Subject: [Monami6] BID sub-option C flag should not be set when R flag is set

From: Heikki Mahkonen <[email-masked]>
Date: Tue, 04 Jul 2006 17:00:51 +0300

Hi Ryuji,

In the MCoA draft you have written the following in section 4.3.1:

4.3. Message Format Changes

4.3.1. Binding Unique Identifier sub-option

Care-of Address (C) flag

When this flag is set, a mobile node can store a Care-of Address
correspondent to BID in the Binding Unique Identifier sub-option.
This flag must be used whenever a mobile node sends multiple
bindings in a single Binding Update, i.e. bulk registration.

Removable (R) flag: TBD

When this flag is set, a mobile node request a Home Agent to
remove the binding correspondent to BID, even if the binding
update is not for de-registration. This flag is valid only when
bulk registration is used (C flag is set). This option may be
obsolete in the future revision.

I think that in some cases the Mobile Node has a need to update some of
the bindings and remove the not needed ones in one BU message.
When this is done in a bulk registration the R-flag is usable for
the BIDs (CoAs) no longer configured to the network interface
of the Mobile Node. However, I don't think it is necessary to set
the C-flag and add the CoA into the sub-option when the Mobile
Node is removing a BID. It should be enough to tell the HA that
this BID must be removed. I mean the BID is used to reference
the BC entry which is to be removed. I think this was the original
idea to add the R-flag in the first place. To make it possible to
remove some of the BIDs and update some in the same bulk
registration BU message.

Best regards,

Heikki Mahkonen

_______________________________________________
Monami6 mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/monami6

---

From: Ryuji Wakikawa <[email-masked]>
Date: Tue, 11 Jul 2006 03:48:47 +0900

Hello Heikki

> remove some of the BIDs and update some in the same bulk

It is clearer to say that the C flag must be set for bulk  
registration BUs,
regardless of registration or de-registration.
I prefer not assigning multiple meanings to a flag.

what do you think
ryuji

---

From: Heikki Mahkonen <[email-masked]>
Date: Tue, 11 Jul 2006 08:34:32 +0300

Hi,

Ryuji Wakikawa wrote:
> It is clearer to say that the C flag must be set for bulk registration BUs,

==> I think that the C flag does not have to be set for every BID
sub-option in a bulk registration BU message. My understanding is that
it is needed to indicate that the BID sub-option carries a CoA not that
this BU message is bulk one. I mean one of the BID sub-options must be
sent in the short format anyway in a bulk BU message. This "short" BID
sub-option carries the BID for the CoA in the IPv6 header or in the ACoA
option. My understanding was/is that the C flag says that this BID
option is 16 bytes longer than the basic/short BID sub-option because it
carries a CoA.

In addition, when MN is removing a binding in bulk registration case, I
don't think that it has to send the CoA that it is removing to the
HA/CN. This is because when the MN is using MCoA mechanism it can use
the BID of the binding it wants to remove to refer to the BUL/BC entry.
This means that the CoA can be left out from the BU message altogether
and just add a BID sub-option in the shorter 4 byte format and set the R
flag to one to indicate that the BC entry with this BID should be
removed/de-registered. This reduces 16 bytes from a bulk BU message. At
least this was my original motivation of suggesting the R flag.

Best regards,

Heikki Mahkonen