We tackle the problem of enabling Autonomous Systems (ASes) to evaluate network providers on the basis of their adherence to Service Level Agreements (SLAs). In current Internet practices, choices of interconnection partners are driven by factors such as word of mouth, personal relationships, brand recognition and market intelligence, and not by proofs of previous performance. Given that Internet eXchange Points provide increasingly more peering choices, rudimentary schemes for picking interconnection partners are not adequate anymore. Although the current interconnection ecosystem is shrouded in confidentiality, our key observation is that recently emerged blockchain technology and advances in cryptography enable a privacy-preserving decentralized solution based on actual performance measurements. We propose the concept of SLA score to evaluate network providers and introduce a privacy- preserving protocol that allows networks to compute and verify SLA scores.