Reverse Address Resolution Protocol (RFC0903)
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
R. Finlayson: AUTHOR [+4]
Network hosts such as diskless workstations frequently do not know their protocol addresses when booted; they often know only their hardware interface addresses. To communicate using higher-level protocols like IP, they must discover their protocol address from some external source. Our problem is that there is no standard mechanism for doing so.
Network Working Group Finlayson, Mann, Mogul, Theimer
Request for Comments: 903 Stanford University
A Reverse Address Resolution Protocol
Ross Finlayson, Timothy Mann, Jeffrey Mogul, Marvin Theimer
Computer Science Department
Status of this Memo
This RFC suggests a method for workstations to dynamically find their
protocol address (e.g., their Internet Address), when they know only
their hardware address (e.g., their attached physical network
This RFC specifies a proposed protocol for the ARPA Internet
community, and requests discussion and suggestions for improvements.
Network hosts such as diskless workstations frequently do not know
their protocol addresses when booted; they often know only their
hardware interface addresses. To communicate using higher-level
protocols like IP, they must discover their protocol address from
some external source. Our problem is that there is no standard
mechanism for doing so.
Plummer's "Address Resolution Protocol" (ARP)  is designed to
solve a complementary problem, resolving a host's hardware address
given its protocol address. This RFC proposes a "Reverse Address
Resolution Protocol" (RARP). As with ARP, we assume a broadcast
medium, such as Ethernet.
II. Design Considerations
The following considerations guided our design of the RARP protocol.
A. ARP and RARP are different operations. ARP assumes that every
host knows the mapping between its own hardware address and protocol
address(es). Information gathered about other hosts is accumulated
in a small cache. All hosts are equal in status; there is no
distinction between clients and servers.
On the other hand, RARP requires one or more server hosts to maintain
a database of mappings from hardware address to protocol address and
respond to requests from client hosts.
RFC 903 June 1984
B. As mentioned, RARP requires that server hosts maintain large
databases. It is undesirable and in some cases impossible to maintain
such a database in the kernel of a host's operating system. Thus,
most implementations will require some form of interaction with a
program outside the kernel.
C. Ease of implementation and minimal impact on existing host
software are important. It would be a mistake to design a protocol
that required modifications to every host's software, whether or not
it intended to participate.
D. It is desirable to allow for the possibility of sharing code with
existing software, to minimize overhead and development costs.
III. The Proposed Protocol
We propose that RARP be specified as a separate protocol at the
data-link level. For example, if the medi...