API Guide

● Xoff threshold (transmit off)—When the system reaches the Xoff threshold, to prevent traffic loss, the system pauses and
does not accept any further packets.
● Xon threshold (transmit on)—When the system reaches the Xon threshold, the system resumes and accepts the packets.
For example, when all ports are allocated as reserved buffers from the lossy (default) pool, the remaining buffers in the lossy
pool are shared across all ports, except the CPU port.
When you enable priority flow control (PFC) on the ports, all the PFC-enabled queues and priority-groups use the buffers from
the lossless pool.
You must use the network QoS policy type to configure PFC on the ports.
OS10 dedicates a separate buffer pool for CPU traffic. All default reserved buffers for the CPU port queues are from the CPU
pool. The remaining buffers are shared across all CPU queues. You can modify the buffer settings of CPU queues.
You can configure the size of the CPU pool using the control-plane-buffer-size command.
OS10 allows configuration of buffers per priority-group and queue for each port.
Buffer-usage accounting happens for ingress packets on ingress pools and egress packets on egress pool. You can configure
ingress-packet buffer accounting per priority-group and egress-packet buffer accounting per queue level.
Configure ingress buffer
By default, all traffic classes map to the default priority group (PG) 7 for ingress buffers. The buffer reservation is based on the
default priority group ID 7. All buffers are part of the default pool and all ports share buffers from the default pool. When you
configure a network qos policy map, a new priority group is created for which buffers are assigned from the lossless pool. The
rest of the traffic classes that are not mapped to any PFC-related PGs, use the default buffer.
The reserved buffer size is 9360 bytes for the speed of 10G, 25G, 40G, 50G, and 100G. The supported speed varies for
different platforms.
Table 119. Maximum buffer size
Platforms Max buffer size
S4000 12 MB
S6010–ON, S4048–ON 16 MB
S4100-ON Series 12 MB
S4200-ON Series 6 GB
S5200-ON Series 32 MB
Z9100–ON 16 MB
Z9264F-ON 42 MB
The following table lists the values allocated for the default ingress buffers on the S4100-ON series platform. These values may
differ for different platforms and speeds. Use the show qos ingress buffers command to view the default ingress
buffers on your switch.
Table 120. Default ingress buffers on the S4100-ON series platform
Speed 10G 25G 40G 50G 100G
Reserved buffers
for PG 7 (default)
9KB 9KB 9KB 9KB 9KB
The following lists the link-level flow control (LLFC) buffer settings for default priority group 7:
Table 121. Default setting for LLFC
Speed 10G 25G 40G 50G 100G
Default reserved buffer 9KB 9KB 18KB 18KB 36KB
Default Xon threshold 36KB 45KB 75KB 91KB 142KB
Default Xoff threshold 9KB 9KB 9KB 9KB 9KB
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