How does Linux implement POLICING?

[dE <de.techno@gmail.com>]

I realized Linux does not have ingress queue. So does it drop packet to 
limit the incoming rate?

Linux's network queueing system is well implemented for servers, but for 
making the desktop Internet more responsive, it doesn't do much in my 
option and the reason is missing ingress queue.

On a desktop system, most of the packets sent are practically empty; the 
incoming packets are filled with data.

So the ISP either drops packets to limit the incoming rate, or queues 
them till a certain limit and sends then at the throttled rate.

Policing combined with ingress queue can effectively implement the queue 
on the local system rather than the queue being formed at the ISPs end 
giving the local user control over the priority of incoming packets.

By not sending the incoming packet to the destined application, it'll 
prevent the application from responding to it.