Port Scheduler Policies - Alcatel-Lucent 7210 SAS M OS Quality Of Service Manual

QoS Overview

Port Scheduler Policies

Port scheduler policies control the traffic behavior on a per-port basis. Associated with each egress
port is a set of eight class of service (CoS) queues and a default port-scheduler-policy named
"default". This default policy makes the port to behave in strict mode. The default policy cannot be
modified. The user can attach another policy to the port to change its scheduling behavior.
Providing the arbitration across these eight CoS queues is a scheduler that may be configured in a
variety of modes. A major aspect of the arbitration mechanism is the ability to provide minimum
and maximum bandwidth guarantees. This is accomplished by tightly integrating into the
scheduler a network queue and access egress policies. After the packets are mapped into a cos
queue, they are forwarded/conditioned using one of these schedulers (such as Strict Priority (SP),
Round-Robin (RR), Weighted Round-Robin (WRR), Weighted Deficit Round-Robin (WDRR),
WRR+SP, WDRR+SP). The traffic shaping aspect is tightly integrated with the scheduler.
Scheduler Modes
The scheduling modes interact with the minimum and maximum bandwidth CoS queue and
maximum bandwidth egress port shaping specifications. Each egress port may be configured to
have a specific scheduling mode. The scheduler first services the queues to meet their CIR and
then services the queues to meet the PIR. There are five possibilities as follows:
•
Table 28: Minimum and Maximum Bandwidth Meters Example
QoS Queue Name
Page 68
Strict priority scheduling across CoS queues — The strict priority scheduler provides strict
priority access to the egress port across the CoS queue from highest CoS queue index (7)
to the lowest (0). The purpose of the strict priority scheduler is to provide lower latency
service to the higher CoS classes of traffic. In this mode, the scheduler services the queues
in order of their prority in both the CIR and PIR loop.
Minimum Bandwidth
7
6
5
4
3
2
1
0
Maximum Bandwidth
10 Mbps
10 Mbps
50 Mbps
50 Mbps
50 Mbps
50 Mbps
50 Mbps
50 Mbps
7210 SAS M OS Quality of Service Guide
1 Gbps
1 Gbps
1 Gbps
1 Gbps
1 Gbps
1 Gbps
1 Gbps
1 Gbps