C
LASS
OF
S
ERVICE
C
ONFIGURATION
2-87

Class of Service Configuration

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 four 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.
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 four priority queues for each port. It uses
Weighted Round Robin to prevent head-of-queue blockage.
• The default priority applies if the incoming frame is an
untagged frame received from a VLAN trunk or a static-access
port. 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.
b_mgmt.book Page 87 Tuesday, July 8, 2003 5:24 PM