Recommendation ITU-T H.644.1 describes a functional architecture for a virtual content delivery network (VCDN). It specifies the overall functional architecture, domains and functional role relationships, functional blocks, reference points, relationships between physical resources, virtual resources and logically isolated network partitions (LINPs), functions and their mutual relationships, and security considerations. VCDNs can realize accurate infrastructure distribution and elastic resource scheduling. VCDNs can integrate the resources of a content delivery network (CDN), reduce construction costs and improve scalability.