I. Introduction
Although IP networks were designed to be best-effort, an increasing number of applications today require performance guarantees. These range from multimedia applications such as voice-over-IP, video, multi-player online gaming, to performance-critical enterprise applications such as online trading. ISPs often provide SLA guarantees to ensure that the performance of their network matches up with the expectations of their customers that want to run these applications. SLA violations typically have heavy financial implications for the ISP; ISPs, therefore, care deeply about ensuring the health of their network.