With the spread of the Internet, services that communicate to other services are increasing. Multimedia applications such as video on demand also ask for network Quality of Service (QoS). Thus, operating systems have to guarantee the allocation of computer resources to services. The computer resources are CPU, disk, network devices and so on. We suppose that the communications have to be controlled well, because services using network are increasing. This paper proposes the communication bandwidth control mechanism by regulating program execution speed. Our proposed mechanism is based on the process schedule method for regulating program execution speed. In the process schedule method, the operating system reserves the amount of CPU time of target processes and guarantees the allocation of CPU time on a sending host. Our proposed mechanism can guarantee a required data rate of target processes by allocating enough CPU time for communications. Because operating systems manage computer resources, they guarantee the allocation of CPU time if the process schedule method is implemented. The allocation of CPU time is not almost affected by non-target processes. This paper introduces the process schedule method and the implementation of it. This paper also shows how to control the communication bandwidth of target processes. Then this paper describes about an evaluation of our proposed mechanism.