Zeroconf

Zeroconf or Zero Configuration Networking is a planned IETF protocol for dynamic configuration of network nodes in an IP network. The standard is still in the works, and no RFC documents have been released by the working group as of 2004, though several implementations of the protocol already exist.

A main idea of Zeroconf is that it should be possible to connect two computers with a cross-over Ethernet cable and have them communicating without any extra configuration. Currently, this operation will typically involve a lot of manual configuration.

The goal is thus to obtain functioning IP networking, without dependence on infrastructure (DHCP server, DNS server, etc.) or expert knowledge (e.g. RFC 1918 addressing). Zeroconf was initially pioneered by Apple as part of Apple's transition from AppleTalk to IP; it is now adopted by many makers of network devices. One good example is network printers. Printers have no screen or keyboard for users to enter IP addresses and subnet masks, so they pretty much have to set themselves up automatically if normal humans are to use them. Almost all network printers available today implement Zeroconf networking.

Apple Computer renamed its initial implementation of the Zeroconf protocol to Apple Rendezvous. Industry watchers suspect that it will be renamed again as a result of a lawsuit with Tibco.

Zeroconf components

Zeroconf builds on many independently-developed ideas:

• Automatic allocation of link-local IPv4 addresses in the 169.254.0.0/16 range, to avoid configuration of IP addresses.
• Distributed multicast DNS (http://www.multicastdns.org/) lookups, allowing each node to be responsible for managing its own names without a central DNS server.
• DNS SRV records (as described in RFC2782 (ftp://ftp.rfc-editor.org/in-notes/rfc2782.txt)) allow a decoupling of names of services from the names of the machines they run on, or even the port numbers they use. DNS service discovery (http://www.dns-sd.org/) adds another level of indirection to this using PTR records, thereby allowing users to browse for available services, without having to know their names to begin with.

External links

• http://www.zeroconf.org/ - working group (also IETF page (http://www.ietf.org/html.charters/OLD/zeroconf-charter.html))
• http://zeroconf.sourceforge.net/ - Zeroconf for Unix and Linux

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