Subject: Re: [MEXT] [netlmm] Conclusion and way forward for PMIP6-MIP6 interactions

From: Basavaraj Patil <[email-masked]>
Date: Fri, 07 Nov 2008 15:35:10 -0600

<ccing MEXT because I think the MCoA discussion has relevance there>

Hi Vijay,

On 11/7/08 1:38 PM, "ext Vijay Devarapalli" <[email-masked]> wrote:

> Hi Vidya, Jonne,
> 
> For a mobile node that has two interfaces and wants to use both
> interfaces, while using the same home address across the two interfaces,
> we need some extensions. Mobile IPv6 [RFC 3775] does not allow a mobile
> node to use both the home link and the visited link simultaneously when
> the mobile node has only one home address.
> 
> For the home agent to allow the mobile node to use both the home link
> and the visited link, we need the MCoA extensions.

The MCoA extension allows the MN to register multiple CoAs associated with
the same HoA. The scenario where the MN is on its home link as a virtue of
PMIP6 on one interface and continues to be on a foreign link on another IMO
are not captured. Sec 5.6.  Returning Home: Simultaneous Home and Visited
Link Operation of I-D: draft-ietf-monami6-multiplecoa does provide some
guidelines but given that the PMIP6 aspect is not covered, it may be
worthwhile to revisit the issue.

> Specifically, the
> mobile node must indicate to the home agent that it wants to do so.

Agree. But this is specified in the MCoA I-D, right?

> 
> It doesn't matter if the home link is provided by PMIPv6, GTP or direct
> attachment to the home link, the above is valid.

In the case of PMIP6, there is a BCE for the MN in the LMA, unlike the MIP6
case where the MN returns home and the BCE is deleted.

> 
> Instead, what I see being designed is a solution where the GTP/PMIPv6
> process on the GGSN/LMA/HA entity maintains state that is independent of
> the HA process on the same GGSN/LMA/HA entity. In fact what you are
> trying to force through consensus here, i.e., keep the MIPv6 and PMIPv6
> BCE separate is actually influenced by an SDO-specific scenario.

While an SDO has an interest in keeping the BCEs separate, why would the
same not apply in general as well? Given the scenario, I do think that
having separate BCEs is the correct approach.

> I 
> believe there is a scenario in 3GPP where folks wanted the mobile node
> to be able to keep its GPRS/UMTS interface up, while using another
> interface like WiFi, so that it can quickly fall back to the GRPS/UMTS
> interface, when it loses WiFi access. And you are saying, we shouldn't
> consider SDO-specific scenarios. When you said that, my initial reaction
> was "you gotta be kidding me". :)

And what is wrong with such a scenario and for the WG to address it. Because
the scenario is not SDO specific.

> 
> I am not saying the above is not a valid scenario. Lets support it, but
> in the right away, by an explicit indication from the mobile node to the
> home agent that it does want to use the home link and the visited link
> at the same time. This would allow the GGSN/LMA/HA entity maintain
> forwarding state for both the home link and the visited link at the same
> time. This would work irrespective of how the home link is created.

Good. As I said it may be worthwhile to add the PMIP6 created home link
scenario to the MCoA I-D.

> Lastly, we do need to consider the single radio handover in the
> PMIPv6-MIPv6 interactions document. I don't understand how you can
> declare that out-of-scope.

The concept of single radio is not applicable in the context of IETF IMO. A
host may be able to use multiple interfaces simultaneously. If we go down
the path where we start discussing why the host may not be able to do so, we
are essentially getting down in to the details of PHY/MAC issues,
interference, spectrums that the interfaces may be operating in, and many
other issues. This is not in the domain of the IETF WGs. It is better to
define optimizations for handovers which do not necessarily assume too much
about whether the underlying interfaces operate (connect/attach)
simultaneously or otherwise.

-Raj

> Vijay

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---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 07 Nov 2008 13:48:09 -0800

> worthwhile to revisit the issue.

This was brought up during the AD review of the MCoA draft. It shouldn't 
matter if the home link is created by the MN attaching directly to the 
home agent or by GTP or PMIPv6. The MCoA extensions can be used. The 
plan is to add some text on this.

> case where the MN returns home and the BCE is deleted.

In the simultaneous home and visited link attachment, there is a binding 
for the home link too.

Vijay