Throttling for fast data packet transfer operations

A fast send method may be selectively implemented for certain data packets received from an application for transmission through a network interface. When the fast send method is triggered for a data packet, the application requesting transmission of the data packet may be provided a completion notice nearly immediately after the data packet is received. The fast send method may be used for data packets similar to previously-transmitted data packets for which the information in the data packet is already vetted. For example, a data packet with a similar source address, destination address, source port, destination port, application identifier, and/or activity identifier may have already been vetted. Data packets sent through the fast send method may be throttled to prevent one communication stream from blocking out other communication streams. For example, every nth data packet queued for the fast send method may be transmitted by a slow send method.