On a desktop Debian Jessie GNU/Linux install, the file /etc/resolvconf/update-libc.d/avahi-daemon
contains:
#!/bin/sh
#
# If we have an unicast .local domain, we immediately disable avahi to avoid
# conflicts with the multicast IP4LL .local domain
if [ -x /usr/lib/avahi/avahi-daemon-check-dns.sh ]; then
exec /usr/lib/avahi/avahi-daemon-check-dns.sh
fi
However, neither man avahi-daemon.conf
nor man avahi-daemon
mention IP4LL.
Wikipedia does not currently mention IP4LL.
Web searches show few hits. This page in the Tin Hat GNU/Linux "Quickstart" manual gives a little information:
Tin Hat assumes that your system has up to four NIC cards, eth0 through eth3. It will try to configure each one using DHCP first and, failing that, will assign an IP4LL address. ...
A thread on the avahi-autoipd mailing list gives a bit more information:
Avahi 0.6.14 will ship with its own implementation of IP4LL (rfc3927). ...
However, RFC 3927 has no mention of the term "IP4LL". It does, however, use the term "IPv4 Link-Local".
Also, the blurb for Cozybit's "Zeroconf module" refers to "IP4LL (Link Local)".
Unfortunately, none of this seems very definitive. Hence my question: what is "IP4LL"? Is it just an abbreviated way of writing "IPv4 Link-Local"? If it is, I would be grateful for a reliable reference to back this up. If it isn't, then what does it refer to?