Information Technology Reference
In-Depth Information
It is also possible to configure CIR and PIR values as a percentage using the
percent
keyword. In this case, burst sizes (Bc and Be)
are configured in milliseconds.
Traffic shaping can be used at the edge of nonbroadcast, multiaccess (NBMA) networks, such as Frame Relay and ATM. It can be
applied in an output direction and is useful in many situations, such as the following:
■
When policing is being performed inbound on a neighboring device
■
When there is a mismatch between link speeds at a central site and remote sites (the central site link speed is greater than that
at the remote sites)
■
When there is the possibility of congestion at a central site because the aggregate link speed at remote sites is greater than that
at the central site
The following is an example of the configuration of class-based Frame Relay traffic shaping:
policy-map
fr-shape
class class-default
shape average
121600
1216 0
service-policy
voice
!
interface Serial 1/0.100 point-to-point
ip address
10.1.1.1 255.255.255.0
frame-relay interface-dlci
100
class
frame-map
!
map-class frame-relay
frame-map
service-policy output fr-shape
frame-relay fragment
160
The
class
name
command is used under the (sub)interface to link to the Frame Relay map class (called, in this example, frame-map).
The Frame Relay map class then links to the policy map called fr-shape using the
service-policy output
policy-map-name
command.
The
shape
[
average
|
peak
]
cir
[
bc
] [
be
] command is used to specify the mean rate (CIR, in bps), the committed burst size (Bc, in bits),
and excess burst (Be, in bits) within the policy map (which, in this example, is called fr-shape). Note that it is also possible to specify
the average or peak rate as a percentage of the bandwidth on the interface by using the
percent
keyword with the
shape
command.
