Re: [dhcwg] DUID+IAID

[Ted Lemon <[e-mail]>]

> So, would the hardware-addr-option (or link-layer option) identify the MAC
> of the interface on which the request was sent, or the MAC of the interface
> "for which configuration information is being requested"?

In practice there's no difference.   But it doesn't identify the interface.  It provides additional information about the interface that can be used as a database key to associate devices to the DUID.   A back-end database initialized by scanning the box a router came in might have four entries for the four hardware addresses of that router.   When a request comes in from that router, the database entry for each hardware address could be updated to refer to the same DUID.   In this way we can tie an existing hardware address-based back-end database to DUID.   That's the point of the exercise.

> Also, I recall a thread on the mailing list that discussed CPE routers which may
> request an address for the WAN-side interface via an IA_NA option along with an
> IA_PD request for the LAN-side interface.  I believe the discussion was focused on
> the renew behavior.  However, IIRC, some implementations may send the IA_NA
> and IA_PD in the same or separate requests.  Regardless of one or two requests
> the packets would (presumably) be sent over the WAN-side interface.  In the
> situation where the client sends the IA_NA and IA_PD in the same request packet,
> the proposed link-layer address option would be the MAC of which interface -
> WAN or LAN?  In the case of separate requests, would you then expect two
> different MACs?  I think were I'm heading with this is that perhaps the link-layer
> option needs to be "inside" the IA option, not at the outermost message level of the packet.

The problem we are trying to solve is twofold.   First, tying the mac address on a shipping box to a device making a query on the network using DUID.   Second, tying the chaddr field from a DHCPv4 message to the DUID of a DHCPv6 message.   So consider the CPE router--it's sending its DHCPv4 packet on the upstream interface, and it's sending its DHCPv6 packet on the upstream interface.   In both cases, the hardware address we want to send is the hardware address of the upstream interface.   It makes no sense to send the hardware address of any of the downstream interfaces.