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Once traffic is identified, it can be treated in a number of different ways.

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You could, as an example, give it a minimum amount of bandwidth.

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You could give it a maximum amount of bandwidth or a limit on the amount of bandwidth that it can send.

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Some queuing mechanisms provide a minimum bandwidth guarantee.

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Policing and shaping the limit.

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The amount of traffic that you can transmit.

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So polices and shapers are both rate limiters, but they differ in how they treat excess traffic.

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As a general rule of thumb polices will drop excess traffic, whereas traffic shapers will delay excess

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traffic.

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In this example, we've got traffic sent at different rates and administrator has configured a maximum

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limit.

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However, as shown by this line here with policing, any excess traffic is automatically dropped.

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So police's will perform checks for traffic violations against a configured rate set by an administrator.

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Which could be you.

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The action that a police takes in response to traffic would either be dropping the traffic as shown

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here, or it could remark excess traffic and still transmit to the traffic.

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There are different options.

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You could just transmit the traffic as long as you are below the threshold.

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You could configure a police to send the traffic without any modification.

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As long as it's below the configured threshold.

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When it goes above the configured threshold, you could remarket but still transmit it.

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And that would be true for traffic between the threshold and a second threshold.

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But any traffic exceeding the second threshold would be dropped.

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We have this concept of a tri tricolor or three color implementation.

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When traffic is below the first threshold, it's transmitted as normal.

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When it exceeds the first threshold, but it's below a second threshold, it will be remarked to a lower

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class.

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So in other words, you are moved from first class to economy as an example, but the traffic is still

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transmitted and when you go above the second threshold, you're simply kicked off the plane or in a

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data network, the traffic is dropped.

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What's important to understand about polices is that they do not delay traffic.

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They will check the traffic and either remarket and transmit it or drop it.

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They do not buffer or delay traffic.

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Shape is, on the other hand, will delay traffic.

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So they try and smooth traffic out by buffering it.

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So if we look at our original traffic when it's shaped, notice the curve here is a lot smoother as

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the traffic is delayed so that it falls within a configured bitrate so the shaper doesn't drop the traffic,

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but smooths it out by delaying the traffic to make sure that over a period of time the traffic falls

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within a configured bitrate.

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Shape is usually used to meet service level agreements.

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When the traffic spikes above the contracted rate, the excess traffic is buffered and is delayed until

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it falls below the contracted rate.

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Polices are a lot harsher.

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They will drop as a quick way as a shaper will try and smooth the traffic out over a period of time

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to get it below a configured rate.