IPv6 packets are forwarded by paths that are different from those for IPv4. QoS features supported for IPv6 environments
include packet classification, queuing, traffic shaping, weighted random early detection (WRED), class-based packet marking,
and policing of IPv6 packets. These features are available at both the process switching and Cisco Express Forwarding switching
paths of IPv6.
All of the QoS features available for IPv6 environments are managed from the modular QoS command-line interface (MQC). The
MQC allows you to define traffic classes, create and configure traffic policies (policy maps), and then attach those traffic
policies to interfaces.
To implement QoS in networks that are running IPv6, follow the same steps that you would follow to implement QoS in networks
running only IPv4. At a very high level, the basic steps for implementing QoS are as follows:
Know which applications in your network need QoS.
Understand the characteristics of the applications so that you can make decisions about which QoS features would be appropriate.
Know your network topology so that you know how link layer header sizes are affected by changes and forwarding.
Create classes based on the criteria that you establish for your network. In particular, if the same network is also carrying
IPv4 traffic along with IPv6 traffic, decide if you want to treat both of them the same way or treat them separately and specify
match criteria accordingly. If you want to treat them the same, use match statements such as
precedence , and
dscp . If you want to treat them separately, add match criteria such as
ipv6 in a match-all class map.
Create a policy to mark each class.
Work from the edge toward the core in applying QoS features.
Build the policy to treat the traffic.
Apply the policy.