast dynamic metadata exchange with other state-of-the-art approaches and present the topology of the dynamic metadata exchange via a TTP. Furthermore, a distributed dynamic metadata exchange is proposed, in order to enhance the current protocol and provide a scalable solution for large-scale infrastructures.
Boyle A.,Max Planck Institute for Astrophysics |
Sim S.A.,Queen's University of Belfast |
Hachinger S.,University of Würzburg |
Hachinger S.,Leibniz Supercomputing Center |
Kerzendorf W.,European Southern Observatory
Astronomy and Astrophysics | Year: 2017
The double-detonation explosion model has been considered a candidate for explaining astrophysical transients with a wide range of luminosities. In this model, a carbon-oxygen white dwarf star explodes following detonation of a surface layer of helium. One potential signature of this explosion mechanism is the presence of unburned helium in the outer ejecta, left over from the surface helium layer. In this paper we present simple approximations to estimate the optical depths of important He i lines in the ejecta of double-detonation models. We use these approximations to compute synthetic spectra, including the He i lines, for double-detonation models obtained from hydrodynamical explosion simulations. Specifically, we focus on photospheric-phase predictions for the near-infrared 10 830 Å and 2 μm lines of He i. We first consider a double detonation model with a luminosity corresponding roughly to normal SNe Ia. This model has a post-explosion unburned He mass of 0.03 M and our calculations suggest that the 2 μm feature is expected to be very weak but that the 10 830 Å feature may have modest opacity in the outer ejecta. Consequently, we suggest that a moderate-To-weak He i 10 830 Å feature may be expected to form in double-detonation explosions at epochs around maximum light. However, the high velocities of unburned helium predicted by the model (~ 19 000 km s-1) mean that the He i 10 830 Å feature may be confused or blended with the C i 10 690 Å line forming at lower velocities. We also present calculations for the He i 10 830 Å and 2 μm lines for a lower mass (low luminosity) double detonation model, which has a post-explosion He mass of 0.077 M. In this case, both the He i features we consider are strong and can provide a clear observational signature of the double-detonation mechanism. © ESO, 2017.
Mendez S.,Leibniz Supercomputing Center |
Rexachs D.,Autonomous University of Barcelona |
Luque E.,Autonomous University of Barcelona
Proceedings - 2017 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, CCGRID 2017 | Year: 2017
Performance evaluation of parallel applications plays an important role in High Performance Computing (HPC). This is also applied to parallel I/O performance evaluation, which requires understanding the I/O pattern of the application and having knowledge about the performance capacity of the HPC I/O system. In this paper, we present a methodology to evaluate the I/O performance of parallel applications based on the I/O severity degree. We define the I/O severity concept taking into account the I/O requirements of a parallel application, the mapping of I/O processes and the configuration of the I/O subsystem. Requirements are expressed in units denominated I/O phases, which are defined using the temporal and spatial pattern of different files of the application. Our approach is applied to the I/O kernels of scientific applications such as S3DIO, FLASH-IO and BT-IO on the SuperMUC supercomputer. Experimental results show that our methodology allows us to identify if a parallel application is limited by the I/O subsystem and identifying possible root causes of the I/O problems. © 2017 IEEE.
Fritz W.,Leibniz Supercomputing Center |
Hanka O.,Ludwig Maximilians University of Munich
9th International Conference on Networks, ICN 2010 | Year: 2010
Security is an essential business requirement towards communication networks and will play a major role in future internet concepts. Many researchers see security functionality as an integral part of a new architecture, which should be thought of as soon as the conceptional phase of any proposal. In this paper we discuss suggested security mechanisms for the so called Locator/Identifier-Split and outline problematic issues found in those concepts. Based on these observations, we propose a security architecture using smart cards, which allows for lifelong assigned identifiers and is able to handle key replacement and revocation. Furthermore, we discuss the aspect of initial bootstrap and how to integrate devices with very low computational power like sensors. © 2010 IEEE.
Pohn D.,Leibniz Supercomputing Center
ICISSP 2016 - Proceedings of the 2nd International Conference on Information Systems Security and Privacy | Year: 2016
Inter-organizational acceb to IT services based on the predominant standard of Federated Identity Management (FIM), the Security Abertion Markup Language (SAML), suffers from scalability ibues related to metadata exchange. In order to overcome these ibues, an approach for automated metadata exchange between Identity Provider (IDP) and Service Provider (SP) via a Trusted Third Party (TTP) is presented in this article. Based on the architecture, risk management with threats and counter measures is applied by using a risk management template. Special emphasis is put on the secure design of the automated metadata exchange. Copyright © 2016 by SCITEPRESS - Science and Technology Publications, Lda.
