Subject: Re: [lisp] Mobile LISP

From: [email-masked] (Noel Chiappa)
Date: Fri, 3 Jul 2009 20:50:24 -0400 (EDT)

> From: Dino Farinacci <[email-masked]>

    > A lot of times radios go down and the MN can't signal to anyone. And
    > when the radios come back up, the MN could be somewhere else
    > topologically.

If the MN is down, or off the air completely, there's no way for anyone to
get any traffic to or from it, no matter what anyone does. So that's an
uninteresting case (and one I wouldn't have mentioned, because of that).

What I'm talking about are cases where the MN _is_ on the air, but not at its
home site. It then has to work out where it is, and tell _somebody_ where
that is, before any communication can happen - in any scheme at all. But that
much is intuitively obvious, no?

    > the ETRs can't tell the difference between the MN roaming or it is just
    > down but stationary in the site. The MN, itself has to solve this
    > problem.

Sure. The MN first has to to be on the air _somewhere_, and know that it's
not at its home site. But, again, those conditions hold true for _any_
mobility solution I can think of.

So, given those necessary preconditions for an interesting case, how does the
'ETR notices inbound traffic for a node which has notified (perhaps
indirectly) the ETRs that it has gone walkabout' approach sound? If you like
the general approach, we can then talk about the details (e.g. how does the
info get from the mobile nodes to the ETRs - directly or indirectly; if the
latter, through who; etc).

    > If no data was moving back and forth .. then we have a problem ..
    > This is where the ETR has to get involved.

Well, that's the question I was effectively raising with my initial message
in the thread - can the ETR be part of the solution for cases where someone
new is trying to contact a mobile node.

    > But this is hard to solve and harder to implement. So let's chew on
    > that for a while.

Ditto previous "how does the 'ETR notices inbound traffic for a node which
has .. gone walkabout' approach sound" comment.

	Noel

---

From: Dino Farinacci <[email-masked]>
Date: Fri, 3 Jul 2009 17:56:02 -0700

> much is intuitively obvious, no?

Right and the LISP-MN spec says it registers to the map-server for new  
cachers to get the latest RLOC and sends SMRs to the existing cachers  
to update the RLOC-set.

> mobility solution I can think of.

Right, my point is that the hand-off is not instantaneous and  
sometimes not graceful.

> latter, through who; etc).

It is a bit challenging because, 1) the ETR has to know which IP  
addresses for the site are mobile nodes, 2) the ETR has to ping or  
poll each one to find out when they are not around anymore.

> new is trying to contact a mobile node.

Okay, the verbs weren't precise, so "contact" here means trying to  
establish a connection.

Dino

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