Subject: Re: [mobile-ip] Mipv6 issue #150: de-reg and failure

From: Jari Arkko <[email-masked]>
Date: Tue, 19 Nov 2002 15:23:13 +0200

Marc Hasson wrote:

> Is that really true that a MN won't respond to the NS?  We have a
> SHOULD in this text from the latest Oct 28 draft in section 13.6.4 on
> Returning Home for the non-error case:
> 
>    After the Mobile Node sends the Binding Update, the Home Agent MUST
>    remove the Proxy Neighbor Cache entry for the Mobile Node and MAY
>    learn its link-layer address based on the link-layer packet or cached
>    information, or if that is not available, it SHOULD send a Neighbor
>    Solicitation with the target address equal to the Binding Update's
>    source IP address.  The Mobile Node MUST then reply with a unicast
>    Neighbor Advertisement to the Home Agent with its link-layer address.
>    While the Mobile Node is waiting for a Binding Acknowledgement, it
>    MUST NOT respond to any Neighbor Solicitations for its Home Address
>    other than those originating from the IP address to which it sent the
>    Binding Update.
> 
> 
> Doesn't the above text about the MN responding only to the HA handle
> the issue of getting back the error'ed BA as well?  That is, assuming one's
> implementation can deal with preserving the Proxy ND cache entry while
> also soliciting for the actual MN just for this particular error case
> packet (whose src on this NS must match the original BU dst)?

Yes.

> If agreed, then the MUST in the latest proposed/included text should
> only be that the packet is sent to the local MN whose link-layer
> address is obtained either through the link-layer address of the
> original BU packet or by NS with the MN itself.  The *protocol*, due to
> the MN responding to HA's NS, handles this error case already.
> Implementations should be free to choose which way to satisfy getting
> the BA back, error'ed or not.  One *could* take the NS approach anyway
> regardless of the spec, since the MN doesn't yet know an error is due
> it, and then send the error'ed BA back.  And things would work except
> for a potential conformance tester complaint seeing the NS/NA, right?

Yes.

> Also, I was concerned about this new link-layer address MUST
> requirement in the text that ended up (now) in 11.0.2 that was
> suggested above to handle this error case.  We didn't have a MUST
> requirement on implementations before to pass/preserve/deal with a
> link-layer address across v6 stack, IPsec, and mobility module, both
> inbound and outbound on MH packets.  I note that ha-ipsec-01 requires
> in section 5.1 that even on the home link a BU MUST come in with an
> IPsec header, so this new link requirement really means at least all those
> areas in my previous sentence must coordinate, even if "passively", on
> the original source link-layer address associated with a packet.  I
> don't think that this error path case is sufficiently different to
> require this link-layer MUST when the non-error case already has a
> protocol way to do it without looking at the original BU's link-layer
> address.

Agreed. Here's proposed fixed text:

    ... MUST send it to the same link-layer address as the Binding
    Update came from.

    =>

    ... MUST send it to the mobile node's link layer address (retrieved
    either from the Binding Update or through Neighbor Solicitation).

Jari

---

From: Marc Hasson <[email-masked]>
Date: Tue, 19 Nov 2002 13:20:29 -0800 (PST)

Jari,

 >     either from the Binding Update or through Neighbor Solicitation).

Sounds good to me.

Thanks.

   -- Marc --