391 research outputs found
Finite-time Convergent Gossiping
Gossip algorithms are widely used in modern distributed systems, with
applications ranging from sensor networks and peer-to-peer networks to mobile
vehicle networks and social networks. A tremendous research effort has been
devoted to analyzing and improving the asymptotic rate of convergence for
gossip algorithms. In this work we study finite-time convergence of
deterministic gossiping. We show that there exists a symmetric gossip algorithm
that converges in finite time if and only if the number of network nodes is a
power of two, while there always exists an asymmetric gossip algorithm with
finite-time convergence, independent of the number of nodes. For nodes,
we prove that a fastest convergence can be reached in node
updates via symmetric gossiping. On the other hand, under asymmetric gossip
among nodes with , it takes at least node
updates for achieving finite-time convergence. It is also shown that the
existence of finite-time convergent gossiping often imposes strong structural
requirements on the underlying interaction graph. Finally, we apply our results
to gossip algorithms in quantum networks, where the goal is to control the
state of a quantum system via pairwise interactions. We show that finite-time
convergence is never possible for such systems.Comment: IEEE/ACM Transactions on Networking, In Pres
Gozar: NAT-friendly Peer Sampling with One-Hop Distributed NAT Traversal
Gossip-based peer sampling protocols have been widely used as a building block for many large-scale distributed applications. However, Network Address Translation gateways (NATs) cause most existing gossiping protocols to break down, as nodes cannot establish direct connections to nodes behind NATs (private nodes). In addition, most of the existing NAT traversal algorithms for establishing connectivity to private nodes rely on third party servers running at a well-known, public IP addresses. In this paper, we present Gozar, a gossip-based peer sampling service that: (i) provides uniform random samples in the presence of NATs, and (ii) enables direct connectivity to sampled nodes using a fully distributed NAT traversal service, where connection messages require only a single
hop to connect to private nodes. We show in simulation that Gozar preserves the randomness properties of a gossip-based peer sampling service. We show the robustness of Gozar when a large fraction of nodes reside behind NATs and also in
catastrophic failure scenarios. For example, if 80% of nodes are behind NATs, and 80% of the nodes fail, more than 92% of the remaining nodes stay connected. In addition, we compare Gozar with existing NAT-friendly gossip-based peer sampling services, Nylon and ARRG. We show that Gozar is the only system that supports one-hop NAT traversal, and its overhead is roughly half of Nylon’s
A Gossip Algorithm based Clock Synchronization Scheme for Smart Grid Applications
The uprising interest in multi-agent based networked system, and the numerous
number of applications in the distributed control of the smart grid leads us to
address the problem of time synchronization in the smart grid. Utility
companies look for new packet based time synchronization solutions with Global
Positioning System (GPS) level accuracies beyond traditional packet methods
such as Network Time Proto- col (NTP). However GPS based solutions have poor
reception in indoor environments and dense urban canyons as well as GPS antenna
installation might be costly. Some smart grid nodes such as Phasor Measurement
Units (PMUs), fault detection, Wide Area Measurement Systems (WAMS) etc.,
requires synchronous accuracy as low as 1 ms. On the other hand, 1 sec accuracy
is acceptable in management information domain. Acknowledging this, in this
study, we introduce gossip algorithm based clock synchronization method among
network entities from the decision control and communication point of view. Our
method synchronizes clock within dense network with a bandwidth limited
environment. Our technique has been tested in different kinds of network
topologies- complete, star and random geometric network and demonstrated
satisfactory performance
Shuffling with a Croupier: Nat-Aware Peer-Sampling
Despite much recent research on peer-to-peer (P2P) protocols for the Internet, there have been relatively few practical protocols designed to explicitly account for Network Address Translation gateways (NATs). Those P2P protocols that do handle NATs circumvent them using relaying and hole-punching techniques to route packets to nodes residing behind NATs. In this paper, we present Croupier, a peer sampling service (PSS) that provides uniform random samples of nodes in the presence of NATs in the network. It is the first NAT-aware PSS that works without the use of relaying or hole-punching. By removing the need for relaying and hole-punching, we decrease the complexity and overhead of our protocol as well as increase
its robustness to churn and failure. We evaluated Croupier in simulation, and, in comparison with existing NAT-aware PSS’, our results show similar randomness properties, but improved robustness in the presence of both high percentages of nodes behind NATs and massive node failures. Croupier also has substantially lower protocol overhead
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