II. Design Considerations

The following considerations guided our design of the RARP protocol.

1. 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.

2. 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.

3. 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.

4. It is desirable to allow for the possibility of sharing code with existing software, to minimize overhead and development costs.