Leong S.H.,Leibniz Supercomputing Center |
Frank A.,Leibniz Supercomputing Center |
Kranzlmuller D.,Leibniz Supercomputing Center |
Kranzlmuller D.,Ludwig Maximilians University of Munich
Procedia Computer Science | Year: 2013
Urgent computing enables responsible authorities to make educated decisions by supporting the computations of simulated predictions of time critical events. Unfortunately, most domains of science cannot afford dedicated resources for their urgent computing problems. As a solution, exploiting existing e-Infrastructures is invaluable for many problems if the wide array of available resources in today's e-Infrastructures can be utilised. In this paper, we focus on rarely occurring events that are best suited for urgent computations on existing HPC, Grid and Cloud e-Infrastructures. Since e-Infrastructures are meant to serve more than just one community of users, they have inherent characteristics that have to be modified or adapted in order to enable them effectively for urgent computing. We hope to demonstrate that there are many existing and on-going developments that can be leveraged to prepare existing e-Infrastructures for urgent computing. © 2013 The Authors. Published by Elsevier B.V.
Metzger S.,Leibniz Supercomputing Center |
Hommel W.,Leibniz Supercomputing Center |
Reiser H.,Leibniz Supercomputing Center
Proceedings - 6th International Conference on IT Security Incident Management and IT Forensics, IMF 2011 | Year: 2011
We present a holistic, process-oriented approach to ISO/IEC 27001 compliant security incident management that integrates multiple state-of-the-art security tools and has been applied to a real-world scenario very successfully for one year so far. The computer security incident response team, CSIRT, is enabled to correlate IT security related events across multiple communication channels and thus to classify any incidents consistently. Depending on an incident's classification, manual intervention or even fully automated reaction steps can be triggered, this starts with simple email notifications of system and network administrators, and scales up to quarantining compromised systems and sub networks automatically. A formally specified security incident response (SIR) process serves as the basis that clearly defines responsibilities, workflows, and interfaces. It has been designed to enable quick reactions to IT security events in a very resource-conserving manner. © 2011 IEEE.
Jamitzky F.,Leibniz Supercomputing Center |
Stark R.W.,Ludwig Maximilians University of Munich
Ultramicroscopy | Year: 2010
From a mathematical point of view, the atomic force microscope (AFM) belongs to a special class of continuous time dynamical systems with intermittent impact collisions. Discontinuities of the velocity result from the collisions of the tip with the surface. Transition to chaos in non-linear systems can occur via the following four routes: bifurcation cascade, crisis, quasi-periodicity, and intermittency. For the AFM period doubling and period-adding cascades are well established. Other routes into chaos, however, also may play an important role. Time series data of a dynamic AFM experiment indicates a chaotic mode that is related to the intermittency route into chaos. The observed intermittency is characterized as a type III intermittency. Understanding the dynamics of the system will help improve the overall system performance by keeping the operation parameters of dynamic AFM in a range, where chaos can be avoided or at least controlled. © 2010 Elsevier B.V.
Bode A.,Leibniz Supercomputing Center |
Bode A.,TU Munich
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013
For a long period in the development of computers and computing efficient applications were only characterized by computational - and memory complexity or in more practical terms elapsed computing time and required main memory capacity. The history of Euro-Par and its predecessor-organizations stands for research on the development of ever more powerful computer architectures that shorten the compute time both by faster clocking and by parallel execution as well as the development of algorithms that can exhibit these parallel architectural features. The success of enhancing architectures and algorithms is best described by exponential curves regarding the peak computing power of architectures and the efficiency of algorithms. As microprocessor parts get more and more power hungry and electricity gets more and more expensive, "energy to solution" is a new optimization criterion for large applications. This calls for energy aware solutions. © 2013 Springer-Verlag.
Heinecke A.,TU Munich |
Klemm M.,Intel Corporation |
Bungartz H.-J.,Leibniz Supercomputing Center
Computing in Science and Engineering | Year: 2012
Comparing the architectures and performance levels of an Nvidia Fermi accelerator with an Intel MIC Architecture coprocessor demonstrates the benefit of the coprocessor for bringing highly parallel applications into, or even beyond, GPGPU performance regions. © 2006 IEEE.