UCARP allows a pair of hosts to share common virtual IP addresses in order to
provide automatic failover. It is a portable userland implementation of the
secure and patent-free Common Address Redundancy Protocol (CARP, OpenBSD's
alternative to the VRRP).
Strong points of the CARP protocol are : very low overhead, cryptographically
signed messages, interoperability between different operating systems and no
need for any dedicated extra network link between redundant hosts.
