Dynamic load balancing in Peer-to-Peer networks

by Miroslaw KorzeniowskiPaderborn, Univ., Diss., 200

Dynamic sharing of a multiple access channel

In this paper we consider the mutual exclusion problem on a multiple access channel. Mutual exclusion is one of the fundamental problems in distributed computing. In the classic version of this problem, n processes perform a concurrent program which occasionally triggers some of them to use shared resources, such as memory, communication channel, device, etc. The goal is to design a distributed algorithm to control entries and exits to/from the shared resource in such a way that in any time there is at most one process accessing it. We consider both the classic and a slightly weaker version of mutual exclusion, called ep-mutual-exclusion, where for each period of a process staying in the critical section the probability that there is some other process in the critical section is at most ep. We show that there are channel settings, where the classic mutual exclusion is not feasible even for randomized algorithms, while ep-mutual-exclusion is. In more relaxed channel settings, we prove an exponential gap between the makespan complexity of the classic mutual exclusion problem and its weaker ep-exclusion version. We also show how to guarantee fairness of mutual exclusion algorithms, i.e., that each process that wants to enter the critical section will eventually succeed

April 8, 1984

Abstract. Distributed Hash Tables (DHTs) enable fully distributed Peer-to-Peer network construction and maintenance with name-driven routing. There exist very few DHT approaches that consider heterogeneity of nodes inside the construction process or properly serve data of different load. To our best knowledge, there is no construction which smoothly addresses both these issues. We propose a Peer-to-Peer construction that explicitly uses heterogeneity to simplify the routing and maintenance process even in the presence of an adaptive adversary. Using a hypercube and cube connected cycles networks as a backbone, we show how to cope with two types of heterogeneity: one for nodes and one for data

Heterogenous dating service with application to rumor spreading

International audienceIn this paper, we describe a fully decentralized algorithm, called "dating service" to organize communications into a fully heterogeneous network, that ensures that communication capabilities of the nodes are not exceeded. We prove that with high probability, this service ensures that a constant fraction of all possible communications is organized. Interestingly enough, this property holds true even if a node is not able to choose another node uniformly at random. We also present, as an application of the dating service, an algorithm for rumor spreading that enables to broadcast a unit-size message to all the nodes of a P2P system in logarithmic number of steps with high probability

Distributed Alarming in the On-Duty and Off-Duty Models

Decentralized monitoring and alarming systems can be an attractive alternative to centralized architectures. Distributed sensor nodes (e.g., in the smart grid's distribution network) are closer to an observed event than a global and remote observer or controller. This improves the visibility and response time of the system. Moreover, in a distributed system, local problems may also be handled locally and without overloading the communication network. This paper studies alarming from a distributed computing perspective and for two fundamentally different scenarios: on-duty and off-duty. We model the alarming system as a sensor network consisting of a set of distributed nodes performing local measurements to sense events. In order to avoid false alarms, the sensor nodes cooperate and only escalate an event (i.e., raise an alarm) if the number of sensor nodes sensing an event exceeds a certain threshold. In the on-duty scenario, nodes not affected by the event can actively help in the communication process, while in the off-duty scenario, non-event nodes are inactive. We present and analyze algorithms that minimize the reaction time of the monitoring system while avoiding unnecessary message transmissions. We investigate time and message complexity tradeoffs in different settings, and also shed light on the optimality of our algorithms by deriving cost lower bounds for distributed alarming systems.13 page(s

Transparent Data Structures, Or How to Make Search Trees Robust in a Distributed Environment

In this paper we propose a new class of memory models, called transparent memory models, for implementing data structures so that they can be emulated in a distributed environment in a scalable, efficient and robust way. Transparent memory models aim at combining the advantages of the pointer model and the linear addressable memory model without inheriting their disadvantages. We demonstrate the effectiveness of our approach by looking at a specific memory model, called the hypertree memory model, and by implementing a search tree in it that matches, in an amortized sense, the performance of the best search trees in the pointer model yet can efficiently recover from arbitrary memory faults. 1

Improved algorithms for dynamic page migration

Abstract The dynamic page migration problem [4] is defined in a distributed network of n mobile nodes sharing one indivisible memory page of size D. During runtime, the nodes can both access a unit of data from the page and move with a constant speed, thus changing the costs of communication. The problem is to compute online a schedule of page movements to minimize the total communication cost. In this paper we construct and analyze the first deterministic algorithm for this problem. We prove that it achieves an (up to a constant factor) optimal competitive ratio O(n · √ D). We show that the randomization of this algorithm improves this ratio to O ( √ D · log n) (against an oblivious adversary). This substantially improves an O(n · √ D) upper bound from [4]. We also give an almost matching lower bound of Ω ( √ D · √ log n) for this problem.

Dynamic page migration under brownian motion

Abstract. We consider Dynamic Page Migration (DPM) problem, one of the fundamental subproblems of data management in dynamically changing networks. We investigate a hybrid scenario, where access patterns to the shared object are dictated by an adversary, and each processor performs a random walk in X. We extend the previous results of [4]: we develop algorithms for the case where X is a ring, and prove that with high probability they achieve a competitive ratio of Õ(min { 4 √ D, n}), where D is the size of the shared object and n is the number of nodes in the network. These results hold also for any d-dimensional torus or mesh with diameter at least ˜ Ω ( √ D).