The MPLS-OPS Archive

[Jean Philippe Vasseur <jvasseur@cisco.com>]

Hi,

At 13:59 12/03/2003 -0300, Lavoisier José Leite Farias wrote:
> Is
> there any advantage by choosing one or other option ? I understood by
> reading Irwin's answer that on-line TE is used as fault
> mechanism.

No, on line TE is not used as a fault mechanism, you have the two
options:

        

- off-line
(centralized): provides global optimization as the set of TE LSPs are
simultaneously computed by a single entity that makes

 

use of search mechanisms, to find a placement that
for instance tries to minimize the average load utilization of each link
(this is just one

  

example),

        

- on-line
(distributed): each LSR independently computes paths for its own set of
TE LSPs using CSPF. Inability to find placement due to

       

bandwidth
fragmentation can be highly reduced by the use of appropriate mechanisms
like (soft) preemption.

Both are currently deployed by Service Providers.

JP.

I believe off-line calculation it seems to keep the whole network optimized. am I correct ?
 
Regards,
Lavoisier.

-----Mensagem original-----

De: Sandmaier, Jan [mailto:Jan.Sandmaier@t-systems.com]

Enviada em: quarta-feira, 12 de março de 2003 11:44

Para: ILazar@burtongroup.com; mpls-ops@mplsrc.com

Assunto: AW: [MPLS-OPS]: On-line TE?

Irwin,

 

the two concepts are not so different. In off-line TE you collect traffic rates from all your LSPs in the network, feed the traffic matrix in an optimization engine which produces explicite routes which are used by a provisioning tool to build up the new paths. It is up to the oparator when he adjusts the model or which triggers are used for ajustment. Engineered paths are also adjusted accordingly based on actual network conditions as with on-line TE. You may use on-line TE/dynamic LSPs as a fallback mechanism in case of a link outage. The triggers in on-line TE are configured thresholds and reoptimization timers so there is no big difference. The difference is more centralized computation versus distributed.

 

Jan

-----Ursprüngliche Nachricht-----

Von: Irwin Lazar [mailto:ILazar@burtongroup.com]

Gesendet: Freitag, 7. März 2003 16:32

An: mpls-ops@mplsrc.com

Betreff: [MPLS-OPS]: On-line TE?

I've seen quite a few vendorst that offer sophisticated systems for off-line TE.  My understanding is that this is done by downloading sample network data into a TE optimization engine?  Correct?

 

Is there anyone out there doing on-line TE - in which real-time network traffic is processed and engineered paths are adjusted accordingly based on actual network conditions?

 

Thanks,

Irwin