Subject: [Monami6] MCoA Issue: Simultaneous Usage of Home and Away interfaces

From: Benjamin Koh Tien-Ming <[email-masked]>
Date: Thu, 14 Jun 2007 20:57:00 +0800

Hi!

I had posted an email to the Monami6 mailing list proposing the adoption
of Section 7 of draft-wakikawa-mip6-no-ndp-00 as a working solution to
resolve the issue of simultaneous usage of home and away interfaces.

See:-
 http://www1.ietf.org/mail-archive/web/monami6/current/msg01051.html

A month has passed and there has been no negative responses. Some small
amount of support has also been expressed.  As such, I'm submitting the
following suggested changes to draft-ietf-monami6-multiplecoa-02.txt for
discussion and action.  The actual text has been heavily plagiarized
from draft-wakikawa-mip6-no-ndp-00.txt. (Apologies to authors)    ;-)

Changes:-

3.3.  Returning Home
"
   In the above two cases, a mobile node cannot use interfaces attached
   to both home and foreign links simultaneously.
<cut>
   If this is what a
   mobile node wants, a home agent can set up another link other than
   home link and uses the link for the mobile node to return virtually
   to home network.  Even though packets from and to the mobile node are
   routed via the home agent, the hop count is kept in one.  The
   overhead should be negligible since it is only for an additional IPv6
   header and processing tunnel (encapsulation and decapsulation) per
   packets.  The detail can be found in Figure 7
</cut>

<paste>
   This restriction is
   related to the Proxy NDP operation on a Home Agent.  The Home Agent
   needs to defend a mobile node's home address by the proxy NDP for
   packet interception, while the mobile node defends its home address
   by regular NDP to send and receive packets at the interface attached
   to the home link.  Two nodes, Home Agent and Mobile Node, compete ND
   state.  This will causes address duplication problem at the end.

   This document recommends not to use the Proxy NDP for this scenario.
   When one of the Mobile Node's interface is attached to the home link
   and the other is attached to the foreign link and it decides to
   utilize both interfaces, it notifies the Home Agent using the H flag
   which means the Mobile Node is attached to the home link. If the
   proxy NDP is disabled, the main problem can be solved.  In the
   Multiple Care-of Address Registration case, the elimination of Proxy
   NDP enable that Mobile Node and Home Agent maintain multiple
   bindings, one of the Mobile Node's interface is attached to the home
   link and the other is attached to the foreign link.
</paste>
"

4.2.1.  Binding Unique Identifier sub-option
"
<replace>
                      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)   |Priority/Status|C|O|H|Reserved |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
       +                                                               +
       +                    care-of address (CoA)                      +
       +                                                               +
       +---------------------------------------------------------------+
</replace>

<paste>
   Home Binding (H) flag
      When this flag is set, a home agent stores a Home Address in the
      Care-of Address field of the binding cache entry.  This flag must
      be used only for binding de-registration.  This flag is not used
      in the bulk registration mode.
</paste>

   Reserved

<replace>
      5 bits Reserved field.  Reserved field must be set with all 0.
</replace>
"

5.6.  Returning Home
"
   no longer receives packets at the interface attached to the home
   link.  All packets are routed to other interfaces attached to a
   foreign link.

<paste>
   Alternatively, the Mobile Node may choose to activate both the
   interfaces attached to the home link and the foreign link, and
   communicates with all of the interfaces.  The Mobile Node notifies
   the Home Agent using the H flag which means the Mobile Node is
   attached to the home link. The Home Agent then no longer
   uses Proxy Neighbor Advertisement to intercept packets and the Mobile
   Node can utilize both of interfaces attached to the home link and the
   foreign link simultaneously.  The Home Agent can intercept packets by
   IP routing, but not by proxy Neighbor Discovery.

   When the Mobile Node returns home, it de-registers a binding for the
   interface.  While the bindings for the interfaces attached to the
   foreign link are still active.  Intercepting packets, the Home Agent
   can decide whether it tunnels to the foreign interface or routes to
   the home interface of the Mobile Node.  To do so, the Home Agent must
   know that the Mobile Node is back to the home link.  However, if the
   binding is deleted according to [2], there is no way for the Home
   Agent to know that the Mobile Node is at the home, too.  The Home
   Agent SHOULD invalidate the binding for the interface attached to the
   home link and MAY NOT delete it.  It can alternatively mark that the
   Mobile Node is at the home link, too.  As an
   example, the Home Agent inserts the Home Address of the Mobile Node
   in the Care-of Address field of the Mobile Node.  The binding is
   named "Home Binding" in this doc.  The Home Agent MAY manage this
   home binding as same as the other binding entry in terms of lifetime
   validation, etc.  The Mobile Node MAY send multiple binding de-
   registration to keep this home binding active.  Alternatively, the
   Home Agent can use infinity lifetime for the lifetime of the home
   binding.  When the Mobile Node leaves the Home Link, it can update
   the home binding to the normal binding.  Before that, the Home Agent
   believes the Mobile Node is at the home and may route packets for the
   Mobile Node to the Home Link.
</paste>
"

