Subject: RE: Should connecting to the Internet be Optional?

From: [email-masked]
Date: Mon, 4 Mar 2002 21:54:30 +0200

Hi!

Just commenting the possible differences between laptops and cellular terminals...

There are different kinds of laptops and also different kinds of cellular hosts. Our intention is to write this specification as "minimum IPv6 functionality for a cellular host", i.e. not defining any kind of 'maximum set of functionality'. And this kind of minimum functionality should be possible to be implemented in even the smallest 2,5G / 3G cellular handsets. An example of dimensions for such a handset could be 11 x 5 x 2 centimeters (1 inch = 2,54 centimeters). Could you compare such a terminal to a laptop computer? Hardly.

Of course, then there are communicator / PDA type of devices having bigger processor capacity and memory making it possible to install more demanding applications in them, but even those devices cannot (in my opinion) be directly compared to laptops.

As a summary, a cellular host (often) has limited size, memory, processor capacity and battery capacity / power consumption. The users would like to see their terminals to be usable for quite a long time (typically for some days, at least stand-by time) without re-charging them.

Cheers,
	 -Juha W.-

-----Original Message-----
From: ext Tony Hain [mailto:[email-masked]]
Sent: 04 March, 2002 21:04
To: [email-masked]
Cc: [email-masked]
Subject: RE: Should connecting to the Internet be Optional? 

Keith Moore wrote:
> I think the cell phone requirements document would do well to break
> down the different cases:
>
> - cell phone with fixed functions vs.
> - cell phone that can host applications
>
> - cell phone that is strictly an endpoint vs.
> - cell phone that can provide net connectivity to other devices
>
> and examine requirements separately for each case.

I agree with one comment:
> > The only way to prevent new applications
> > from appearing on computing devices is to put the executable code in
> > non-rewritable, non-replaceable, rom.
> And require these devices to be tamper-proof ;-}.
>
> Feico.

Tony

Actually another thought; what is the difference between a handset and a
laptop that has an embedded 3G radio? Are they both cellular hosts?

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---

From: "Tony Hain" <[email-masked]>
Date: Mon, 4 Mar 2002 12:52:53 -0800

[email-masked] wrote:
> ...
> Our intention is to write this specification as "minimum
> IPv6 functionality for a cellular host", i.e. not defining
> any kind of 'maximum set of functionality'.
> ...
> As a summary, a cellular host (often) has limited size,
> memory, processor capacity and battery capacity / power
> consumption. The users would like to see their terminals to
> be usable for quite a long time (typically for some days, at
> least stand-by time) without re-charging them.

You are focused on the engineering constraints of a particular device
(host) that is *only useful* in a cellular context as the definition. My
point was that there are many other devices that could take advantage of
the cellular link technology, and therefore MUST be considered 'cellular
hosts'. Statements in the document like: 'A cellular host SHOULD NOT
perform Duplicate Address Detection ...' or lack of support for IPsec
that is justified as too hard for a small device to implement are
focused on engineering issues for a particular product, not the
architectural minimum. If there are characteristics of the cellular link
that make the current standards inappropriate as written, we should
address those. If you are looking for concessions simply for marketing
reasons related to a particular target product, this document should die
right here.

The statement 'We can not list all possible services here, and in
general we expect application protocol RFCs to have requirements on what
security services they MUST employ.' is both an unrealistic expectation,
and the fundamental reason that we are being so insistent about the
requirement for IPsec. As a general rule, we don't expect (or have the
means to require) that every application define security requirements;
and even if they did evolving the security infrastructure to meet the
needs of every new application would be insane. On the other hand by
providing a secure channel for use by any application we can build an
infrastructure that scales. The argument that a cellular host is exempt
only ensures that the application developer can't count on that secure
channel being available, so each one has to do something specific to
address their needs. If you want to do as Keith suggested and split off
fixed-function as a special case, I won't object too loudly. Even there
you preclude something like a Java app, that comes in over the TLS
channel, from opening a non-TLS secure channel to get additional
content. Yes it is a fixed function web-browser, but do you really know
how every web site is designed, and can you ensure that all bits in and
out of the device can be protected by TLS?

Tony

---

From: Jari Arkko <[email-masked]>
Date: Mon, 04 Mar 2002 23:25:25 +0200

Tony Hain wrote:

> Statements in the document like: 'A cellular host SHOULD NOT
> architectural minimum.

I don't think this was exactly as we wanted to see the document.
First, engineering issues are important, but if we would only follow
them, why didn't the draft say MUST NOT implement RFCs of over 5
pages ;-) ? Secondly, there are two main classes of engineering issues:
those internal to the device and not (so) relevant, and those
related to the characteristics of the communications interfaces
which typically do need to be addressed in some manner.

In any case both examples you cite have NOT been done just
in order to save space. Consider the small amount saved by
DAD, or the recommendations to implement something equally
complicated to IPsec in certain cases. Instead, what we tried
to do was to evaluate the specific conditions in cellular
networks and devices, and figure out if the function was
technically necessary in that context. We may have done
our analysis right, or wrong -- and that's the reason we
are having this discussion. As an example, it isn't just
necessary to show that DAD is expensive, you also have
to show that on a particular class of links you don't need
it. I seem to recall some discussion today on DAD not
being necessary in PPP; I don't know what the conclusion
of the discussion will be but that's the kind of result
we are looking for - please work with us on the technical
analysis.

Jari