BT BT Azuki Systems Content Delivery Networks (CDNs) are commonly used for improving the End User experience of a content delivery service while keeping cost at a reasonable level. This document focuses on use cases that correspond to identified industry needs and that are expected to be realized once open interfaces and protocols supporting the interconnection of CDNs are specified and implemented. This document can be used to motivate the definition of the requirements to be supported by CDN Interconnection (CDNI) interfaces. It obsoletes RFC 3570. This document is not an Internet Standards Track specification; it is published for informational purposes.