MPLS Protection
In looking at the subject of MPLS protection it is important to consider the MPLS OAM
mechanisms that may be used for fault detection and diagnosis, as well as the traffic
protection mechanisms that may be used to route traffic away from a failed link or
node, and the node protection mechanisms that have been developed to enhance node
availability in IP/MPLS networks.
MPLS OAM Since MPLS reuses IP addressing and IP routing protocols and transports
its signalling over IP, the key tools used in MPLS network operation are the same as
those defined for use in IP networks. If LSPs are established dynamically using RSVPTE
or LDP, and if the network elements operate correctly, then IP tools themselves are
sufficient for network operation. However, additional tools and protocols have been
defined to enable detection of MPLS data plane failures.
LSP ping is defined in RFC 4379. LSP ping may be used to verify connectivity along
an MPLS LSP, and if the ping fails, then LSP pings may be sent in traceroute mode
to diagnose the location of the fault. The key to LSP ping is to ensure that packets are
forwarded along the LSP rather than using hop by hop IP forwarding, and if the LSP
is broken, that the LSP ping is dropped.
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