Connectivity Guide

• Payload—variable
• Cyclic redundancy check—4 bytes
• Inter-frame gap—variable
The rate adjustment feature is disabled by default. To enable rate adjustment, use the qos-rate-adjust value_of_rate_adjust
command. For example:
qos-rate-adjust 8
If you have congured WDRR and shaping on a particular queue, the queue can become congested. You should congure the QoS rate
adjust value considering the overhead eld size to avoid trac drops on uncongested queues.
If you have multiple streams within a queue, you must nd the overhead size for the dierent streams and the QoS rate adjust value should
be the highest overhead size from among the various streams within that queue.
Consider the example where you have congured WDRR and shaping on a queue that has two dierent trac streams, TS1 and TS2, that
uses preamble, SFD, and IFG overhead elds:
• If the IFG in TS1 uses 16 bytes, QoS rate adjust value should be 24 (preamble + SFD requires 8 bytes and IFG 16 bytes).
• If the IFG in TS2 uses 12 bytes, QoS rate adjust value should be 20 (preamble + SFD requires 8 bytes and IFG 12 bytes).
In this case, the highest QoS rate adjust value between the two streams is 24 bytes. Hence, you must congure the QoS rate adjust value
as 24.
NOTE: This feature is not supported on the S4200-ON Series and S5148F-ON platforms.
Buer management
OS10 devices distribute the total available buer resources into two buer pools at ingress direction and three buer pools at egress
direction of all physical ports.
All ports in a system are allocated a certain amount of buers from corresponding pools based on the conguration state of each priority-
group or queue. The remaining buers in the pool are shared across all similarly congured ports.
The following buer pools are available:
• Ingress buer pools:
– Lossy pool (default)
– Lossless pool (PFC)
• Egress buer pools:
– Lossy pool (default)
– Lossless pool (PFC)
– CPU pool (CPU control trac)
For example, when all ports are allocated as reserved buers from the lossy (default) pool, the remaining buers in the lossy pool are
shared across all ports, except the CPU port.
When you enable priority ow control (PFC) on the ports, all the PFC-enabled queues and priority-groups use the buers from the lossless
pool.
OS10 dedicates a separate buer pool for CPU trac. All default reserved buers for the CPU port queues are from the CPU pool. The
remaining buers are shared across all CPU queues. You can modify the buer settings of CPU queues.
You can congure the size of the CPU pool using the control-plane-buffer-size command.
OS10 allows conguration of buers per priority-group and queue for each port.
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