Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring QoS (Rev. 03)
Overview
© 2008 Foundry Networks, Inc.
Page 6 of 62
Figure 3: Type of Service (ToS) Header Fields
When a packet arrives at the device on an ingress port, the device examines the first six of eight
ToS bits, called the
code poin
t. The device can assign the QoS priority used to subsequently
transmit the packet based on the code point. The QoS priority controls a hardware queue used
when transmitting the packet out of the device, and determines the forwarding characteristics of a
particular code point.
An advantage in using marking of The DSCP field is that the class of service information can be
carried throughout the network infrastructure, without repeating complex traffic policies at each
device location. Another advantage is that end stations can perform their own packet marking on
an application-specific basis. The application software can observe and manipulate the DSCP
information with no performance penalty.
The mapping of DSCP values can be done by using the Access Control List feature. For more
information on how to use the Access Control List (ACL) to employ QoS on the device, see
chapter “
Configuring Access Control Lists (ACL)”
.
MAC-Based Traffic Grouping
QoS priority values can be assigned to packets destined for a specific MAC address.
The MAC address options, defined below, are as follows:
•
For static and secured MAC addresses, this can be done by using the
qos mac
command in
Global Configuration mode. This command creates a static MAC address with the specified
priority.
•
For dynamic MAC addresses, the MAC address inherits the priority from the port on which it
was learned.
The priority on the port is configured by the
qos priority
command in Interface Configuration
mode.