Traffic Shaping

An even more proactive approach to handling traffic is traffic shaping . By using traffic shaping, we can ensure a certain amount of bandwidth for certain traffic. With the shape command, we can assign a CIR value, which is the committed information rate in bits per second.

Some optional keywords for the shape command are average, peak, bc-value, and be-value. Table 11-9 lists keywords for this command.

 shape {average  | peak } cir-value  [bc-value ] [be-value ]

Table 11-9. Shape command keywords

Shape keyword	Description
average	Specifies the average rate, which ensures an expected bandwidth.
peak	Specifies the peak rate, which allows the traffic to peak to if there is enough bandwidth available.
cir-value	The committed information rate in bits per second, which is used to define our average or peak values.
bc-value	The committed burst size, in bits.
be-value	The excess burst size, in bits.

 

11.6.1. Traffic Shaping Example

In this example , we attempt to ensure that our traffic can have at least 300 Kbps, but we are going to allow it to peak to 512 Kbps if there is enough bandwidth available on the interface.

 policy-map policy1
 class premium
 bandwidth 300
 shape peak 512000

 

11.6.2. Frame-Relay Shaping

For frame-relay, we can apply traffic shaping commands directly to the interface with the command traffic-shape. For more information and examples, see Chapter 6.