Set Thresholds

Note: This feature is not available on PacketShaper ISP models.

Total Delay Threshold

The total delay threshold allows you to specify acceptable response times for selected traffic classes. Response times are defined as "bad" or "good" according to the threshold you set. When a transaction's total delay is lower than the threshold, the transaction is considered good. When the total delay is higher, the transaction is considered bad.

PacketWise allows you to have an unlimited number of classes with RTM thresholds.

To set the total delay threshold value for a class:

1. Click the manage tab on the navigation bar. The Traffic Class window appears.

2. In the left window pane, select the traffic class. The Traffic Class window displays the definition for the selected class.

3. Click statistics and select response time from the drop-down list. The Statistics: Response Time screen appears.  show screen

Note: If response time is not listed on the statistics menu, PacketWise does not have any RTM data for the selected class.

4. Enter the desired threshold value in the Total Delay Threshold field. To determine the number of milliseconds that constitute "too slow" for a total delay, use one of following methods:

• Use the value PacketWise suggests.
• Determine the current average total delay for the traffic class. To determine the current average total delay, compare the average total delay with users' perception of performance. Increase this number until it represents an unacceptable delay (not a typical delay).

5. Click apply changes.

The accumulated delay statistics for the class are deleted, and PacketWise begins timing new transactions and calculating new running delay averages. In addition, the Service Level Threshold field is now available. (See Service Level Threshold.)

Once you have set a threshold, the Statistics:Response Time window displays a transaction count and the percentage of good transactions. This enables you to quickly evaluate the percentage of transactions that are within an acceptable limit of the required service level.

Service Level Threshold

After setting the total delay threshold, use the service level threshold to specify an acceptable percentage of transactions completed within one-minute intervals.

PacketWise tracks the percentage of transactions during each one-minute interval that complete within the number of milliseconds indicated in the total delay threshold. If the percentage is below the specified service level threshold, that interval is considered unacceptable. PacketWise indicates the number of unacceptable intervals and the time of the last unacceptable interval in the Statistics: Response Time window.

To set the service level threshold:

1. In the Service Level Threshold field ( show screen), enter a percentage that represents the minimum level of good transactions that is acceptable for that traffic class. For example, if you enter 90 for the service level threshold, then 90 percent of transactions in the class must be good (that is, below the total delay threshold).

Tip: Use a number that will prompt a corrective action or investigation if the percentage falls below the acceptable level.

2. Click apply changes.

Tracking Service Level Agreements

PacketWise's two performance thresholds (the total delay threshold and the service level threshold) enable you to quantify and track Service Level Agreements.

For example, say you promise your users that 90 percent of their HTTP transactions in each one-minute interval will complete in under 600 ms. To track this, set the total delay threshold to define a good transaction as being under 600 ms. Then, use the service level threshold to define acceptable performance over time as being 90 percent good transactions. You may want to create an event to automatically notify you if the percentage of good transactions drops under the service level threshold.

See also:

RTM Overview

Monitor Response Times

Analyze Application Response Times

Troubleshooting Response Time Measurement Issues