Before You Begin

Before you begin configuring a Services Router for CoS with DiffServ, complete the following tasks:

• If you do not already have a basic understanding of CoS and DiffServ, read Policy, Firewall Filter, and Class-of-Service Overview.
• Determine whether the Services Router needs to support different traffic streams, such as voice or video. If so, CoS with DiffServ helps to make sure this traffic receives more than basic best-effort packet delivery service.
• Determine whether the Services Router is directly attached to any applications that send DiffServ packets. If no sources are enabled for DiffServ, you must configure and apply rewrite rules on the interfaces to the sources.
• Determine whether the Services Router must support DiffServ assured forwarding (AF) classes. Assured forwarding usually requires random early detection (RED) drop profiles to be configured and applied.
• Determine whether the Services Router must support DiffServ expedited forwarding (EF) classes with a policer. Policers require you to apply a burst size and bandwidth limit to the traffic flow, and set a consequence for packets that exceed these limits—usually a high loss priority, so that packets exceeding the policer limits are discarded first.