@inproceedings{4563, abstract = {{Routing is a challenging problem for wireless ad hoc networks, especially when the nodes are mobile and spread so widely that in most cases multiple hops are needed to route a message from one node to another. In fact, it is known that any online routing protocol has a poor performance in the worst case, in a sense that there is a distribution of nodes resulting in bad routing paths for that protocol, even if the nodes know their geographic positions and the geographic position of the destination of a message is known. The reason for that is that radio holes in the ad hoc network may require messages to take long detours in order to get to a destination, which are hard to find in an online fashion. In this paper, we assume that the wireless ad hoc network can make limited use of long-range links provided by a global communication infrastructure like a cellular infrastructure or a satellite in order to compute an abstraction of the wireless ad hoc network that allows the messages to be sent along near-shortest paths in the ad hoc network. We present distributed algorithms that compute an abstraction of the ad hoc network in $\mathcal{O}\left(\log ^2 n\right)$ time using long-range links, which results in $c$-competitive routing paths between any two nodes of the ad hoc network for some constant $c$ if the convex hulls of the radio holes do not intersect. We also show that the storage needed for the abstraction just depends on the number and size of the radio holes in the wireless ad hoc network and is independent on the total number of nodes, and this information just has to be known to a few nodes for the routing to work. }}, author = {{Jung, Daniel and Kolb, Christina and Scheideler, Christian and Sundermeier, Jannik}}, booktitle = {{Proceedings of the 14th International Symposium on Algorithms and Experiments for Wireless Networks (ALGOSENSORS) }}, keywords = {{greedy routing, ad hoc networks, convex hulls, c-competitiveness}}, location = {{Helsinki}}, publisher = {{Springer}}, title = {{{Competitive Routing in Hybrid Communication Networks}}}, year = {{2018}}, } @inproceedings{4565, author = {{Jung, Daniel and Kolb, Christina and Scheideler, Christian and Sundermeier, Jannik}}, booktitle = {{Proceedings of the 30th on Symposium on Parallelism in Algorithms and Architectures (SPAA)}}, isbn = {{9781450357999}}, location = {{Wien}}, publisher = {{ACM Press}}, title = {{{Brief Announcement: Competitive Routing in Hybrid Communication Networks}}}, doi = {{10.1145/3210377.3210663}}, year = {{2018}}, } @inproceedings{4351, abstract = {{ We extend the concept of monotonic searchability~\cite{DBLP:conf/opodis/ScheidelerSS15}~\cite{DBLP:conf/wdag/ScheidelerSS16} for self-stabilizing systems from one to multiple dimensions. A system is self-stabilizing if it can recover to a legitimate state from any initial illegal state. These kind of systems are most often used in distributed applications. Monotonic searchability provides guarantees when searching for nodes while the recovery process is going on. More precisely, if a search request started at some node $u$ succeeds in reaching its destination $v$, then all future search requests from $u$ to $v$ succeed as well. Although there already exists a self-stabilizing protocol for a two-dimensional topology~\cite{DBLP:journals/tcs/JacobRSS12} and an universal approach for monotonic searchability~\cite{DBLP:conf/wdag/ScheidelerSS16}, it is not clear how both of these concepts fit together effectively. The latter concept even comes with some restrictive assumptions on messages, which is not the case for our protocol. We propose a simple novel protocol for a self-stabilizing two-dimensional quadtree that satisfies monotonic searchability. Our protocol can easily be extended to higher dimensions and offers routing in $\mathcal O(\log n)$ hops for any search request. }}, author = {{Feldmann, Michael and Kolb, Christina and Scheideler, Christian}}, booktitle = {{Proceedings of the 20th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, pages = {{16--31 }}, publisher = {{Springer, Cham}}, title = {{{Self-stabilizing Overlays for high-dimensional Monotonic Searchability}}}, doi = {{10.1007/978-3-030-03232-6_2}}, volume = {{11201}}, year = {{2018}}, } @inproceedings{5216, 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. To rigorously study self-stabilizing solutions to this problem, the Finite Departure Problem (FDP) has been proposed [9]. In the FDP we are given a network of processes in an arbitrary state, and the goal is to eventually arrive at (and stay in) a state in which all leaving processes irrevocably decided to leave the system while for all weakly-connected components in the initial overlay network, all staying processes in that component will still form a weakly connected component. In the standard interconnection model, the FDP is known to be unsolvable by local control protocols, so oracles have been investigated that allow the problem to be solved [9]. To avoid the use of oracles, we introduce a new interconnection model based on relays. Despite the relay model appearing to be rather restrictive, we show that it is universal, i.e., it is possible to transform any weakly-connected topology into any other weakly-connected topology, which is important for being a useful interconnection model for overlay networks. Apart from this, our model allows processes to grant and revoke access rights, which is why we believe it to be of interest beyond the scope of this paper. We show how to implement the relay layer in a self-stabilizing way and identify properties protocols need to satisfy so that the relay layer can recover while serving protocol requests.