Re: [netext] Update on flow mobility following discussion with ADs

[<[e-mail]>]

Hi Stefano,

Inline below:

From: ext Stefano Faccin <[e-mail]<mailto:[e-mail]>>
Date: Wed, 2 Mar 2011 13:51:25 -0600
To: Patil Basavaraj <[e-mail]<mailto:[e-mail]>>, Netext <[e-mail]<mailto:[e-mail]>>
Subject: RE: [netext] Update on flow mobility following discussion with ADs

Raj,
Thanks for the notes. There is one aspect that concerns me, and is related to :

“2. There is no plan or expectation that there would be a way for the
   MN/host to do signaling related to flow mobility with a MAG at
   layer 3. Layer 2 is an option but obviously this requires such
   enhancements to be done in other SDOs. The preference is to develop
   a flow mobility solution that works with policies and signaling
   that is network centric (i.e MAG/LMA entities).
”

Personally I am concerned about this. What is the usefulness in netext providing an “alternative” IP flow mobility solution that provides only a subset of the functionality of a host-based solution. Deployments of such so called alternative would provide a limited services with respect to deployments of the host-based solution. Why would anybody want to step back in time?

Raj> I would not consider PMIP6 based flow mobility as an alternative to the host based solution that is specified in RFCs 6088/9. The type of mobility capability in a deployment can vary. The PMIP6 based flow mobility would be applicable in deployments which leverage network based mobility. Whether the functionality provided by this capability is sufficient, is a conscientious decision that will be made by the operator. It is a matter of choice and what I am saying is that the scope of this work is NOT intended to provide the same set of capabilities that exist in the host based flow mobility solution.


As for:

“The preference is to develop
   a flow mobility solution that works with policies and signaling
   that is network centric (i.e MAG/LMA entities).
”
I can understand the point, but I have a question. As an example, 3GPP (that can be one of the potential customers and that we can surely not disregard) has been very keen in indicating that the user (whether it be the actual human being using the MN or e.g. the enterprise owning the MN) has priority wrt the policies defined by the operator. This is because in several scenarios the user may have preference for certain accesses (e.g. the enterprise WiFi) that are not provided by the operator for certain services (e.g. access to the enterprise resources). In such case, 3GPP has recognized the need to allow the user to have precedence. If the solution designed by netext is based solely on network policies and decisions, I am afraid we would have a solution that does not allow valid scenarios that have been identified by one of the potential customers for the solution.

Raj> A network centric flow-mobility solution may not be able to address all the scenarios that 3GPP is considering. But a subset of those may be dealt with via this feature. As long as the document is clear about what is in scope and possibly documenting some of the limitations as well, it would be useful to specify it. There could be other types of networks that could use such a solution as well.

-Raj

Cheers,
Stefano Faccin

Standards Manager
Research In Motion Corporation
5000 Riverside Drive
Building 6, Brazos East, Ste. 100
Irving, Texas 75039 USA
Office: [phone]
Internal: 820.63451
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From: [e-mail]<mailto:[e-mail]> [mailto:[e-mail]] On Behalf Of [e-mail]<mailto:[e-mail]>
Sent: Wednesday, March 02, 2011 9:04 AM
To: [e-mail]<mailto:[e-mail]>
Subject: [netext] Update on flow mobility following discussion with ADs


Just wanted to provide an update regarding the ongoing work on flow
mobility for PMIP6 and my discussion with our ADs (Jari and Ralph) on
March 1st:

I have apprised our ADs about the state of the ongoing discussion on
flow mobility. One of the concerns about the ongoing work on flow
mobility was related to the logical interface feature. Flow mobility
depends on the existence of a logical interface on the host. The WG
has not addressed the concerns related to the logical interface I-D,
that were raised at the previous WG meetings. Emphasised that we
should get the logical interface spec done soon since it is a
fundamental dependency for flow mobility.

Regarding the current scope of the flow mobility work and the I-D
which is now in consensus call, there are a few issues that need to be
resolved. A few points below:

1. Flow mobility in the context of Proxy MIP6 is not analogous to the
   solution that has been developed for host based MIP6. The
   featureset and capabilities developed in Netext does not have to
   mirror, parallel or be equivalent to that of RFCs 6088/9.

2. There is no plan or expectation that there would be a way for the
   MN/host to do signaling related to flow mobility with a MAG at
   layer 3. Layer 2 is an option but obviously this requires such
   enhancements to be done in other SDOs. The preference is to develop
   a flow mobility solution that works with policies and signaling
   that is network centric (i.e MAG/LMA entities).

3. One of the major concerns raised on the mailing list is related to
   how flow mobility would work when an MN attaches to a wifi access
   and the LMA switches a flow(s) to the MAG serving the MN via that
   wifi. The MN has no way of indicating to the LMA if the wifi access
   is congested or for the MAG to indicate to the LMA about the state
   of the MNs attachment to the AP. Packets forwarded by the LMA to
   the MN via the wifi-MAG could be sent into a void.
   Without a solution for the above scenario, flow mobility would not
   be robust. Some clear answers are needed here.

   One option is that flow mobility for PMIP6 is applicable only in
   those access networks wherein the access network elements are aware
   of the state of the MNs connection and congestion state. The MAG
   can use this information to signal to an LMA attachment state and
   potentially cause flows to be switched to an alternative MAG. It
   may be okay to have specific statements about the limitations of
   flow mobility for PMIP6 documented as a sort of disclaimer.

   Other options?

4. The WG is free to extend the PMIP6 signaling between MAG/LMA to
   accomplish flow mobility.

5. And lastly the question about who is the customer for this work at
   this time is irrelevant. We have had this discussion during the
   chartering phase and there is no reason to revisit it.

If I have missed any other significant (show-stopper) concern
regarding the flow mobility feature, please do raise them.

-Raj
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