Cisco 3845 - Security Bundle Router Software Manual page 510

Understanding QoS
Table 27-1 Options for Input and Output Policies
Action
Scheduling
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:
•
•
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:
•
•
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
on page 27-10
Output policies do not support marking or policing. There is no egress packet marking on the switch (no
set command in an output policy).
•
•
•
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.
Cisco ME 3800X and 3600X Switch Software Configuration Guide
27-22
Feature
Class-based weighted fair queuing
(bandwidth)
Class-based shaping (shape average)
Class-based excess bandwidth
Strict priority
Queuing (queue-limit)
Scheduling (bandwidth, priority, and shape average)
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.
for more information.
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.
Chapter 27
Applicable Level
VLAN or class level.
All levels
VLAN or class level.
VLAN or class level.
"Classification Based on QoS Groups" section
Configuring QoS
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