Self-Organization in Peer-to-Peer Systems

Peer-to-Peer Systems are about community-based cooperations. The peers share responsibilities and benefits by cooperating in a distributed and decentralized environment. To carry out tasks sensibly, however, a more or less rigid order is required for efficiency and reliability reasons. This order can be partially imposed from the outside, for example within so-called "structed" Peer-to-Peer systems. A common approach here is the use of Distributed Hash Tables. Alternatively, Peer-to-Peer systems can be "unstructured" in the sense that an useful order emerges from own internal processes. Unstructured and structured Peer-to-Peer systems rely both on a more or less decentralized overlay management. Self-organization, therefore, is a key to the success of Peer-to-Peer systems in various forms. This presentation gives an overview of the role of self-organization in Peer-to-Peer systems

An Arbitrary 2D Structured Replica Control Protocol

Traditional replication protocols that logically arrange the replicas into a specific structure have reasonable availability, lower communication cost as well as system load than those that do not require any logical organisation of replicas. We propose in this paper the A2DS protocol: a single protocol that, unlike the existing proposed protocols, can be adapted to any 2D structure. Its read operation is carried out on any replica of every level of the structure whereas write operations are performed on all replicas of a single level of the structure. We present several basic 2D structures and introduce the new idea of obtaining other 2D structures by the composition of several basic ones. Two structures are proposed that have near optimal performance in terms of the communication cost, availability and system load of their read and write operations. Also, we introduce a new protocol that provides better performance for its write operations than those of ROWA protocol while preserving similar read performance

Decision Support in Cooperative QoS Management

Cooperative QoS management is a new quality of service management scheme which is based on QoS agents distributed within a system and cooperating with each other to provide the QoS negotiated with users, thereby ameliorating the overail system's resource usage and decreasing the communication costs. During their operations, agents have to take decisions in order to react on QoS violations, initiate QoS renegotiation processes or react on renegotiation requests from other QoS agents. In this paper, we present two tools which support cooperating QoS agents in their decision processes: a model called Quality of Operation, based on a mathematical formula, and an approach based on a new variant of Stochastic Petri Nets, so-called Controlled Stochastic Petri Nets

Using System Virtualization to Create Virtualized Networks

The method of system virtualization is very popular for the use in data centers and desktop virtualization today. In this work, system virtualization is applied to core network elements (routers and links) in order to create a virtualized network. The selection of this virtualization method crucially determines the emerging network model. The network model consists of virtual networks, virtual routers, and virtual links that form overlays on top of the physical network. The properties, features, and limitations of this network model are analyzed and described in this paper. Additionally, a proof of concept implementation using currently available technology and infrastructure is presented. Finally the dynamic configurability of virtual resources in such a system virtualization based virtualized network is evaluated

Modeling of Self-Organizing Systems: An Overview

This paper gives a systematic overview on modeling formalisms suitable for modeling self-organizing systems. We distinguish between micro-level modeling and macro-level modeling. On the micro level, the behavior of each entity and the interaction between different object must be described by the model. Macrolevel modeling abstracts from the individual entities and only looks at the behavior of the system variables of interest. The differentiations between discrete and continuous time and between discrete and continuous state space lead to different descriptions of the model

04411 Abtracts Collection -- Service Management and Self-Organization in IP-based Networks

From 03.10.04 to 06.10.04, the Dagstuhl Seminar 04411 ``Service Management and Self-Organization in IP-based Networks\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Modeling Wireless Sensor Networks Using Finite-Source Retrial Queues with Unreliable Orbit

Abstract. Motivated by the need for performance models suitable for modeling and evaluation of wireless sensor networks, we introduce a retrial queueing system with a finite number of homogeneous sources, unreliable servers, orbital search, and unreliable orbit. All random variables involved in model construction are assumed to be independent and exponentially distributed. Providing a generalized stochastic Petri net model of the system, steady-state analysis of the underlying continuous-time Markov chain is performed and steady-state performance measures are computed by the help of the MOSEL-2 tool. The main novelty of this investigation is the introduction of an unreliable orbit and its application to wireless sensor networks. Numerical examples are derived to show the influence of sleep/awake time ratio, message dropping, and message blocking on the senor nodes' performance

Investigating the mean response time in finite-source retrial queues using the algorithm by Gaver, Jacobs, and Latouche

In this paper, we discuss the maximum of the mean response time that appears in finite-source retrial queues with orbital search when the arrival rate is varied. We show that explicit closed-form equations of the mean response time can be derived by exploiting the block-structure of the finite Markov chain underlying the model and using an efficient computational algorithm proposed by Gaver, Jacobs, and Latouche. However, we also show that already for the discussed relatively simple model, the resulting equation is rather complex which hampers further evaluation