# QoS Parameter Terms

Table 22 defines terms used in this discussion of QoS parameters.

Table 22: QoS Parameter Terminology Used in This Chapter

Term | Description
--- | ---
Downreference | QoS feature that controls a node or queue lower in the scheduler hierarchy. For example, a QoS profile that is attached to an ATM virtual circuit (ATM VC) modifies QoS settings on ATM virtual path (VP) nodes. You cannot configure downreferences for QoS parameters. We also recommend that you do not configure downreferences for QoS profiles.
Explicit parameter instance | Hierarchical parameter instance whose value is explicitly specified by a client. This term is meaningful only when referring to hierarchical parameter instances; non-hierarchical parameter instances are always explicit.
Hierarchical parameter | Parameter with both explicit instances that are configured by a QoS client, and with implicit instances that are automatically generated for all controlled interfaces. The value for the implicit instance is the sum of the explicit instances for interfaces stacked above the controlled interface.
Implicit parameter instance | Hierarchical parameter instance where the value is the sum of explicit parameter instances on scheduler nodes and queues stacked above them in the scheduler hierarchy.
Parameter definition | Definition of a parameter name and attributes that a QoS administrator creates.
Parameter expression | Parameters used in conjunction with operators. Scheduler profiles reference a parameter definition name within a parameter expression.
Parameter instance | Parameter name and value that a QoS client associates with a logical interface.
Parameter value | 32-byte unsigned integer value associated with a parameter instance.
QoS administrator | Person responsible for implementing a QoS queuing architecture by configuring QoS profiles, scheduler profiles, and parameter definitions.
QoS client | Person responsible for configuring services for individual subscribers and setting rates for those services by using the parameter definitions and QoS profiles that the QoS administrator configures. QoS clients can use the CLI, SRC, Service Manager, IP multicast bandwidth adjustment, or RADIUS.

#### Related Documentation

- For definitions of other common QoS terms, see QoS Terms