SMC Networks WPCI-G - annexe 1, Management Manual

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12-1
C
HAPTER
12
C
LASS OF
S
ERVICE
Class of Service (CoS) allows you to specify which data packets have
greater precedence when traffic is buffered in the switch due to
congestion. This switch supports CoS with eight priority queues for each
port. Data packets in a port’s high-priority queue will be transmitted before
those in the lower-priority queues. You can set the default priority for each
interface, and configure the mapping of frame priority tags to the switch’s
priority queues.
Layer 2 Queue Settings
Setting the Default Priority for Interfaces
You can specify the default port priority for each interface on the switch.
All untagged packets entering the switch are tagged with the specified
default port priority, and then sorted into the appropriate priority queue at
the output port.
Command Usage
• This switch provides eight priority queues for each port. It uses
Weighted Round Robin to prevent head-of-queue blockage.
• The default priority applies for an untagged frame received on a port set
to accept all frame types (i.e, receives both untagged and tagged frames).
This priority does not apply to IEEE 802.1Q VLAN tagged frames. If
the incoming frame is an IEEE 802.1Q VLAN tagged frame, the IEEE
802.1p User Priority bits will be used.
• If the output port is an untagged member of the associated VLAN, these
frames are stripped of all VLAN tags prior to transmission.