}}, author = {{Scheideler, Christian and Setzer, Alexander}}, booktitle = {{Proceedings of the 20th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS 2018)}}, location = {{Tokyo, Japan}}, title = {{{Relays: A New Approach for the Finite Departure Problem in Overlay Networks}}}, doi = {{10.1007/978-3-030-03232-6_16}}, year = {{2018}}, } @inproceedings{5222, abstract = {{We present a self-stabilizing protocol for an overlay network that constructs the Minimum Spanning Tree (MST) for an underlay that is modeled by a weighted tree. The weight of an overlay edge between two nodes is the weighted length of their shortest path in the tree. We rigorously prove that our protocol works correctly under asynchronous and non-FIFO message delivery. Further, the protocol stabilizes after O(N^2) asynchronous rounds where N is the number of nodes in the overlay. }}, author = {{Götte, Thorsten and Scheideler, Christian and Setzer, Alexander}}, booktitle = {{Proceedings of the 20th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS 2018)}}, location = {{Tokyo, Japan}}, pages = {{50--64}}, publisher = {{Springer}}, title = {{{On Underlay-Aware Self-Stabilizing Overlay Networks}}}, volume = {{11201}}, year = {{2018}}, } @article{3872, abstract = {{This paper considers the problem of how to efficiently share a wireless medium which is subject to harsh external interference or even jamming. So far, this problem is understood only in simplistic single-hop or unit disk graph models. We in this paper initiate the study of MAC protocols for the SINR interference model (a.k.a. physical model). This paper makes two contributions. First, we introduce a new adversarial SINR model which captures a wide range of interference phenomena. Concretely, we consider a powerful, adaptive adversary which can jam nodes at arbitrary times and which is only limited by some energy budget. Our second contribution is a distributed MAC protocol called Sade which provably achieves a constant competitive throughput in this environment: we show that, with high probability, the protocol ensures that a constant fraction of the non-blocked time periods is used for successful transmissions.}}, author = {{Ogierman, Adrian and Richa, Andrea and Scheideler, Christian and Schmid, Stefan and Zhang, Jin}}, issn = {{0178-2770}}, journal = {{Distributed Computing}}, number = {{3}}, pages = {{241--254}}, publisher = {{Springer Nature}}, title = {{{Sade: competitive MAC under adversarial SINR}}}, doi = {{10.1007/s00446-017-0307-1}}, volume = {{31}}, year = {{2017}}, } @article{1812, author = {{Koutsopoulos, Andreas and Scheideler, Christian and Strothmann, Thim Frederik}}, journal = {{Inf. Comput.}}, pages = {{408----424}}, title = {{{Towards a universal approach for the finite departure problem in overlay networks}}}, doi = {{10.1016/j.ic.2016.12.006}}, year = {{2017}}, } @article{1813, author = {{P. Fekete, Sandor and W. Richa, Andrea and Römer, Kay and Scheideler, Christian}}, journal = {{SIGACT News}}, number = {{2}}, pages = {{87----94}}, title = {{{Algorithmic Foundations of Programmable Matter Dagstuhl Seminar 16271}}}, doi = {{10.1145/3106700.3106713}}, year = {{2017}}, } @article{1814, author = {{Derakhshandeh, Zahra and Gmyr, Robert and W. Richa, Andrea and Scheideler, Christian and Strothmann, Thim Frederik}}, journal = {{Theor. Comput. Sci.}}, pages = {{56----68}}, title = {{{Universal coating for programmable matter}}}, doi = {{10.1016/j.tcs.2016.02.039}}, year = {{2017}}, } @inproceedings{1815, author = {{J. Daymude, Joshua and Gmyr, Robert and W. Richa, Andrea and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{Algorithms for Sensor Systems - 13th International Symposium on Algorithms and Experiments for Wireless Sensor Networks, ALGOSENSORS 2017, Vienna, Austria, September 7-8, 2017, Revised Selected Papers}}, pages = {{127----140}}, title = {{{Improved Leader Election for Self-organizing Programmable Matter}}}, doi = {{10.1007/978-3-319-72751-6_10}}, year = {{2017}}, } @inproceedings{105, abstract = {{We initiate the study of network monitoring algorithms in a class of hybrid networks in which the nodes are connected by an external network and an internal network (as a short form for externally and internally controlled network). While the external network lies outside of the control of the nodes (or in our case, the monitoring protocol running in them) and might be exposed to continuous changes, the internal network is fully under the control of the nodes. As an example, consider a