Subject: RE: Layer 3.5 is actually layer 4

From: "Christian Huitema" <[email-masked]>
Date: Mon, 26 Jan 2004 16:37:57 -0800

> > UDP being a special case
> > there will be other special cases for non-TCP protocols including
> > ones we have not invented yet
> 
> UDP is a special case because it doesn't provide reliability or
> congestion control. There is no reason why UDP should necessarily be a
> special case for multihoming. The only reason to make it a special
case
> would be because UDP interactions are often very short-lived.

Thinking of UDP as a transport protocol is misleading. UDP is not really
a transport protocol, it is a pass-through. It only performs one of the
classic TP functions: multiplexing. The idea is to provide the
application with a "raw" service from the network. Transport functions
such as reliability are commonly provided as part of the application, or
a layer inside the application (e.g. RPC, RTP). In a multi-homed
environment, the application will also handle multi-homing.

-- Christian Huitema

---

From: Masataka Ohta <[email-masked]>
Date: Tue, 27 Jan 2004 10:03:01 +0900

Christian;
 
> classic TP functions: multiplexing.

We can be fine to say UDP is a transport layer protocol to
pass-through.

OTOH, if you implement TCP in a way that kernel does multiplexing
only and all the other TCP functionality (connection management,
congention avoidance, retransmission and so on) is performed in
user space, it is no different from UDP doing similar things in
user space.

So, we can also be fine to say TCP is a combination of a transport
layer protocol to pass-through and an application layer protocol
to do other things.

Note that there are OSes where kernel and user spaces are not
separated.

That is, debate on what funcitonality is of transport and what
else is of application is not meaningful, because the difference
is internal implementation one not visible from the network.

There can be a difference when the network support port number
based QoS assurance, as is the case with networks with RSVP,
where we can definitely say that the multiplexing functionality
does belong to the transport layer.

Anyway, that

> In a multi-homed

is enough to deny 3.5 fallacy and UDP is not the only special
case.

						Masataka Ohta

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 27 Jan 2004 09:19:57 +0100

Masataka,

You have made your point repeatedly. Some people disagree with you,
and at this point, more repeating will not change that. So could
we please close this discussion?

Of course, the architectural analysis to be developed in and
following Seoul will have to take this discussion into account.

Thanks

    Brian

---

From: Masataka Ohta <[email-masked]>
Date: Tue, 27 Jan 2004 19:49:48 +0900

Brian;

> we please close this discussion?

I repeat my point repeatedly and others are agreeing with
me more and more that the discussion has almost converged.

It should be noted that, during the discussion, no one have
give any support for your sweeping statement that:

	The systems level argument for a layer 3.5 solution is that
	it can cover all cases, including ones we have not
	invented yet.

So, it is simply that you withdraw your fallacy of layer 3.5 and
the discussion is closed.

To save bandwidth, you can do so silently by not responding this
mail.

> following Seoul will have to take this discussion into account.

The architectural analysis is already developed by me before
the WG was formed and we have seen any input not denied yet
to change it.

							Masataka Ohta

---

From: "marcelo bagnulo" <[email-masked]>
Date: Tue, 27 Jan 2004 12:03:13 +0100

Hi Masataka,

> 	it can cover all cases, including ones we have not

Just to state the obvious, I agree with this statement, and i guess that the
authors of the several so called 3.5 layer solution do too (some of them
have stated it clearly in some mails).

> To save bandwidth, you can do so silently by not responding this

Please do not assume that silence means that people agree with you, assume
that people are just tired to continue endless discussions

Regards, marcelo

---

From: Masataka Ohta <[email-masked]>
Date: Tue, 27 Jan 2004 21:11:06 +0900

marcelo;
 
> have stated it clearly in some mails).

Thank you agreeing with my statement.

However, as Brian said

	So could we please close this discussion?

it is too late for Brian to make your support valid.

Your statement is invalid also because you give any technical
points at all.

You should be also aware that if authors of the several so called
layer 3 solutions agree with the fallacy, they should have stated
so cleary. But, they didn't. It is not your job to speak for them.

> that people are just tired to continue endless discussions

Which is why raising new technical points is important, though it
is poor couter argument if the points raised are already
denied by the existing argument.

A simple fact is that:

	TCP is not IP.

							Masataka Ohta

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 27 Jan 2004 14:11:29 +0100

Brian

---

From: Masataka Ohta <[email-masked]>
Date: Tue, 27 Jan 2004 22:28:15 +0900

Brian;

> So could we please close this discussion?

As I wrote, you can, as all the people participated with
reasons admit against you that there are special cases.

						Masataka Ohta