Establishing RLFA Tunnel
To calculate the Remote LFA backup path and to determines the Remote LFA node the software requirement can be broadly classified as below:
OSPF
OSPF shall calculate Repair path that are P space (routers it can reach without traversing the protected link) and Q space (routers that can reach the protected destination without traversing the protected link). Hence routers that belong to both spaces called as PQ routers has to be calculated. It has to inform LDP about PQ node so that RLFA tunnel can be established.
LDP
LDP shall establish targeted session with PQ node and shall advertise label to peer node for the destination FEC. LDP shall send primary and backup path FTN/ILM add/delete info to NSM for further programing.
NSM
NSM shall maintain Primary and Backup path FTN/ILM and shall send information to HSL for data-plane programing.
HSL
HSL program primary and backup FTN/ILM entry in hardware.
Configure LDP Remote Loop-Free Alternate (RLFA)
The LDP RLFA configuration process can be divided into the following tasks:
1. Enable label-switching on the interface on NSM.
2. Establish ospf routing between the nodes (to distribute reachability information within the MPLS cloud)
3. Configure ospf RLFA on Source node
4. Enabling LDP on an interface in the LDP daemon
5. Configure LDP FRR with Auto-targeted-session (Allow creating TLDP session dynamically)
6. Enable BFD interval globally and for all ISIS enabled interfaces
Note: Faster convergence can be achieved with lower BFD interval enabled globally.
Note: Dynamically created RLFA T-LDP sessions will be removed only after disabling LDP auto-targeted-session CLI or LDP FRR.
Note: When targeted-peer ipv4 CLI is configured with auto-targeted-session CLI, T-LDP session created for targeted-peer only remove after disabling auto-targeted-session CLI.
Note: After Enabling Ospf RLFA, Both LFA and RLFA computation will be done and RLFA path will be preferred to provide node-protection.
Note: Better convergence can be achieved with LDP-IGP-SYNC enabled.
Last modified date: 10/16/2023