[ IANA | RFC 1918 | RFC 6304 | RFC 6305 | RootOps | AS112 Ops listing ]
Many private and some public networks generate PTR (reverse lookup) queries for RFC 1918 addresses, dynamic DNS updates and other ambiguous addresses, such as the ones below:
This happens because many of the same people running those networks neglect to run a DNS server of their own, or worse, simply don't enumerate their IP address use in both forward and reverse DNS zones. This creates many queries which are ultimately sent up to the root DNS server system which in turn responds with negative answers. So what? The problem is the load this creates on the overall global DNS system: As more devices with private addresses connect to the Internet, the higher the load becomes without properly administered DNS servers for those devices.
There are now separate (non-root) servers for answering these queries on behalf of the global DNS system, described here.
As a way to distribute the load across the Internet for RFC1918-related queries, we use IPv4 anycast addressing. The address block is
22.214.171.124/24 and its origin AS is
112. This address block is advertised from multiple points around the Internet, and these distributed servers coordinate their responses back to networks making those requests. These servers also co-ordinate back-end statistical analyses.
The people who run these anycast AS112 DNS servers are known as the AS112 operators. They operate these servers using a constellation of anycast DNS servers using a certain set of well-known addresses. The operations are described in greater detail through IETF RFC 6304 and RFC 6305.
An experiment using IPv6 is also under way to not only dual-stack AS112 but also to see about serving IPv6 zones that would qualify the same as their IPv4 counterparts.
A mailing list for AS112 operators is open. For subscription information, please visit the list website and follow the instructions.
Finally there are several important references which should be consulted by current and prospective AS112 operators and others with an interest in general subjects on AS112 and anycast DNS operations.