Subject: RE: [mobile-ip] question on BET tear down

From: James Kempf <[email-masked]>
Date: Thu, 6 Sep 2001 14:25:01 -0700 (PDT)

>> >> 
>> >	=> Only in one direction, because packets may stillbe forwarded 
>> >	from the old AR. 
>> >
>> 
>> If the nAR notices that packets are no longer being sent from the MN
>> with the old CoA, it can send a HRqst(r) with lifetime 0 to the old AR.
>> The old AR can return an HRqst(r) with lifetime nonzero to indicate
>> that it would like to prolong the forward tunnel, if there are 
>> still packets coming from CNs with the MN's old CoA. 
>> 
>	=> hmm, starting to look a bit messy though.
>

But doable. :-)

>> Anyway, the definitive indication is for the MN to send a BU to the
>> old AR, as per FMIPv6, when the BU/BAcks are in, and for old AR
>> to send the HRqst(r) to new AR with lifetime zero. This technique
>> is only for when there is no security association between the
>> MN and the old AR.
>> 
>	=> I'm not sure that relying on the BU to the oAR is a good
>	idea. In some cases there can be one BU sent if the HA is close
>	(local) or a MAP...etc.
>	I don't have an answer though as to how the tunnel should be torn.
>

What solution did the original FMIPv6 design team envision for this? 
The original design also had a forward tunnel to the new AR, though not the 
reverse tunnel, possibly for bicasting. I thought that the original
idea was to send the BU to the old AR  after the MN had completed
everyting for new CoA establishment. 

We could write the spec to discourage using a tunnel lifetime of
0xffff, which is good till cancelled, unless the ARs have some
means of definitively telling that the MN has completed L3 handover,
such as the BU or maybe the HRqst(r)/HRply(r) exchange. That way,
the tunnel will time out eventually if not renewed.

		jak

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 14 Sep 2001 14:49:35 -0700

James Kempf wrote:

> The original design also had a forward tunnel to the new AR, though not the

a binding cache entry created at the oldAR when a FBU was sent by
the MN to the oldAR. the FBU has a definite lifetime.

> everyting for new CoA establishment.

sending a BU to the oldAR after moving to the newAR is done only
in standard MIPv6. this is not needed in case of Fast MIPv6. this
is because FBU does this. the lifetime value in FBU can be large
enough to take care of all inflight packets between the CN and
the oldAR.

Vijay