Research On Resource Discovery In Distributed Systems

One of the goals of constructing distributed systems is to share resource. Both Grids, which has the same scale of the Internet, and Mobile Ad-hoc Networks (MANETs), which is based on wireless technology and don't depends on any fixed infrastructure, are for sharing resources more conveniently and effectively. At the same time, pervasion of distributed sys-tems enables not only scientists and engineers but commercial clients and common people to benefit.In a distributed system to share resources, resource discovery is a dispensable component. 1) It is the base of resource sharing. From both functionality and performance perspectives, it is a service which is directly tangible by users. 2) It is a footstone for many applications. A good resource discovery service can enable many new applications, or promote performance of ex-isted ones or enrich their functions. 3) It can support resource scheduling or resource charging.Due to complexity of distributed systems, resource discovery faces many difficulties. For example, in both Grids and MANETs, resources are heterogeneous, autonomous, as well as dynamic. In Grids, there are large amount of resources and resource types. While in Partially Connected MANETs, there may be no any contemporaneous path between nodes. All these conditions make resource discovery a challenging problem.This thesis focuses on two typical distributed systems: Grids and Partially Connected Mo-bile Ad-hoc Networks. A resource discovery service is composed of resource description, re-source information organization, resource request processing and resource selection. The main contributions are listed below:1) A C/S and P2P hybrid resource discovery framework in Grids, VIRD, is proposed. VIRD makes full use of the physical topology and logical topology of the physical network to avoid inaccurate estimation of delays on the overlay network. Its layered architecture can not only improve searching effectiveness but also be of good scalability.2) A resource discovery framework based on clusters in Partially Connected MANETs is de-veloped. Due to long delay caused by disconnectivity, it duplicates resource information among clusters and employs anycast technology for resource request processing, which ef-ficiently reduce response delay.3) Resource Discovery Agent placement problem in Partially Connected MANETs is ana-lyzed and two heuristics are provided. The problem is analyzed and formulated. A greedy...