Subject: [MOBILE-IP] [Fwd: Thought.. when a CN should send Binding Request]

From: Timothy J Kniveton <[email-masked]>
Date: Wed, 13 Dec 2000 08:21:53 -0800

-------- Original Message --------
Subject: Thought.. when a CN should send Binding Request
Date: Tue, 12 Dec 2000 14:38:22 -0800
From: "T.J. Kniveton" <[email-masked]>
To: <[email-masked]>

Hi,

I am curious whether anyone has opinions on how to formulate a policy
for
sending Binding Requests from a Correspondent Node in Mobile IPv6. The
draft
suggests that it be done whenever a Binding is about to expire, if there
is
active communication happening with that Mobile Node and it "has
indications, such as an open TCP connection to the mobile node, that it
will
continue this communication in the future."

Since it's possible that the two nodes are engaging in connectionless
communication, looking at state such as an open TCP connection, is not
really sufficient to gauge whether communications will continue in the
future.

One simple policy is to define a BR trigger value, such that when the
Binding Cache Entry's timeout falls below this value, any packet sent to
the
Mobile will include a Binding Request.

In this way, a BR is sent when there is active communication (regardless
of
whether it's stateful), but it is not sent if there is nothing traveling
between the CN and the MN. The interval between the trigger value and
the
BCE timeout should be set large enough so it is sufficient to pick up
active
traffic.

Any comments or suggestions?

Thanks,

--
TJ Kniveton
NOKIA Research

---

From: Francis Dupont <[email-masked]>
Date: Wed, 13 Dec 2000 19:04:31 +0100

I am curious whether anyone has opinions on how to formulate a
  policy for sending Binding Requests from a Correspondent Node in
  Mobile IPv6. The draft suggests that it be done whenever a Binding is
  about to expire, if there is active communication happening with that
  Mobile Node and it "has indications, such as an open TCP connection to
  the mobile node, that it will continue this communication in the
  future."

=> specs suggests this because this is very easy to implement but you
can use what you want, for instance a real inactivity detection.
It is not critical to send BRs because if a binding times out then the
first packet on the unoptimized path will recreate it. This is just
a trade-off between a proactive and a reactive way to refresh bindings...
The MN can refresh bindings too (and should do it in some cases, for
instance for home registrations).

=> I agree and you have the same issue for the IPsec security association
(there should be one for BU).

   One simple policy is to define a BR trigger value, such that when the
   Binding Cache Entry's timeout falls below this value, any packet sent to
   the Mobile will include a Binding Request.

=> this is a possibility. It can be very easy or a bit expensive depending
of your implementation (binding cache management) and/or context (for
instance the number of bindings). Do what you'd like... and keep specs
as simple as possible!

=> done!

[email-masked]