Subject: [MEXT] DSMIP applicability to MCoA

From: RYUJI WAKIKAWA <[email-masked]>
Date: Wed, 26 Dec 2007 15:59:05 +0900

Hi all,

Here is the proposed text of DSMIP support on MCoA.

thanks
ryuji

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- DSMIP applicability

DSMIP extends Mobile IPv6 to register IPv4 care-of address, IPv4 home
address or both. The following scenarios can be supported by DSMIP
and MCoA.

  - IPv6/v4 HoA and IPv4/v6 CoAs
  - IPv6/v4 HoA and IPv4 CoAs
  - IPv6/v4 HoA and IPv6 CoAs
  - IPv6 HoA and IPv4/v6 CoAs
  - IPv6 HoA and IPv4 CoAs

- BID Sub-option Format Change

                      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 = TBD   
|     Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Binding Unique ID (BID)   |     Status    |C|O|H|D|Reservd|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
       +                                                               +
       +                    care-of address (CoA)                      +
       +                                                               +
       +---------------------------------------------------------------+

                         Figure 1: BID Sub-Option

A new D flag is reserved for DSMIP.
When D flag is set, the CoA address filed MUST be set to IPv4 Care-of  
Address.

- IPv4 CoA registration

In DSMIP, the binding update and acknowledgment exchange is used to
detect NAT. Thus, when a mobile node registers its IPv4 CoA bound to
IPv6 HoA, it MUST first attempts to send BU with BID sub-option
independently. The bulk registration MUST NOT be used for the first
binding update of the IPv4 CoA. The Binding Update MUST be sent to the
IPv4 home agent address by using UDP and IPv4 headers as shown in
Fig-1. It is similar to [DSMIP] except for using BID sub-option
instead of IPv4 CoA option.

           IPv4 header (src=V4ADDR, dst=HA_V4ADDR)
             UDP Header
               IPv6 header (src=V6HoA, dst=HAADDR)
                    ESP Header
                    Mobility header
                        -BU
                       Mobility Options
                          - Binding Identifier sub-option (IPv4 CoA)

             Figure 1: Initial Binding Update for IPv4 CoA

When the home agent detects NAT for the received binding update, it
MUST send the NAT detection option in the Binding
Acknowledgment. Whenever the NAT detection option is found, the
mobile node MUST NOT use the bulk registration for the IPv4
CoA. Otherwise, it can send the IPv4 CoA with other CoAs in the bulk
registration mode. How to handle NAT is same as [DSMIP].

If no NAT is detected, the mobile node can update the IPv4 CoA by
using BULK registration.  The mobile node can register the IPv4 CoA
with other CoAs.  Fig-2 shows the binding update format when the
mobile node sends a Binding Update from one of its IPv6 CoAs. If the
mobile node sends a BU from IPv4 CoA, it MUST follows the Fig-1 and
store more BID sub-options in the mobility options field.  Note that
it must be registered by a no bulk Binding registration, whenever the
IPv4 CoA is changed.

               IPv6 header (src=V6CoA, dst=HAADDR)
                    IPv6 Home Address Option
                    ESP Header
                    Mobility header
                        -BU
                       Mobility Options
                          - Binding Identifier sub-option (IPv6/v4 CoA)
                          - Binding Identifier sub-option (IPv6/v4 CoA)
                          - ...

             Figure 2: Binding Bulk Registration for IPv4 CoA

If the IPv4 CoA is successfully registered, the mobile node set up a
relevant tunnel to the home agent according to [DSMIP].

When the home agent rejects the IPv4 CoA, it MUST stores the error
code value in the Status field of the BID sub-option and MUST sends
the binding acknowledgment and all the received BID sub-options to the
mobile node. In this case, the IPv4 address acknowledgment option
MUST NOT be included in the Binding Acknowledgment. All the error
codes for IPv4 care-of address registration MUST be stored in the
Status field of the BID sub-option. The IPv4 address acknowledgment
option is used only when a mobile node requests IPv4 home address
management.

- IPv4 HoA management

When the mobile node obtains an IPv4 home address, it MUST stores the
IPv4 Home Address option in the Binding Update. If the home agent
accepts the binding update, the mobile node can also registers
multiple care-of addresses for the IPv4 home address in addition to
the IPv6 home address. The same set of care-of addresses will be
registered for both IPv6 and IPv4 home addresses. The mobile node
cannot binding different set of care-of addresses to each home
address.

The home agent MUST returns a binding acknowledgment and IPv4 address
acknowledgment option to the mobile node only when a mobile node
requests IPv4 home address mobility management. In this case, this
option MUST be presented before any BID options. The status field of
the IPv4 address acknowledgment option contains only the error code
regarding IPv4 home address management. The error value of the IPv4
CoA registration MUST be stored in the BID sub-option.

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