The IETF Committee (Internet Engineering Task Force), which develops the protocols and architecture of the Internet, formation of an RFC for the "DNS Push Notifications" mechanism and published the specification associated with it under the identifier . RFC received the status of "Proposed Standard", after which work will begin on giving RFC the status of a draft standard (Draft Standard), which actually means the complete stabilization of the protocol and taking into account all the comments made.
The "DNS Push Notification" mechanism allows the client to asynchronously receive notifications from the DNS server about changes in DNS records, without the need to periodically poll them. Push notifications are processed only using the TCP transport with communication channel security using "TLS over TCP". An authoritative DNS server can accept TCP connections from DNS Push Notification clients that send subscription requests to specific DNS record names and types. After receiving a subscription request, the server itself will send notifications to the client about changes to the specified records.
The client determines whether DNS Push Notification is supported by sending a regular DNS query that checks for the existence of the "_dns-push-tls._tcp.zone_name" SRV record that points to the DNS servers serving the subscriptions. The client can also subscribe to a non-existent entry, and the server must notify the client if one appears in the future. Notifications are sent only when there is an established TCP connection with the server and are not designed to be monitored 24 hours a day, 7 days a week - the subscription should be canceled when inactive (for example, when the device goes into standby mode) and used only when there is a direct need to track changes in live mode. Regular DSN requests can also be sent through the TCP channel set for push notifications.
Source: opennet.ru