CANOGA PERKINS 9175 Configuration Guide - Manual (Page 212)

CanogaOS Configuration Guide
31-6
Tail drop is the default congestion-avoidance technique on every egress queue. With tail
drop, packets are queued until the thresholds are exceeded.
The following shows configuring tail drop threshold for different drop-precedence. Follow
these steps from Privileged Exec mode.
• configure
terminal
• interface IFNAME to specify the interface to match to the policy map. IFNAME =
name of interface
• queue <0-7> threshold THRESHOLD1 THRESHOLD2 THRESHOLD3 to set
threshold for different drop-precedence. THRESHOLD1 = threshold for
drop-precedence 0. Range is 0-62. THRESHOLD2 = threshold for
drop-precedence 1. Range is 1-63. THRESHOLD3 = threshold for
drop-precedence 2. Range is 2-64.
The following example shows configuring tail drop threshold for queue 3. In this example,
drop-precedence-0‘s threshold is 20, drop-precedence 1 is 30, drop-precedence 2 is 40.
DUT(config)# interface eth-0-1
DUT(config-if)# queue 3 threshold 20 30 40
WRED
WRED reduces the chances of tail drop by selectively dropping packets when the output
interface begins
to show signs of congestion. By dropping some packets early rather than waiting until the
queue is full, WRED avoids dropping large numbers of packets at once.
The following shows configuring WRED threshold for different drop-precedence. Follow
these steps from Privileged Exec mode.
• configure
terminal.
• interface IFNAME to specify the interface to match to the policy map. IFNAME =
name of interface
• queue <0-7> random-detect to set WRED mode.
•
queue <0-7> random-detect min-threshold MIN_THRESHOLD1
MIN_THRESHOLD2 MIN_THRESHOLD3 to set min threshold for different
drop-precedence.
•
queue <0-7> random-detect max-threshold MAX_THRESHOLD1
MAX_THRESHOLD2 MAX_THRESHOLD3 to set max threshold for different
drop-precedence.
• queue <0-7> random-detect drop-probability DROP_PRO1 DROP_PRO2
DROP_PRO3 to set drop probability for different drop-precedence.
The following example shows configuring WRED threshold for queue 1. In this example,
drop-precedence-0‘s min-threshold is 20, drop-precedence 1 is 30, drop-precedence 2 is
40, and drop-precedence-0‘s max-threshold is 35, drop-precedence 1 is 45,
drop-precedence 2 is 55. If buffered packets exceeds min-threshold, the subsequent
packet will be dropped randomly with rate of (drop-probability /256)
DUT(config)# interface eth-0-1
DUT(config-if)# queue 1 random-detect
DUT(config-if)# queue 1 random-detect min-threshold 20 30 40
DUT(config-if)# queue 1 random-detect max-threshold 35 45 55
Schedule
Packets are scheduled by SP between classes and WRR between queues in a class.