RADIUS attribute from rfc6572


specifies extensions to Proxy Mobile IPv6 protocol that
   enable IPv4 home address mobility support to the MN.  The PMIP6-Home-
   IPv4-HoA attribute (Type value 155) is of type Address and contains
   the IPv4 Home Address of the MN.  The primary use of this attribute
   is to deliver the assigned IPv4-HoA from HAAA to the MAG.

   The PMIP6-Home-IPv4-HoA is also used on the LMA-to-HAAA interface.
   If the LMA in the home network delegates the assignment of the
   IPv4-HoA to the HAAA, the attribute MUST contain an address of all
   zeroes (i.e., in the Access-Request message.  The attribute
   MUST be included in by HAAA in the Access-Accept message if the
   previous request included it, and it contains the IPv4-HoA assigned
   to the MN.0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |     Type      |    Length     |     Reserved      |Prefix-Len |
   |                       Home IPv4 HoA                           |

      PMIP6-Home-IPv4-HoA 155.

      = 8 octets

      The 10-bit field reserved for future use.  The value MUST be
      initialized to zero by sender and MUST be ignored by the

      The 6-bit unsigned integer indicating the prefix length of the
      IPv4 HoA.  If the Home IPv4 HoA contains an address of all zeroes
      (i.e., ''), then the Prefix-Len MUST be set to 32.

   Home IPv4 HoA:
      This field is of type Address and contains the IPv4 home
      address of the MN in the home network.