Support for Layer 3 Differentiated Services is relegated primarily to traditional software-based routers. Once a traffic flow has been defined in the policy server and identified by the switching or routing hardware, a number of actions can be applied to that flow. The role of a particular router interface describes how that router interface will enforce an action. For some vendors, such as Extreme and Lucent, the role applies to the entire device. For others, such as HP, roles cannot be configured in their current software release.
Roles affect traffic only when the network is congested.
These parameters are the most important for defining your network application behavior, but their effects are the most difficult to measure. Roles were best supported by Cisco, IPHighway, and Orchestream. Every vendor whose products we tested plans to roll out support for these features in a future release.