Configuring Dynamic Bandwidth Reservation
This section describes how to configure dynamic bandwidth reservation on an MPLS TE interface. This configuration enables the MPLS TE interface dynamically reserve bandwidth for an MPLS TE tunnel to account for the fact that physical bandwidth is variable.
Usage Scenario
A reservable bandwidth value is set on each interface along an MPLS TE tunnel. The MPLS TE module checks whether links meets the bandwidth requirements of all tunnels based on the reservable bandwidth. If a reservable bandwidth value is set on an interface and the physical bandwidth changes on the interface, the MPLS TE module cannot correctly evaluate link bandwidth resources because the available bandwidth may be less than the configured reservable bandwidth. For example, a trunk interface has 1 Gbit/s physical bandwidth. Its maximum reservable bandwidth is set to 800 Mbit/s, and its reserved bandwidth in the BC0 pool is set to 600 Mbit/s. If a trunk member fails, the trunk interface has its physical bandwidth reduced to 500 Mbit/s, which fails to meet the requirements for the maximum reservable bandwidth or the bandwidth in the BC0 pool. The MPLS TE module, however, still attempts to reserve the configured bandwidth, and the bandwidth reservation attempt fails.
- mpls te bandwidth max-reservable-bandwidth dynamic: sets the proportion of the maximum reservable bandwidth to the physical bandwidth on the interface.
- mpls te bandwidth dynamic: sets the proportion of the bandwidth in each BC pool to the maximum reservable bandwidth.
The two proportions are used to enable MPLS TE to detect physical bandwidth changes along links and preempt the bandwidth of an MPLS TE tunnel that requires bandwidth exceeding the available link bandwidth. If soft preemption is supported by the preempted tunnel, traffic on the tunnel can be smoothly switched to another links with sufficient bandwidth. The smooth traffic switchover is also performed when an interface fails, which minimizes traffic loss.
Pre-configuration Tasks
Before configuring dynamic bandwidth reservation, enable MPLS TE on the interface.
Procedure
- Run system-view
The system view is displayed.
- Run interface interface-type interface-number
The view of an MPLS TE-enabled interface is displayed.
- Run mpls te bandwidth max-reservable-bandwidth dynamic max-dynamic-bw-value
The proportion of the maximum reservable bandwidth to the physical bandwidth is set.
When both the mpls te bandwidth max-reservable-bandwidth dynamic command and the mpls te bandwidth max-reservable-bandwidth command are run in a random order on an interface, the last executed command takes effect.
- Run mpls te bandwidth dynamic bc0 bc0-bw-percentage
The proportion of the bandwidth in each BC pool to the maximum reservable bandwidth is set.
When both the mpls te bandwidth dynamic command and the mpls te bandwidth command are run in a random order on an interface, the last executed command takes effect.
- Run commit
The configurations are committed.
Verifying the Configuration
Run the display mpls te link-administration bandwidth-allocation [ interface interface-type interface-number ] command to check bandwidth information on a specified or all MPLS TE interfaces.