Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 964)

934 Multi-Service IronWare Switching Configuration Guide
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BFD for RSVP-TE LSP
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Because the source IP address cannot be changed for MPLS BFD session after the session has
comes up, the LSR-ID is used as the source IP address for all MPLS BFD packets. This guarantees
that the session does not go down when the LSP path switch occurs.
FRR LSP
Only one BFD session is created for a FRR LSP. When a switchover from protected to detour path
occurs, and when the detour is on a different LP, the BFD session is moved to the LP where the
detour path resides. The BFD session can go down when the LP already has a maximum number of
BFD sessions running. When the detour is on the same LP, the outgoing interface and label stack is
updated on the existing LP.
A BFD session is not created for detour path originating on a transit LSR.
Redundant LSP
One BFD session is created for a primary path of a redundant LSP. When the secondary path is
hot-standby, a separate BFD session is created for it if and only if BFD is enabled for a secondary
path. The two sessions operate independently.
Adaptive LSP
When a new instance of an adaptive LSP comes UP, a BFD session automatically moves to a new
LP when the new instance is created on a different LP. Otherwise, the local outgoing interface and
label stack updates on the existing LP. When the BFD session needs to be moved to a different LP,
it is possible that the BFD session may be down when the LP already has maximum number of BFD
sessions running.
BFD session deletion
A BFD session is deleted when any of the following events happen:
• LSP goes down
• BFD is disabled for the LSP
• BFD is disabled for all LSP (example: through global MPLS configuration)
BFD session modification
You can change the BFD parameters globally or for an individual LSP without program shutdown
without affecting the operational status of the LSP and the BFD session. When you change the
global configuration, the change is applied to all egress MPLS BFD sessions and only to those
ingress BFD sessions whose parameters are derived from the global configuration.
BFD session down handling
When a BFD session for a LSP goes down on ingress LSR because BFD detection time has expired,
it may trigger path switchover if possible (protected to detour or primary to secondary path
switchover). In the case where there is no alternative path, the LSP is brought down and the BFD
session is deleted. The LSP goes through the normal retry mechanism in order to come back UP.
On egress LSR, BFD session down does not have any impact on the RSVP session.