Subject: RE: FW: [seamoby] CT trigger or CT completion? was: proactive an d re active CT definitions

From: Nakhjiri Madjid-MNAKHJI1 <[email-masked]>
Date: Thu, 28 Jun 2001 15:18:19 -0500

Hi Rajeev,

-Rajeev: I have a question here. Is it possible that you can establish a new
L2
and still not change your AR ? If yes, if you don't change AR, is there is
still any CT ? Is this too naive ?
It seems to me that the AR is the key entity (for our defintion) since that
holds the feature contexts.

MN>>> But without broadening the scope of CT, lets assume that CT is AR1-AR2

(change of AR is part of the scenario)

*So the discussion is what is difference between new-L2 establishment and
change
of default router. I say difference is the timing.*

The case that comes to my mind, when you change L2 but newAR is still not
your default router, is say: 
MN is at new L2, but did not have time to sent binding update to 
the oldAR before moving, so its using new L2 to start the L3 routing
change procedure, it does not have newAR as default router but
has L2 with newAR.
The other case is, if it has obtained its new IP address through
stateless autoconfiguration, but the new address is rejected by
newAR, although MN has L2 with newAR.

So you can base your proactive CT on *predictions* based on L2 information
Do the proactive CT and manage to get your context over to newAR

>
>  I don't see how this new definition that pop up everyday are
> making the CT better.
>
> I am the newAR, How long do I have to wait until I make sure
> I am the default router, say in a FMIPv6 case: until I get
> the NA and make sure MN has a valid newCoA?
> What if the MN still has to use its oldCoA and a tunnel between
> newAR and oldAR, how long do I have to wait to start CT, this
> introduces unnecessary delay for CT.
>

Rajeev: There is IP router discovery that indicates to a node when some AR
has
become the default AR.

Any CT that happens prior to this phase is "Pre"-something. This includes
using
L2 triggers etc. When none of this is possible, the MN realizes that it has
changed its AR through router advertisements and does CT, which is
"Post"-something. Sure there is delay here. It is a matter of
classification,
not debating performance.
Anyway, let's see if we can resolve the previous question.

MN>> as I said earlier, the important point is to cover all the scenarios.
whether proactive is pre-A or Pre-B is not important, but I think using
default router which is probably one of the absolute last things that 
happens in handover might not be very suitable and is at least as ambiguous 
as other definitions, so we should not be creating new ambiguous definitions
everyday.

Madjid

---

From: Rajeev Koodli <[email-masked]>
Date: Thu, 28 Jun 2001 15:50:46 -0700

Hello madjid,

> of default router. I say difference is the timing.*

Rajeev: Actually, I am not sure if this is all..If you only change APs and are
still with the same AR, you don't change your default router. So, the point is
that changing L2 does not necessarily constitute changing AR, independent of
time.

> change procedure, it does not have newAR as default router but

Rajeev: The new AR needs an entry in its neighbor cache before it could forward
packets, including Binding Updates.

> newAR, although MN has L2 with newAR.

Rajeev: In this case, it (the MN) has not completed acquiring an IP address
yet.

In both the two cases you mentioned, you are assuming that new L2 implies new
AR. This need not be the case. So, the only definitive point of reference is if
the MN changes its default AR.

> Do the proactive CT and manage to get your context over to newAR

[snip].

> as other definitions, so we should not be creating new ambiguous definitions

Rajeev: could you say why it is ambiguous and why is it not very suitable ?

Regards,

-Rajeev