The mDNSResponder project is a component of Bonjour, Apple's ease-of-use IP
networking initiative: <http://developer.apple.com/bonjour/>

Apple's Bonjour software derives from the ongoing standardization work of the
IETF Zero Configuration Networking Working Group: <http://zeroconf.org/>

The Zeroconf Working Group has identified three requirements for Zero
Configuration Networking:
1. An IP address (even when there is no DHCP server to assign one)
2. Name-to-address translation (even when there is no DNS server)
3. Discovery of Services on the network (again, without infrastucture)

Requirement 1 is met by self-assigned link-local addresses, as
described in "Dynamic Configuration of IPv4 Link-Local Addresses"
<http://files.zeroconf.org/draft-ietf-zeroconf-ipv4-linklocal.txt>

Requirement 2 is met by sending DNS-like queries via Multicast (mDNS).

Requirement 3 is met by DNS Service Discovery (DNS-SD).

Self-assigned link-local address capability has been available since
1998, when it first appeared in Windows '98 and in Mac OS 8.5.
Implementations for other platforms also exist.