4000 Router Series MPLS Configuration Guide

Tunnel reoptimization

Tunnel reoptimization allows you to manually or dynamically trigger the ingress node to recalculate a

path. If the ingress node recalculates a better path, it creates a new CRLSP, switches traffic from the old

CRLSP to the new, and then deletes the old CRLSP.

MPLS TE uses the tunnel reoptimization function to implement dynamic CRLSP optimization. For example,

when MPLS TE sets up a tunnel, if a link on the optimal path does not have enough reservable bandwidth,

MPLS TE sets up the tunnel on another path. When the link has enough bandwidth, the tunnel

optimization function can switch the MPLS TE tunnel to the optimal path.

CRLSP backup

CRLSP backup uses a CRLSP to back up a primary CRLSP. When the ingress detects that the primary

CRLSP fails, it switches traffic to the backup CRLSP. When the primary CRLSP recovers, the ingress

switches traffic back.

CRLSP backup has the following modes:

• Hot standby—A backup CRLSP is created immediately after a primary CRLSP is created.

• Ordinary—A backup CRLSP is created after the primary CR-LSP fails.

FRR

Fast reroute (FRR) protects CRLSPs from link and node failures. FRR can implement 50-millisecond CRLSP

failover.

After FRR is enabled for an MPLS TE tunnel, once a link or node fails on the primary CRLSP, FRR reroutes

the traffic to a bypass CRLSP, and the ingress node attempts to set up a new CRLSP. After the new CRLSP

is set up, traffic is forwarded on the new CRLSP.

CRLSP backup provides end-to-end path protection for a CRLSP without time limitation. FRR provides

quick but temporary protection for a link or node on a CRLSP.

Basic concepts

• Primary CRLSP—Protected CRLSP.

• Bypass CRLSP—Used to protect the primary CRLSP.

• Point of local repair—An PLR is the ingress node of the bypass CRLSP. It must be located on the

primary CRLSP but must not be the egress node of the primary CRLSP.

• Merge point—An MP is the egress node of the bypass CRLSP. It must be located on the primary

CRLSP but must not be the ingress node of the primary CRLSP.

Protection modes

FRR provides the following protection modes:

• Link protection—The PLR and the MP are connected through a direct link and the primary CRLSP

traverses this link. When the link fails, traffic is switched to the bypass CRLSP. As shown in Figure 20,

the

primary CRLSP is Router A—Router B—Router C—Router D, and the bypass CRLSP is Router

B—Router F—Router C.