Cisco 3845 Software Guide - Page 510

Understanding QoS Chapter 27 Configuring QoS Table 27-1 Action Scheduling Options for Input and Output Policies Feature Class-based weighted fair queuing (bandwidth) Class-based shaping (shape average) Class-based excess bandwidth Strict priority Applicable Level VLAN or class level. All levels VLAN or class level. VLAN or class level. Input Policy Maps Input policy map classification criteria include matching CoS, DSCP, IP precedence, or MPLS EXP values or matching an ACL or VLAN ID (for per-port, per-VLAN QoS). Input policy maps support two actions: marking and policing. You can specify these actions in any one level of the hierarchical policy map, but actions cannot be nested. That is, if a child policy has a policer, then the parent policy map cannot have a policer. Likewise, if there is marking in a child policy, there cannot be marking in a parent policy. Only input policies provide matching on access groups, and only output policies provide matching on QoS groups and discard classes. The class class-default is used in a policy map for any traffic that does not explicitly match any other class in the policy map. Input policy maps do not support queuing and scheduling keywords, such as bandwidth, queue-limit, priority, and shape average. Output Policy Maps Output policy map classification criteria include matching CoS, DSCP, an IP precedence, MPLS EXP, or QoS group. or a discard-class value. Output policy maps can have any of these actions: • Queuing (queue-limit) • Scheduling (bandwidth, priority, and shape average) Policies attached to an EFP support only 2-level scheduling. Although you can attach a 3-level hierarchical policy to an EFP, the policy should conform to these rules: • Only two or the three levels can have a scheduling action (bandwidth, priority, or shape). • One of the two levels must be the class (bottom-most) level. Output policy maps do not support matching of access groups. You can use QoS groups as an alternative by matching the appropriate access group in the input policy map and setting a QoS group. In the output policy map, you can then match the QoS group. See the "Classification Based on QoS Groups" section on page 27-10 for more information. Output policies do not support marking or policing. There is no egress packet marking on the switch (no set command in an output policy). • A class-level policy (a child policy with class maps matching CoS, DSCP, IP precedence, MPLS EXP, QoS group, or discard-class) can have a maximum of eight classes including class default. • A VLAN-level policy (a parent policy that has classes matching VLANs) can have a maximum of 4000 classes, including class default. • A physical-level policy can have only class-default in the entire policy map. You can attach an output policy map to any or all targets on the switch. The switch supports configuration and attachment of a unique output policy map for each port or service instance. 27-22 Cisco ME 3800X and 3600X Switch Software Configuration Guide OL-23400-01