Class of service, In this chapter, Layer 2 queue settings – Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual

Page 839: Setting the default priority for interfaces, Chapter 38

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Brocade 6910 Ethernet Access Switch Configuration Guide

789

53-1002581-01

Chapter

38

Class of Service

In this chapter

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.

CLI References

“switchport priority default”

on page 422

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 queueing.

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.

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