group of users with mobile devices having access to the cell phone infrastructure. While the network formed by the WiFi connections of the devices is an external network (as its structure is not necessarily under the control of the monitoring protocol), the connections between the devices via the cell phone infrastructure represent an internal network (as it can be controlled by the monitoring protocol). Our goal is to continuously monitor properties of the external network with the help of the internal network. We present scalable distributed algorithms that efficiently monitor the number of edges, the average node degree, the clustering coefficient, the bipartiteness, and the weight of a minimum spanning tree. Their performance bounds demonstrate that monitoring the external network state with the help of an internal network can be done much more efficiently than just using the external network, as is usually done in the literature.}}, author = {{Gmyr, Robert and Hinnenthal, Kristian and Scheideler, Christian and Sohler, Christian}}, booktitle = {{Proceedings of the 44th International Colloquium on Automata, Languages, and Programming (ICALP)}}, pages = {{137:1----137:15}}, title = {{{Distributed Monitoring of Network Properties: The Power of Hybrid Networks}}}, doi = {{10.4230/LIPIcs.ICALP.2017.137}}, year = {{2017}}, } @inproceedings{125, abstract = {{Searching for other participants is one of the most important operations in a distributed system.We are interested in topologies in which it is possible to route a packet in a fixed number of hops until it arrives at its destination.Given a constant $d$, this paper introduces a new self-stabilizing protocol for the $q$-ary $d$-dimensional de Bruijn graph ($q = \sqrt[d]{n}$) that is able to route any search request in at most $d$ hops w.h.p., while significantly lowering the node degree compared to the clique: We require nodes to have a degree of $\mathcal O(\sqrt[d]{n})$, which is asymptotically optimal for a fixed diameter $d$.The protocol keeps the expected amount of edge redirections per node in $\mathcal O(\sqrt[d]{n})$, when the number of nodes in the system increases by factor $2^d$.The number of messages that are periodically sent out by nodes is constant.}}, author = {{Feldmann, Michael and Scheideler, Christian}}, booktitle = {{Proceedings of the 19th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, isbn = {{978-3-319-69083-4}}, pages = {{250--264 }}, publisher = {{Springer, Cham}}, title = {{{A Self-Stabilizing General De Bruijn Graph}}}, doi = {{10.1007/978-3-319-69084-1_17}}, volume = {{10616}}, year = {{2017}}, } @inproceedings{215, abstract = {{We present three robust overlay networks: First, we present a network that organizes the nodes into an expander and is resistant to even massive adversarial churn. Second, we develop a network based on the hypercube that maintains connectivity under adversarial DoS-attacks. For the DoS-attacks we use the notion of a Omega(log log n)-late adversary which only has access to topological information that is at least Omega(log log n) rounds old. Finally, we develop a network that combines both churn- and DoS-resistance. The networks gain their robustness through constant network reconfiguration, i.e., the topology of the networks changes constantly. Our reconguration algorithms are based on node sampling primitives for expanders and hypercubes that allow each node to sample a logarithmic number of nodes uniformly at random in O(log log n) communication rounds. These primitives are specific to overlay networks and their optimal runtime represents an exponential improvement over known techniques. Our results have a wide range of applications, for example in the area of scalable and robust peer-to-peer systems.}}, author = {{Drees, Maximilian and Gmyr, Robert and Scheideler, Christian}}, booktitle = {{Proceedings of the 28th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA)}}, pages = {{417----427}}, title = {{{Churn- and DoS-resistant Overlay Networks Based on Network Reconfiguration}}}, doi = {{10.1145/2935764.2935783}}, year = {{2016}}, } @article{1835, author = {{Schmid, Stefan and Avin, Chen and Scheideler, Christian and Borokhovich, Michael and Haeupler, Bernhard and Lotker, Zvi}}, journal = {{IEEE/ACM Trans. Netw.}}, number = {{3}}, pages = {{1421----1433}}, title = {{{SplayNet: Towards Locally Self-Adjusting Networks}}}, doi = {{10.1109/TNET.2015.2410313}}, year = {{2016}}, } @inproceedings{1836, author = {{Derakhshandeh, Zahra and Gmyr, Robert and Porter, Alexandra and W. Richa, Andrea and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{DNA Computing and Molecular Programming - 22nd International Conference, DNA 22, Munich, Germany, September 4-8, 2016, Proceedings}}, pages = {{148----164}}, title = {{{On the Runtime of Universal Coating for Programmable Matter}}}, doi = {{10.1007/978-3-319-43994-5_10}}, volume = {{9818}}, year = {{2016}}, } @inproceedings{1837, author = {{Derakhshandeh, Zahra and Gmyr, Robert and W. Richa, Andrea and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 28th ACM Symposium on Parallelism