Subject: [Monami6] (Issue-1 MCoA) Changing Semantics of Bulk Registration

From: RYUJI WAKIKAWA <[email-masked]>
Date: Mon, 20 Nov 2006 03:36:17 +0900

Dear all

Here is an issue of MCoA.
Your comments are appreciated.

"Issue-1"

It is complicated for MN and HA to process active CoAs and failed CoAs
in a single BU with the Removable flag.

* Proposal: Changing the semantics of the bulk registration.
- (Current)
    Bulk Registration
       A mobile node can register multiple bindings by sending a binding
       update.  Several care-of addresses can be stored in a Binding
       Update.  The bulk registration is supported only for home
       registration.  Note that a mobile node should not try to perform
       bulk registration with Correspondent Nodes.
       Note that the reciever only updates the received binding.

- (Propose)
    Bulk Registration
       A mobile node can register all the active bindings at a time by
       sending a binding update.  All the active care-of addresses must
       be stored in a Binding Update.  The bulk registration is
       supported only for home registration.  Note that a mobile node
       should not try to perform bulk registration with Correspondent
       Nodes.  The receiver of this binding update, it replaces all the
       bindings to the received bindings.
     * NO need to store removed CoAs with the removable flag in a BU,
       but always store all the active CoAs.

* pros & cons

When a mobile node reboots and forgets the BIDs it had, it has to send
a legacy BU first to make sure all binding entries are deleted.
Otherwise, the garbage bindings may be left on the HA.  Ideally, the
MN should verify whether the HA keeps garbage bindings or not, by
sending a legacy BU. This may be redundant operation in the most of
scenarios.

With the proposed semantics, the MN sends only a BU in the bulk
registration mode, though the MN MUST always use the bulk registration
for its first registration to its HA.
On the other hand, there is undesirable scenario that MN wants to
update only two CoA when ten CoAs are available.  The 8 CoAs are
redundant for MN and HA.  It consumes bits on the air and causes
additional processing overhead to MN and HA.  Therefore, Jari propose
"Add-on Flag" for bulk registration.  If this Add-on flag is set, HA
adds the received CoAs in HA's binding cache database.  This flag
isn't so important since MN can send two non-bulk BUs for the two new
CoAs. There is also similar scenario when two binding needs to be
deleted when 10 bindings are active.  In this case, 8 active CoAs are
redundant.  Thus, tMN can sends two non-bulk de-registration BUs for
the two CoAs instead of using the bulk registration.

* Conclusion. (PENDING)

1. (REJECTED) Keep the current semantics and Removable flag
2. (ACCEPTED) Change the semantics, but  no add-on flag
3. (ACCEPTED) Change the semantics and define add-on flag, too.
4. !?

any comments?

regards,
ryuji

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From: "Tsirtsis, George" <[email-masked]>
Date: Mon, 20 Nov 2006 13:20:44 -0800

Hi Ryuji,

I think if bulk registration is used all the time, all the CoAs will end
up having the same lifetime. So, there should be no reason to refresh
only some of them....which seems to be the purpose of the "add-on flag".
The only reason to send a BU (other than refreshing all the CoAs) would
then be to either add or remove CoAs.

Unless I am missing something, I am in favor of:
 2. (ACCEPTED) Change the semantics, but  no add-on flag

Regards
George

> -----Original Message-----
> From: RYUJI WAKIKAWA [mailto:[email-masked]]
> Sent: Sunday, November 19, 2006 1:36 PM
> To: Monami6 WG
> Subject: [Monami6] (Issue-1 MCoA) Changing Semantics of Bulk
Registration

---

From: Romain KUNTZ <[email-masked]>
Date: Wed, 29 Nov 2006 11:15:30 +0700

Hi Ryuji,

The proposition is still quite unclear for me, comments below.

>       bindings to the received bindings.

I guess this means that bindings not updated by the BU must be removed? 
It should be explicitely said in the text:

"The receiver of the bulk registration BU must replace all the bindings 
for the HoA and BID specified in the BU to the received bindings, and 
remove all the other ones that are not updated by the BU for this 
specific HoA."

> for its first registration to its HA.

This "MUST use the bulk registration" should appear in the text above. 
But if the multihomed MN wants to register only one CoA/BID at startup 
(because another interfaces are not ready yet), what should be its 
behaviour? Use the Bulk BU with bulk reg. flag, but only with one CoA in it?

> the two CoAs instead of using the bulk registration.

But the text above states that "The bulk registration is supported only 
for home registration", so when the MN wants to update/delete two CoAs 
over 10, it has to use legacy BUs, right?

Another observation: when I usually use a MN/MR with multiple 
interfaces, all the interfaces are never configured and ready-to-use at 
the same time at the booting time. And introducing some mechanisms in 
the implementation to wait for all the interfaces to be up and 
configured is too complex and useless IMHO. So I would personally 
implement a MN that sends a BU with a single CoA/BID each time an 
interface is ready to be registered.

To summarize my point, is Bulk BU at booting time really useful? I think 
BULK BU may be more interesting when the MN wants to update several 
CoAs, after the booting time (to refresh the lifetime for example, or 
de-registrate several CoAs at the same time, for example when the MN 
returns home). But this is forbidden by your proposal ("The bulk 
registration is supported only for home registration"

> 3. (ACCEPTED) Change the semantics and define add-on flag, too.

4. rejected and new proposal:

[sorry if it has already been discussed before, looks like I missed the 
discussion]:

- either do not use bulk registration and keep the draft as it was 
initially (ie always use usual BU). If the point is the garbage bindings 
on the HA on reboot, then we can certainly do something with the home 
registration flag when the HA receives a new home registration BU from a MN.

- or use bulk registration for home registration and/or to update/delete 
CoAs, but with no obligations, and only CoAs in the bulk-bu are treated, 
other CoAs (the one not in the BU) not being touched nor deleted.

Regards,

-- 
Romain KUNTZ
[email-masked]