H3C Technologies H3C S6800 Series Switches - Manual (Page 425)

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Configuring MPLS OAM
Overview
MPLS Operation, Administration, and Maintenance (OAM) provides fault management tools for the
following purposes:
• MPLS data plane connectivity verification.
• Data plane and control plane consistency verification.
• Fault locating.
These fault management tools include the following types:
• On-demand tools—Tools that need to be triggered manually, such as MPLS ping and MPLS tracert.
• Proactive tools—Tools that are triggered by the system automatically, such as BFD for MPLS, and
periodic MPLS tracert.
You can use these tools to detect and locate faults of LSPs, MPLS TE tunnels, and MPLS PWs.
MPLS ping
MPLS ping tests the connectivity of an LSP tunnel or a PW. At the ingress node, MPLS ping adds the label
associated with a tunnel into an MPLS echo request and sends it to the egress node over the tunnel. The
egress node processes the request and returns an MPLS echo reply to the ingress node. An MPLS echo
reply with a success notification indicates that the tunnel is available for data forwarding, and an MPLS
echo reply with an error code indicates that the tunnel has failed.
MPLS tracert
MPLS tracert displays the path that an MPLS LSP tunnel travels from the ingress node to the egress node
to locate errors on the tunnel. MPLS tracert consecutively sends MPLS echo requests along the LSP tunnel,
with the TTL increasing from 1 to a specific value. Each hop along the tunnel returns an MPLS echo reply
to the ingress due to TTL timeout so the ingress can collect information about each hop along the tunnel.
This information allows you to locate the failed node or access information for each hop, for example, the
label allocated by each downstream hop.
BFD for MPLS
BFD for MPLS uses a BFD session to proactively verify the connectivity of an LSP tunnel, an MPLS TE tunnel,
or a PW tunnel.
BFD for MPLS does the following:
1. Establishes a BFD session between the ingress and egress of the tunnel to be inspected.
2. Adds the label associated with the tunnel into a BFD control packet at the ingress.
3. Sends the packet to the egress node over the tunnel.
4. Determines the tunnel status according to the BFD control packet returned by the egress.