Calculating Units

When and Where Units Are Calculated

There are two places on the platform that use unit calculation. The first is your existing Cloud and Enterprise test configuration, which calculates the units per test for which you are charged at the end of a billing period. For these tests, units are calculated based on your test configurations and instant tests (see How Units Are Consumed for more information about how units are charged to your account). The second is the unit calculator, which is a test simulator where you can see how changes to test configurations could affect the number of units you consume.

Units are calculated the same way in the calculator as they are calculated for real tests. Likewise, the projection mechanism in the calculator works in the same way as the projection mechanism for real tests on the Usage page, except that the calculator always projects the unit cost over a 31-day period, whereas the Usage page projection projects both from today to the end of the current billing period (which could be any number of days up to 31), and for the next billing period.

This article will use the unit calculator to help illustrate how units are calculated because it provides a visible interface for interacting with tests in a way that immediately shows their impact on unit consumption. The unit calculator also has a unique function on the platform that merits its own discussion; this article will help you understand how the unit calculator works and why to use it.

What the Unit Calculator Is

The ThousandEyes unit calculator is a tool you can use to test the impact of changes to your existing Cloud and Enterprise test configurations, or to determine the estimated cost of a specific test. When you open it up, it is pre-populated with all of your current tests and test settings. It shows the number of units that you are projected to incur over a 31-day period given your current test configurations, and if you add or delete tests or change the configuration of a test in the calculator, it estimates the impact of this change on your usage projection.

Using the unit calculator does NOT change the test settings for which you are currently charged. The calculator is a simulation environment where you can see how changes would impact your unit consumption should they be made in real life.

This is a powerful tool for customers who are at risk of going over their monthly plan allowance, for customers who feel they are underutilizing their allowance, or for customers who want to make adjustments to their test settings to optimize their test performance, add new use cases or reduce alert noise.

It is important to note that the projections the calculator makes are estimates only. For example, the calculator does not consider any instant tests that may be run during a billing period.

Where to Find the Unit Calculator

You can find a link to the calculator at Account Settings > Usage and Billing > Usage: click Calculate the units you need for this account group located on the right of the page.

The unit calculator is not in the main menu on the platform. You can also access it directly by going to app.thousandeyes.com/calculator.

The calculator opens in a new window.

How Units Are Calculated

Generally, the number of units you use per month depends on the type of tests you run, on how many and what kind of agents those tests use, and how many times you run your tests. Details about each element of the equation are explained below.

Test Variables

All test units are calculated per test based on:

Type of test.
Test interval setting (frequency).
Number and type of agents running the test.
The test’s timeout setting (for tests with timeout settings – see Base Equation, below).

In addition to the above, some tests have particular features that, when modified, can increase or decrease unit count. These are:

DNS Server: the number of servers tested.
Agent to Agent: Whether using Cloud or Enterprise Agents as the source agent, and whether test direction is one-way or bi-directional. If bi-directional, both directions incur units.
RTP Stream: duration of the stream.
Page Load: HTTP server timeout.

The calculator pulls the data for your pre-populated test configurations from your Test Settings page, on the Basic Configuration tab (1 - 3) and the Advanced Settings tab (4):

If you make changes to your test settings on the Test Settings page, the calculator will automatically update to reflect these changes the next time you open the calculator (or refresh).

Each calculator “session” always starts from the point of your current test configurations. It will not remember the settings from your last calculator session and will not update changes to your Test Settings page “in session”. If you have changed a test setting on the Test Settings page during a calculator session and you want the change reflected on the calculator without losing any of your other calculator settings, you must update the calculator with the test setting change manually.

Do not close or refresh the calculator if you want to save the settings from your current session. You can use the Share button to generate a link to a snapshot of your current calculator session if you want to save your session settings somewhere. See Using the Share Button for more information about how to use the Share button.

