Buffering And Queue Limits On The Cisco Nexus 5000 Platform - Cisco Nexus 5000 NX-OS Service Configuration Manual

Buffering and Queue Limits on the Cisco Nexus 5000 Platform

• FCoE traffic (traffic that maps to the FCoE system class) is assigned a queue. This queue uses weighted
• Standard Ethernet traffic in the default drop system class is assigned a queue. This queue uses WRR
If you add a system class, a queue is assigned to the class. You must reconfigure the bandwidth allocation on
all affected interfaces. Bandwidth is not dedicated automatically to user-defined system classes.
You can configure one strict priority queue. This queue is serviced before all other queues except the control
traffic queue (which carries control rather than data traffic).
Buffering and Queue Limits on the Cisco Nexus 5000 Platform
The following buffering limits exist for the Cisco Nexus 5000 Platform:
• Maximum ingress port buffering: 320KB per port.
• Maximum egress port buffering: 160KB per port.
The following default buffer allocations per port exist for the Cisco Nexus 5000 Platform:
Table 9: Cisco Nexus 5000 Platform Default Buffer Allocations Per Port
Traffic Class
Class-fcoe
User-defined no-drop class of service with an MTU
less than 2240
User-defined no-drop class of service with an MTU
greater than 2240
Tail drop class of service
Class-default
The default buffer allocation varies depending on the type of class. For example, if you create a regular tail
drop traffic class the default allocation is 20.48KB, unless you specify a larger size using the queue-limit
command.
To increase the buffer space available to a user-created qos-group, from a network-qos policy-map, use the
queue-limit command.
All of the available buffer is allocated to the class-default. When you define a new qos-group, the required
buffer for the new qos-group is taken from the class-default buffer.
Each new class requires an additional 18.880KB, so the exact amount of buffer that is left in the class
Note
default is 243.2KB minus the buffer used by other qos-groups minus 18.880KB times the number of
qos-groups.
Cisco Nexus 5000 NX-OS Quality of Service Configuration Guide, Release 5.1(3)N2(1)
58
round-robin (WRR) scheduling with 50 percent of the bandwidth.
scheduling with 100 percent of the bandwidth.
Configuring Queuing and Flow Control
Ingress Buffer (KB)
76.8
76.8
81.9
20.48
All of the remaining buffer (243.2KB with the default
QoS configuration)
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