@misc{2865, author = {{Strotmann, Daniela}}, title = {{{Singulärwertzerlegung für μ-ähnliche Bregman-Divergenzen}}}, year = {{2015}}, } @inproceedings{287, abstract = {{The size of modern data centers is constantly increasing. As it is not economic to interconnect all machines in the data center using a full-bisection-bandwidth network, techniques have to be developed to increase the efficiency of data-center networks. The Software-Defined Network paradigm opened the door for centralized traffic engineering (TE) in such environments. Up to now, there were already a number of TE proposals for SDN-controlled data centers that all work very well. However, these techniques either use a high amount of flow table entries or a high flow installation rate that overwhelms available switching hardware, or they require custom or very expensive end-of-line equipment to be usable in practice. We present HybridTE, a TE technique that uses (uncertain) information about large flows. Using this extra information, our technique has very low hardware requirements while maintaining better performance than existing TE techniques. This enables us to build very low-cost, high performance data-center networks.}}, author = {{Wette, Philip and Karl, Holger}}, booktitle = {{Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015)}}, pages = {{1----7}}, title = {{{HybridTE: Traffic Engineering for Very Low-Cost Software-Defined Data-Center Networks}}}, doi = {{10.1109/EWSDN.2015.57}}, year = {{2015}}, } @inproceedings{241, abstract = {{Distributed applications are commonly based on overlay networks interconnecting their sites so that they can exchange information. For these overlay networks to preserve their functionality, they should be able to recover from various problems like membership changes or faults. Various self-stabilizing overlay networks have already been proposed in recent years, which have the advantage of being able to recover from any illegal state, but none of these networks can give any guarantees on its functionality while the recovery process is going on. We initiate research on overlay networks that are not only self-stabilizing but that also ensure that searchability is maintained while the recovery process is going on, as long as there are no corrupted messages in the system. More precisely, once a search message from node u to another node v is successfully delivered, all future search messages from u to v succeed as well. We call this property monotonic searchability. We show that in general it is impossible to provide monotonic searchability if corrupted messages are present in the system, which justifies the restriction to system states without corrupted messages. Furthermore, we provide a self-stabilizing protocol for the line for which we can also show monotonic searchability. It turns out that even for the line it is non-trivial to achieve this property. Additionally, we extend our protocol to deal with node departures in terms of the Finite Departure Problem of Foreback et. al (SSS 2014). This makes our protocol even capable of handling node dynamics.}}, author = {{Scheideler, Christian and Setzer, Alexander and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 19th International Conference on Principles of Distributed Systems (OPODIS)}}, title = {{{Towards Establishing Monotonic Searchability in Self-Stabilizing Data Structures}}}, doi = {{10.4230/LIPIcs.OPODIS.2015.24}}, year = {{2015}}, } @inproceedings{242, abstract = {{A fundamental problem for overlay networks is to safely exclude leaving nodes, i.e., the nodes requesting to leave the overlay network are excluded from it without affecting its connectivity. There are a number of studies for safe node exclusion if the overlay is in a well-defined state, but almost no formal results are known for the case in which the overlay network is in an arbitrary initial state, i.e., when looking for a self-stabilizing solution for excluding leaving nodes. We study this problem in two variants: the Finite Departure Problem (FDP) and the Finite Sleep Problem (FSP). In the FDP the leaving nodes have to irrevocably decide when it is safe to leave the network, whereas in the FSP, this leaving decision does not have to be final: the nodes may resume computation when woken up by an incoming message. We are the first to present a self-stabilizing protocol for the FDP and the FSP that can be combined with a large class of overlay maintenance protocols so that these are then guaranteed to safely exclude leaving nodes from the system from any initial state while operating as specified for the staying nodes. In order to formally define the properties these overlay maintenance protocols have to satisfy, we identify four basic primitives for manipulating edges in an overlay network that might be of independent interest.