Allied Telesis AT-S63 - Manual (Page 227)

AT-S63 Management Software Menus Interface User’s Guide
Section II: Advanced Features 227
Configuring CoS
As explained in ”Quality of Service Overview” on page 222, a tagged
packet received on a port is placed it into one of four priority queues on
the egress port according to the switch’s mapping of 802.1p priority
levels to egress priority queues. The default mappings are shown in
Table 8, ”Default Mappings of IEEE 802.1p Priority Levels to Priority
Queues” on page 223. These mappings apply at the switch level.
However, you can override the mappings at the port level so that all
tagged packets are placed into a specific egress priority queue
regardless of the priority level in the packets themselves.
Note that this determination is made when a packet is received on the
ingress port and before the frame is forwarded to the egress port.
Consequently, configuring this feature on a switch port influences the
ingress frames.
For example, when you configure a switch port so that all ingress tagged
frames are handled by the egress priority queue Q2, all tagged frames
received on the port are directed to the Q2 priority egress queue on the
egress ports, regardless of the priority levels in the packets themselves.
You can also use CoS to control which priority queue handles untagged
frames that ingress a port. By default, untagged frames (that is, frames
without VLAN or priority level information) are automatically assigned to
Q0, the lowest priority queue. But you can configure CoS on a port so
that all untagged frames received on the port are directed to one of the
other queues.
To configure CoS for a port, perform the following procedure:
1. From the Main Menu, type 7 to select Quality of Service (QoS)
Configuration.