A mobile computing device that supports cost aware network behavior. An operating system of the mobile computing device may associate data for transmission with a entity and, based on a policy applicable to that entity and information on data usage, determine appropriate processing for the data. The processing may include transmitting the data, with or without throttling, or blocking transmission of the data. The policy, for example, may be supplied by a user or may be encoded in a tag supplied with the data for transmission. The policies may be specified for entities such as an application, an operating system service, a user account or a category of applications. Enforcement of the determined processing may be based on action within the stack or a separate enforcement mechanism, such as a firewall.