Source : Free On-Line Dictionary of Computing

Inverse Address Resolution Protocol
     
         (InARP) Additions to {ARP} typically
        used for {Frame Relay}.  [Any other examples of its use?]
     
        {Frame Relay} stations {route} {frames} of a higher level
        protocol between {LANs}, across a {Permanent Virtual Circuit}.
        These stations are identified by their {Data Link Control
        Identifier} (DLCI), equivalent to an {Ethernet address} in a
        {LAN} itself.
     
        InARP allows a station to determine a protocol address (e.g.
        {IP address}) from a DLCI. This is useful if a new {virtual
        circuit} becomes available.  Signalling messages announce its
        DLCI, but without the corresponding protocol address it is
        unusable: no {frames} can be {routed} to it.
     
        {Reverse ARP} (RARP) performs a similar task on an {Ethernet}
        {LAN}, however RARP answers the question "What is my IP
        Address?" whereas InARP answers the question "What is your
        protocol address?".
     
        See {RFC 2390}.
     
        (2000-01-15)