Determine whether the device needs to support different
traffic streams, such as voice or video. If so, CoS helps to make
sure this traffic receives more than basic best-effort packet delivery
service.
Determine whether the device is directly attached to any
applications that send CoS-classified packets. If no sources are enabled
for CoS, you must configure and apply rewrite rules on the interfaces
facing the sources.
Determine whether the device must support assured forwarding
(AF) classes. Assured forwarding usually requires random early detection
(RED) drop profiles to be configured and applied.
Determine whether the device must support 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.