Base Equation

There are three main elements that make up the formula for each test projection. The basic formula is:

The above formula applies to Network, DNS, and Routing tests as follows:

Agent to server
Agent to agent
DNS server
DNS trace
DNSSEC
BGP
- The cost of a BGP test is independent of the number of BGP monitors selected. The BGP test runs every 15 minutes (4 test rounds per hour).

For tests with timeout settings, the basic formula is also multiplied by the timeout in seconds. The minimum timeout is 5 seconds, the maximum is 180 seconds. This extended formula applies to Web and Voice tests as follows:

HTTP server
FTP server
Page load
Transaction
SIP server
RTP stream

Milli-Unit Cost by Test and Agent Type

For billing purposes, units are considered in lots of thousands. This is because many test configurations can run over many millions of rounds per month. At this scale, unit numbers begin to look meaningless. Therefore, when we refer to unit usage, and when you see units shown on the calculator, we are referring to units per thousand rounds, which we call milli-units.

In the table below, note that Enterprise Agents use only half the number of milli-units that Cloud Agents do. This is because Cloud Agents are maintained by ThousandEyes while Enterprise Agents are maintained by customers.

Test Type

Cloud Agent (milli-units)

Enterprise Agent (milli-units)

For reference, 1000 rounds of a test at 5-minute intervals would be around 3.5 days’ worth of tests, while a test at 1-minute intervals would be around 17 hours’ worth of tests.

Example Calculation

If you want to set up an HTTP Server web test, you could set the following test variables:

Test type: HTTP Server
Interval: 1 minute
Agents: 1 Cloud
Timeout Setting: 5 Seconds

First, calculate the milli-unit cost of the test (see Milli-unit Cost by Test and Agent Type).

HTTP server test milli-unit cost per Cloud Agent =
Timeout (seconds) * 1 milli-unit =
5 * 1 =
5 milli-units.

Now, calculate the number of rounds across 31 days using the base equation.

Milli-units * number of rounds per hour over 31 days * number (and type) of agents =
5 milli-units * ((60 minutes/1 minute interval) * 24 hours * 31 days) * 1 Cloud Agent =
5 * 44,640 * 1 =
223,200 milli-units

Because units are calculated per 1000 rounds, the actual cost is 223 units (223,200/1000). Note, units are rounded to the nearest 1000 milli-unit. This displays as the following on the calculator:

The calculator also sums the number of tests with this same configuration. The monthly usage simply increases by the unit amount with each test added. Adding two more of the same HTTP server test, for example, would add up to (223,200 * 3)/1000 = 670 units (when rounded).

Calculator Reconfiguration Use Case: PseudoCo

Consider the following scenario: PseudoCo needs to monitor ten separate targets, from various locations around the world. These targets are all various PseudoCo websites and portals with related domain names such as pseudo.com and pseudo.cloud.com.

For the purposes of this example, let’s assume that PseudoCo has configured a total of 10 page load tests running at 5-minute intervals from 20 cloud agent locations, with a 30-second timeout. The test interval for the page load and HTTP server portions of this are both configured as 5 minutes. The same page load test specifies a separate HTTP server timeout of 5 seconds – but because the test interval is still the same, there is no additional charge for the HTTP server portion of this test.

PseudoCo subsequently purchases another company called NymCo, and needs to monitor two new targets: a new website for NymCo, as well as an API integration website for their own product. In addition to their original page load tests, PseudoCo wants to add a few more tests, including additional HTTP server targets, and one DNS trace test to validate the new company’s DNS configuration.

PseudoCo can use the ThousandEyes unit calculator to understand how best to rearrange their test settings to enable them to monitor these two new websites without going over their monthly unit limit.

For example, rather than increasing the monthly allowable usage ceiling in the contract, PseudoCo can be flexible in the deployment of the new tests by reducing the number of agents running the original page load test from 20 to 16, and re-allocating the saved units to the new tests.

