FastNetMon community - very fast DDoS analyzer with sflow/netflow/mirror support - pavel-odintsov/fastnetmon

The Domain Name System (DNS) was designed to return matching records
     efficiently for queries for data that are relatively static.  When those
     records change frequently, DNS is still efficient at returning the
     updated results when polled, as long as the polling rate is not too
     high.
     But, there exists no mechanism for a client to be asynchronously
     notified
     when these changes occur.  This document defines a mechanism for a
     client to be notified of such changes to DNS records, called DNS Push
     Notifications.