Re: [netext] NETEXT2 BOF conclusion

["Mohana Jeyatharan" <Mohana.Jeyatharan at sg.panasonic.com>]

Hello Jari,

Thanks for the mail.

The informational document based on approach 1, is it going to analyze
or identify requirements needed to perform inter RAT handoff and
multihoming(flow mobility) etc for PMIP?  Is that the goal of the
document?


BR,
Mohana

> -----Original Message-----
> From: netext-bounces at ietf.org [mailto:netext-bounces at ietf.org] On
Behalf
> Of Jari Arkko
> Sent: Thursday, October 22, 2009 5:29 AM
> To: netext at ietf.org
> Subject: [netext] NETEXT2 BOF conclusion
> 
> I have been trying to come up with a way forward on this, but its
hard.
> To recap, there are a few different technical possibilities for
> multi-interface mobility:
> 
> 1) Link layer hides interface variants behind one logical interface.
For
> instance, an IP stack does not see the change from GSM to UMTS radio
or
> 802.11b to 802.11g; its handled as a part of the link layer. Such link
> layer operations need to be supported both by the host and the
network.
> This approach has the minimum impacts on IP stack, but requires
> specification of the link layer mechanisms across the used interfaces.
> 
> 2) Different interfaces are handled via existing host-based mobility
> mechanisms (Mobile IPv6, MOBIKE, HIP, application layer). Within one
> interface the link layer handles mobility, possibly using Proxy MIP
> internally. Both the host and the network need to support the
host-based
> mobility mechanism, but the link layer does not have to aware of the
> other interfaces in any way.
> 
> 3) We extend Proxy MIP with capabilities to handle cross-interface
> handovers. This is similar to approach #1, but the signaling messages
> are at the IP layer. The benefit is that this could be used across
> different types of link layers even if they do not support handovers.
> The downside is that just as with approach #2, the IP stack has to be
> capable of these operations.
> 
> The big argument we have been stuck with since San Francisco is
between
> #2 and #3. One group believes that existing mechanisms are sufficient,
> and they are -- it is indeed possible to do this. Another group
believes
> that they need a different solution based on Proxy MIP. Such a
solution
> is also of course possible. But we've made very little headway in
> resolving the question on what should be done. In particular, we've
not
> been able to describe very well why some technical reasons would
dictate
> one or the other solution. I believe that is likely because they are
> really very similar solutions.
> 
> At this point I do not believe we have consensus to go forward. We
left
> the BOF with the idea that requirements work would solve this issue.
If
> I'm right the solutions really are very similar, this work may not be
> able to resolve the conflict, and it would take a long time. I think
it
> would actually serve as better if we were to decide now, as opposed to
> pretending that more details will make the decision easier.
> 
> With this in mind, I have a proposal for a way forward. Given that I
do
> not see consensus for approach #3, I do not think we can go ahead with
> that. I also personally believe that #2 and #3 are functionally
similar
> enough that there's no requirement that forces us to pick #3. In
> addition, approach makes mobility end-to-end between the host and a
> network node; approach #3 ties the use of mobility to a particular
link.
> If the router on that link does not support the mobility mechanism,
> mobility service is not possible. I think it would be architecturally
> better to separate access and mobility.
> 
> However, I would like to move forward with a different work item. The
> IETF has never really explored approach #1, even if it is commonly
used.
> Of course, the IETF's role is not to design these link layer
mechanisms,
> but I believe it would be valuable for the IETF to publish an
> informational document on considerations for building such mechanisms.
> This document would talk about the requirements that the mechanisms
must
> fulfill in order for IP to work correctly, when such mechanisms are
> recommended and when not, what their advantages and downsides are,
what
> happens if MTUs or routers differ, and so on. At the same time this
> document would describe the "virtual link" model that some people have
> been using in the context of Proxy MIP. The idea is to add this work
> to the NETEXT WG charter.
> 
> I realize this does not make everyone happy, but I'm not sure there
> is an outcome that does. What we lose by not doing solution 3 is
> a design that that simultaneously allows something to be done
> in a link-layer agnostic manner _and_ employs PMIP as a part of the
> solution.
> 
> Thoughts?
> 
> Jari
> 
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