Subject: RE: [Diffserv] QoSSIG BOF

From: "Manfredi, Albert E" <[email-masked]>
Date: Sun, 23 Jan 2000 17:44:58 -0500

Bob Braden wrote:

> I would seriously question whether there are "much simpler ways of
> solving the same problems".
> 
> However, there certainly would be simpler ways to solve a simpler
> problem.

Amen to that.

Before Brian gets this thread banished from diffserv, one interesting new
requirement for CoS/QoS signaling, that might not be doable with something
simpler and less capable, is going to be this new idea of doing real, direct
routing of IP datagrams through routers ported to WDM optical backbones. The
problems seem to emerge whenever channels (circuits) must defined, for
whatever set of reasons. And, especially, when one of these channels must be
chosen, packet by packet, based on a multivariate set of criteria.

When these circumstances occur, people scramble for that simple solution,
and it historically doesn't seem to matrialize.

Locking a few good people in a room until the work is done is an attractive
but politically incorrect solution these days. Companies have resorted to
this method, sometimes in exasperation, only to have their solution labeled
"proprietary," to be further "enhanced" by a standards body.

Examples, of course, are legion. Maybe some problems are irreducible.

Bert
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From: Masataka Ohta <[email-masked]>
Date: Mon, 24 Jan 0 15:11:08 JST

Bert;

> Before Brian gets this thread banished from diffserv,

That is the proper behaviour because CoS and QoS are totally different.

Brian is a honest person that I notice he always distinguishes them.

> one interesting new
> routing of IP datagrams through routers ported to WDM optical backbones.

Label switching by physical layer labels is not a new idea.

I wrote it in one of my INET'97 papers (there are three) titled "Hop,
Step, but Don't Jump for Scalable Lower-Layer Forwarding of Best-Effort
Traffic".

It says thing like:

	Hence, it's better to reuse an existing
	mechanism, RSVP, for the signaling of virtual links. 

	As the virtual link is best effort, all we need is a
	specification of "best effort" service class. A possible
	interpretation is that the absence of service class in
	RSVP messages means "best effort" class.

something like which is seemingly reinvented elsewhere.

But the main point of the paper is that best effort label switching
does not scale and performance improvement, if any, is limited to a
small constant. Especially, label switching is useless for multicast.

In short, the approach has a dead end.

Note also that WDM cross connect is a waste of budget because Spatial DM
is more than enough unless you need Internet backbone much faster than
Tbps.

> and it historically doesn't seem to matrialize.

What's happening is that people do not describe the problems and
misunderstand them unsolvable,

Then, some people seeks alternatives, such as CoS, however poor they are,
even though the alternatives does not satisfy the requirements of
most real world applications.

Other people, like Ping, makes protocol complex only to make the
unsolvability obscure.

> Examples, of course, are legion. Maybe some problems are irreducible.

QoS scalability problems are easily reducible by properly architected
parallel processors.

							Masataka Ohta