One way to achieve a threshold is to define a table which can give the absolute threshold based on the current traffic rate. Below is an example of how a typical threshold table looks. An additional column is added for illustrating that how the percentage threshold varies as the current bandwidth increases.
| Range of actual traffic rate | Threshold | Percentage threshold range |
|---|---|---|
| 0-1000 kbps | 2000 kbps | ?? - 200% |
| 1000 kbps to 10 Mbps | 3000 kbps | 300% - 30% |
| 10 Mbps to 100 Mbps | 5000 kbps | 50% - 5% |
| 100 Mbps to 1Gbps | 7000 kbps | 7% - 4% |
Note that the absolute threshold values increase with the actual-traffic rate but the percentage threshold decreases. This way, the user can make sure that for low traffic-rate LSPs, insignificant bandwidth changes are ignored. This saves costly make-before-break procedures and provides a scalability benefit over the current uniform percentage based method. This is particularly beneficial in cases where a router is having LSPs with a wide range of actual-traffic rates.
Pros of the threshold-table based method:
It is important that the range of values and the corresponding thresholds are chosen carefully.
The percentage-based threshold method and table-based threshold methods co-exist. There is another option to configure if an LSP is using the percentage-based threshold or the table-based threshold. Note that there is a single global table only to be used system-wide by all LSPs. An LSP is allowed to chose from either the threshold-table or the LSP level percentage threshold configured. This flag behaves in the same way as the other LSP level auto-bandwidth parameters. This flag also allows configuration on an auto-bandwidth template. It follows the same inheritance mechanism as other parameters. This threshold is valid for both overflow and underflow determination.