On the Internet today, a growing number of QoS sensitive network applications exist, such as VoIP, imposing more stringent requirements on ISPs besides the basic reachability assurance. Thus, the demand on ISPs for Service Level Agreements (SLAs) with better guarantees is increasing. However, despite overprovisioning in core ISP networks, resource contention still exists leading to congestion and associated performance degradations. For example, residential broadband networks rate-limit or even block bandwidth intensive applications such as peer-to-peer file sharing thereby violating network neutrality. In addition, traffic associated with specific applications, such as Skype, could also be discriminated against for competitive business reasons. So far, little work has been done regarding the existence of traffic discrimination inside the core of the Internet. Due to the technical challenges and widespread impact, it seems somewhat inconceivable that ISPs are performing such fine-grained discrimination based on the application content. Our study is the first to demonstrate evidence of network neutrality violations within backbone ISPs. We used a scalable and accurate monitoring system – NVLens – to detect traffic discrimination based on various factors such as application types, previous-hop, and next-hop ASes. We discuss the implication of such discrimination and how users can counter such unfair practices.