Chapter 16: Quality of Service (QoS) (CLI)
Configuring Scheduling (CLI)
phn-3963_008v000
Page 16-38
Configuring Scheduling (CLI)
This section includes:
•
Overview of Egress Scheduling (CLI)
•
Configuring Queue Priority (CLI)
•
Configuring Interface Priority Profiles (CLI)
•
Attaching a Priority Profile to an Interface (CLI)
•
Configuring Weighted Fair Queuing (WFQ) (CLI)
Overview of Egress Scheduling (CLI)
Egress scheduling is responsible for transmission from the priority queues. PTP 850 uses a unique algorithm with a
hierarchical scheduling model over the three levels of the egress path that enables compliance with SLA
requirements.
The scheduler scans all the queues over all the service bundles, per interface, and determines which queue is ready
to transmit. If more than one queue is ready to transmit, the scheduler determines which queue transmits first
based on:
•
Queue Priority
– A queue with higher priority is served before lower-priority queues.
•
Weighted Fair Queuing (WFQ)
– If two or more queues have the same priority and are ready to transmit, the
scheduler transmits frames from the queues based on a WFQ algorithm that determines the ratio of frames
per queue based on a predefined weight assigned to each queue.
Configuring Queue Priority (CLI)
A priority profile defines the exact order for serving the eight priority queues in a single service bundle. When you
attach a priority profile to an interface, all the service bundles under the interface inherit the profile.
The priority mechanism distinguishes between two states of the service bundle:
•
Green State – Committed state
•
Yellow state – Best effort state
Green State refers to any time when the service bundle rate is below the user-defined CIR. Yellow State refers to
any time when the service bundle is above the user-defined CIR but below the PIR.
You can define up to four Green priority profiles, from 4 (highest) to 1 (lowest). An additional four Yellow priority
profiles are defined automatically and cannot be changed or edited.
The following table provides a sample of an interface priority profile. This profile is also used as the default
interface priority profile.
Table 149
Interface Priority Profile Example
