Dell Force10 S2410-01-10GE-24P Command Reference Manual page 336

| Quality of Service (QoS) Commands
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• show service-policy on page 364
For examples of using these commands, see the DiffServ chapter in the SFTOS Configuration Guide.
The user configures DiffServ in several stages by specifying:
• Class:
Creating and deleting classes
Defining match criteria for a class. Note: The only way to remove an individual match
criterion from an existing class definition is to delete the class and re-create it.
• Policy:
Creating and deleting policies
Associating classes with a policy
Defining policy statements for a policy/class combination
• Service: Adding and removing a policy to/from a directional (i.e., inbound, outbound) interface
Packets are filtered and processed based on defined criteria. The filtering criteria is defined by a class.
The processing is defined by a policy's attributes. Policy attributes may be defined on a per-class
instance basis, and it is these attributes that are applied when a match occurs.
Packet processing begins by testing the match criteria for a packet. A policy is applied to a packet
when a class match within that policy is found.
Note that the type of class—all, any, or acl—has a bearing on the validity of match criteria specified
when defining the class. A class type of 'any' processes its match rules in an ordered sequence;
additional rules specified for such a class simply extend this list. A class type of 'acl' obtains its rule
list by interpreting each ACL rule definition at the time the Diffserv class is created. Differences arise
when specifying match criteria for a class type 'all', since only one value for each non-excluded match
field is allowed within a class definition. If a field is already specified for a class, all subsequent
attempts to specify the same field fail, including the cases where a field can be specified multiple ways
through alternative formats. The exception to this is when the 'exclude' option is specified, in which
case this restriction does not apply to the excluded fields.
The following class restrictions are imposed by the SFTOS DiffServ design:
• Nested class support limited to:
— 'all' within 'all'
— no nested 'not' conditions
— no nested 'acl' class types
— each class contains at most one referenced class
• Hierarchical service policies not supported in a class definition
• Access list matched by reference only, and must be sole criterion in a class
— implicit ACL 'deny all' rule also copied
— no nesting of class type 'acl'
Regarding nested classes, referred to here as class references, a given class definition can contain at
most one reference to another class, which can be combined with other match criteria. The referenced
class is truly a reference and not a copy, since additions to a referenced class affect all classes that
reference it. Changes to any class definition currently referenced by any other class must result in valid
class definitions for all derived classes otherwise the change is rejected. A class reference may be
removed from a class definition.