Once traffic is identified, it can be treated in a number of different ways.
You could, as an example, give it a minimum amount of bandwidth.
You could give it a maximum amount of bandwidth or a limit on the amount of bandwidth that it can send.
Some queuing mechanisms provide a minimum bandwidth guarantee.
Policing and shaping the limit.
The amount of traffic that you can transmit.
So polices and shapers are both rate limiters, but they differ in how they treat excess traffic.
As a general rule of thumb polices will drop excess traffic, whereas traffic shapers will delay excess
traffic.
In this example, we've got traffic sent at different rates and administrator has configured a maximum
limit.
However, as shown by this line here with policing, any excess traffic is automatically dropped.
So police's will perform checks for traffic violations against a configured rate set by an administrator.
Which could be you.
The action that a police takes in response to traffic would either be dropping the traffic as shown
here, or it could remark excess traffic and still transmit to the traffic.
There are different options.
You could just transmit the traffic as long as you are below the threshold.
You could configure a police to send the traffic without any modification.
As long as it's below the configured threshold.
When it goes above the configured threshold, you could remarket but still transmit it.
And that would be true for traffic between the threshold and a second threshold.
But any traffic exceeding the second threshold would be dropped.
We have this concept of a tri tricolor or three color implementation.
When traffic is below the first threshold, it's transmitted as normal.
When it exceeds the first threshold, but it's below a second threshold, it will be remarked to a lower
class.
So in other words, you are moved from first class to economy as an example, but the traffic is still
transmitted and when you go above the second threshold, you're simply kicked off the plane or in a
data network, the traffic is dropped.
What's important to understand about polices is that they do not delay traffic.
They will check the traffic and either remarket and transmit it or drop it.
They do not buffer or delay traffic.
Shape is, on the other hand, will delay traffic.
So they try and smooth traffic out by buffering it.
So if we look at our original traffic when it's shaped, notice the curve here is a lot smoother as
the traffic is delayed so that it falls within a configured bitrate so the shaper doesn't drop the traffic,
but smooths it out by delaying the traffic to make sure that over a period of time the traffic falls
within a configured bitrate.
Shape is usually used to meet service level agreements.
When the traffic spikes above the contracted rate, the excess traffic is buffered and is delayed until
it falls below the contracted rate.
Polices are a lot harsher.
They will drop as a quick way as a shaper will try and smooth the traffic out over a period of time
to get it below a configured rate.