6.3.  Processing Binding Update
"
   o  If the Lifetime field of the Binding Update is zero, the receiver
      node deletes the binding entry which BID is same as BID sent by
      the Binding Unique Identifier sub-option.  If the receiver node
      does not have appropriate binding which BID is matched with the
      Binding Update, it MUST reject this de-registration Binding
      Update.  If the receiver is a Home Agent, it SHOULD also return a
      Binding Acknowledgment to the mobile node, in which the Status
      field is set to [not Home Agent for this mobile node, 133].  If O
      flag is set in the deregistering Binding Update, the receiver can
      ignore this flag for deregistration.
<paste>
      If the H flag is set, the home agent stores a Home Address in the
      Care-of Address field of the binding cache entry.  The home agent
      no longer performs proxy NDP for this mobile node until this
      entry is deleted.
</paste>
"

Appendix A.  Example Configurations
"
<cut>
   Figure 7 depicts the scenario where interfaces of MN are attached to
   the foreign links.  One of foreign link is managed by the home agent.
   The HA and CN have the binding entries listed in Figure 7 in their
   binding cache database.  The home agent advertises a prefix which is
   other than home prefix.  The mobile node will generate a care-of
   address from the prefix and registers it to the home agent.  Even if
   the mobile node attaches to a foreign link, the link is managed by
   its home agent.  It will tunnel the packets to the home agent, but
   the home agent is one-hop neighbor.  The cost of tunnel is
   negligible.  If the mobile node wants to utilize not only an
   interface attached to home but also interfaces attached to foreign
   link, it can use this foreign link of the home agent to return a one
   hop foreign link on behalf of a home link.  This is different from
   the general returning home, but this enable the capability of using
   interfaces attached to both home and foreign link without any
   modifications to Mobile IPv6 and NEMO basic support.

                    +----+
                    | CN |
                    +--+-+
                       |
                   +---+------+          +----+
            +------+ Internet |----------+ HA |
            |      +----+-----+          ++-+-+
        CoA2|           |                 | |   Home Link
         +--+--+        |             ----|-+------
         |  MN +========+                 |
         +--+--+ CoA1                ---+-+------
       CoA3 |                           |  Foreign Link
            +---------------------------+

     Binding Cache Database:
        home agent's binding (Proxy neighbor advertisement is active)
              binding [a:b:c:d::EUI  care-of address1  BID1]
              binding [a:b:c:d::EUI  care-of address2  BID2]
              binding [a:b:c:d::EUI  care-of address3  BID3]
        correspondent node's binding
              binding [a:b:c:d::EUI  care-of address1  BID1]
              binding [a:b:c:d::EUI  care-of address2  BID2]
              binding [a:b:c:d::EUI  care-of address3  BID3]

    Figure 7: Emulating to Utilize Interfaces Attached to both Home and
                               Foreign Links
</cut>
"

Regards,
Ben

-- 

/<<<<<<<<<<<<<<<<<<<<++>>>>>>>>>>>>>>>>>>>>\
| Benjamin Koh Tien-Ming                   |
| R & D Engineer                           |
| Panasonic Singapore Laboratories Pte Ltd |
| Tel: (65)6550 5481 Fax: (65)6550 5459    |
| E-mail: [email-masked]  |
\>>>>>>>>>>>>>>>>>>>>--<<<<<<<<<<<<<<<<<<<</

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---

From: RYUJI WAKIKAWA <[email-masked]>
Date: Fri, 15 Jun 2007 10:34:34 +0900

Hi All,

Thanks for Benjamin.
I am revising the MCoA draft for the IETF Chicago now.
It looks there is no objection on this changes, i plan to include  
this option.

regards,
ryuji

On 2007/06/14, at 21:57, Benjamin Koh Tien-Ming wrote:

>                                        |   Type = TBD  |      
> Length    |
>        +                    care-of address  
> (CoA)                      +