Services
7210 SAS-X, R6 OS Services Guide Page 39
At any given time, the service manager programs only one type of LSP in the linecard that will
activate it to forward service packets according to the following priority order:
1. RSVP LSP type. One RSVP LSP can be configured per SDP. This is the highest priority
LSP type.
2. LDP LSP type. One LDP FEC will be used per SDP. 7210 SAS does not support LDP
ECMP.
3. BGP LSP type. One RFC 3107-labeled BGP prefix programmed by the service manager.
In the case of the RSVP/LDP SDP, the service manager will program the NHLFE(s) for the active
LSP type preferring the RSVP LSP type over the LDP LSP type. If no RSVP LSP is configured or
all configured RSVP LSPs go down, the service manager will re-program the linecard with the
LDP LSP if available. If not, the SDP goes operationally down.
When a higher priority type LSP becomes available, the service manager reverts back to this LSP
at the expiry of the revert-time timer or the failure of the currently active LSP, whichever comes
first. The service manager then re-programs the linecard accordingly. If the infinite value is
configured, then the SDP reverts to the highest priority type LSP only if the currently active LSP
failed.
Note however, that LDP uses a tunnel down damp timer which is set to three seconds by default.
When the LDP LSP fails, the SDP will revert to the RSVP LSP type after the expiry of this timer.
For an immediate switchover this timer must be set to zero.
Use the configure>router>ldp>tunnel-down-damp-time command. For more information, see
7210 SAS M, X, T, and R6 OS MPLS User Guide.
If the value of the revert-time timer is changed, it will take effect only at the next use of the timer.
Any timer which is outstanding at the time of the change will be restarted with the new value.
In the case of the LDP/BGP SDP, the service manager will prefer the LDP LSP type over the BGP
LSP type. The service manager will re-program the line card with the BGP LSP if available
otherwise it brings down the SDP operationally.
Also note the following difference in behavior of the LDP/BGP SDP compared to that of an
RSVP/LDP SDP. For a given /32 prefix, only a single route will exist in the routing table: the IGP
route or the BGP route. Thus, either the LDP FEC or the BGP label route is active at any given
time. The impact of this is that the tunnel table needs to be re-programmed each time a route is
deactivated and the other is activated. Furthermore, the SDP revert-time cannot be used as there is
no situation where both LSP types are active for the same /32 prefix.
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