Subject: RE: [Seamoby] Examples of CAR discovery

From: Phillip Neumiller <[email-masked]>
Date: Fri, 29 Mar 2002 11:12:23 -0500

Hi,

Don't want to be a butinsky, but oh well.
> Hello again,
> 
> James Kempf wrote:
> 
> > > Does this mean that the access points themselves cannot use CAR to
> > > prepare for a network-controlled handover?  Darn ...!
> >
> > They can, but in a typical cellular system, they won't. The 
> access points
> >
> > don't move around much, so this can be preprogrammed into tables.
> 
> I'd like it if, eventually, availability of QoS would be considered
> a "Capability", and discoverable by way of this CAR protocol that
> is under discussion. Such information is not static.
> 
> Indeed, I'd like it if the actual qualifications for candidacy of an
> access router were _data_, separated from the actual discovery
> protocol, as far as possible.

I like what Charlie is saying here and that was my original thoughts with
contract NET protocols (CNP) being used to decide on the best handoff 
candidate based on vectors of metrics exchanged between the mobile and the
AR/AP (watcha callits).

Cheers,

phil
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From: "James Kempf" <[email-masked]>
Date: Fri, 29 Mar 2002 09:11:08 -0800

OK, I wasn't going to respond to this in an attempt to reduce my
email volume, but what the hey...

> candidate based on vectors of metrics exchanged between the mobile and
the

So the problem I have with this is that, given one (1) specific wireless
link protocol,
I can't see why the QoS or any other characteristic should differ
between one access
point and another.

There is an issue about link congestion, of course, but I'm not sure if
the IP level is really the
right place to handle issues of link congestion (for end to end
congestion, of course, the
situation is quite different). Some wireless protocols have more
effective ways of handling
link congestion.

For intertechnology handover, I agree that there are differences, but I
wonder where to
draw the line between dynamic, quickly changing characteristics like QoS
and static
qualities, such as the link media type. For static qualities, I can see
an obvious benefit,
but for more dynamic qualities, the characteristics may change so
quickly that the
information is out of date by the time the MN has made the decision to
move.

            jak

---

From: "James Kempf" <[email-masked]>
Date: Fri, 29 Mar 2002 09:11:08 -0800

jak

---

From: Charlie Perkins <[email-masked]>
Date: Fri, 29 Mar 2002 11:23:40 -0800

Hello Jim,

If one access router has 5 Mb/s available, and another only has
10 Kb/s available, I would like to get my streaming video from
the first access router.  I might be able to have the choice.

IP is exactly the right place for this to be disseminated, assuming
that we even have IP QoS in the first place.  I do not think
that this information would typically change much over the
10-150 milliseconds that it "should" take to accomplish a
handover.  If this is a problem, though, one could define a
"special" kind of CAR discovery protocol that makes the
candidate access router reserve the bandwidth for 200 milliseconds,
or else not claim that it has the bandwidth available.

Regards,
Charlie P.

---

From: Charlie Perkins <[email-masked]>
Date: Fri, 29 Mar 2002 11:23:40 -0800

Hello Jim,

Regards,
Charlie P.

---

From: "James Kempf" <[email-masked]>
Date: Fri, 29 Mar 2002 19:10:03 -0800

> the first access router.  I might be able to have the choice.

Wouldn't it be better to let the IP QoS signaling protocol handle this?
I believe this is exactly what NSIS is working on,
but John Loughny could say more.

> that we even have IP QoS in the first place.

I was speaking of last hop link capacity. I agree that IP is the right
place to handle next to last hop QoS (i.e. DiffServ). I believe the NSIS
charter also speaks about last hop QoS signaling as well. There is some
interest in NSIS to tie Layer 2 QoS and  IP QoS together on the last
hop, but there has not yet been much work done on it.

> I do not think

I did not mean just during the handover. If the information provided by
the CAR discovery protocol has a lifetime of 200 msec, then if the total
L2 + L3 handover time is 40 ms, 5 mobile nodes could move into the cell
during the time between when a mobile node gets its last CAR discovery
update and when it decides to move to the cell. At that point, the QoS
due to the new load may be below the decision point where the mobile
node would want to move into the cell.

                jak

---

From: "James Kempf" <[email-masked]>
Date: Fri, 29 Mar 2002 19:10:03 -0800

jak

---

From: Charlie Perkins <[email-masked]>
Date: Fri, 29 Mar 2002 20:09:37 -0800

Hello again,

> but John Loughny could say more.

