Tunnel Reoptimization
The MPLS TE tunnel reoptimization function enables the ingress node to automatically optimize the path of an MPLS TE tunnel when topology information is updated. This function ensures that an MPLS TE tunnel always uses the optimal path.
Background
MPLS TE tunnels are used to optimize traffic distribution on a network. An MPLS TE tunnel is configured using the initial bandwidth required for services and initial network topology. The network topology often changes, so the ingress node may not use the optimal path to forward MPLS packets, causing a waste of network resources. MPLS TE tunnels need to be optimized after being established.
Implementation
A specific event that occurs on the ingress node can trigger optimization of a CR-LSP. The optimization enables the CR-LSP to be reestablished over the optimal path with the smallest metric.
The FF reservation style and tunnel reoptimization cannot be configured together.
Reoptimization cannot be performed for a CR-LSP that is established over an explicit path.
Automatic mode
When the configured reoptimization interval expires, the ingress node uses the Constrained Shortest Path First (CSPF) algorithm to calculate a new path. If the calculated path has a smaller metric than the existing path, a CR-LSP is set up over the new path. After the CR-LSP is successfully set up, the ingress node instructs the forwarding plane to switch traffic to the new CR-LSP and to tear down the original CR-LSP. After the original CR-LSP is torn down, reoptimization is complete. If the CR-LSP fails to be set up, traffic is still forwarded along the existing CR-LSP.
Manual mode
An administrator can run a reoptimization command to trigger reoptimization.
The Make-Before-Break mechanism is used to ensure nonstop service transmission during reoptimization. Traffic must switch to a new CR-LSP before the original CR-LSP is torn down.