The commonBehaviors section can only be defined in the machine.config file. It defines two child collections named endpointBehaviors and serviceBehaviors. Each collection defines behavior elements consumed by all WCF endpoints and services on the machine respectively. Behaviors defined in endpointBehaviors are only applied to clients, and behaviors defined in serviceBehaviors are only applied to services. If a behavior is defined in both commonBehaviors and behaviors sections, the behavior in the behaviors section is given preference.