A common method for dealing with unwanted traffic is to direct that traffic at nominated addresses within a network that are null-routed; that is, packets with such destination addresses are discarded silently by routers with a null route for that destination configured. These addresses are colloquially known as black holes, by analogy with the same term used in astrophysics to describe a void in spacetime where gravity prohibits anything from escaping once having crossed the event horizon. Alternatively, traffic may be redirected to quarantine, to isolate, contain and limit any potentially harmful effects. Quarantine addresses may permit some bidirectional communications whereas a black hole may receive, but never originate traffic.
This document describes an Internet-scope anycast black hole and quarantine service with associated well-known, permanent IPv4 and IPv6 address assignments, and provides guidance both for network operators and for those wishing to use the service to discard unwanted traffic efficiently.