Subject: [MEXT] Comments to draft-ietf-monami6-multiplecoa-13.txt

From: Benjamin Lim <[email-masked]>
Date: Thu, 23 Apr 2009 12:14:23 +0800

Hi all,

Following are some of my comments to v13 of the draft.

Regards,
Benjamin Lim

-------------------

First comment.

<snip from section 5.5.2>
The mobile node returns home physically but shuts down the interface
attached to the home link.  As a result, a mobile node does not
return home even though it attaches to the home link by one of
interfaces.  Before shutting down the interface, any binding for the
care-of address previously associated with the interface should be
deleted as defined in .
                     ^^^
                 missing reference?
</snip>

Second comment.

<snip from section 5.1>
When a mobile node registers a given BID for the first time it MUST
include the care of address field in the Binding Identifier mobility
option.  For any subsequent registrations that either re-register or
de-register the same BID, the MN SHOULD NOT include the care of
address field in the Binding Identifier mobility option.
</snip>

I think MN SHOULD NOT include CoA in BID option for subsequent
registration is a bit too harsh.  What is the justification of SHOULD
NOT here?  Suggest to change to 'MAY NOT'.

Third comment.

For section 6.2 on how HA/CN process BU.  I believe it is mention in
section 5.1 that when MN registers BID for first time, MN must include
CoA field in BID option.  For subsequent registration for this BID, MN
can choose not include CoA field in BID option. I cannot find such
action reflected in section 6.2.  Propose to add the following for cases
when BU is sent w/o bulk registration

-----------------------
New text to section 6.2
-----------------------

If the Lifetime field is not set to zero and the Length value of the
Binding Identifier mobility option is 4, the receiving node MUST check
if the Binding Identifier specified in the Binding Identifier mobility
option is an existing binding in its Binding Cache.

  * If the Binding Identifier is present in the Binding Cache, the
    receiving node MUST update the associated binding entry in its
    Binding Cache.

  * If the Binding Identifier is not present in the Binding Cache, the
    receiving node MUST reject the Binding Update and send a Binding
    Acknowledgment set to [MCOA UNKNOWN].

------------------------------
End of new text to section 6.2
------------------------------

Propose to add the following for cases when BU is sent with bulk
registration

-----------------------
New text to section 6.2
-----------------------

If the Lifetime field is not set to zero, the Length value of the
Binding Identifier mobility option is 4 and when multiple Binding
Identifier mobility options are present, the receiving node MUST check
for each of the Binding Identifier mobility option present, if the
Binding Identifier specified in the Binding Identifier mobility option
is an existing binding in its Binding Cache.

  * If the Binding Identifier is present in the Binding Cache, the
    receiving node MUST update the associated binding entry in its
    Binding Cache.

  * If the Binding Identifier is not present in the Binding Cache, the
    receiving node MUST reject that Binding Identifier mobility option
    and send a Binding Acknowledgment with the status for that Binding
    Identifier mobility option set to [MCOA UNKNOWN].

------------------------------
End of new text to section 6.2
------------------------------

Fourth comment.

For section 6.3 on how HA sends BA for home link registration.  In
section 4.4, it states a new status value for BA called [MCOA
SIMULTANEOUS HOME AND FOREIGN PROHIBITED].  This is not reflected in
this section that when HA sends this.  Propose to add

-----------------------
New text to section 6.3
-----------------------

If the home agent is unable to support simultaneous home and foreign
attachment operation for a mobile node (e.g. due to administrative
policy), the home agent MUST reject the Binding Update and return [MCOA
SIMULTANEOUS HOME AND FOREIGN PROHIBITED] in the Status field of the
Binding Identifier mobility option.

------------------------------
End of new text to section 6.3
------------------------------

Fifth comment.

To be inline with the fourth comment, section 5.7 should state the
action for MN when receiving [MCOA SIMULTANEOUS HOME AND FOREIGN
PROHIBITED]. Propose to add text under the status code greater than 128
bullet.

-----------------------
New text to section 5.7
-----------------------

If [MCOA SIMULTANEOUS HOME AND FOREIGN PROHIBITED] is specified, it
indicates that the home agent is unable to support the simultaneous home
and foreign attachment operation for the mobile node.  The mobile node
SHOULD select to use either its home link attached interface or its
foreign link attached interface.  If the mobile node selects its home
link interface, the mobile node SHOULD follow the procedure defined in
section 5.5.1.  If the mobile node selects its foreign link interface,
the mobile node SHOULD follow the procedure defined in section 5.5.2.
Alternatively, the mobile node can discover another home agent that is
able to provide the simultaneous home and foreign attachment service.

------------------------------
End of new text to section 5.7
------------------------------

Sixth comment.

<snip from section 6.3>
If BID option is not included in the Binding Acknowledgement, the
home agent might not recognize the home registration.  The home
agent might have processed the home registration Binding Update as
a regular de-registration as described in [RFC-3775] and deletes
all the registered binding cache entries for the mobile node.
Thus, the mobile node SHOULD stop using the interface attached to
foreign link and use only the interface attached to the home link.
</snip>

The above text pertains more towards MN action rather that HA action.
Suggest the following proposal:

1) Remove the below old text from section 6.3

-----------------------
Old text in section 6.3
-----------------------

If BID option is not included in the Binding Acknowledgement, the
home agent might not recognize the home registration.  The home
agent might have processed the home registration Binding Update as
a regular de-registration as described in [RFC-3775] and deletes
all the registered binding cache entries for the mobile node.
Thus, the mobile node SHOULD stop using the interface attached to
foreign link and use only the interface attached to the home link.

2) Add new text to section 5.7

-----------------------
New text in section 5.7
-----------------------

If a mobile node attempts simultaneous home and foreign registration and
receives a Binding Acknowledgment with no Binding Identifier mobility
option present, the mobile node understands that the home agent does not
support the simultaneous home and foreign attachment operation.  Thus,
the mobile node SHOULD select to use only one of its interface.  If the
mobile node selects its home link interface, the mobile node SHOULD
follow the procedure defined in section 5.5.1.  If the mobile node
selects its foreign link interface, the mobile node SHOULD follow the
procedure defined in section 5.5.2.

------------------------------
End of new text to section 5.7
------------------------------