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

From: Benjamin Koh Tien-Ming <[email-masked]>
Date: Thu, 26 Apr 2007 15:54:18 +0800

Hi All!

As mentioned previously in this list, the current MCoA draft does not
fully address the issue of MN being unable to utilise both interfaces
attached to home and foreign links.

See:-
 http://www1.ietf.org/mail-archive/web/monami6/current/msg00943.html
 http://www1.ietf.org/mail-archive/web/monami6/current/msg01049.html

As a suggested resolution to this issue, I would like to propose that
Section 7 of draft-wakikawa-mip6-no-ndp-00
 http://tools.ietf.org/id/draft-wakikawa-mip6-no-ndp-00.txt
be adopted as a working solution to the problem and incorporated into
the current MCoA document. Proposers of the two previous solutions
(Wakikawa-san, Keigo-san and myself) are amenable to this new solution.

Would like to hear if there are any strong opinions from the people on
this list. I have reproduced the relevant section below.

Regards,
Ben

7.  Multiple Care-of Address Registration

   In the Multiple Care-of Address Registration [2], the Mobile Node
   MUST disable either the interface attached to the home link or the
   interfaces attached to the foreign link.  This is because the Home
   Agent defends the home address of the Mobile Node by proxy neighbor
   advertisements.  So as to avoid the home address duplication at the
   home link, the Mobile Node MUST select whether it returns home or
   not.  If a binding is active for the Mobile Node, all packets routed
   to the home link are intercepted by the Home Agent.  On the other
   hand, if the Mobile Node returns home, the Home Agent no longer
   intercept packets and cannot tunnel the packets to the Mobile Node's
   interface attached to the foreign link.

   Figure 9 depicts the scenario where Mobile Node activates the
   interface attached to the home link and the foreign link, and
   communicates with all of the interfaces.  Since the Home Agent does
   not use Proxy Neighbor Advertisement to intercept packets, 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.

             +----+
             | CN |
             +--+-+
                |
           +----+-----+              +----+
           | Internet |--------------+ HA |
           +----+---+-+              +--+-+
                |Foreign Link           |Home Link
        --------+------------     ------+------
                |                       |
                |CoA1                   |
             +--+--+                    |
             |  MN +--------------------+
             +-----+

     Binding Cache Database:
        Home Agent's binding (No Proxy neighbor advertisement)
              binding [a:b:c:d::EUI  a:b:c:d::EUI      BID1] (Home BC)
              binding [a:b:c:d::EUI  Care-of Address1  BID2]
        Correspondent Node's binding
              binding [a:b:c:d::EUI  a:b:c:d::EUI      BID1] (Home BC)
              binding [a:b:c:d::EUI  Care-of Address1  BID2]
                        or
              None

    Figure 9: Utilizing of both an interface attached to the Home Link
               and an interface attached to the Foreign Link

   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 [7], 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.  In this document, 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.

   For this operation, the Binding Unique Identifier sub-option is
   modified as described in Figure Figure 10.  The new Home flag is
   introduced.  When the H flag is set, the Home Agent MUST treat the
   binding as the home binding.  After intercepting the packets, the
   Home Agent may tunnel the packets according to the active binding
   cache(s) or route the packets to the home link according to the home
   binding cache.  Note that the H flag MUST be used only for the
   binding de-registration.  Note that the same mechanism is used for
   the correspondent node.

                      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|R|H|Reserved |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
       +                                                               +
       +                    Care-of Address (CoA)                      +
       +                                                               +
       +---------------------------------------------------------------+

Wakikawa & Aramoto       Expires August 5, 2007                [Page 17]

Internet-Draft            HA Limited Proxy NDP             February 2007

                         Figure 10: BID Sub-Option

   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.

   Reserved

      5 bits Reserved field.  Reserved field must be set with all 0.

-- 

/<<<<<<<<<<<<<<<<<<<<++>>>>>>>>>>>>>>>>>>>>\
| 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: Romain KUNTZ <[email-masked]>
Date: Mon, 30 Apr 2007 23:21:12 +0200

Hi,

> (Wakikawa-san, Keigo-san and myself) are amenable to this new  

I like the solution discussed in this draft and would agree to  
integrate it to the MCoA draft to solve the  "simultaneous location  
in home and foreign" issue. It has the advantage to avoid tunneling  
in the home network and is IMO pretty easy to implement.

Regards,

-- 
Romain KUNTZ
[email-masked]
Louis Pasteur University - Networks and Protocols Team