The 7705 SAR LSP diagnostics are implementations of LSP ping and LSP traceroute based on RFC 4379, Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures. LSP ping and LSP traceroute are modeled after the ICMP echo request/reply used by ping and traceroute to detect and localize faults in IP networks.
The downstream mapping TLV is used in LSP ping and LSP trace to allow the sender and responder nodes to exchange and validate interface and label stack information for each downstream hop of an LDP FEC, an RSVP LSP, a BGP-labeled IPv4 route, an SR-ISIS node SID, or an SR-OSPF node SID. The 7705 SAR supports two downstream mapping TLVs: the original Downstream Mapping (DSMAP) TLV defined in RFC 4379 and the Downstream Detailed Mapping (DDMAP) TLV defined in RFC 6424.
This section describes the following topics: