How does a shaper rate-limit a traffic stream?

Packets that arrive in a burst are immediately dropped; packets that arrive with the proper in between space are immediately.

Packets are buffered on arrival and are forwarded at an average rate conforming with PIR, typically, with a reduced burstiness.

Packets with an average arrival rate higher than PIR are immediately dropped; conforming packets are forwarded at the same rate at which they arrive.

Packets with an average arrival rate higher than PIR are buffered for future processing; conforming packets are immediately forwarded.