}}, author = {{Koutsopoulos, Andreas and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 17th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, pages = {{201--216}}, title = {{{Towards a Universal Approach for the Finite Departure Problem in Overlay Networks}}}, doi = {{10.1007/978-3-319-21741-3_14}}, year = {{2015}}, } @inproceedings{243, abstract = {{This paper introduces the problem of communication pattern adaption for a distributed self-adjusting binary search tree. We propose a simple local algorithm, which is closely related to the nearly thirty-year-old idea of splay trees and evaluate its adaption performance in the distributed scenario if different communication patterns are provided.To do so, the process of self-adjustment is modeled similarly to a basic network creation game, in which the nodes want to communicate with only a certain subset of all nodes. We show that, in general, the game (i.e., the process of local adjustments) does not converge, and convergence is related to certain structures of the communication interests, which we call conflicts.We classify conflicts and show that for two communication scenarios in which convergence is guaranteed, the self-adjusting tree performs well.Furthermore, we investigate the different classes of conflicts separately and show that, for a certain class of conflicts, the performance of the tree network is asymptotically as good as the performance for converging instances. However, for the other conflict classes, a distributed self-adjusting binary search tree adapts poorly.}}, author = {{Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 9th International Workshop on Algorithms and Computation (WALCOM)}}, pages = {{175----186}}, title = {{{The impact of communication patterns on distributed locally self-adjusting binary search trees}}}, doi = {{10.1007/978-3-319-15612-5_16}}, year = {{2015}}, } @phdthesis{246, author = {{Besova, Galina}}, publisher = {{Universität Paderborn}}, title = {{{Systematic Development and Re-Use of Model Tranformations}}}, year = {{2015}}, } @inproceedings{247, abstract = {{Multi-rooted trees are becoming the norm for modern data-center networks. In these networks, scalable flow routing is challenging owing to vast number of flows. Current approaches either employ a central controller that can have scalability issues or a scalable decentralized algorithm only considering local information. In this paper we present a new decentralized approach to least-congested path routing in software-defined data center networks that has neither of these issues: By duplicating the initial (or SYN) packet of a flow and estimating the data rate of multiple flows in parallel, we exploit TCP’s habit to fill buffers to find the least congested path. We show that our algorithm significantly improves flow completion time without the need for a central controller or specialized hardware.}}, author = {{Schwabe, Arne and Karl, Holger}}, booktitle = {{Proceedings of the 4th European Workshop on Software Defined Networks (EWSDN 2015)}}, pages = {{37--42}}, title = {{{SynRace: Decentralized Load-Adaptive Multi-path Routing without Collecting Statistics}}}, doi = {{10.1109/EWSDN.2015.58}}, year = {{2015}}, } @misc{261, author = {{Eisenhofer, Thorsten}}, publisher = {{Universität Paderborn}}, title = {{{Protokolle zur authentifizierten Schüsselvereinbarung}}}, year = {{2015}}, } @inproceedings{262, abstract = {{Programs from Proofs" is a generic method which generates new programs out of correctness proofs of given programs. The technique ensures that the new and given program are behaviorally equivalent and that the new program is easily verifiable, thus serving as an alternative to proof-carrying code concepts. So far, this generic method has one instantiation that verifies type-state properties of programs. In this paper, we present a whole range of new instantiations, all based on data ow analyses. More precisely, we show how an imprecise but fast data ow analysis can be enhanced with a predicate analysis as to yield a precise but expensive analysis. Out of the safety proofs of this analysis, we generate new programs, again behaviorally equivalent to the given ones, which are easily verifiable" in the sense that now the data ow analysis alone can yield precise results. An experimental evaluation practically supports our claim of easy verification.