Outline Of The Qos Processing Flow; Initial Mapping To An Egress Queue, Based On 802.1P Value - Allied Telesis AlliedWare Plus Overview

Outline of the QoS processing flow

Let's look at each QoS process in the order that they are applied to a packet. The following
figure gives a quick view of the QoS features we are about to discuss.
Initial mapping to an egress queue, based on 802.1p
value
Immediately after ingress, a VLAN-tagged Ethernet frame can be assigned to the appropriate
egress queue on the basis of the value of its VLAN Tag User Priority. This means that
incoming frames that already carry meaningful priority information can be forwarded on the
basis of that information. The mapping of the User Priority value to an egress queue is
configurable, so the administrator can decide, for example, to send frames with a Priority
value of 7 to queue 3 and frames with a Priority of 2 to queue 7.
Untagged frames don't have a VLAN Tag User Priority, so these frames can be assigned to a
default queue of the administrator's choice.
The net effect of this process is to set a value on the Egress Queue marker that the packet is
carrying.
Page 5 | AlliedWare Plus™ OS: Overview of QoS
Packet
Ingress port
Tagged: priority mapped to queue
Untagged: mapped to default queue
Ingress
Classification using ACLs
Premarking
Remarking
Limiting (dropping non-conformant)
Egress
Queue shaping
Queue emptying and egress
Policing
QoS4.eps