31,145 research outputs found
Self-Stabilizing Supervised Publish-Subscribe Systems
In this paper we present two major results: First, we introduce the first
self-stabilizing version of a supervised overlay network by presenting a
self-stabilizing supervised skip ring. Secondly, we show how to use the
self-stabilizing supervised skip ring to construct an efficient
self-stabilizing publish-subscribe system. That is, in addition to stabilizing
the overlay network, every subscriber of a topic will eventually know all of
the publications that have been issued so far for that topic. The communication
work needed to processes a subscribe or unsubscribe operation is just a
constant in a legitimate state, and the communication work of checking whether
the system is still in a legitimate state is just a constant on expectation for
the supervisor as well as any process in the system
Bounds for self-stabilization in unidirectional networks
A distributed algorithm is self-stabilizing if after faults and attacks hit
the system and place it in some arbitrary global state, the systems recovers
from this catastrophic situation without external intervention in finite time.
Unidirectional networks preclude many common techniques in self-stabilization
from being used, such as preserving local predicates. In this paper, we
investigate the intrinsic complexity of achieving self-stabilization in
unidirectional networks, and focus on the classical vertex coloring problem.
When deterministic solutions are considered, we prove a lower bound of
states per process (where is the network size) and a recovery time of at
least actions in total. We present a deterministic algorithm with
matching upper bounds that performs in arbitrary graphs. When probabilistic
solutions are considered, we observe that at least states per
process and a recovery time of actions in total are required (where
denotes the maximal degree of the underlying simple undirected graph).
We present a probabilistically self-stabilizing algorithm that uses
states per process, where is a parameter of the
algorithm. When , the algorithm recovers in expected
actions. When may grow arbitrarily, the algorithm
recovers in expected O(n) actions in total. Thus, our algorithm can be made
optimal with respect to space or time complexity
HSkip+: A Self-Stabilizing Overlay Network for Nodes with Heterogeneous Bandwidths
In this paper we present and analyze HSkip+, a self-stabilizing overlay
network for nodes with arbitrary heterogeneous bandwidths. HSkip+ has the same
topology as the Skip+ graph proposed by Jacob et al. [PODC 2009] but its
self-stabilization mechanism significantly outperforms the self-stabilization
mechanism proposed for Skip+. Also, the nodes are now ordered according to
their bandwidths and not according to their identifiers. Various other
solutions have already been proposed for overlay networks with heterogeneous
bandwidths, but they are not self-stabilizing. In addition to HSkip+ being
self-stabilizing, its performance is on par with the best previous bounds on
the time and work for joining or leaving a network of peers of logarithmic
diameter and degree and arbitrary bandwidths. Also, the dilation and congestion
for routing messages is on par with the best previous bounds for such networks,
so that HSkip+ combines the advantages of both worlds. Our theoretical
investigations are backed by simulations demonstrating that HSkip+ is indeed
performing much better than Skip+ and working correctly under high churn rates.Comment: This is a long version of a paper published by IEEE in the
Proceedings of the 14-th IEEE International Conference on Peer-to-Peer
Computin
Stabilizing data-link over non-FIFO channels with optimal fault-resilience
Self-stabilizing systems have the ability to converge to a correct behavior
when started in any configuration. Most of the work done so far in the
self-stabilization area assumed either communication via shared memory or via
FIFO channels. This paper is the first to lay the bases for the design of
self-stabilizing message passing algorithms over unreliable non-FIFO channels.
We propose a fault-send-deliver optimal stabilizing data-link layer that
emulates a reliable FIFO communication channel over unreliable capacity bounded
non-FIFO channels
Design and analysis of adaptive hierarchical low-power long-range networks
A new phase of evolution of Machine-to-Machine (M2M) communication has started where vertical Internet of Things (IoT) deployments dedicated to a single application domain gradually change to multi-purpose IoT infrastructures that service different applications across multiple industries. New networking technologies are being deployed operating over sub-GHz frequency bands that enable multi-tenant connectivity over long distances and increase network capacity by enforcing low transmission rates to increase network capacity. Such networking technologies allow cloud-based platforms to be connected with large numbers of IoT devices deployed several kilometres from the edges of the network. Despite the rapid uptake of Long-power Wide-area Networks (LPWANs), it remains unclear how to organize the wireless sensor network in a scaleable and adaptive way. This paper introduces a hierarchical communication scheme that utilizes the new capabilities of Long-Range Wireless Sensor Networking technologies by combining them with broadly used 802.11.4-based low-range low-power technologies. The design of the hierarchical scheme is presented in detail along with the technical details on the implementation in real-world hardware platforms. A platform-agnostic software firmware is produced that is evaluated in real-world large-scale testbeds. The performance of the networking scheme is evaluated through a series of experimental scenarios that generate environments with varying channel quality, failing nodes, and mobile nodes. The performance is evaluated in terms of the overall time required to organize the network and setup a hierarchy, the energy consumption and the overall lifetime of the network, as well as the ability to adapt to channel failures. The experimental analysis indicate that the combination of long-range and short-range networking technologies can lead to scalable solutions that can service concurrently multiple applications
The robustness of democratic consensus
In linear models of consensus dynamics, the state of the various agents
converges to a value which is a convex combination of the agents' initial
states. We call it democratic if in the large scale limit (number of agents
going to infinity) the vector of convex weights converges to 0 uniformly.
Democracy is a relevant property which naturally shows up when we deal with
opinion dynamic models and cooperative algorithms such as consensus over a
network: it says that each agent's measure/opinion is going to play a
negligeable role in the asymptotic behavior of the global system. It can be
seen as a relaxation of average consensus, where all agents have exactly the
same weight in the final value, which becomes negligible for a large number of
agents.Comment: 13 pages, 2 fig
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