Subject: [netext] comments/question on draft-ietf-netext-pmipv6-flowmob

From: <[email-masked]>
Date: Fri, 3 Feb 2012 14:58:20 +0100

Hi Carlos and flowmob authors,

In draft-ietf-netext-pmipv6-flowmob-02, LMA-initiated handover is
supposed to be out-of-scope
(http://www.ietf.org/mail-archive/web/netext/current/msg02184.html).

However, on section 3.2.2, it is stated:

The trigger for the flow movement can be on the mobile node (e.g., by
using layer-2 signaling, by explicitly start sending flow packets via a
new interface, etc.) or on the network (e.g., based on congestion and
measurements performed at the network).

It should be:

------------------------

The trigger for the flow movement is on the mobile node (e.g., by using
layer-2 signaling, by explicitly start sending flow packets via a new
interface, etc.).

-------------------------

Moreover, call-flows (figures 2 and 4) show the operation "handover
decision" over multiple entities, including MN, MAGs and LMA. It is
confusing; the handover decision should be only on the MN side. Example:

                 +-----+           +------+        +------+      +-----+
   Internet      | LMA |           | MAG1 |        | MAG2 |      | MN1 |
                 +-----+           +------+        +------+      +-----+
      |             |                 |               |             |
      |  flow X to  |    flow X to    |           flow X to         |
      |  pref1::lif |    pref1::lif   |           pref1::lif        |
      |<----------->|<--------------->|<-------------------------->if1
      |  flow Y to  |             flow Y to           |  flow Y to  |
      |  pref1::lif |             pref1::lif          |  pref1::lif |
      |<----------->|<------------------------------->|<---------->if2
      |             |                 |               |             |
      |             |                 |               |
===========
      |             |                 |               |          |
decision to 
      |             |                 |               |          | move
flow Y 
      |             |                 |               |
============
      |             |                 |               |             |
      |  flow Y to  |    flow Y to    |          flow Y to          |
      |  pref1::lif |    pref1::lif   |          pref1::lif         |
      |<----------->|<--------------->|<-------------------------->if1
      |             |                 |               |             |

Now, my question:

With a MN driven handover decision, I do not understand the scenario "MN
with different sets of prefixes on each MAG". Quoting section 3.2.2:

"If the flow is being moved from its default path (which is determined
by the destination prefix) to a different one, the LMA constructs a Flow
Mobility Initiate (FMI) message." 

I understand the reason for FMI, but how the LMA can be aware of the
handover if the decision is made by the MN? In other words, what is the
trigger for FMI initiation? My understanding is that the scenario
relying on FMI/FMA can only be a LMA-initiated handover scenario; thus
should be addressed in another document.

BR,
Pierrick

---

From: Carlos Jesús Bernardos Cano <[email-masked]>
Date: Mon, 13 Feb 2012 17:51:19 +0100

Hi Pierrick,

Sorry for the late answer, last week I was on a business trip.

Thanks for your comments. Please see inline below.

> measurements performed at the network).

That part of the text just provides some examples of potential triggers,
but the draft now only describes MN-initiated handovers. The specific
triggers for initiating a handover are out of the scope of the document.

> confusing; the handover decision should be only on the MN side. Example:

Again, this trigger is outside of the scope of the document.

Thanks,

Carlos

> 
> BR,
> Pierrick
> _______________________________________________
> netext mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/netext

-- 
Carlos Jesús Bernardos Cano  http://www.netcom.it.uc3m.es/
GPG FP: D29B 0A6A 639A A561 93CA  4D55 35DC BA4D D170 4F67

---

From: <[email-masked]>
Date: Tue, 14 Feb 2012 11:17:59 +0100

Hi Carlos,

I agree that triggers are out of scope and that we can leave the door open to different scenarios. But, at least, the I-D should clearly describe the scenario where the MN sends flow packets via a new interface. It would remove any ambiguity on protocol operation as it does not rely on unknown triggers. I don't want to reopen long ML discussion we had on triggers, but I think that the document would have more weight if implementers could have a clear understanding of the protocol in above simple handover scenario. So, I'm not suggesting deep modification of the I-D, I'm just suggesting to stress and clarify some points. 

Pierrick

> -----Message d'origine-----
> De : Carlos Jesús Bernardos Cano [mailto:[email-masked]]
> Envoyé : lundi 13 février 2012 17:51
> À : SEITE Pierrick RD-RESA-REN
> Cc : [email-masked]
> Objet : Re: [netext] comments/question on draft-ietf-netext-pmipv6-
> flowmob
> 
> Hi Pierrick,
> 
> > using layer-2 signaling, by explicitly start sending flow packets via
> > a new interface, etc.) or on the network (e.g., based on congestion
> > and measurements performed at the network).
> >
> > It should be:
> >
> > ------------------------
> >
> That part of the text just provides some examples of potential
> triggers, but the draft now only describes MN-initiated handovers. The
> specific triggers for initiating a handover are out of the scope of the
> document.
> 
> >       |<----------->|<--------------->|<--------------------------
> >if1
> >       |<----------->|<------------------------------->|<----------
> >if2
> >       |             |                 |               |             |
> >       |             |                 |               |
> > ===========
> >       |             |                 |               |          |
> > decision to
> >       |             |                 |               |          |
> move
> > flow Y
> >       |             |                 |               |
> > ============
> >       |             |                 |               |             |
> >       |<----------->|<--------------->|<--------------------------
> >if1
> >       |             |                 |               |             |
> >
> >
> > Now, my question:
> >
> > With a MN driven handover decision, I do not understand the scenario
> > "MN with different sets of prefixes on each MAG". Quoting section
> 3.2.2:
> >
> > by the destination prefix) to a different one, the LMA constructs a
> > Flow Mobility Initiate (FMI) message."
> >
> > handover if the decision is made by the MN? In other words, what is
> > the trigger for FMI initiation? My understanding is that the scenario
> Carlos Jesús Bernardos Cano  http://www.netcom.it.uc3m.es/ GPG FP: D29B
> 0A6A 639A A561 93CA  4D55 35DC BA4D D170 4F67

---

From: Carlos Jesús Bernardos Cano <[email-masked]>
Date: Thu, 16 Feb 2012 22:22:22 +0100

Hi Pierrick,

OK, thanks for the comment. We'll try to improve the document including
the scenario you mentioned.

Thanks,

Carlos