Today Sam asked a question about the EAP end-points with respect to
dhcp-auth proposal.

The answers we got were either not clear or not accurate.

It is not true that EAP authenticator is always on the DHCP server. In
Figure 5 of their I-D, EAP authenticator and DHCP relay are co-located in
NAS:


        (HGW)                (NAS)                (AAA)           (DHCP)
     DHCP Client           AAA Client        RADIUS Server   DHCP Server
                          AAA Client

    DHCPDISCOVER ------->
    (w/DHCP-auth-proto EAP)

                 <------- DHCPEAP
                          (w/EAP Message)

    DHCPEAP ------->
    (w/EAP Message)

                          RADIUS Access-Request ------->
                          (w/EAP Message)

                                                <-------- RADIUS
                                    Access-Accept (w/EAP Message)
                                   (Access-Reject (w/EAP Message)
                                                 if unsuccessful)

               (DHCP messages continue normally from
               this point forward if successful)
                          DHCPDISCOVER ------------------------------>
                          (w/RADIUS attributes suboption)

                               <----------------------------- DHCPOFFER

                 <------- DHCPOFFER (w/EAP Success Message)
                          (w/yiaddr)

    DHCPREQUEST  ------->

                 <------- DHCPACK

         Figure 5: Message Flow with new message and a DHCP relay


As for EAP peer and DHCP client, we never got a clear acknowledgement that
it may be on a device sitting behind the CPE (HGW) at home, like a PC. It
has to be so because:
- There are clear DSLF requirements for that [e.g., IPAuth-9 Should be
simple to implement on client (PC or CPE)],
- Replacing PPPoE means doing that on the home PCs as well, and
- The I-D clearly states "The DHCP Client resides either on a home network
device or the HGW,..."


Alper




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