[$] Time-based packet transmission

Normally, when an application sends data over the network, it wants thatdata to be transmitted as quickly as possible; the kernel's network stacktries to oblige. But there are applications that need their packets to betransmitted within specific time windows. This behavior can beapproximated in user space now, but a better solution is in the works inthe form of the time-based packettransmission patch set.