Subject: Re: [MEXT] Text to close issue #9 (Simultaneous Mobility)

From: Hesham Soliman <[email-masked]>
Date: Thu, 05 Mar 2009 22:00:58 +1100

Hi Charlie, 

Please find a suggestion below.

<text> In some scenarios, such as simultaneous mobility, where both
correspondent host and mobile host move at the same time, or in the case
where the correspondent node reboots and loses data, route optimization may
not complete, or its data in the binding cache might be lost.

To provide graceful recovery from those cases, the following should be done:

- Return Routability signalling MUST be sent to the correspondent node's
home address if it has one (i.e. If the correspondent node is also mobile)

- If Return Routability signalling timed out after MAX_RO_FAILURE attempts,
the mobile node MUST fallback to sending packets through its home agent, to
the correspondent node's home address.

The mobile node may run the bidirectional tunnelling in parallel with the
return routability procedure until it is successful. Exponential backoff
SHOULD be used for retransmission of return routability messages.

The return routability procedure may be triggered but movement or sustained
loss of end-to-end communication with the correspondent node (e.g. based on
indications from upper-layers). If such indications are received, the mobile
node may revert to bi-directional tunnelling while re-starting the return
routability procedure.

</text>

MAX_RO_FAILURE = 3

I hope this is a good start. I tried to account for both simultaneous
mobility and loss of the BC entry.

Hesham

On 28/02/09 4:50 AM, "Charles E. Perkins" <[email-masked]>
wrote:

> 
> Hello Hesham,
> 
> You are on the hook for some text to close issue #9.
> According to the minutes:
>> - issue #9, simultaneous mobility (defect)
>>   Nobody has observed this in practice, it may be a rare case that doesn't
>>   require a solution.  There are multiple proposals and possibilities, but
>>   none are clearly winners.
>>   Raj Patil thinks we should pull RO out and publish separately, fixing
>>     this problem there.
>>   Julien proposes to leave it as an implementation issue.
>>   Hesham says we can explain the tradeoffs.
>>   *HESHAM WILL SUPPLY CHARLIE WITH A ROUGH DRAFT OF DESCRIBING TRADEOFFS OF
>>     DIFFERENT METHODS TO DETECT WHEN TO FALL BACK TO REVERSE TUNNELLING*
>>   
> 
> I looked, and I don't think I ever received anything from
> you about this.  Could you supply some text in the next
> few days?
> 
> Thanks in advance for your consideration of my request!
> 
> Regards,
> Charlie P.
> 
>

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From: <[email-masked]>
Date: Thu, 5 Mar 2009 20:08:43 +0100

Hi Hesham,

While your text does propose some corrective actions that the MN could take
in the scenario where the MN and CN are mobile, I do not believe it is going
to make the RO feature in the base spec any more usable. I am fine with
having this text included in the 377bis version of the I-D if there is
consensus that it covers a missing scenario and is useful to do so. I would
also be okay if nothing is changed with the route optimization feature in
the base spec and instead the WG decides to work on specifying this feature
in a separate spec and address all scenarios.

-Raj

On 3/5/09 5:00 AM, "ext Hesham Soliman" <[email-masked]> wrote:

> _______________________________________________
> MEXT mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mext

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From: Ashutosh Dutta <[email-masked]>
Date: Thu, 05 Mar 2009 14:19:07 -0500

Hesham, Raj,

I am Ok with the suggested text, and I also think it is probably good to 
have this text in 3775bis version to cover the simultaneous mobility 
scenario.

Also, the following paragraph (first sentence) does not read well, there 
is perhaps a typo.

"The return routability procedure may be triggered but movement or 
sustained loss of end-to-end communication with the correspondent node 
(e.g. based onindications from upper-layers). If such indications are 
received, the mobile node may revert to bi-directional tunnelling while 
re-starting the return routability procedure."

Thanks
Ashutosh

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From: Hesham Soliman <[email-masked]>
Date: Fri, 06 Mar 2009 13:41:44 +1100

> "The return routability procedure may be triggered but movement or

=> sorry s/but/by

Hesham