The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Curtis,
 
> ICMP is sent to detect failure.  UDP based LSP Ping is sent after an
> failure is detected using ICMP.  Why we need the latter is somewhat of
> a mystery to me, apparently to either distinguish a data plane from
> control plane failure or to to circumvent anti-ICMP religion.
> 

May be that is why you advocate that LSP-Ping could be easily extended to other types
of MPLS control-planes. 

The reason that you need LSP-ping after the ICMP-ping failure is that, the 
ICMP failure could have been due to reverse IP (hop-by-hop) path failure. So
to determine whether the LSP is down or the reverse IP path, you need a disjoint
reverse path => RSVP reverse path :)

-Shahram