H3C Technologies H3C S6800 Series Switches - Manual (Page 71)

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computes the average output rate within the sampling interval. When the auto bandwidth adjustment
frequency timer expires, MPLS TE resizes the tunnel bandwidth to the maximum average output rate
sampled during the adjustment time to set up a new CRLSP. If the new CRLSP is set up successfully, MPLS
TE switches traffic to the new CRLSP and clears the old CRLSP.
You can use a command to limit the maximum and minimum bandwidth. If the tunnel bandwidth
calculated by auto bandwidth adjustment is greater than the maximum bandwidth, MPLS TE uses the
maximum bandwidth to set up the new CRLSP. If it is smaller than the minimum bandwidth, MPLS TE uses
the minimum bandwidth to set up the new CRLSP.
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 tunnel, 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 tunnel—An MPLS TE tunnel used to protect a link or node of the primary CRLSP.
• Point of local repair—A PLR is the ingress node of the bypass tunnel. 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 tunnel. 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 tunnel. As shown in Figure 23 ,
the primary CRLSP is Router A—Router B—Router C—Router D, and the bypass tunnel is Router
B—Router F—Router C. This mode is also called next-hop (NHOP) protection.