RFC 2794 (rfc2794) - Page 3 of 9

Mobile IP Network Access Identifier Extension for IPv4

RFC 2794                    Mobile Node NAI                   March 2000


       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     |           MN-NAI ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 1: The Mobile Node NAI Extension


      Type       131 (skippable) [7]

      Length     The length in bytes of the MN-NAI field

      MN-NAI     A string in the NAI format defined in [1].

3. Foreign Agent Considerations

   If Home Address is zero in the Registration Request, the foreign
   agent MUST use the NAI instead in its pending registration request
   records, along with the Identification field as usual.  If the
   foreign agent cannot manage pending registration request records in
   this way, it MUST return a Registration Reply with Code indicating
   NONZERO_HOMEADDR_REQD (see section 5).

   If the mobile node includes the Mobile Node NAI extension in its
   Registration Request, then the Registration Reply from the home agent
   MUST include the Mobile Node NAI extension.  If not, the foreign
   agent SHOULD send the Registration Reply to the mobile node, changing
   the Code to the value MISSING_NAI (see section 5).  The Registration
   Reply MUST include a nonzero Home Agent address and mobile node's
   Home Address.  If not, the foreign agent SHOULD send the Registration
   Reply to the mobile node, changing the Code to the value
   MISSING_HOME_AGENT or MISSING_HOMEADDR, respectively (see section 5).

4. Interactions with Mobile-IPv4 Configuration Option to IPCP

   In the Mobile-IPv4 Configuration Option to IPCP [8], the Mobile
   Node's Home Address field may be zero.  In this section, we specify
   the action to be taken in that case, when the mobile node is using
   the Mobile Node NAI extension in the Mobile IP Registration Request.
   Whether or not the IP Address Configuration Option contains a nonzero
   IP address, the mobile node will subsequently attempt to obtain a
   home address from the Mobile IP Registration Reply.

   If the IP Address Configuration Option to IPCP has IP address equal
   to zero, the PPP peer is expected to allocate and assign a co-located
   care-of address to the Mobile Node.  If, on the other hand, the IP




Calhoun & Perkins           Standards Track