[c-nsp] MPLS FRR with auto-bw

[Oliver Boehmer (oboehmer)]

> 
> Lets say we have a MPLS-enabled triangle:
> 
> http://i54.tinypic.com/k2lcw2.jpg
> 
> Path AB is being crossed by a couple of MPLS TE Tunnels within
automatic
> bandwidth adjustment (tunnel mpls traffic-eng auto-bw). At the any
given
> point of time summary bandwidth of these tunnels is never exceeded the
> capacity of the part AB. So bandwidth requests by these tunnels are
always
> satisfied.
> 
> Also, assume that there is a tunnel AC with explicit path option. The
total
> bandwidth for this tunnel is unknown and is requested by automatic
bandwidth
> adjustment every 5 min as well.
>
> The question is, is there any way to provide backup facility for path
AC via
> path ABC only if enough bandwidth available at the path AB. For
simplicity
> assume that at the path BC bandwidth is always available.
 
can you clarify what you mean by "provide backup" for path AC via ABC?  

Looking at the picture alone I'm guessing: are you asking to only use
the path ABC for the tunnel AC if the other tunnels crossing AB leave
enough bandwidth for the AC tunnel? If tunnel AC bw requirements can't
be met on link AB, then you want it to use the AC link?

If that's the case, you are asking for a) two path options on tunnel AC
(the primary being the ABC path, the secondary the AC direct link, or
dynamic if this is also the shortest path), and b) for different tunnel
priorities so an increase in bandwidth of the "AB"-Tunnels could
actually lead to tunnel AC using the ABC path being preempted. 

So if you configure the "couple of MPLS TE tunnels" crossing the link AB
with "tunnel mpls traffic-eng priority 4 4" (or another number lower
than the default of 7), they will preempt the AC tunnel if it is
configured with the default 7 (lower number is higher priority).

If you mean some form of FRR, please clarify the exact requirements..

	oli