Digisol DG-FS4528P, Management Manual

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15
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 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.
This chapter describes the following basic topics:
Layer 2 Queue Settings – Configures each queue, including the default
priority, queue mode, queue weight, and mapping of packets to queues
based on CoS tags.
Layer 3/4 Priority Settings – Selects the method by which inbound
packets are processed (DSCP or CoS), and sets the per-hop behavior
and drop precedence for internal processing.
L
AYER
2 Q
UEUE
S
ETTINGS
This section describes how to configure the default priority for untagged
frames, set the queue mode, and map class of service tags to queues.
S
ETTING THE
D
EFAULT
P
RIORITY FOR
I
NTERFACES
Use the Priority > Default Port Priority or Default Trunk Priority page to
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.
CLI R
EFERENCES
"switchport priority default" on page 843
C
OMMAND
U
SAGE
This switch provides four 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.