Cloud computing has opened a new paradigm in the area of distributed computing in which users lease computing resources from large scale data centers operated by service providers. It delivers the large scale computation and data processing operation in a scalable and flexible manner. It provides the opportunity for small organizations and individuals to deploy applications by paying a minimal cost of actual resource usage [8]. Cloud resources such as virtual machine [52] can be provisioned on-demand on a Pay-As-You-Go basis [9]. Current resources provisioning approaches [9] [11] rely on monitoring the state of system resources such as CPU or memory utilization of virtual machines to determine the required size of the system. Most cloud service providers use machine virtualization to provide flexible and cost effective resource sharing. The cloud service provider is responsible to make the needed resources available on demand to the cloud users. Out of the three types (Infrastructure-as-a-Service IaaS, Platform-as-a-Service PaaS and Software-as-a-Service SaaS) of computing capacities as a service [12] in different abstraction levels, this thesis focused on Infrastructure-as-a-Service (IaaS) [5] only to provide computing resources as a service to customers. It introduces dynamic resource allocation mechanisms for infrastructure provisioning where there is a fixed time-limit as well as a resource budget for a particular task.