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Configuring Reporting of Automatic Bandwidth Allocation Statistics 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 the device to collect statistics related to automatic bandwidth allocation by completing the following steps:

  1. To collect statistics related to automatic bandwidth allocation, configure the auto-bandwidth option for the statistics statement at the [edit protocols mpls] hierarchy level. These settings apply to all LSPs configured on the router on which you have also configured the auto-bandwidth statement at the [edit protocols mpls label-switched-path label-switched-path-name] hierarchy level.
  2. Specify the filename for the files used to store the MPLS trace operation output using the file option. All files are placed in the directory /var/log. We recommend that you place MPLS tracing output in the file mpls-log.
  3. Specify the maximum number of trace files using the files number option. When a trace file named trace-file reaches its maximum size, it is renamed trace-file.0, then trace-file.1, and so on, until the maximum number of trace files is reached. Then the oldest trace file is overwritten.
  4. Specify the interval for calculating the average bandwidth usage by configuring a time in seconds using the interval option. You can also set the adjustment interval on a specific LSP by configuring the interval option at the [edit protocols mpls label-switch-path label-switched-path-name statistics] hierarchy level.Note

    To prevent unnecessary resignaling of LSPs, it is best to configure an LSP adjustment interval that is at least three times longer than the MPLS automatic bandwidth statistics interval. For example, if you configure a value of 30 seconds for the MPLS automatic bandwidth statistics interval (interval statement at the [edit protocols mpls statistics] hierarchy level), you should configure a value of at least 90 seconds for the LSP adjustment interval (adjust-interval statement at the [edit protocols mpls label-switched-path label-switched-path-name auto-bandwidth] hierarchy level).

  5. To trace automatic bandwidth allocation, include the autobw-state flag for the MPLS traceoptions statement at the [edit protocols mpls] hierarchy level.

    The following configuration enables the MPLS traceoptions for automatic bandwidth allocation. The trace records are stored in a file called auto-band-trace (the filename is user configurable):

  6. Using the show log command, you can display the automatic bandwidth allocation statistics file generated when you configure the auto-bandwidth (MPLS Statistics) statement. The following shows sample log file output taken from an MPLS statistics file named auto-band-stats on a router configured with an LSP named E-D. The log file shows that LSP E-D is operating over its reserved bandwidth limit initially. Before Oct 30 17:14:57, the router triggered an automatic bandwidth adjustment (you might see two sessions for an LSP undergoing an automatic bandwidth adjustment). By Oct 30 17:16:57, the LSP has been reestablished at a higher bandwidth and is now shown using less than 100 percent of its Reserved Bw (reserved bandwidth).

  7. Issue the show mpls lsp autobandwidth command to display current information about automatic bandwidth allocation. The following shows sample output from the show mpls lsp autobandwidth command taken at about the same time as the log file shown previously:

  8. Issue the file show command to display the MPLS trace file. You need to specify the file location and file name (the file is located in /var/log/. The following shows sample trace file output is taken from an MPLS trace file named auto-band-trace.0.gz on a router configured with an LSP named E-D. The trace file shows that LSP E-D is operating over its reserved bandwidth limit initially. At Oct 30 17:15:26, the router triggers an automatic bandwidth adjustment (you might see two sessions for an LSP undergoing an automatic bandwidth adjustment). By Oct 30 17:15:57, the LSP has been reestablished at a higher bandwidth and is now shown using less than 100 percent of its Reserved Bw (reserved bandwidth).