From Apple's web site...
(http://developer.apple.com/darwin/projects/rendezvous/)

Rendezvous

Rendezvous is a revolutionary networking technology that lets you create an
instant network of computers and devices without any configuration, allows
the services and capabilities such as file sharing and printing of each
device to be registered on the network, and allows these services to be
dynamically discoverable by other devices on the network. Rendezvous
enables this seamless networking and service discovery over the standard
and ubiquitous IP networking protocol.

On Jaguar systems the main components of Rendezvous are:

* link-local addressing which is established as part of a systems IP
configuration

* Service Registration is done by the client that is registering service
(ex: file server, printer, iChat user)

* Service Discovery is handled by the client application that browses the
network looking for services (ex: printing, iChat)

For more information, see the Rendezvous Developer Support page.

Source Code

If you have registered with this site, you can download the source code
components of Rendezvous:

* Multicast DNS Responder (mDNSResponder), the component that listens for
and responds to DNS-format query packets, sent via IP Multicast to UDP port
5353.

* IP configuration (the bootp project, which also handles DHCP and
link-local addressing)

* The lower level C APIs to allow servers and clients to communicate with
the mdns subproject of Libinfo

CVS users can check out the mDNSResponder module from CVS to get the latest
Rendezvous code.