71
Figure 25 Diagram for make-before-break
171B
Route pinning
Route pinning enables CRLSPs to always use the original optimal path even if a new optimal route
has been learned.
On a network where route changes frequently occur, you can use route pinning to avoid
re-establishing CRLSPs upon route changes.
172B
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 feature to implement dynamic CRLSP optimization. For
example, 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 feature can
switch the MPLS TE tunnel to the optimal path.
173B
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 CRLSP fails.
174B
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 tunnel. 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.
374B
Basic concepts
•
Primary
CRLSP
—Protected CRLSP.
