RE: WG last call: draft-ietf-tewg-diff-te-russian-02.txt

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

Waisum,

So the bottom line is that we assumed different definitions for MAM.
Your analysis assumed the model recently discussed on the list (ie "MAM
with the additional implied bandwidth constraint") as opposed to MAM as
currently defined. We do need to make some decision on this issue. And
then your analysis should be based on the outcome of that discussion.

Let me think more about the MAM definition issue.

Cheers

Francois

PS: What I mean by QoS degradation does not relate to blocking
probability. It refers to ensuring that the maximum amount of
established LSPs for a given CT is in line with the service rate that
the scheduler can provide to that CT. Please see the draft I issued a
while back on "BC Model considerations".

>> -----Original Message-----
>> From: Lai, Wai S (Waisum), ALABS [mailto:wlai@att.com] 
>> Sent: 21 April 2003 18:28
>> To: Francois Le Faucheur (flefauch)
>> Cc: Jim Boyle; te-wg@ops.ietf.org
>> Subject: RE: WG last call: draft-ietf-tewg-diff-te-russian-02.txt
>> 
>> 
>> Francois,
>>    This message addresses Comment 1 in your message
>> http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00228.html
>> as it relates to the Russian Dolls draft Last Call.
>> 
>>    Your following statement in the above message correctly 
>> reflects my
>> intent:
>> "Now, if I understand correctly, the approach you took for 
>> selecting BC
>> vales for RDM, was to pick BC values so that RDM would 
>> exhibit the same
>> blocking probabilities as MAM for a given reference LSP load."
>> 
>>   However, this statement is incorrect with respect to my comparison:
>> "For example, these values would accept a total load of 6+7+15=28
>> with MAM , while the maximum load is limited to BC3=15 with RDM."
>> 
>>   In <draft-wlai-tewg-bcmodel>, first of all, both MAM and RDM are
>> being offered the same load: 2.7 + 3.5 + 3.5 units as stated on the
>> top of page 5.  Furthermore, it is stated that
>> "As an example, consider a link with a capacity that allows 
>> a maximum 
>> of 15 LSPs from different classes to be established simultaneously.  
>> Overbooking is allowed, ..."
>>   Also, 
>> "bandwidth constraints (for MAM) are: 
>> up to 6 simultaneous LSPs for class 1,
>> up to 7 simultaneous LSPs for class 2, and 
>> up to 15 simultaneous LSPs for class 3."
>> 
>>   Note the wording "up to."  Thus, while it is true that the sum of
>> *maximum* bandwidth constraints can add up to 28, there can be no
>> more than 15 *simultaneous* LSPs allowed for all classes, since
>> this is the ultimate constraint imposed by the link capacity
>> (which is the same link for both MAM and RDM).
>> Thus, using your terminology in the above message, both MAM and RDM
>> in my draft are either (1) both are Porsches, or (2) both are backed
>> up by 3-ton-trailers.
>> 
>>   Per your request, the attached diagram shows the result for the
>> case you suggested for RDM: BC1=6, BC2=13, and BC3=28.  Comparing
>> this result with Figures 1 and 2 in <draft-wlai-tewg-bcmodel>,
>> it can be seen that the QoS degradation for class 1 is the same in
>> all three cases, even though the link capacity is now 28 is 
>> your case,
>> and 15 in the other two cases in my draft.
>> 
>>   This is contrary to the following claim made in
>> <draft-ietf-tewg-diff-te-russian-02.txt>:
>> "RDM can be used to simultaneously ensure bandwidth efficiency 
>> and protection against QoS degradation of all Class-Types"
>> 
>> Thanks, Wai Sum
>> 
>> -----Original Message-----
>> From: Jim Boyle [mailto:jboyle@pdnets.com]
>> Sent: Tuesday, April 08, 2003 10:51 AM
>> To: te-wg@ops.ietf.org
>> Subject: WG last call: draft-ietf-tewg-diff-te-russian-02.txt
>> 
>> 
>> 
>> 
http://www.ietf.org/internet-drafts/draft-ietf-tewg-diff-te-russian-02.t
xt

This is WG last call for this draft to be advanced as expiremental RFC.

Last call ends in 2 weeks (4/22).

thanks,

Jim Boyle