The MPLS-OPS Archive

[Sebastien.Spas@alcatel.be]

Hi,

 

Off-line TE approach is always centralized and requires utilization of a specific tool (a software product). The main advantages are :

-averaging link utilization. This is reducing impact on your service when one link goes down, avoid congestion, and allows to route 35% more traffic than online TE approach (that 35% is actual value of tests on a 16 routers, 80 links and 40 bi-directional LSPs network we made with 5620 TSOM, the Alcatel MPLS-TE product). The final reach is reducing equipment cost by 35% for the same ammount of traffic.

-implementing LSPs protection in a centralized way, which is much more efficient

-the possibility to use lot of very interesting features in the offline tools, like performance management, support for planning, auto-discovery and provisioning, which makes the off-line TE process much more easier, and then can allow to start it each week of 2 weeks. This makes the off-line tool much more reactive, and allow to perform network planning every week or 2 weeks, allowing to follow closer the network traffic evolution, and so allowing to reduce the risk marging implemented by over-provisioning. You can them in a unique tool perform the traffic monitoring, mandatory for planning the LSPs, test different planning scenarios and finalyl implement them, with only few clicks in a single product.

-this approach can also cope with multi-vendors networks since it's software based.

 

On-line : CSPF online approach is directly implemented by the routers, so it's totally transparent, you don't have much control about the paths used by the LSPs, and the total traffic increase with this approach is pretty poor compares to off-line solutions. The on-line TE is not needed as fallback in case of link failures. Off-line TE approach allow to also provision backup disjoint paths, and supports fast reroute.

 

On-line TE approach can be more interesting to first provision new LSPs quickly, which are optimized on a regular basis with an Off-line tool.

 

 

you can find more information about alcatel product there : http://www.alcatel.com/products/productsummary.jhtml?_DARGS=/common/opg/products/include/productbrief.jhtml_A&_DAV=/x/opgproduct/a5620tsom.jhtml

 

 

kind regards,

sebastien.

-----Original Message-----
From: Jean Philippe Vasseur [mailto:jvasseur@cisco.com]
Sent: jeudi 13 mars 2003 15:17
To: Lavoisier José Leite Farias
Cc: Sandmaier, Jan; ILazar@burtongroup.com; mpls-ops@mplsrc.com
Subject: Re: RES: [MPLS-OPS]: On-line TE?

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