tools for traffic engineering networks

Hi there, I'm curious to know what tools (in traffic engineering arena) people use in order to manage and verify their service assurance that they are providing and / or receiving they think they are. How do you know the policers are functioning correctly? How do you know whether your service provider and / or your internal traffic is not being over-book? Any recommendations, thoughts, white papers, pointers will be greatly appreciated. regards, /vicky