Re: DHCP clarification

Kanoj,

How about the following:

2.2 Use of the BROADCAST flag

        A DHCP client on IPoIB MUST set the BROADCAST flag and set
        'ciaddr' to zero in DHCPDISCOVER and DHCPREQUEST messages
        when it is not in BOUND or RENEWING states. This ensures that
        the server (or the relay agent) broadcasts its reply to
        the client.

        In the BOUND, RENEWING or REBINDING states 'ciaddr' MUST be
        filled in with the client's IP address [RFC2131]. The
        BROADCAST flag MUST NOT be set in these cases since the DHCP
        server, after resolving the 'ciaddr' address using ARP,
        unicasts the DHCPACK message to the client.


Vivek




> Hi,
>
> While going over section 2 of ipoib/dhcp draft, I realized that it
> can be cleaned up somewhat (in my opinion, ie; to others, it might
> be quite clear already). Accordingly, I came up with the following
> verbiage. If there are some improvements in here, it should be used
> to reword the section.
>
> 2.2 Use of the BROADCAST flag
>
>         A DHCP client on IPoIB MUST set the BROADCAST flag (and
>         set 'ciaddr' to zero) in DHCPREQUEST messages and
>         DHCPDISCOVER messages sent when it is not in the BOUND
>         or RENEWING states (ie it is in INIT-REBOOT or SELECTING
>         states).
>
>         For other cases, the client SHOULD NOT set the BROADCAST
>         flag if it can receive the server's unicast responses.
>         As described in [RFC2131], 'ciaddr' MUST be filled in
>         with client's IP address during BOUND, RENEWING or
>         REBINDING states. In these cases,
>         the DHCP server attempts to unicast DHCP responses to
>         the address filled in by the client in 'ciaddr' by using
>         IPoIB ARP to resolve the link address.
>
> The reason I think this is clearer is because:
> 1. It makes it clear that the BROADCAST flag has to be set in
> DHCPDISCOVER.
> 2. It makes it clear that the BROADCAST flag needs to be set
> for DHCPREQUEST only in INIT-REBOOT/SELECTING states.
> 3. It allows that servers might broadcast responses
> (allowed per 2131, see last paragraph section 4.1).
> 4. It allows that servers might respond with DHCPNAK.
> 5. It allows that there might be other reasons for clients to
> set BROADCAST bit (specifically for INFORM, see 2131 table 5).
> 6. It does not make it illegal for clients to set BROADCAST bit
> for whatever other reason. Unless there is a good reason (other
> than known issues) to make it illegal, I am not sure if this
> was intended. I could not find any MUST NOT reference wrt BROADCAST
> bit in 2131.
>
> Thanks.
>
> Kanoj
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>

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Vivek Kashyap
Linux Technology Center, IBM