In a method for regulating network bandwidth in a virtualized computer environment, a computer having a hypervisor program receives a request from a first virtual client to transmit data. In response, the computer transfers the data from a memory of the first virtual client to a memory of a virtual server. The computer receives an error notification from a shared virtual network adapter of the virtual server, indicative of insufficient network bandwidth available to transmit the data. In response, the computer notifies the first virtual client that insufficient network bandwidth is available to transmit the data.