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Automatic Bandwidth Allocation for LSPs


Automatic bandwidth allocation allows an MPLS tunnel to automatically adjust its bandwidth allocation based on the volume of traffic flowing through the tunnel. You can configure an LSP with minimal bandwidth; this feature can dynamically adjust the LSP’s bandwidth allocation based on current traffic patterns. The bandwidth adjustments do not interrupt traffic flow through the tunnel.

You set a sampling interval on an LSP configured with automatic bandwidth allocation. The average bandwidth is monitored during this interval. At the end of the interval, an attempt is made to signal a new path for the LSP with the bandwidth allocation set to the maximum average value for the preceding sampling interval. If the new path is successfully established and the original path is removed, the LSP is switched over to the new path. If a new path is not created, the LSP continues to use its current path until the end of the next sampling interval, when another attempt is made to establish a new path. Note that you can set minimum and maximum bandwidth values for the LSP.

During the automatic bandwidth allocation interval, the router might receive a steady increase in traffic (increasing bandwidth utilization) on an LSP, potentially causing congestion or packet loss. To prevent this, you can define a second trigger to prematurely expire the automatic bandwidth adjustment timer before the end of the current adjustment interval.