The Origins of RARP | History, BOOTP and DHCP
The Origins of RARP | History, BOOTP and DHCP

Networking explained

The origins of RARP

RARP helped a computer discover its network address when it knew only its hardware address. Here is the problem it solved and how later boot protocols went further.

Who introduced RARP?

RFC 903, published in June 1984, was written by Ross Finlayson, Timothy Mann, Jeffrey Mogul and Marvin Theimer at Stanford University. David C. Plummer authored the earlier ARP specification, RFC 826; he was not an author of RFC 903. Source: RFC 903.

The problem it solved

A diskless workstation could know its hardware address at startup without knowing its IP address. RARP let it request the corresponding network address from a server. The server needed a database mapping hardware addresses to network addresses.

ARP resolves a known network address to a hardware address. RARP handles the reverse lookup. It reuses ARP's packet format, with different operation codes, but is a separate data-link protocol. On Ethernet it uses a different EtherType. Read the protocol design.

Why BOOTP went further

RARP addresses a narrow startup question: which network address corresponds to this hardware address? BOOTP, described in RFC 951 in September 1985, supplies more of what a machine needs to boot, including its address, the server address and a boot-file name.

BOOTP uses UDP/IP, and its specification describes forwarding requests between networks. That gives it a different deployment model from a link-level RARP exchange. Source: RFC 951.

From BOOTP to DHCP

DHCP builds on BOOTP's message format and adds facilities for allocating reusable network addresses and delivering configuration parameters. RFC 2131, published in March 1997, describes automatic, dynamic and manual allocation.

Dynamic allocation can lease an address for a limited time. That is a broader role than RARP's lookup of an address from a hardware-to-network mapping. Source: RFC 2131.

How does this relate to a USip VPN address?

These protocols concern network configuration. They do not make an address residential or place it in the US. USip VPN provides a residential US IP through actual US home broadband. See how USip assigns your IP for the service's connection and reconnection rules.

Primary references