The Bootstrap Protocol (BOOTP)

The Bootstrap Protocol (BOOTP) is a UDP/IP-based protocol that allows a booting host to configure itself dynamically, and more significantly, without user supervision. BOOTP is fully defined in RFC-1497. A server's BOOTP response includes several configuration items, and fits in a single (Ethernet) packet. It provides a means to assign a host its IP address, a file from which to download a boot program from some server, that server's address, and (if present) the address of an Internet gateway. One problem appears to have been introduced - how can BOOTP use a 'higher' protocol from the TCP/IP suite (in this case UDP) if it is trying to determine IP-level information? The answer lies in the use of special IP addresses within the BOOTP request packet: To send the BOOTP datagram, the client machine sets the destination IP address to the global broadcast (255.255.255.255), and its own source IP address to 0.0.0.0. The responding BOOTP server either replies with an IP broadcast (heard by the requesting client), or responds directly to the client's MAC address.

Booting over a Network

• The client may provide a generic string, such as UNIX or NCD-XTERM-1320, in the TFTP-boot-filename field of its request,
• The BOOTP server may accept this part of the request, and respond with the pathname of an operating system's kernel image available from the server, such as /tftp/bootimages/vmlinuz-4.14
• The client may then use this pathname in a subsequent request using the Trivial File Transfer Protocol (TFTP, [RFC-783]) to fetch its boot image (loading it directly into memory).
• This feature is excellent for maintaining identical operating system kernels, or booting diskless machines.