qos

Brief and clear step by step definition of COS process.

Packet Flow Through the Junos OS CoS Process Overview

Full brochure.

Junos® OS Class of Service Feature Guide for Routing Devices

By the way, few epic black books about network testing/validation methodology from Ixia.

Ixia Black Book - Video over IP
Ixia Black Book - Advanced MPLS
Ixia Black Book - QoS Validation