Class of Service
119
Instruction Manual - NXA-ENET8-POE+
Class of Service
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.
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.
Layer 2 Queue Settings
This section describes how to configure the default priority for untagged frames, set the queue mode, set the weights assigned to
each queue, and map class of service tags to queues.
Setting the Default Priority for Interfaces
Use the Traffic > Priority > Default 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.
Command Usage
This switch provides eight priority queues for each port. It uses Weighted Round Robin to prevent head-of-queue blockage,
but can be configured to process each queue in strict order, or use a combination of strict and weighted queuing.
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.
The following table lists the options on this page:
Perform these steps to configure the queue mode:
1.
Click
Traffic
>
Priority
>
Default Priority
.
2.
Select the interface type to display (Port or Trunk).
3.
Modify the default priority for any interface.
4.
Click
Apply
.
Traffic - Priority (Default Priority) Options
Interface
Displays a list of ports or trunks.
CoS
The priority that is assigned to untagged frames received on the specified interface. (Range: 0-7;
Default: 0)
FIG. 131
Setting the Default Port Priority