| 1. |
- Barbosa, Raul, 1981
(författare)
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Monitoring local progress with watchdog timers deduced from global properties
- 2010
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Ingår i: 29th IEEE Symposium on Reliable Distributed Systems, SRDS 2010; New Delhi; India; 31 October 2010 through 3 November 2010. - 1060-9857. - 9780769542508 ; , s. 131-140
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Distributed systems are used in numerous applications where failures can be costly. Due to concerns that some of the nodes may become faulty, critical services are usually replicated across several nodes, which execute distributed algorithms to ensure correct service in spite of failures. To prevent replica-exhaustion, it is fundamental to detect errors and trigger appropriate recovery actions. In particular, it is important to detect situations in which nodes cease to execute the intended algorithm, e.g., when a replica is compromised by an attacker or when a hardware fault causes the node to behave erratically. This paper proposes a method for monitoring the local execution of nodes using watchdog timers. The approach consists in deducing, from the global system properties, local states that must be visited periodically by nodes that execute the intended algorithm correctly. When a node fails to trigger a watchdog before the time limit, an appropriate response can be initiated. The approach is applied to a well-known Byzantine consensus algorithm. The algorithm is modeled in the PROMELA language and the SPIN model checker is used to identify local states that must be visited periodically by correct nodes. Such states are suitable for online monitoring using watchdog timers.
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| 2. |
- Casimiro, A.C., et al.
(författare)
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Self-stabilizing manoeuvre negotiation: The case of virtual traffic lights
- 2019
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Ingår i: Proceedings of the IEEE Symposium on Reliable Distributed Systems. - 1060-9857. ; , s. 354-356
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Konferensbidrag (refereegranskat)abstract
- The vision of automated driving promises to have safer and more cost-efficient transport systems. Automated driving systems have to demonstrate high levels of dependability and affordability. Recent advances of new communication technologies, e.g., 5G, allow significant cost reduction of timely shared sensory information. However, the design of fault-tolerant automated driving systems remains an open challenge. This work considers the design of automated driving systems through the lenses of self-stabilization - a very strong notion of fault-tolerance. Our self-stabilizing algorithms guarantee, within a bounded period, recovery from a broad fault model and arbitrary state corruption. After this recovery period, our algorithms provide safe maneuver execution despite the presence of failures, such as unbounded periods of packet loss and timing failures as well as inaccurate sensory information and malicious behavior. We evaluate the proposed algorithms through a rigorous correctness proof and a worst-case analysis as well as a prototype that focuses on an intersection crossing protocol. We validate our prototype via computer simulations and a testbed implementation. Our preliminary results show a reduction in the number of vehicle collisions and dangerous situations.
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| 3. |
- Fu, Zhang, 1982, et al.
(författare)
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Mitigating Distributed Denial of Service Attacks in Multiparty Applications in the Presence of Clock Drifts
- 2008
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Ingår i: Proceedings of 27th IEEE International Symposium on Reliable Distributed Systems (SRDS 2008). - 1060-9857. - 9780769534107 ; , s. 63-72
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Konferensbidrag (refereegranskat)abstract
- A weak point in network-based applications is that they commonly open some known communication port(s), making themselves targets for denial of service (DoS) attacks. Considering adversaries that can eavesdrop and launch directed DoS attacks to the applications' open ports, solutions based on pseudo-random port-hopping have been suggested. As port-hopping needs that the communicating parties hop in a synchronized manner, these solutions suggest acknowledgment-based protocols between a client-server pair or assume the presence of synchronized clocks. Acknowledgments, if lost, can cause a port to be open for a longer time and thus be vulnerable to DoS attacks; Time servers for synchronizing clocks can become targets to DoS attack themselves. Here we study the case where the communicating parties have clocks with rate drift, which is common in networking. We propose an algorithm, BigWheel, for servers to communicate with multiple clients in a port-hopping manner, thus enabling support to multi-party applications as well. The algorithm does not rely on the server having a fixed port open in the beginning, neither does it require from the client to get a "first-contact" port from a third party. We also present an adaptive algorithm, HoPerAA, for hopping in the presence of clock-drift, as well as the analysis and evaluation of the methods. The solutions are simple, based on each client interacting with the server independently of the other clients, without the need of acknowledgments or time server. Provided that one has an estimation of the time it takes for the adversary to detect that a port is open and launch an attack, the method we propose doesnot make it possible to the eavesdropping adversary to launch an attack directed to the application's open port(s).
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| 4. |
- Fu, Zhang, 1982, et al.
(författare)
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Off-the-wall: Lightweight Distributed Filtering to Mitigate Distributed Denial of Service Attacks
- 2012
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Ingår i: Proceedings of the IEEE Symposium on Reliable Distributed Systems. - 1060-9857. - 9780769547848 ; :Article number 6424855, s. 207-212
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Konferensbidrag (refereegranskat)abstract
- Distributed Denial of Service (DDoS) attacks are hard todeal with, due to the fact that it is difficult to distinguish legitimatetraffic from malicious traffic, especially since the latter is fromdistributed sources. To accurately filter malicious traffic one needs(strong but costly) packet authentication primitives which increase thedesign complexity and typically affect throughput. It is a challengeto keep a balance between throughput and security/protection of thenetwork core and end resources. In this paper, we propose SIEVE,a lightweight distributed filtering protocol/method. Depending on theattacker’s ability, SIEVE can provide a standalone filter for moderateadversary models and a complementary filter which can enhancethe performance of strong and more complex methods for strongeradversary models.
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| 5. |
- Koldehofe, Boris, 1971
(författare)
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Buffer management in probabilistic peer-to-peer communication protocols
- 2003
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Ingår i: 22nd International Symposium on Reliable Distributed Systems. FLORENCE, ITALY. OCT 06-08, 2003. SYMPOSIUM ON RELIABLE DISTRIBUTED SYSTEMS, PROCEEDINGS. - 1060-9857. - 0769519555 ; , s. 76-85
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Konferensbidrag (refereegranskat)abstract
- In multipeer communication decentralised probabilistic protocols have received a lot of attention because of their robustness against faults in the communication traffic and their potential to provide scalability for large groups. These protocols provide a probabilistic guarantee for a propagated event to reach every group member Recent work aims to improve the scalability of such protocols by reducing memory requirements. In saving memory resources, the history buffer which is used to "remember" received events and to prevent multiple deliveries of events to the application, plays a very significant role. We examine how the buffer size should be chosen to challenge the multiple delivery problem. Further we propose and evaluate several methods of organising the dissemination of events in order to provide high reliability and reduce the number of multiple deliveries at the same time.
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