Zeroconf

(redirected from Multicast DNS)

Zeroconf

(1) See zero configuration.

(2) (ZERO CONFiguration) An IETF specification that enables devices on an IP network to automatically configure themselves and be discovered without manual intervention. If required, Zeroconf can assign an IP address and alternate hostname to a device. Once assigned, Zeroconf lets users and applications readily discover the service it offers. Apple's Bonjour is the major implementation of Zeroconf (see Bonjour), and Porchdog Software's Howl (www.porchdogsoft.com) and freedesktop.org's Avahi (www.avahi.org) are other fine examples.

Automatic IP Address Assignment
If a device does not have an IP address and there is no DHCP server in the network, Zeroconf employs link-local addressing to create one. See link-local address and DHCP.

Name Handling and Discovery
The DNS Service Discovery (DNS-SD) protocol is used to identify and discover Zeroconf-enabled devices on the network. DNS-SD employs multicast DNS (mDNS), which sends packets to every node on the network for resolving duplicate hostnames that might occur and to query the network for services.

Port Forwarding (Port Mapping)
Zeroconf uses the NAT Port Mapping Protocol (NAT-PMP) to open ports in a router to let a party from the outside world contact a user inside the network. For example, opening ports for VoIP and videoconferencing traffic makes two-way communications easier no matter which side initiates the call. See TCP/IP port.

Zeroconf vs. UPnP
Zeroconf shares three functions with the Universal Plug and Play (UPnP) family of protocols: IP address assignment, service discovery and port forwarding. They both use link-local addressing for IP assignment, but different methods for discovery and port mapping. Zeroconf is noted for its greater simplicity, however. See UPnP and Bonjour.


Zeroconf and Bonjour
An excellent reference from O'Reilly covers Zeroconf in splendid detail. If you want the scoop on Bonjour, mDNS, DNS-SD and more, read "Zero Configuration Networking" by Stuart Cheshire and Daniel H. Steinberg. (O'Reilly Media, Inc. 2006, ISBN 0-596-10100-7).
References in periodicals archive ?
"This is achieved by obfuscating IP addresses with dynamically generated Multicast DNS (mDNS) names." The mDNS naming scheme falls under rfc6762, which spells out the benefits of an mDNS approach (go2sm.com/mdns).
The primary benefits of multicast DNS, as noted in the documentation for rfc6762, "are that (i) they require little or no administration or configuration to set them up, (ii) they work when no infrastructure is present, and (iii) they work during infrastructure failures."
Includes inter-VLAN routing, DHCP for each VLAN, DNS for VLANs, multicast DNS (Bonjour), RADIUS enterprise authentication, and VLAN firewalls.
Apple has made the source code of the Bonjour multicast DNS responder, the core component of service discovery, available as a Darwin open source project.

Full browser ?