Exemplified system and method optimizes dynamic Quality of Service (QoS) operation across a network infrastructure to alleviate time constraints when applying dynamic QoS policy on newly initiated traffic flow, particularly for various data streams. Initially, and by default, the exemplified system and method temporarily applies a high QoS policy to a newly initiated traffic flow and then verifies the QoS legitimacy of the flow to which the high QoS policy for the newly initiated traffic flow is maintained or is reduced to a lower-priority QoS policy. This trust-but-verify QoS operation allows new traffic, e.g., with voice and video components, to receive a high QoS PHB treatment as transmission of the traffic is initiated without having a nominal delay at the beginning of the call before QoS is applied while allowing the QoS legitimacy to be validated and maintained.