Monitoring and Maintenance

RFC 4379 defines a diagnostic protocol for testing the continuity and connectivity of MPLS LSPs. This technique is commonly referred to as LSP Ping and provides a mechanism to trace the LSP in the forwarding plane under the control, and coordination of the control plane. The core of LSP Ping is an Echo Request message that is sent as a UDP datagram encapsulated as an IP packet, and then as an MPLS packet, and is forwarded along the path of the LSP. If the message is correctly received at the destination or is incorrectly received at some other LSR, it is responded to with an Echo Response that travels back as an IP datagram. Bidirectional Forwarding Detection (BFD) is a protocol intended to provide a lightweight method to detect faults in the bidirectional paths between forwarding engines. It can be applied in IP or MPLS networks, and it can be used to detect faults between neighbors at the ends of interfaces, data links, or LSPs. Its function is independent of data plane technologies or protocols. Virtual Circuit Connectivity Verification (VCCV) is a connection verification protocol developed specifically for application to virtual circuits such as pseudowires. A pseudowire is achieved by installing an MPLS LSP between two provider-edge LSRs, and encapsulating the signal from a native service for transmission down that LSP.