Re: [MEXT] simultaneous mobility

[Ashutosh Dutta <adutta at research.telcordia.com>]

Marcelo,
         As per your suggestion and brief discussion during IETF 
meeting, I looked at RFC 3775. However, I have not seen anywhere about 
the fall back option if the mobile is already operating in RO mode. 
Section 11.8 in RFC 3775 discusses about the re-transmission of Care-of 
Test Init messages and Binding Update that may go on indefinitely.

"The retransmissions by the mobile node MUST use an exponential back-
off process in which the timeout period is doubled upon each
retransmission, until either the node receives a response or the
timeout period reaches the value MAX_BINDACK_TIMEOUT.  The mobile
node MAY continue to send these messages at this slower rate
indefinitely."


However, if the retransmission goes on for indefinitely due to 
simultaneous mobility and there is no fall back option, it might affect 
the real-time communication because of the delayed RO. Thus, we will 
probably need to find some solution either by specifying it as part of 
RFC 3775bis or some other solution.

It would be good to have some discussion on how to take care of this 
specific problem.

Regards
Ashutosh

marcelo bagnulo wrote:
>> b) it was suggested that it is not a problem when route optimization 
>> signaling is lost, because it will then fall back to bidirectional 
>> tunneling. However, once the communication session has been started 
>> and route optimization is in use, there is no mechanism specified in 
>> RFC 3775 to fall back to bidirectional tunneling (I'll let Ashutosh 
>> comment more on this point). Perhaps the introduction of such a 
>> fallback mechanism could be considered a candidate solution.
>>
> FWIW, imho this is how i would expect RFC3775 should behave, so imho 
> this is simply something that was not fully specified in rfc3775.
> I would treat it as an update in rfc3775bis
> 
> regards, marcelo
> 
> 
> 
>> thanks
>> Daniel
>>
>> -- 
>> Dr. Daniel Wong
>> Assistant Professor
>> Malaysia University of Science and Technology
>> ** check out my book on wireless IP at 
>> http://www.must.edu.my/~dwong/book.html 
>> <http://www.must.edu.my/%7Edwong/book.html> **
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>>
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