Subject: Re: [MOBILE-IP] handover: proactive versus reactive

From: "[email-masked]" <[email-masked]>
Date: Mon, 1 May 2000 04:59:09 -0700

>
> Below are some of my doubts.
> Why use a "connection oriented" MIP layer that as well require
> 10 round trips in order to get IP packet delivered?
> Why develop alternatives where PPP is already doing the job?
>
First, off, let me state that my position is not that PPP is utterly useless.
In fact, it is a very useful protocol that has made connectivity MUCH simpler
than what we had before.

However, sometimes we need to evaluate whether the use of a protocol, just
because it exists, is appropriate in a specific problem space. Now, let's use
the 3GPP2 architecture model, and see how useful PPP really is. In their
architecture, when Mobile IP is used, home address negotiation and  user
authentication is done through the Mobile IP registration sequence, so:

LCP:
        - Authentication negotiation (disabled, not needed)
        - MTU negotiation (this one *could* be useful)
Auth:
        - Not needed since it is handled by MIP
IPCP:
        - Address Negotiation (not done since it is handled by MIP)
Framing:
        - yes, this is needed

So, as you can see above, some of the networks make use of PPP simply to
negotiation framing, when in fact framing could be done without the need for
all of the negotiations. We could use the same HDLC framing that PPP uses, if
need be, and that still reduces the initial connection setup time.

So, since we are looking to move away from the circuit switched model in
wireless networks, we should strive for a link layer that is stateless.

PatC

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From: Jim Willkie <[email-masked]>
Date: Mon, 1 May 2000 08:31:44 -0700

>wireless networks, we should strive for a link layer that is stateless.

Folks:
Here's a couple of counter points to the above well focused thoughts:

If MobileIP was a required piece of the wireless packet network then the
above arguments hold and a state-less link layer is viable. But the current
(at least CDMA) wireless network does not have MobileIP and uses PPP to
negotiate IP addresses. This capability will have to continue to exist when
a mobileIP solution is rolled out.

Many deployed cellular packet network use PAP or CHAP to authenticate the
packet user. One would think that this capability will continue to be
desired by operators.

So it would seem that for at least the CDMA packet network both
MobileIP-capable and the the so-called simple IP capabilities will continue
to co-exist. This reality would seem to make the on-going need for PPP to
remain.

Comments please....

Jim Willkie

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From: "[email-masked]" <[email-masked]>
Date: Mon, 1 May 2000 09:04:37 -0700

> >First, off, let me state that my position is not that PPP is utterly
> useless. >In fact, it is a very useful protocol that has made connectivity
> MUCH simpler >than what we had before.
> >
> >because it exists, is appropriate in a specific problem space. Now, let's
> use >the 3GPP2 architecture model, and see how useful PPP really is. In their
> >authentication is done through the Mobile IP registration sequence, so: >
> >LCP:
> >all of the negotiations. We could use the same HDLC framing that PPP uses,
> if >need be, and that still reduces the initial connection setup time.
> >

Jim, you are correct. Even 3G supports simple IP, which is essentially dial-up
PPP over a wireless link. So, PPP is still in the architecture for legacy
devices, and I agree that this service will remain to be provided as long as
there are some legacy devices around.

However, there is an opportunity to redesign the network, and it seems like
the best time to move away from PPP. This new design would be similar to the
thoughts that I've been discussing in various threads.

So, while I agree with your comments, let's see if we can move forward and do
it right. I don't think that creating next generation networks that rely on
antiquated technology that does nothing but add overhead seems pointless.

PatC

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From: cnyap <[email-masked]>
Date: Mon, 1 May 2000 15:37:59 +0100

> antiquated technology that does nothing but add overhead seems pointless.

Hi

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From: cnyap <[email-masked]>
Date: Mon, 1 May 2000 16:33:12 +0100

Hi PatC

1) What would you suggest of a link layer hint to IP layer?
2) Isn't air link essential as a perquisite for link layer hint?
3) Why would not be nice to use the confirmation of IP address negotiation
as a link layer hint?

Cheers
-------------------------------------------------------------------
Chern Nam Yap
Mobile Communication System Researcher
University of Sheffield
Department of Electronic and Electrical Engineering
Regent Court
211 Portobello Street
Sheffield S1 4DP, England
Tel: +44 114 222 3308
Web: http://www.mobile1.net
E-mail: [email-masked]

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From: "[email-masked]" <[email-masked]>
Date: Mon, 1 May 2000 10:51:22 -0700

> 1) What would you suggest of a link layer hint to IP layer?

Well, first off, PPP doesn't provide any mobility "hints" per say. PPP is a
method of negotiating configuration, and framing. We can keep the framing, but
the actual air interface is the one that provides the "hints" we need.

> 2) Isn't air link essential as a perquisite for link layer hint?
absolutely! And it has nothing to do with PPP

> 3) Why would not be nice to use the confirmation of IP address negotiation
Because Mobile IP always does it, and it does so in a single round trip. Why
add more latency and packets at the problem than necessary?

PatC

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From: cnyap <[email-masked]>
Date: Mon, 1 May 2000 17:42:04 +0100

Hi PatC

> the actual air interface is the one that provides the "hints" we need.

1a) "hints" can be in any form.
It is really depend on how view it.

> absolutely! And it has nothing to do with PPP

2a) PPP confirmed air link follow directly, providing mobile node
an IP addess which is used as a link layer hint for IIP. That is
essentially,
the type of "hints" you mentioned above.

> add more latency and packets at the problem than necessary?

3a) This need to based on an assumption there is always a link below IP,
which is not necessary always true.

Even so, Mobile IP always have to do it, even there is no occurance of
handoffs.

In Itinerant IP (IIP) model of mobility.
PPP does it ONCE in a SINGLE trip with much higher confident during handoffs
ONLY.
In comparsion to wasteful, undetermistic Mobile IP advertisments model.

Cheers

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From: Jim Willkie <[email-masked]>
Date: Tue, 2 May 2000 07:45:37 -0700

At 09:04 AM 5/1/00 -0700, [email-masked] wrote:
--cut--
>antiquated technology that does nothing but add overhead seems pointless.

Pat:
I can see the need to specify a more optimized and focused link layer for
mobileIP. If it is done correctly and fills a valid need then perhaps the
next wave of info devices could utilize it. But the reasons stated so far
are 1) the only piece of PPP used is encapsulation and 2) the dialup aspect
of PPP should be removed. I may be missing something (in fact I probably
am) but the threshold to toss away PPP should be a little higher, given all
the flexibility it has.

However it seems very prudent to pursue this optimized-for-mobileIP link
layer. But be very careful not to invent another PPP. For example if this
new layer needs a negotiation mechanism then one would question the effort.

Thank you for the forum... please let me know what list this topic will be
moving to...

Jim Willkie

On the other hand if this link layer needs to put a negotiation mechanism
in then there would need to be a very valid reason to