This Recommendation describes the requirement for a peer-to-peer content delivery network (P2P CDN). It specifies the overall functional architecture, domains and functional role relationships, functional blocks and their mutual relationships, service provision requirement, availability requirement, scalability requirement and security considerations. P2P CDN provides a scalable and elastic CDN function pool of shareable terminal devices computing resources, storage resources and uplink bandwidth to save loads of current CDN and improve user experience.