in Algorithms and Architectures, SPAA 2016, Asilomar State Beach/Pacific Grove, CA, USA, July 11-13, 2016}}, pages = {{289----299}}, publisher = {{ACM}}, title = {{{Universal Shape Formation for Programmable Matter}}}, doi = {{10.1145/2935764.2935784}}, year = {{2016}}, } @inbook{1845, author = {{W. Richa, Andrea and Scheideler, Christian}}, booktitle = {{Encyclopedia of Algorithms}}, pages = {{999----1002}}, title = {{{Jamming-Resistant MAC Protocols for Wireless Networks}}}, doi = {{10.1007/978-1-4939-2864-4_593}}, year = {{2016}}, } @inproceedings{155, abstract = {{We present a self-stabilizing algorithm for overlay networks that, for an arbitrary metric given by a distance oracle, constructs the graph representing that metric. The graph representing a metric is the unique minimal undirected graph such that for any pair of nodes the length of a shortest path between the nodes corresponds to the distance between the nodes according to the metric. The algorithm works under both an asynchronous and a synchronous daemon. In the synchronous case, the algorithm stablizes in time O(n) and it is almost silent in that after stabilization a node sends and receives a constant number of messages per round.}}, author = {{Gmyr, Robert and Lefèvre, Jonas and Scheideler, Christian}}, booktitle = {{Proceedings of the 18th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, pages = {{248----262}}, title = {{{Self-stabilizing Metric Graphs}}}, doi = {{10.1007/978-3-319-49259-9_20}}, year = {{2016}}, } @inproceedings{142, abstract = {{For overlay networks, the ability to recover from a variety of problems like membership changes or faults is a key element to preserve their functionality. In recent years, various self-stabilizing overlay networks have been proposed that have the advantage of being able to recover from any illegal state. However, the vast majority of these networks cannot give any guarantees on its functionality while the recovery process is going on. We are especially interested in searchability, i.e., the functionality that search messages for a specific identifier are answered successfully if a node with that identifier exists in the network. We investigate overlay networks that are not only self-stabilizing but that also ensure that monotonic 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. Monotonic searchability was recently introduced in OPODIS 2015, in which the authors provide a solution for a simple line topology.We present the first universal approach to maintain monotonic searchability that is applicable to a wide range of topologies. As the base for our approach, we introduce a set of primitives for manipulating overlay networks that allows us to maintain searchability and show how existing protocols can be transformed to use theses primitives.We complement this result with a generic search protocol that together with the use of our primitives guarantees monotonic searchability.As an additional feature, searching existing nodes with the generic search protocol is as fast as searching a node with any other fixed routing protocol once the topology has stabilized.}}, author = {{Scheideler, Christian and Setzer, Alexander and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 30th International Symposium on Distributed Computing (DISC)}}, pages = {{71----84}}, title = {{{Towards a Universal Approach for Monotonic Searchability in Self-stabilizing Overlay Networks}}}, doi = {{10.1007/978-3-662-53426-7_6}}, year = {{2016}}, } @article{284, abstract = {{In this work, we present the first scalable distributed information system, that is, a system with low storage overhead, that is provably robust against denial-of-service (DoS) attacks by a current insider. We allow a current insider to have complete knowledge about the information system and to have the power to block any ϵ-fraction of its servers by a DoS attack, where ϵ can be chosen up to a constant. The task of the system is to serve any collection of lookup requests with at most one per nonblocked server in an efficient way despite this attack. Previously, scalable solutions were only known for DoS attacks of past insiders, where a past insider only has complete knowledge about some past time point t0 of the information system. Scheideler et al. [Awerbuch and Scheideler 2007; Baumgart et al. 2009] showed that in this case, it is possible to design an information system so that any information that was inserted or last updated after t0 is safe against a DoS attack. But their constructions would not work at all for a current insider. The key idea behind our IRIS system is to make extensive use of coding. More precisely, we present two alternative distributed coding strategies with an at most logarithmic storage overhead that can handle up to a constant fraction of blocked servers.}}, author = {{Eikel, Martina and Scheideler, Christian}}, journal = {{Transactions on Parallel Computing}}, number = {{3}}, pages = {{18:1----18:33}}, publisher = {{ACM}}, title = {{{IRIS: A Robust Information System Against Insider DoS Attacks}}}, doi = {{10.1145/2809806}}, year = {{2015}}, }