An extension of GridSim for quality of service

GridSim is a well known and useful open software product through which users can simulate a Grid environment. At present Qualities of Service are not modeled in GridSim. When utilising a Grid a user may wish to make decisions about type of service to be contracted. For instance performance and security are two levels of service upon which different decisions may be made. Subsequently during operation a grid may not be able to fulfill its contractual obligations. In this case renegotiation is necessary. This paper describes an extension to GridSim that enables various Qualities of Service to be modeled together with Service Level Agreements and renegotiation of contract with associated costs. The extension is useful as it will allow users to make better estimates of potential costs and will also enable grid service suppliers to more accurately predict costs and thus provide better service to users.