Reference Guide
You can override the default priority group settings when LLFC or PFC is enabled.
1 Create network-qos type class-map to match the trac classes. For LLFC match all the trac classes(0-7) and for PFC, match the
required trac class.
OS10(config)# class-map type network-qos tc
OS10 (config-cmap-nqos)# match qos-group 0-7
2 Create network-qos type policy-map to dene the actions for trac classes, like buer conguration and thresholds.
OS10(config)# policy-map type network-qos buffer
OS10(config-pmap-network-qos)# class tc
OS10 (config-pmap-c-nqos)# pause buffer-size 300 pause-threshold 200 resume-threshold 100
OS10 (config-pmap-c-nqos)# queue-limit thresh-mode dynamic 5
Congure egress buer
Default settings
All port queues are allocated with reserved buers and when the reserved buers are consumed, each queue starts using the shared buer
from the default pool.
The reserved buer per queue is 1664 bytes for the speed of 10G, 25G, 40G, 50G, and 100G. The default dynamic shared buer threshold
value is 8.
Congure queue buer settings
1 Create queuing type class-map to match the queue.
OS10(config)# class-map type queuing q1
OS10(config-cmap-queuing)# match queue 1
2 Create queuing type policy-map to dene the actions for queues, like buer conguration and thresholds.
OS10(config)# policy-map type queuing q-buffer
OS10(config-pmap-queuing)# class q1
OS10(config-pmap-c-que)# queue-limit queue-len 200 thresh-mode dynamic 5
Congestion avoidance
Congestion avoidance is a predictive method to anticipate and take necessary action to avoid congestion. The following are the dierent
mechanisms used to avoid congestion:
• Tail drop—Packets are buered at trac queues. When the buers are exhausted or reach the congured threshold, excess packets
are dropped. By default, OS10 uses tail drop for congestion avoidance.
• Random early detection (RED)—In tail drop mechanism, dierent ows are not considered in buer utilization. When multiple hosts
start retransmission, tail drop causes TCP global re-synchronization. Instead of waiting for the queue to get lled up completely, RED
starts dropping excess packets with a certain drop-probability, when the average queue length exceeds the congured minimum
threshold. The early drop ensures that only some of TCP sources slow down, which avoids global TCP re-synchronization.
• Weighted random early detection (WRED)—This mechanism allows dierent drop-probabilities and thresholds for each color (red,
yellow, green) of trac. You can congure the drop characteristics for 3 dierent ows by assigning the colors to the ow. You can
assign colors to a particular ow or trac by various methods, like ingress policing, qos input policy-maps, and so on.
• Explicit congestion notication (ECN)—This is an extension of WRED. Instead of dropping the packets when the average queue
length crosses the minimum threshold values, ECN marks the CE bit of ECN eld in a packet as ECN-capable trac.
Congure congestion avoidance
1 Congure WRED prole in the CONFIGURATION mode.
OS10(config)# wred wred_prof_1
2 Congure WRED threshold parameters for dierent colors in the WRED CONFIGURATION mode.
OS10(config-wred)# random-detect color yellow minimum-threshold 100 maximum-threshold 300
drop-probability 40
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Quality of service