The present invention relates to computer networks, and more specifically, to managing data flows in overlay networks. 
In a data center environment, a typical host machine runs many virtual machines (VMs) that provide services to or receive services from other virtual or non-virtualized machines.  In providing or receiving services, the VMs in the host may communicate among each other or may communicate with other VMs executing in other hosts.  The communications between the machines are in the form of data flows, which include data packets that have common properties (e.g., common headers).  In some cases, the VMs in the host share one or more network interface cards attached to the host to send or receive data flows.