For cases where the measured bandwidth of an LSP has increased significantly since the start of the current adjust interval, it may be desirable for the system to preemptively adjust the bandwidth of the LSP and not wait until the end of the adjust interval.
The following parameters are defined:
current_bw — The currently reserved bandwidth of the LSP.
sampled_bw — The average data rate of the sample interval that just ended.
measured_bw — The maximum average data rate in the current adjust interval.
signaled_bw — The bandwidth that is provided to the CSPF algorithm and signaled in the SENDER_TSPEC and FLOWSPEC objects when an auto-bandwidth adjustment is attempted.
max — The configured max-bandwidth of the LSP.
%_threshold — The minimum difference between sampled_bw and current_bw, expressed as a percentage of the current_bw, for counting an overflow event.
min_threshold — The minimum difference between sampled_bw and current_bw, expressed as an absolute bandwidth relative to current_bw, for counting an overflow event. This is an optional parameter; if not defined the value is 0.
When a sample interval ends it is counted as an overflow if:
The sampled bandwidth exceeds the current bandwidth by more than the percentage threshold and by more than the absolute bandwidth threshold (if defined).
When the number of overflow samples reaches a configured limit, an immediate attempt is made to adjust the bandwidth to the measured bandwidth (subject to the min and max constraints).
If the bandwidth adjustment is successful, then the adjust-interval, maximum average data rate, and overflow count are all reset. If the bandwidth adjustment fails, then the overflow count is reset but the adjust-interval and maximum average data rate continue with current values. It is possible that the overflow count reach the configured limit again before the end of adjust-interval is reached and this triggers again an immediate auto-bandwidth adjustment attempt.
The overflow configuration command fails if the max-bandwidth of the LSP has not been defined.
The threshold limit can be changed on an operational auto-bandwidth LSP at any time and the change should take effect at the end of the current sample interval (for example, if the user decreases the overflow limit to a value lower than the current overflow count, then auto-bandwidth adjustment takes place as soon as the sample interval ends). The threshold values can also be changed at any time (for example, %_threshold and min_threshold), but the new values do not take effect until the end of the current sample interval.