The MPLS-OPS Archive

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

At 10:00 PM 11/7/2003 -0800, Carlos Patriawan wrote:

> ----- Original Message ----- 
> From: "Jean Philippe Vasseur" <jvasseur@cisco.com>
> To: <Devendra.Vyas@relianceinfo.com>
> Cc: <mpls-ops@mplsrc.com>
> Sent: Friday, November 07, 2003 5:45 AM
> Subject: Re: [MPLS-OPS]: CSPF-C=SPF?
>
>
> > At 06:32 PM 11/7/2003 +0530, Devendra.Vyas@relianceinfo.com
> wrote:
> >
> > >in the abscence of
> > >*Administrative groups (that is, link color requirements)
> > >*Priority (setup and hold)
> > >*Explicit route (strict or loose)
> > >i.e., without any constraints>>
> > >is the CSPF path=IGP path??
> >
> > if you do not have any constraint, yes, CSPF will select the IGP
> shortest
> > path, with the appropriate metric (could be the TE metric or the
> IGP
> metric)
> >
> > JP.
> >
>
> This is implementation specific.
>
> Some vendor may force unconstrained cspf output to be equal with IGP
> best
> path,while other vendor can give different path for load-balancing
> reason,
> for example if least-fill or most-fill link bw is used in cspf
> computation.

The question, "if you do not have any constraint" then in this
case, you will follow the IGP shortest path (or any other shortest path
based on the selected metric) and this is not implementation
specific. Now if you have ECMP, you may decide to select specific paths
among the set of ECMP based on various criteria but you still follow
the shortest IGP path. Note that you also have similar scheme with IP
load balancing.

JP.

> Both are valid.
>
>
> Thanks,
>
>
>
> Carlos