LSP Self-ping is specified in RFC 7746, Label Switched Path (LSP) Self-Ping. LSP Self-ping provides a lightweight, periodic connectivity check by the head-end LER of an LSP with no session state in the tail-end LER. LSP Self-ping checks that an LSP data path has been programmed following the receipt of the RESV message for the path. LSP Self-ping defines a new OAM packet with a locally unique session ID. The IP source address of this packet is set to the address of the egress LER, and the destination address is set to that of the ingress LER, such that when the packet exits the egress LER the packet is simply forwarded back to the ingress LER. LSP Self-ping is a distinct OAM mechanism from LSP ping, despite the similar name.
SR OS supports LSP Self-ping for point-to-point RSVP-TE LSPs and point-to-point RSVP auto-LSPs, including PCC-initiated and PCC-controlled LSPs, and PCC-initiated and PCE-controlled LSPs.
An SR OS router can use LSP Self-ping to test that the data path of an LSP has been fully programmed along its length before moving traffic onto it. When enabled, LSP Self-ping packets are periodically sent on a candidate path that the router intends to switch to, for example, during primary or secondary switching (with FRR on the primary) or MBB of a path, following the receipt of the RESV message, until a reply is received from the far end. When a reply is received, the system determines that the data path of the LSP must have been programmed. LSP Self-ping is used instead of the LSP hold timer (config>router>mpls>hold-timer). This is particularly useful in multi-vendor networks where specific nodes may take unexpectedly long times to program their data path.
LSP BFD is not supported if LSP Self-ping is enabled. The router ignores the LSP Self Ping configuration if configure>router>mpls>lsp>bfd>failure-action failover-or-down is configured for an LSP.
LSP Self-ping is configured under the MPLS context using the lsp-self-ping command.
configure
router
mpls
[no] lsp-self-ping
interval <seconds>
timeout <seconds>
timeout-action {retry | switch}
rsvp-te {enable | disable}
LSP Self-ping is enabled for all RSVP-TE LSPs using the rsvp-te enable command. However, it is possible to enable or disable LSP Self-ping for a specific LSP or LSP template regardless of the setting at the MPLS level.
The interval command sets the interval, in seconds, that periodic LSP Self-ping packets are sent. The timeout command configures a timer that is started when the first LSP Self-ping packet for a specific event is sent on an LSP path. The timeout-action specifies what action to take if no LSP Self-ping reply is received before the timer expires. If timeout-action is set to retry, then the router tries to signal a new path and the process repeats (see Detailed Behavior of LSP Self-Ping for more information). If timeout-action is set to switch, then the router uses the new path regardless and stops the LSP Self-ping cycle.
LSP Self-ping can also be enabled or disabled for a specific LSP or LSP template:
configure router mpls
lsp
lsp-self-ping {enable | disable | inherit}
configure router mpls
lsp-template
lsp-self-ping {enable | disable | inherit}
By default, LSPs and LSP templates inherit the configuration at the MPLS level. However, LSP Self-ping may be enabled for a specific LSP or LSP template using the lsp-self-ping enable command. LSP Self-ping may be explicitly disabled for a specific LSP or LSP template, even if enabled at the MPLS level, using the lsp-self-ping disable command.