Subject: [mobile-ip] Receiving Binding Refresh Request

From: [email-masked]
Date: Thu, 16 May 2002 15:08:43 +0530

Hi Kalyan,
You wrote:

>    Any node which is observing the traffic can pretend like a CN and it
may
> send a BRR with the CN's address.

> As per the security is concerned,MN MUST communicate with those CNs only
for
> which it is having entry in the BUL.

This is fine, for a BRR message from an unknown CN.
The draft also has clearly mentioned that "the mobile node SHOULD NOT
respond Binding Requests from previously unknown nodes due to
Denial-of-Service concerns."

My question is, MN has a valid binding with a CN and communication to that
node is in progress, & still requires Route optimization. In the meantime
(i.e., assume when 90% of the lifetime is over), MN get's a BRR message
from CN.  MN starts initiating RR procedure and changes state from "Bound"
to "WaitHC". MN looses route optimization during the 10% of MN's valid
lifetime or till BU procedure is complete, whichever is less.

Here the purpose of initiating BRR message before binding expires, is to
maintain route optimization steadily.

Even if the BRR message is not there, once when the lifetime expires, the
packets will be tunneled to MN and MN will initiate the RR procedure.
Inorder to avoid this, CN initiates BRR when the lifetime is about to
expire.

But I feel the purpose of BRR, is not met...

regards
srinivasan

---

From: Jari Arkko <[email-masked]>
Date: Fri, 17 May 2002 19:13:49 +0300

> But I feel the purpose of BRR, is not met...

You are right; if bidir routing is immediately adopted, the BRR functionality
would be equivalent to the BM functionality!

It seems though that the current specifications are unclear with respect to
whether bidir routing should be adopted immediately upon receiving a BRR.
Specifically, it doesn't say anywhere that if your state is WaitHC then you
should not use Route Optimization. (In fact, if it would not have required doubling
the number of states, I would have written the state machine in a way that
you would have had WaitHC-Nobinding and WaitHC-Binding.)

We need to clarify this issue. This can probably be done at the same
time as the state machine is being rewritten in a more compact form, based
on an idea from Charlie that we could keep the binding and the rr state machines
separate.

In conclusion, the specification should say that route optimization can continue
even after receiving a BRR until the lifetime of the binding expires or a BM
is received.

Assigned issue #28.

Jari