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Top1. Introduction
A service specific overlay network (Shmid, Hartung, & Kampmann, 2005; Capone, Elias, & Martignon 2008) is an overlay network built on top of the physical network and is designed to provide end-to-end quality of service guarantees in the internet and to facilitate the creation and deployment of value added functionality to the service without needing support by the underlying network. It consists of Media Ports (MPs), Media Servers (MSs), and Media Clients (MCs). MPs are specific intermediate nodes perform service specific data forwarding and control functions in order to enable the correct media delivery of the service to the end user as required. Also the SSON consists of MS, the provider of the requested service, and the MC whose request the service. However, designing services to meet users' specific requirements implies that huge number of services will exist in the network thus managing them is not an easy task. Management complexity can be tackled using the IBM self-management concept (IBM Corporation, 2006). IBM introduced this concept through Autonomic Computing (AC) to enable systems to manage themselves according to administrative objectives. The term autonomic is inspired from human biology autonomic nervous system.
AC system simplifies the design and development of systems that can adapt themselves to changes in their environment to meet requirements of performance, fault tolerance, reliability and security with minimum human intervention. The result is a great improvement in management costs, reduced time and skills requirements to perform the tasks. Hence IT professionals can focus on improving their overall services rather than on managing them. AC divides self-management into four functional areas (Kephart & Chess, 2003; Parashar & Hariri, 2005): 1) Self-configuration where an autonomic system should be able to configure components automatically to adapt them to varying conditions, 2) Self-healing where an autonomic system should be able to detect, diagnose and repair potential problems resulting from failures in hardware and software, 3) Self-optimization where an autonomic system should be able to monitor and seek ways to improve their operations and to ensure optimal functioning, and 4) Self-protection where an autonomic system should be able to detect, identify and protect its resources from malevolent attacks and cascading failures.
In this paper, self-healing systems for overlay networks are surveyed. Self-healing is the property that allows a system to perceive that is not working properly and without human intervention, make the necessary adjustment that can automatically restore the services affected by a failure in a manner that is seamless to the end systems. Defects may occur due to overlay nodes that may join or leave the network, the congestion on overlay links, or the ever changing of routing information. This in addition to the rapid evolution of overlay networks technologies and the various proposed schemes that are based on self-healing. As the number of mobile users increase, the demand of self-healing overlay services will also increase. This paper serves to capture a snapshot of current design trends and techniques in self-healing overlay networks. The goal is not to compare one solution with another, but to identify the common design goals and put them in context. In this paper we also propose a self-healing mechanism for services that are built to deliver media and designed to meet users' particular requirements. Our proposed solution is oriented to discover new approaches for monitoring, diagnosing and recovering of services thus achieving self-healing.
The rest of this paper is organized as follows. Section 2 discusses self-healing architecture models and requirements. Section 3 outlines and reviews the proposed self-healing approaches. Section 4 briefly introduces our proposed overlay self-healing architecture while Section 5 provides the results of the evaluation experiments. In Section 6 we conclude the paper.