Description Markus Kuppe 2010-08-06 05:23:00 EDT

"Internet Draft           Dynamic DNS Update Leases      10th August 2006
1. Introduction
   Dynamic DNS Update [RFC 2136] allows for a mapping from a persistent
   hostname to a dynamic IP address. This capability is particularly
   beneficial to mobile hosts, whose IP address may frequently change
   with location. However, the mobile nature of such hosts often means
   that dynamically updated resource records are often not properly
   deleted. Consider, for instance, a mobile user who publishes address
   records via dynamic update. If this user unplugs the Ethernet cable
   from their laptop, the address record containing stale information
   will remain on the server indefinitely.  "DNS Scavenging" attempts to
   address this issue by configuring clients and servers with a preset
   refresh interval, however, this approach does not extend to
   zero-configuration environments in which the client and server are
   not under the same administration. An extension to Dynamic Update is
   thus required to tell the server to automatically delete resource
   records if they are not refreshed after a period of time." [0]
   
An alternative is to do this in the provider by using something like a deregister thread. However and implementation following the given spec is greatly superior.
   
[0] http://files.dns-sd.org/draft-sekar-dns-ul.txt