}}, author = {{Jakobs, Marie-Christine and Wehrheim, Heike}}, booktitle = {{Proceedings of the 30th Annual ACM Symposium on Applied Computing}}, pages = {{1729--1736}}, title = {{{Programs from Proofs of Predicated Dataflow Analyses}}}, doi = {{10.1145/2695664.2695690}}, year = {{2015}}, } @phdthesis{264, author = {{Wette, Philip}}, publisher = {{Universität Paderborn}}, title = {{{Optimizing Software-Defined Networks using Application-Layer Knowledge}}}, year = {{2015}}, } @book{26446, author = {{Pongratz, Hans and Keil, Reinhard}}, publisher = {{Koellen Druck + Verlag GmbH}}, title = {{{DeLFI 2015 - The 13th e-Learning Conference on Computer Science of the E-Learning Section of the Society for Computer Science eV}}}, year = {{2015}}, } @inproceedings{26449, author = {{Winkelnkemper, Felix and Oberhoff, Andreas}}, editor = {{wedge, Reinhard and Selke, Harald}}, pages = {{103--117}}, publisher = {{Publication series of the Heinz Nixdorf Institute, Paderborn}}, title = {{{WebArena - R {\ "a} spacious structures for {\" u} r the learning locations of the future}}}, volume = {{330}}, year = {{2015}}, } @book{26531, editor = {{Keil, Reinhard and Selke, Harald}}, publisher = {{publishing series of the Heinz Nixdorf Institute, Paderborn}}, title = {{{20 years of learning with the World Wide Web - technology and education in dialogue}}}, volume = {{330}}, year = {{2015}}, } @inproceedings{26532, author = {{Keil, Reinhard and Selke, Harald}}, editor = {{Keil, Reinhard and Selke, Harald}}, pages = {{1--7}}, publisher = {{Publishing series of the Heinz Nixdorf Institute, Paderborn}}, title = {{{Learn with, through and {\ "about the WWW}}}, volume = {{330}}, year = {{2015}}, } @inproceedings{26533, author = {{Keil, Reinhard and Selke, Harald}}, editor = {{Keil, Reinhard and Selke, Harald}}, pages = {{39--53}}, publisher = {{publishing series of the Heinz Nixdorf Institute, Paderborn}}, title = {{{Virtual knowledge {\ "a} ume - From the presentation of content to virtual learning {\" a} tten}}}, volume = {{330}}, year = {{2015}}, } @phdthesis{26534, author = {{Klompmaker, Florian}}, publisher = {{Universitaetsbibliothek Paderborn}}, title = {{{Development of a structured process of interaction design for {\ "u} r nat {\" u} local user interfaces}}}, year = {{2015}}, } @inproceedings{26536, abstract = {{Patterns serve to codify design knowledge. By embedding them in a hypothesis-driven design, it is possible to develop them further into sample languages. For this it is necessary to resolve the underlying conflicts in the form of design hypotheses and to validate them empirically in order to enable further use and generalization. In this article, an experiment is presented that describes this procedure and demonstrates the interplay between theory formation and codification of design knowledge using two examples. }}, author = {{Schild, Christian and Petrausch, Vanessa}}, booktitle = {{Human and Computer 2015 - Proceedings}}, pages = {{173--182}}, publisher = {{De Gruyter Oldenbourg}}, title = {{{Empirical validation of design patterns}}}, year = {{2015}}, } @inproceedings{266, abstract = {{Many markets have seen a shift from the idea of buying and moved to leasing instead. Arguably, the latter has been the major catalyst for their success. Ten years ago, research realized this shift and initiated the study of "online leasing problems" by introducing leasing to online optimization problems. Resources required to provide a service in an "online leasing problem" are no more bought but leased for different durations. In this paper, we provide an overview of results that contribute to the understanding of "online resource leasing problems". }}, author = {{Markarian, Christine and Meyer auf der Heide, Friedhelm}}, booktitle = {{Proceedings of the 2015 ACM Symposium on Principles of Distributed Computing (PODC)}}, pages = {{343--344}}, title = {{{Online Resource Leasing}}}, doi = {{10.1145/2767386.2767454}}, year = {{2015}}, } @phdthesis{267, author = {{Markarian, Christine}}, publisher = {{Universität Paderborn}}, title = {{{Online Resource Leasing}}}, year = {{2015}}, } @inproceedings{269, abstract = {{Proof-carrying hardware is an approach that has recently been proposed for the efficient verification of reconfigurable modules. We present an application of proof-carrying hardware to guarantee the correct functionality of dynamically reconfigured image processing modules. Our prototype comprises a reconfigurable-system-on-chip with an embedded virtual FPGA fabric. This setup allows us to leverage open source FPGA synthesis and backend tools to produce FPGA configuration bitstreams with an open format and, thus, to demonstrate and experimentally evaluate proof-carrying hardware at the bitstream level.}}, author = {{Wiersema, Tobias and Wu, Sen and Platzner, Marco}}, booktitle = {{Proceedings of the International Symposium in Reconfigurable Computing (ARC)}}, pages = {{365----372}}, title = {{{On-The-Fly Verification of Reconfigurable Image Processing Modules based on a Proof-Carrying Hardware Approach}}}, doi = {{10.1007/978-3-319-16214-0_32}}, year = {{2015}}, }