MPLS TE Tunnel Protection Group
A tunnel protection group protects E2E MPLS TE tunnels. If a working tunnel in a protection group fails, traffic switches to a protection tunnel, minimizing traffic interruptions.
Related Concepts
Concepts related to a tunnel protection group are as follows:
Working tunnel: a tunnel to be protected.
Protection tunnel: a tunnel that protects a working tunnel.
Protection switchover: switches traffic from a faulty working tunnel to a protection tunnel in a tunnel protection group, which improves network reliability.
Figure 4-31 illustrates a tunnel protection group.
Primary tunnels tunnel-1 and the protection tunnel tunnel-2 are established on the ingress LSRA on the network shown in Figure 4-31.
Tunnel-2 is configured as a protection tunnel for primary tunnel tunnel-1 on LSRA. If the configured fault detection mechanism on the ingress detects a fault in tunnel-1, traffic switches to tunnel-2. LSRA attempts to reestablish tunnel-1. If tunnel-1 is successfully established, traffic switches back to the primary tunnel.
Implementation
An MPLS TE tunnel protection group uses a configured protection tunnel to protect traffic on the working tunnel to improve tunnel reliability. To ensure the improved performance of the protection tunnel, the protection tunnel must exclude links and nodes through which the working tunnel passes during network planning.
Table 4-12 describes the implementation procedure of a tunnel protection group.
Sequence Number |
Process |
Description |
|---|---|---|
1 |
Establishment |
The working and protection tunnels must have the same ingress
and destination address. The protection tunnel is established in the
same procedure as a regular tunnel. The protection tunnel can use
attributes that differ from those for the working tunnel. Ensure that
the working and protection tunnels are established over different
paths as much as possible.
NOTE:
|
2 |
Binding between the working and protection tunnels |
The protection tunnel is bound to the tunnel ID of the working tunnel so that the two tunnels form a tunnel protection group. |
3 |
Fault detection |
MPLS OAM/MPLS-TP OAM is used to detect faults in a tunnel protection group to speed up protection switching. |
4 |
Protection switching |
The tunnel protection group supports either of the following
protection switching modes:
An MPLS TE tunnel protection group only supports bidirectional switching. If a traffic switchover is performed for traffic in one direction, a traffic switchover is also performed for traffic in the opposite direction. |
5 |
Switchback |
After a traffic switchover is implemented, the ingress attempts to reestablish the working tunnel. If the working tunnel is reestablished, the ingress can switch traffic back to the working tunnel or still forward traffic over the protection tunnel. |
Differences Between CR-LSP Backup and a Tunnel Protection Group
CR-LSP backup and a tunnel protection group are both E2E protection mechanisms for MPLS TE. Table 4-13 shows the comparison between these two mechanisms.
Item |
CR-LSP Backup |
Tunnel Protection Group |
|---|---|---|
Object to be protected |
Primary and backup CR-LSPs are established on the same tunnel interface. A backup CR-LSP protects traffic on a primary CR-LSP. |
One tunnel protects traffic over another tunnel in a tunnel protection group. |
TE FRR |
A primary CR-LSP supports TE FRR. A backup CR-LSP does not support TE FRR. |
A working tunnel supports TE FRR. A protection tunnel does not support TE FRR. |
LSP attributes |
Primary and backup CR-LSPs have the same attributes, except for the TE FRR attribute. In addition, the bandwidth for the backup CR-LSP can be set separately. |
The attributes of one tunnel in a tunnel protection group are independent of the attributes of the other tunnel. For example, a protection tunnel with no bandwidth can protect traffic on a working tunnel that has a bandwidth. |
