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 trac classes. For LLFC match all the trac classes(0-7) and for PFC, match the
required trac 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 dene the actions for trac classes, like buer conguration 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
Congure egress buer
Default settings
All port queues are allocated with reserved buers and when the reserved buers are consumed, each queue starts using the shared buer
from the default pool.
The reserved buer per queue is 1664 bytes for the speed of 10G, 25G, 40G, 50G, and 100G. The default dynamic shared buer threshold
value is 8.
Congure queue buer 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 dene the actions for queues, like buer conguration 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 dierent
mechanisms used to avoid congestion:
• Tail drop—Packets are buered at trac queues. When the buers are exhausted or reach the congured threshold, excess packets
are dropped. By default, OS10 uses tail drop for congestion avoidance.
• Random early detection (RED)—In tail drop mechanism, dierent ows are not considered in buer 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 congured 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 dierent drop-probabilities and thresholds for each color (red,
yellow, green) of trac. You can congure the drop characteristics for 3 dierent ows by assigning the colors to the ow. You can
assign colors to a particular ow or trac by various methods, like ingress policing, qos input policy-maps, and so on.
• Explicit congestion notication (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 trac.
Congure congestion avoidance
1 Congure WRED prole in the CONFIGURATION mode.
OS10(config)# wred wred_prof_1
2 Congure WRED threshold parameters for dierent 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