FG Verteilte Systeme und Betriebssysteme
Refine
Year of publication
- 2016 (11) (remove)
Document Type
Language
- English (11)
Keywords
- Ad hoc networks (1)
- Fault tolerant systems (1)
- Wireless sensor networks (1)
- network topology (1)
- self-stabilization (1)
- stability analysis (1)
- topology (1)
- wireless networks (1)
- wireless sensor networks (1)
Institute
The erratic behavior of wireless channels is still a major hurdle in the implementation of robust applications in wireless networks. In the past it has been argued that self-stabilization is a remedy to provide the needed robustness. This assumption has not been verified to the extent necessary to convince engineers implementing such applications. A major reason is that the time in which a self-stabilizing system returns to a valid state is unpredictable and potentially unbound. Failure rates typically depend on physical phenomena and in self-stabilizing systems each node tries to react to failures in an inherently adaptive fashion by the cyclic observation of its neighbors' states. When the frequency of state changes is too high, the system may never reach a state sufficiently stable for a specific task. In this paper we substantiate the conditions under which self-stabilization leads to fault tolerance in wireless networks and look at the myths about the power of self-stabilization as a particular instance of self-organization. We investigate the influences of the error rate and the neighbor state exchange rate on the stability and the convergence time on topology information acquired in real network experiments.
Self-stabilizing systems have in theory the unique and provable ability, to always return to a valid system state even in the face of failures. These properties are certainly desirable for domains like wireless ad-hoc networks with numerous unpredictable faults. Unfortunately, the time in which the system returns to a valid state is not predictable and potentially unbound. The failure rate typically depends on physical phenomena and in self-stabilizing systems each node tries to react to failures in an inherently adaptive fashion by the cyclic observation of the states of its neighbors. When state changes are either too quick or too slow the system might never reach a state that is sufficiently stable for a specific task. In this paper, we investigate the influences of the error rate on the (stability) convergence time on the basis of topology information acquired in real network experiments. This allows us to asses the asymptotic behavior of relevant self-stabilizing algorithms in typical wireless networks.
Many-core architectures trade single-thread performance for a larger number of cores. Scalable throughput can be attained only by a high degree of parallelism, minimized synchronization. Whilst this is achievable for many applications, the operating system still introduces bottlenecks through non-local sharing, synchronization,, message passing. A particular challenge for highly dynamic applications, for example invasive HPC applications, elastic compute clouds, is the management of short-living application threads, processes. This paper discusses OS architecture choices based on microkernel, multikernel, distributed systems designs, our development experience in the context of the MyThOS project. Initial experiments show a much faster thread creation, activation compared to monolithic systems like Linux while providing a more flexible protection, threading model that is better suited for dynamic scenarios. However, despite significant progress in the overall domain of operating systems, the design space for scalable many-core operating systems is yet to be fully explored.