Subject: [mobile-ip] Closing issue #279 (NS source while returning home)

From: Jari Arkko <[email-masked]>
Date: Fri, 11 Apr 2003 12:35:48 +0300

I'm trying to close issue #279, which had to do with the
source address of Neighbor Solicitations from the home agent
when the mobile node is returning home. In IETF-56, we discussed a
number of alternatives. Most people seemed to favor an approach
originally suggested by Vijay, where the mobile node can start
answering Neighbor Solicitations sent from any address, right after it
has sent a Binding Update, even before receiving a Binding
Acknowledgement.

The current text is

     After the Mobile Node sends the Binding Update, it MUST be
     prepared to reply to Neighbor Solicitations from its home
     agent. The replies MUST be sent using a unicast Neighbor
     Advertisement to the home agent's link-layer address.

The problem was that we didn't know which address the home agent would
use, so it couldn't really be implemented. Here's the text proposal
that relaxes the rule so that the check for the home agent is no
longer necessary:

     After the Mobile Node sends the Binding Update, it MUST be
     prepared to reply to Neighbor Solicitations for its home address.
     Such replies MUST be sent using a unicast Neighbor Advertisement
     to the sender's link-layer address. It is necessary to reply,
     since sending the Binding Acknowledgement from the home agent may
     require performing Neighbor Discovery, and the mobile node may not
     be able to distinguish Neighbor Solications coming from the home
     agent from other Neighbor Solications. Note that a race condition
     exists where both the mobile node and the home agent respond to
     the same solicitations sent by other nodes; this will be only
     temporary, however, until the Binding Update is accepted.

Comments appreciated.

--Jari

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From: "Ed Remmell" <[email-masked]>
Date: Fri, 11 Apr 2003 08:36:00 -0700

>      temporary, however, until the Binding Update is accepted.

Looks good to me.

Thanks!
- Ed