Today, IP networks are required to provide secure, predictable, measurable, and guaranteed services for business-critical applications. Quality of Service (QoS) is an infrastructure data-plane feature that will enable support of multiple services such as video, voice, and mission-critical data. Achieving the required level of QoS by managing delay, delay variation (a.k.a. jitter), bandwidth, and packet loss parameters on a network enables an end-to-end business solution. DSCP marking of a packet is being used by IP service providers to differentiate different types of services such as video, voice, vs. best effort data services. Queuing and congestion avoidance mechanisms, such as WRR and WRED, are used to treat packets differently with distinct DSCP markings. Filtering based on DSCP marking is also being employed to provide additional layer of security. As a consequence, change of a packet?s DSCP marking can have adverse effect on the treatment the packet will experience along its flight path to destination. The packet can even get discarded because of the ?incorrect? marking due to unintentional or malicious change. Video and voice traffic are sensitive to packet loss and delay/jitter. It requires consistent DSCP marking once it enters a service provider?s network.