Quick Reference Guide

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Creating a Policy-Map
The second step in deploying DiffServ is to create a policy-map. From the Global Config mode, use the
policy-map command (Figure 12-139) to create or identify an existing policy-map. The policy-map
defines:
• Traffic Conditioning—Specify traffic conditioning actions (policing, marking, shaping) to apply to
traffic classes
• Service Provisioning—Specify bandwidth and queue depth management requirements of service
levels — EF (expedited forwarding), AF (assured forwarding), BE (best effort), and CS (class
selector). See the explanation of those
dscpval parameter options in the match ip dscp command syntax
statement in the QoS chapter of the SFTOS Command Reference.
The policy commands associate a traffic class, which was defined by the class command set, with one or
more QoS policy attributes. This association is then assigned to an interface to form a service. The user
specifies the policy name when the policy is created.
The DiffServ CLI does not necessarily require that users associate only one traffic class to one policy. In
fact, multiple traffic classes can be associated with a single policy, each defining a particular treatment for
packets that match the class definition. When a packet satisfies the conditions of more than one class,
preference is based on the order in which the classes were added to the policy, with the foremost class
taking highest precedence.
This set of commands consists of policy creation/deletion, class addition/removal, and individual policy
attributes. Note that the only way to remove an individual policy attribute from a class instance within a
policy is to remove the class instance and re-add it to the policy. The values associated with an existing
policy attribute can be changed without removing the class instance.
The
policy-map command establishes a new DiffServ policy. The syntax is policy-map policyname in, where
policyname is a case-sensitive alphanumeric string from 1 to 31 characters uniquely identifying the policy.
The
in keyword indicates that the policy is specific to inbound traffic, because SFTOS supports only the
inbound (ingress) direction.
The following example shows the use of the
policy-map command:
Note: Class instances are always added to the end of an existing policy. While existing class
instances may be removed, their previous location in the policy is not reused, so the number of
class instance additions/removals is limited. In general, significant changes to a policy definition
require that the entire policy be deleted and re-created with the desired configuration.
Note: The policy type dictates which of the individual policy attribute commands are valid
within the policy definition.
Note: The CLI mode is changed to Policy-Map when this command is successfully executed.