I didn't know that NSIS was gearing up to supply the needs
of handovers -- and, in a way, I hope they don't because I
can't follow that many mailing litss.  And besides, if smooth
handovers is not part of [seamoby] charter, what is?!
Lastly, I claim that QoS management in the small is a
pretty essential requirement for smooth handovers.
Surely, remote signaling is to be avoided.

> place to handle next to last hop QoS (i.e. DiffServ).

I am also talking about last hop link capacity.  That is what is
most important (typically) for the mobile node, and thus is
relevant for seamless mobility.  Links on the other side
of the access routers (away from the mobile node) should be
considered irrelevant for this discussion, I hope.  Otherwise,
we might as well give up.  I do not think DiffServ has a role
to play in [seamoby] protocols, but I certainly do think that
IP has a role to play.

> I believe the NSIS

Ouch.  Somehow I thought NSIS was end-to-end, not localized to handovers.

> CAR discovery protocol has a lifetime of 200 msec, then if the total L2 +
> L3
> handover time is 40 ms, 5 mobile nodes could move into the cell during
> update and when it decides to move to the cell.   ...

This is true, but that's the breaks.  A lot of bad things could happen,
and if there is a recognized danger, then we should go with the provisional
short-lived reservations.

Regards,
Charlie P.

---

From: Charlie Perkins <[email-masked]>
Date: Fri, 29 Mar 2002 20:09:37 -0800

Hello again,

Regards,
Charlie P.

---

From: "Eunsoo Shim" <[email-masked]>
Date: Sat, 30 Mar 2002 13:26:23 -0800

----- Original Message -----
From: "James Kempf" <[email-masked]>
To: "Charlie Perkins" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, March 29, 2002 7:10 PM
Subject: Re: [Seamoby] Examples of CAR discovery

> node would want to move into the cell.
I think that's where the network can do some more intelligent work, that is,
the network could make selective recommendations to the mobile nodes.
Thanks.

Eunsoo

---

From: "Eunsoo Shim" <[email-masked]>
Date: Sat, 30 Mar 2002 13:26:23 -0800

----- Original Message -----
From: "James Kempf" <[email-masked]>
To: "Charlie Perkins" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, March 29, 2002 7:10 PM
Subject: Re: [Seamoby] Examples of CAR discovery

Eunsoo

---

From: "James Kempf" <[email-masked]>
Date: Sun, 31 Mar 2002 10:35:26 -0800

Hi Charlie,

> Surely, remote signaling is to be avoided.

Well, we need to confirm this with Allison, but my reading of the
Seamoby charter does not include anything on doing QoS for handover. I
believe NSIS was established for purposes of consolidating all the QoS
for wireless work. Of course, if that isn't covered and the WG wants to
expand the charter we could discuss it when we finish our current work
items.

> short-lived reservations.

Right, well, some of the bad things that can happen are large scale
hysterisis in which MNs rythmically switch between cells. There are
explicit measures taken in cellular protocols to avoid this kind of
behavior (e.g. add and delete power levels for adding or removing BTSs
from the active set), because it makes load management difficult. Such
nonlinear effects are typical when the time constants between two
different but linked processes are an order of magnitude or more
different. Of course, simulations are in order here to see if this
intuition applies to this particular case, mitigation may be possible
and even easy as in the CDMA power level case.

BTW, I was not speaking here about, for example, advertising that a
particular wireless link was configured with so-and-so much bandwidth
capacity. I think that could be useful, for example, in order for an MN
to determine whether it wanted to make use of some hotspot support. A
specific example, suppose I have two choices for hotspot support,
802.11b at 5 Mbps and Bluetooth at 600 kbps. and suppose that the type
of media didnt' allow me to differentiate, ie. I could have 802.11 at a
lower or higher rate. The MN could use this information to determine
what kind of hotspot media it wanted.

                jak

---

From: "James Kempf" <[email-masked]>
Date: Sun, 31 Mar 2002 10:35:26 -0800

Hi Charlie,

                jak