dhcprequest function (dhcp: message 4 of 20)

[dhcp.50.CHRIS94561 at spamgourmet.com]

On Mon, 29 Mar 2004, Ted Lemon  - mellon at fugue.com wrote:

> On Mar 29, 2004, at 5:33 PM, dhcp.50.CHRIS94561 at spamgourmet.com wrote:
> > I've gone throught rfc2131 and Figure 5 on page 34 in section 4.4 "DHCP
> > client behavior" seems to imply that the client can indeed be NAKed
> > when
> > renewing or rebinding. I was unsure if this group or dhcp-server was
> > the
> > right place to ask. Many appologies if I picked the wrong one.
>
> Maybe it would have been better to say "the protocol describes how
> DHCPNAKs should be sent in a way that precludes sending DHCPNAKs to a
> RENEWING client."
>
> Because a RENEWING client unicast its renewal, you can't broadcast the
> response, and DHCPNAKs are always supposed to be broadcast.

I went looking for this requirement vis a vis NAKs and I think I found
it in section 4.1 "Constructing and sending DHCP messages" page 22: "In
all cases, when 'giaddr' is zero, the server broadcasts any DHCPNAK
messages to 0xffffffff." Is this what you are referring to?

If so then the same section offers contradiction. Section 4.1 page 24
says: "Normally, DHCP servers and BOOTP relay agents attempt to deliver
DHCPOFFER, DHCPACK and DHCPNAK messages directly to the client using
uicast delivery."

To complicate things even more in my mind is the paragraph that follows
later on page 24: "A server or relay agent sending or relaying a DHCP
message directly to a DHCP client (i.e., not to a relay agent specified in
the 'giaddr' field) SHOULD examine the BROADCAST bit in the 'flags' field.
If this bit is set to 1, the DHCP message SHOULD be sent as an IP
broadcast using an IP broadcast address (preferably 0xffffffff) as the IP
destination address and the link-layer broadcast address as the link-layer
destination address. If the BROADCAST bit is cleared to 0, the message
SHOULD be sent as an IP unicast to the IP address specified in the
'yiaddr' field and the link-layer address specified in the 'chaddr'
field."

Am I missing something? Is there some clarification to be made? Is there a
clear statement somewhere including "MUST" or "required" that clearly
illustrates the requirement to broadcast NAKs?

C