On 11/4/2011 12:00 PM, harbor235 wrote:
I am also looking at FRR which uses a backup tunnel for fast convergence. I
did however not think
about the dynamic nature of the tunnel and the potential for
reestablishment.
Even with primary/secondary paths, the secondary path will normally not
get used if the primary can resignal to a different path.
Implementations can get very vendor specific. Each vendor supports
different subsets of the necessary protocols. I just had a single vendor
network, that due to lack of SRLG support in their lower end boxes (and
lack of admin-group in FRR) required setting facility based FRR with
many bypasses (which luckily they did support at all levels and the
manual bypasses did support admin-groups for setup).
The only time I usually use dual LSPs is to support load balancing
across multiple circuits where vendor support is limited (1 LSP down
each pipe, IGP balance between them, each LSP has secondary path on
opposite pipe). The idea of MPLS is that the LSP should NOT be down. A
path might go down and FRR/secondy paths might come into play, but the
LSP itself should still be handling traffic. Even in complicated QOS
setups, you can have primary, and multiple secondaries to allow stepdown
of what a circuit should be reserving, and priorities to even preempt
circuits to lower class of service (imagine a secondary trying for what
it currently has without preemption, but then that failing, sets
different requirements and preempts lesser circuits).
In simpler topologies where I don't need TE and I just want FRR, I've
been playing with Juniper's LFA implementation. One of my current plans
is using RSVP/FRR for mpls only services and using LFA for global
routing. It works for my specific layout, and the only annoyance is
setting BGP next-hops correctly.
Jack
