Zeroing in on instant networks

It’s no secret that network configuration is responsible for keeping a lot of IT people busy from one day to the next. Before rise to prominence , network devices were designed to require a minimum amount of manual intervention; protocols such as IPX were designed around device-unique addresses that were burned into the network interface itself. In today’s IPv4-focused world, addresses are in short supply, and configuring a device requires manually entering three or four pieces of information, or using a well-maintained DHCP server.

This, of course, is a pain to anyone who’s had to support remote or smaller offices lacking the budget for any IT staff of its own. The simple answer is to build an infrastructure for IP that removes the need for configuration, but until recently, that was a pipedream.

It’s not surprising that Apple has a headstart in the race to zero-configuration networking, given that the company’s proprietary AppleTalk protocol required even less configuration than did IPX. Thus, the company’s announcement last September of its Rendezvous technology built on commonly accepted standards including ARP (Address Resolution Protocol) and DNS, and currently kicking around the ( ) in draft standard form piqued our interest.

In brief, network devices that understand zero-configuration networking methods such as Rendezvous use the 164.254/16 address space, which is reserved for so-called link-local IP addresses; these are most often seen by support staff and users when a conventional DHCP server is unavailable. Devices assign themselves a link-local address and, using ARP or another method, verify that this address is indeed unused. Services provided by the device (file, print, etc.) are then advertised in a DNS variant referred to as ( ), and each host builds its own mDNS resolution table as devices add or remove themselves from the network.

As we noted, zero-configuration networking is ideal for small-office situations or transient networking environments. But can it save larger organizations money? Probably not because one, it isn’t here yet for the non-Apple world and two, after one gets to about 1,300 hosts on a single network, the time required to find a usable link-local address becomes an issue, in the view of the authors of one of the IETF drafts on the subject.

While zero-configuration networking might well reduce the complexity of networking at the desktop level, it won’t be putting a generation of network managers on the street.