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

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

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.

>  I believe we should state a requirement surrounding where the preemptee 
> is chosen from or else it will be open to interpretation and lead to 
> confusion.

Yes, we should cover that point in the next version.
Thanks

Francois

>Any comments/views?
>Darek
>
>
>--
>Darek Skalecki
>Nortel
>(613) 765-2252
>
>

_______________________
Francois Le Faucheur
Development Engineer, IOS Layer 3 Services
Cisco Systems
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