RFC 2855 (rfc2855) - Page 2 of 5
DHCP for IEEE 1394
Alternative Format: Original Text Document
RFC 2855 DHCP for IEEE 1394 June 2000
2. Issues related to 1394 link address
With conventional link-layer protocols, such as an Ethernet, the
'chaddr' (client hardware address) field may be used to return a
reply message from a DHCP server (or relay-agent) to a client. Since
a 1394 link address (node_ID) is transient and will not be consistent
across the 1394 bridge, we have chosen not to put it in the 'chaddr'
field. A DHCP client should request that the server sends a
broadcast reply by setting the BROADCAST flag when 1394 ARP is not
possible yet.
Note: In general, the use of a broadcast reply is discouraged, but
we consider the impact in a 1394 network as a non issue.
3. 1394 specific usage of DHCP message fields
Following rules should be used when a DHCP client is connected to an
IEEE1394 network.
'htype' (hardware address type) MUST be 24 [ARPPARAM].
'hlen' (hardware address length) MUST be 0.
The 'chaddr' (client hardware address) field is reserved. The sender
MUST set this field to zero, and the recipient and the relay agent
MUST ignore its value on receipt.
A DHCP client on 1394 SHOULD set a BROADCAST flag in DHCPDISCOVER and
DHCPREQUEST messages (and set 'ciaddr' to zero) to ensure that the
server (or the relay agent) broadcasts its reply to the client.
Note: As described in [RFC 2131], 'ciaddr' MUST be filled in with
client's IP address during BOUND, RENEWING or REBINDING state,
therefore, the BROADCAST flag MUST NOT be set. In these cases,
the DHCP server unicasts DHCPACK message to the address in
'ciaddr'. The link address will be resolved by 1394 ARP.
'client identifier' option MUST be used in DHCP messages from the
client to the server due to the lack of the 'chaddr'. 'client
identifier' option may consist of any data. Because every IP over
1394 node has an EUI-64 (node unique ID), the EUI-64 makes an obvious
'client identifier'. 1394 clients SHOULD include an EUI-64
identifier in the 'client identifier' option. The type value for the
EUI-64 is 27 [ARPPARAM], and the format is illustrated as follows.
Fujisawa Standards Track