Wred Aggregate Drop Profiles - Cisco 10000 Series Configuration Manual

Chapter 11 Managing Packet Queue Congestion
2. See footnote 1.
3. Includes profiles for class-default, net-control, and two priority queues.

WRED Aggregate Drop Profiles

On the PRE3 and PRE4, WRED is extended to support an aggregate drop profile. A single
random-detect command with multiple subclasses specified is used to configure the profile. The
subclasses (for example, multiple DSCP values) share one specified minimum and maximum threshold
and one specified mark-probability denominator.
Although the PRE3 and PRE4 allow you to specify only one DSCP or IP precedence value in the
random-detect command (which is equivalent to the PRE2 form of the command), the advantage of
aggregating DSCP or IP precedence values is that an aggregate drop profile only counts as one profile
toward the maximum number of profiles allowed. As a result, you can configure drop profiles for more
DSCPs or IP precedence levels using aggregation than you can when specifying only one value for each
WRED profile.
The PRE3 and PRE4 random-detect commands have the following syntax:
random-detect aggregate [minimum-thresh min-thresh-value maximum-thresh max-thresh-value
mark-prob mark-prob-value]
random-detect {precedence-based | dscp-based} aggregate [minimum-thresh min-thresh-value
maximum-thresh max-thresh-value mark-prob mark-prob-value]
random-detect {precedence | dscp} values [sub-class-val1 [...sub-class-val8]
[minimum-thresh min-thresh-value maximum-thresh max-thresh-value mark-prob
mark-prob-value]]
If you enter the random detect command without the aggregate profile, the PRE3 and PRE4 accept the
Note
command, but the default action is to tail drop. For example:
random-detect {precedence-based | dscp-based}
The PRE3 and PRE4 also supports drop profiles based on discard class and cell loss priority (CLP), but
do not use the aggregate form of the command. Instead, the PRE3 and PRE4 support the PRE2 form of
the commands:
random-detect {discard-class-based | atm-clp-based}
random-detect {discard-class discard-class-value | clp clp-value} [min-thresh-value]
[max-thresh-value] [mark-probability-denominator-value]
For example, to configure a WRED DSCP profile, the following command creates drop profiles for
DSCP value 1, DSCP value 2, and so on. Each profile has the same specified drop threshold and
mark-probability denominator. The router aggregates these drop profiles, that is statistics are counted for
the group of all of the DSCP values together.
random-detect dscp values [dscp-val1 [...dscp-val8] [minimum-thresh min-thresh-value
maximum-thresh max-thresh-value mark-prob mark-prob-value]
To have the statistics counted for each DSCP separately, enter the random-detect command once for
each DSCP value, using the same threshold values and mark-probability denominator.
Statistics displayed for the subclasses are aggregated and shown in one line. If some subclasses do not
have a user-defined WRED profile, the router collects the statistics as an aggregate for the unconfigured
subclasses and displays the statistics in one line. The router maintains separate statistics for each
random-detect command with a group of subclasses.
OL-7433-09
Controlling Congestion Using Weighted Random Early Detection
Cisco 10000 Series Router Quality of Service Configuration Guide
11-17