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Quality of Service (QoS): Managing Bandwidth More Effectively
Using QoS Types To Configure QoS for Outbound Traffic
Figure 6-6. Example of a Type-of-Service Configuration Enabling Both Direct 802.1p Priority Assignment and
DSCP Policy Assignment
Assigning a DSCP Policy on the Basis of the DSCP in IPv4
Packets Received from Upstream Devices
The preceding section describes how to forward a policy set by an edge (or
upstream) switch. This option changes a DSCP policy in an IPv4 packet by
changing its IP ToS codepoint and applying the priority associated with the
new codepoint. (A DSCP policy consists of a differentiated services codepoint
and an associated 802.1p priority.) You can use this option concurrently with
the diffserv 802.1p priority option (above), as long as the DSCPs specified in
the two options do not match.
To use this option to configure a change in policy:
1. Identify a DSCP used to set a policy in packets received from an upstream
or edge switch.
2. Create a new policy by using qos dscp-map < codepoint > priority < 0 - 7 > to
configure an 802.1p priority for the codepoint you will use to overwrite
the DSCP the packet carries from upstream. (For more on this topic, refer
to “Differentiated Services Codepoint (DSCP) Mapping” on page 6-32.)
Notice that codepoints 000000 and 001001 are named as DSCP
policies by other codepoints (000001 and 000110 respectively). This
means they are not available for changing to a different 802.1p priority.
Outbound IP packets
with a DSCP of 000110
will have a priority of 7.
