Priority Queuing - Allied Telesis SwitchBlade x3100 Series Manual

Introduction

6.7 Priority Queuing

6.7.1 Overview
A priority may be set on the p-bit ingress (by a remarking action on a classifier), and then that priority is used
throughout the system at each egress queue. Tagged traffic retains its p-bit settings if it is not remarked and
untagged traffic receives a p-bit setting of 0 if not remarked. The values in the SET QoS VLANQUEUEMAP
command accept a queue number (0 = lowest priority; higher numbers = higher priority).
There are two system settings which indicate which egress queue a packet is inserted into based on the p-bit
value of the packet, one for 4 queues and one for 8 queues. There is one system setting for supporting 4 egress
queues and one for supporting 8 egress queues. (For the SBx3112, there are always 8 queues.)
The user can map the 4 queue and 8 queue settings. The system will validate the attempted settings and will
not allow the user to provision conflicting values for the 4 queue and 8 queue map settings. Conflicting values
are those that give a different relative priority for any particular p-bit when comparing each set of values. For
example:
If the user entered 3,3,0,0,2,2,1,1 and 6,7,1,0,4,5,3,2 for the 4 and 8 queue map respectively, this would be valid
as both settings order the p-bit in the relative priority order of p-bit 3,2,7,6,4,5,0,1.
However, if the user had entered 3,3,0,3,2,2,1,1 and 6,7,1,0,4,5,3,2 for the 4 and 8 queue map respectively, it
would be rejected by the system as p-bit 3 has a different relative priority in each p-bit to queue map.
p-bit values range from 0, lowest priority, to 7, the highest priority. Only strict priority (SP) is supported.
Weighted round robin (WRR) scheduling or any other scheduling algorithm is not supported.
The user can provision and display the p-bit to queue mappings for the system with
The value-map is a list of eight integers, 0-7 for the VLAN8QUEUEMAP. The "eight" is the number of p-bit val-
ues which is independent of the number of queues.
show qos
--- Quality of Service Queue Mapping ------------------------------------
Priority Level
-------------- ---------------------------------------------------------
p-bit value 8 Queue Capable Interface
-------------- ------------------------------- -------------------------
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
6-68
Software Reference for SwitchBlade x3100 Series Switches (Access and Security)
QoS Egress Queue
4 Queue Capable Interface
0
0
1
1
2
2
3
3
Overview
SET QOS, SHOW QOS