What functions does MPLS ping provide

In MPLS, the control panel used for establishing an LSP cannot detect the failure in data forwarding of the LSP. This makes network maintenance difficult.

The MPLS ping mechanism detects LSP errors and locates faulty nodes. Similar to IP ping, MPLS ping checks LSP connectivity through MPLS Echo Request and MPLS Echo Reply messages. These messages are transmitted in User Datagram Protocol (UDP) packets with the port number being 3503.

An MPLS Echo Request message carries FEC information to be detected, and is sent along the same LSP as other packets with the same FEC. In this manner, LSP connectivity is checked. In MPLS ping, an MPLS Echo Request message reaches the egress node of the LSP, and the control panel of the egress node checks whether the local LSR is the egress of the FEC.

To prevent the egress node from forwarding the received Echo Request message to other nodes, the destination address in the IP header of the Echo Request message is set to (the local loopback address), and the TTL value contained in the IP header is set to 1.

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