HTTP/2: server push. Resources to be pushed are configured with the "http2_push" directive. Also, preload links from the Link response headers, as described in https://www.w3.org/TR/preload/#server-push-http-2, can be pushed, if enabled with the "http2_push_preload" directive. Only relative URIs with absolute paths can be pushed. The number of concurrent pushes is normally limited by a client, but cannot exceed a hard limit set by the "http2_max_concurrent_pushes" directive.