C613-16120-00 REV A
www.alliedtelesis.com
AlliedWare Plus
TM
OS
Overview of |
Introduction
This How To Note describes the main features of QoS on switches running the
AlliedWare Plus OS. The main features include:
z
Prioritisation and marking
Right at the point of ingress into the QoS process, packets classified to particular class
maps can have values written to one or more of their associated “markers”. The markers
can be externally visible fields (DSCP value, 802.
1
p value) and/or internally visible fields
(bandwidth class and queue number). These markers are explained in
"Packet markers" on
page 4
.
z
Policing
Packets belonging to any given class map can be assigned a colour (bandwidth class) based
on whether they are inside or outside the bandwidth limits set for that class map. The
packets are marked with the colour that was applied to them, and at various points in the
QoS process, decisions on the packets' fate can be made on the basis of what colour they
have been marked with.
z
Remarking
After policing, remarking can update packets’ QoS markers depending on how well the
flow conforms to its bandwidth limits. For example, if a flow exceeds its bandwidth
requirements, QoS can update the packets’ DSCP values.
z
Per-port control over egress queue parameters
Queue lengths, scheduling process, relative weights, etc can be set on all queues on a per-
port basis.
z
Highly configurable default class map
All the parameters that can be set on a normal class map can also be set on the default
class map (the catch-all class map that matches all traffic that does not explicitly match any
other class map).
Quality of Service Features on x900-
1
2,
x900-24, and SwitchBlade x908 Switches
