Subject: [MOBILE-IP] Deregistration question...

From: Jonathan Khoo <[email-masked]>
Date: Tue, 13 Jun 2000 23:06:16 SGT

Hi there,

A great thanks for all those who replied my previous mail! :)

I was reading the latest draft revision of RFC2002 and I came across the
part on the deregistration with HA.

It was mentioned in the draft that the HA should transmit gratuitous ARP
together with the (de)Registration Reply. The MN must transmit the
gratuitous ARP before the HA begins the deregistration process.

It was also mentioned later in the draft the if the HA rejects the
(de)registration process, then no ARP processing is perform by the HA.

Now, please correct me if I am wrong, if the MN sends the ARP packet before
the deregistration process and the process fails, isn't there a possibility
that some of the packets might be sent to this MN as their ARP tables might
be updated with the gratutious ARP sent by the MN earlier?

Thanks and have a nice day.

Jonathan Khoo
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---

From: Steven Glass - Solaris Software <[email-masked]>
Date: Tue, 13 Jun 2000 12:17:25 -0400

> be updated with the gratutious ARP sent by the MN earlier?

    I suppose the ordering of most events is implimentation specific, but...

    The MN has to begins the deregistration process, as this is based on its
move detection.  The HA processes the deregistration requests, if it's
acceptable, removes the MN's binding, and sends a deregistration reply.  The
MN processes the deregistration reply, and if it's acceptable, sends its
address-claiming gratuitous arp.

     Yes, there is a non-zero amount of time between being removed from the
HA's binding, and reclaiming your address, but that's not really relavent.
One of the risks of roaming is not being where your traffic is going, and
happens everytime a MN roams, and many drafts specify FA's caching packets,
then delivering them to the new CoA upon getting binding updates.  To get a
clearer picture, try any that deal with fast handoff or route optimization.

                              Cheers,
                                  Steve