DHCP for IEEE 1394
Extracted elements (14)
Although broadcast replies are generally discouraged in DHCP, the impact of using them on a 1394 network is considered a non-issue, justifying the SHOULD-level recommendation to set the BROADCAST flag.
EUI-64 is chosen as the obvious basis for the 'client identifier' option because every IP-over-1394 node already possesses a globally unique EUI-64 node ID, providing a stable substitute for the unavailable 'chaddr'.
The 1394 link address (node_ID) is transient and not consistent across 1394 bridges, so it was deliberately not placed in the 'chaddr' field. Instead, the broadcast reply mechanism is used to reach clients.
This specification applies only to DHCP clients connected to IEEE 1394 networks; the field rules (htype=24, hlen=0, chaddr=zero) differ from conventional IEEE 802/Ethernet DHCP usage and must not be conflated with it.
A DHCP client on 1394 SHOULD set the BROADCAST flag in DHCPDISCOVER and DHCPREQUEST messages (and set 'ciaddr' to zero) to ensure the server or relay agent broadcasts its reply, since 1394 ARP may not yet be possible.
During BOUND, RENEWING, or REBINDING states, 'ciaddr' MUST be filled with the client's IP address and the BROADCAST flag MUST NOT be set; the server unicasts DHCPACK to 'ciaddr', resolving the link address via 1394 ARP.
IEEE 1394 DHCP clients SHOULD include an EUI-64 identifier in the 'client identifier' option, using type value 27 as assigned in the ARPPARAM registry, since every IP-over-1394 node has a unique EUI-64.
The 'chaddr' field is reserved for IEEE 1394 use: the sender MUST set it to zero, and both the recipient and relay agent MUST ignore its value on receipt.
The 'client identifier' option MUST be used in all DHCP messages from the client to the server, because 'chaddr' is not available on 1394 networks.
The 'hlen' (hardware address length) field MUST be 0 for IEEE 1394 DHCP clients, reflecting that the 1394 link address is not placed in 'chaddr'.
The 'htype' (hardware address type) field in DHCP messages MUST be set to 24 when the client is connected to an IEEE 1394 network, as assigned by IANA in the ARPPARAM registry.
The EUI-64 client identifier type value is 27, as registered in the IANA ARPPARAM registry. This type distinguishes EUI-64-based client identifiers from other forms such as FQDNs, whose use is not precluded.
DHCP provides no authentication or security mechanisms. A malicious 1394 client can falsify its EUI-64 identifier and masquerade as another client, since EUI-64 values in the 'client identifier' option are self-reported and unverified.
The 'client identifier' option for EUI-64 uses code 61, length 9, type 27, followed by the 8-byte EUI-64 node unique ID. The total option length is 11 octets including code and length fields.