RE: Progressing MAR

["Francois Le Faucheur (flefauch)" <flefauch@cisco.com>]

Jerry,

I believe the conclusion of our long discussion on BC Model was that we
agreed to specify RDM and MAM and to investigate further other models
including MAR.
I don't believe there is an agreement (at this stage anyway) that the WG
needs to produce a spec for MAR. So my view is that it would be
premature to have a WG document for MAR.

When we discussed the previous version of your MAR spec, if I remember
correctly I think we ended up concluding that your claim that "it
simultaneously achieves bandwidth efficiency, bandwidth isolation, and
protection against QoS degradation without preemption" is ONLY true
under the assumptions that :
	(i) the bandwidth that will be actually reserved by each CT is
known fairly accurately ahead of time for every link (ie you need to be
sure that on every link a CT will not, or only very temporarily, exceed
its Bwalloc).
	(ii) you configure the Bwalloc of each CT based on the expected
(and accurate) demand.
Is this not the case?

Personnally, I see these assumptions as a serious problem. Basically it
seems to defeit the whole purpose of DSTE: With DSTE you want to
configure some limits for each CT based on resources available and
engineering rules and have traffic redistributed in accordance with
that. Its seems with -00.txt MAR description, you need to do the
opposite ie configure the Bwalloac based on what the load will actually
and you assume that every link is engneered according to the actual
demand without redistribution of load (which makes you wonder why you
need DSTE in the first place).

Has something changed between -00.txt and -01.txt with respect to the
above assumptions?

As discussed last time, MAR seems to contain a very good idea of
allowing CTs to borrow bandwdith but I think we need to somehow enhance
MAR to avoid the above assumptions/constraints (unless you've already
done that in -01). 


Thanks

Francois


>> -----Original Message-----
>> From: Ash, Gerald R (Jerry), ALABS [mailto:gash@att.com] 
>> Sent: 07 March 2003 16:08
>> To: te-wg@ops.ietf.org
>> Cc: Ash, Gerald R (Jerry), ALABS; Lai, Wai S (Waisum), 
>> ALABS; Francois Le Faucheur (flefauch); Jim Boyle; Ed Kern (ejk)
>> Subject: Progressing MAR
>> 
>> 
>> All,
>> 
>> A specification for the Maximum Allocation with Reservation 
>> (MAR) bandwidth constraint (BC) model is proposed in 
http://www.ietf.org/internet-drafts/draft-ash-mpls-dste-bcmodel-max-allo
c-resv-01.txt.  

MAR is an extension of the Maximum Allocation Model (MAM).  MAR is
similar to  MAM in that a maximum bandwidth allocation is given to each
class type (CT).  However, through the use of bandwidth reservation and
protection mechanisms, CTs are allowed to exceed their bandwidth
allocations under conditions of no congestion but revert to their
allocated bandwidths when overload and congestion occurs.  

Analysis is presented in an ANNEX which shows that the MAR model meets
all the objectives for BC models, and that it simultaneously achieves
bandwidth efficiency, bandwidth isolation, and protection against QoS
degradation without preemption.  The analysis information provides
critical guidance to users' implementation of the BC models and some
important guidelines which users should be aware of before choosing a BC
model for their network.

I would like to get a sense of the list for using this I-D as the basis
for the MAR specification and for accepting this as a WG document.  

Comments are welcome.

Thanks,
Jerry