Re: draft-ietf-tewg-diff-te-reqts-01.txt

[Jim Boyle <jimpb@nc.rr.com>]

Assuming that EF is in one class type, and these particular LSPs are 
split across priorities 0 and 8 (7, more likely) and that all the BE 
ones are at priority 2 is presupposing a specific technical solution, 
which is Francois et. al.'s approach.  That is not the only technical 
approach, I've heard others discussed.

If what you are asking though is "should traffic in one class (type) be 
able to preempt traffic in another to claim resources, and should this 
be configurable as possible/impossible by operator" - good requirements 
question.  I'd reply as the others have as "yeah".  Is that not covered 
in 2.5.2?

At this time, let's try to make sure that we have covered the 
requirements in requisite, but not exhaustive detail in the draft.If 
there's something major missing, let's make that clear.

As for technical solutions, anyone who feels they have a technical 
approaches to solving the problems and detailed requirements outlined 
should be working on articulating their technical proposal.  If anyone 
has something ready for discussion, I don't see why delay in posting it. 
(currently, only francois's are documented)

After we have the requirements kicked around a bit in the WG, then I 
think it would be the right time to discussing pros/cons on difft. 
approaches.

regards.

Jim

Francois Le Faucheur wrote:

> Darek,
> 
> taking this discussion onto the TEWG list:
> 
> At 15:12 19/06/2001 -0400, Darek Skalecki wrote:
> 
>> Hi,
>> 
>> The requirements draft is really well written. I have however a 
>> concern with respect to preemption between/within class-types (Section 
>> 2.5). Basically, what governs whether preemptee should be chosen from 
>> our class-type or another class-type.
>> 
>> To illustrate my point, the following example is taken from the 
>> document but is extended with priorities.
>> 
>>> 
>>> 
>>>    As an example, let's consider the case described in section 2.2
>>>    where the following bandwidth constraints are configured:
>>>    - DS-TE never routes more than say 70% of EF on a given link
>>>    - DS-TE never routes more than 100% of EF+BE on that link.
>>> 
>>>    Let's assume that DS-TE has actually established at a given time:
>>>    - 50% worth of EF TE-LSPs and
>> 
>> Assume 30% is at priority 0 and 20% at priority 8

>> 
>>> 
>>>    - 50% worth of BE TE-LSPs.
>> 
>> Assume all 50% is at priority 2.
>> 
>>> 
>>>    Let's also assume that a new EF TE-LSP worth 10% now needs to be
>>>    established and contends for this link.
>> 
>> Assume this new EF TE-LSP wants resources at priority 1. Question now 
>> becomes: should this new EF TE-LSP preempt some of the BE TE-LSPs 
>> which are all at priority 2 or should it preempt some of the EF 
>> TE-LSPs at priority 8?, i.e. should it preempt from its own class-type 
>> or another class-type?.
> 
> 
> good point. this needs to be defined.
> 
>> I believe that since preemption is needed then the lowest possible 
>> priority preemptee should be chosen even if it comes from our class-type.
> 
> 
> I personally agree. Let's hear other views.
>