Subject: RE: WG last call: draft-ietf-tewg-diff-te-reqts-04.txt

From: "Lai, Wai S (Waisum), ALASO" <[email-masked]>
Date: Thu, 30 May 2002 18:56:39 -0400

As stated in page 9 of the draft:
   "At the time of writing this document, it is not clear whether a 
   single model of Bandwidth Constraints is sufficient, which one it 
   should be and how flexible this model really needs to be and what 
   are the implications on the DS-TE technical solution and its 
   implementations. The DS-TE technical solution must specify one 
   default bandwidth constraint model which must be supported by any 
   DS-TE implementation."

We have now completed a study to investigate the performance of the
different Bandwidth Constraints models.  We will document in details
our findings in a forthcoming draft.

We propose that the following highlights be included in the DS-TE
Requirements draft to provide guidance to protocol development.
One place to put the text is perhaps at the end of Section 3.3:

"Work is in progress [reference of the draft to be provided] to
investigate the performance of the different Bandwidth Constraints
models.  Preliminary results indicate that in comparison to the
maximum allocation model above (first example), the Russian Doll
model: 
a) permits a greater degree of bandwidth sharing among different
traffic classes and hence gives better performance under normal
conditions than other Bandwidth Constraints models,
b) under overload, such sharing leads to a tighter coupling
between various classes and is not able to provide robust service
protection/isolation, and
c) is not well-suited to a CAC/blocking operational mode when
preemption is disabled.
Such analysis should be used to provide guidance to DS-TE protocol
development.  Furthermore, a model more like the maximum allocation
model may be more appropriate as a default model because of the
observed behavior."

Thanks, Wai Sum.

-----Original Message-----
From: Jim Boyle [mailto:[email-masked]]
Sent: Sunday, May 19, 2002 10:04 PM
To: [email-masked]
Subject: WG last call: draft-ietf-tewg-diff-te-reqts-04.txt

This message begins a WG last call for the following:

	draft-ietf-tewg-diff-te-reqts-04.txt

This WG document addresses a WG milestone.  It is proposed as an
Informational RFC.  WG last call ends May 31, 2002.

---

From: Jim Boyle <[email-masked]>
Date: Fri, 31 May 2002 09:44:47 -0400 (EDT)

At a higher level, in essence you are stating that we should change our
tact from:

	o) we agree that there needs to be at least one common
	   bandwidth contraint model across implementations.  Technical
	   proposals need one specified andrequired for implementation

to adding:

	o) a few of us have looked into something called maximum
	   allocation and think it's better than russian dolls.

I don't think the requirements document is the place to resolve what the
default model should be.  Are you saying that there shouldn't be a default
model - or just that you have a difference of opinion on what the default
should be?

If the former - then please suggest revised text for the paragraph you
quoted.  If it is the latter - then I think that is another thread for the
list against the protocol draft.

Jim