Allied Telesis at-8516f User Guide

Software Release 2.6.1
C613-02025-00 REV C

Once the Forwarding Process has determined which ports and transmission 
queues to forward a frame from, the Egress Rules for each port determine 
whether or not the outgoing frame is VLAN-tagged with its numerical VLAN 
Identifier (VID). (See “Virtual Local Area Networks (VLANs)” on page 74).

When a port is added to a VLAN, it is configured to transmit either untagged 
or VLAN tagged packets, using the command:

ADD VLAN={vlanname|1..4094} PORT={port-list|ALL} 

[FRAME={TAGGED|UNTAGGED}]

This setting can be changed for a port which is already part of a VLAN, using 
the command:

SET VLAN={vlanname|1..4094} PORT={port-list|ALL} 

FRAME={UNTAGGED|TAGGED}

The switch hardware has a number of Quality of Service (QOS) egress queues 
that can be used to give priority to the transmission of some frames over other 
frames on the basis of their user priority tagging. The user priority field in an 
incoming frame (with value 0 to 7) determines which of the eight priority levels 
the frame is allocated. When a frame is forwarded, it is sent to a QOS egress 
queue on the port determined by the mapping of priority levels to QOS egress 
queues. All frames in the first QOS queue are sent before any frames in the 
second QOS egress queue, and so on, until frames in the last QOS egress queue, 
which are only sent when there are no frames waiting to be sent in any of the 
higher QOS egress queues.

The mapping between user priority and a QOS egress queue can be configured 
using the command:

SET SWITCH QOS=P0,P1,P2,P3,P4,P5,P6,P7 

The switch has four QOS egress queues. It has a default mapping of priority 
levels to QOS egress queues as defined in IEEE Standard 802.1Q (Table 13).

0

1

1

0

2

0

3

1

4

2

5

2

6

3

7

3