Overages: For customers who have overages enabled, there would be no need to reduce the number of Cloud Agents to stay within plan, as overages allow customers to go over their plan limit. For more information about overages, see Overages.

How to Use the Unit Calculator

Configure Tab

The unit calculator opens to the Configure tab, which displays the existing test configurations in your current account group, and their projected monthly usage.

Top panel

The top panel shows your organization name, your consumption model, and the sum of units your test configurations amount to across 31 days. This sum will update as you add, remove, or change test configurations. A link below the organization name opens a window with a summary of how tests are calculated. There is also a Share button. Click this button to generate a snapshot of the calculator and copy the link to the snapshot for saving or sharing purposes. See Using the Share Button for more information about using the Share button.

Middle panel

The middle panel contains settings that apply to the calculator in general. Along the top are the two main tabs: Summary and Configure. See below for more about the Summary tab. This panel also features:

Account Group dropdown: switch between account groups.
Tests/Agents toggle: The calculator defaults to the Tests view. You can also toggle to the Agents view, which provides a summary of the number of tests and units per agent type. This can be helpful to understand and manage cost by agent type, since using Cloud Agents costs twice as much as Enterprise Agents.
Show filter: Filter by test type. There are two Quick Filters: All Tests and Manually Added Tests. Test Type allows you to filter by any test type currently visible on the calculator.
Add Row button: Allows you to add a new row to your test table in which you can configure a new test. A summary of the number of table rows and unit subtotal displays beneath the button.
Ellipsis button: Allows you to clear all the table rows.

Bottom panel

The bottom panel contains the table of tests. When first opened, the calculator displays all of your current test configurations here. You can also add new tests using the Add Row button from the middle panel.

Across the top are the table columns:

Test Description: Displays the test layer and type. In each row beneath, upon hover, you can add a more meaningful description – useful if you have several of the same type of test and want to align with a use case or team – or you can change the test type with the dropdown arrow.
Interval: A slider that allows you to view and change the frequency of your tests.
- For the Page Load test type, two sliders appear; one for Page Load and one for HTTP server.
- There is no slider for BGP test types as the interval is always set to 15 minutes.
Details: If a test has additional variables that affect unit consumption, this column displays the additional configurable fields, which change depending on test type. The following list explains which field displays for which test types.
- Timeout: HTTP server, FTP server, Page load, Transaction, SIP server, Agent to Agent w/throughput enabled
- Servers: DNS Server
- Duration: RTP stream
- Direction: Agent to Agent, Agent to Agent w/throughput enabled
- HTTP Server Timeout: Page Load
Agents: Allows you to view and change the number of Cloud (indicated by the cloud symbol) and Enterprise (indicated by the server symbol) Agents used in each test.
- For Agent to Agent tests, the first column of agents allows you to choose which type (and number) of agent to use for your source, while the second column of agents allows you to choose which type of agent to use for your target. Source agents determine the unit count for one-way tests, while units will accrue for both directions on a bi-directional test.
- For Agent to Agent w/throughput enabled tests, only Enterprise Agents are available.
- For BGP tests, no agents are available because BGP tests do not use agents.
No. of tests: Allows you to view and change the number of tests.
Monthly Usage: Displays the number of units the test configuration would consume over the course of 31 days if deployed and left unchanged. In each row, upon hover, you can click the trash can symbol to delete the row from the table or click the copy symbol to duplicate the row.

The Share button on the top panel allows you to generate a snapshot and a link to the snapshot of your calculator as it currently stands. You can use this link either to keep a record of (save) this snapshot for your own purposes or to share it with others.

Saving

As there is no “save” button on the calculator, generating a link using the Share button is the only way to capture the work you have put into the calculator. Calculator snapshots do not work like dashboard or test view snapshots, which get saved to the platform. Calculator snapshots are only available through the generated link. To save your calculator snapshot, therefore, you must paste the link somewhere you can access it again, such as to a bookmark folder on your browser or a personal file on your computer. As such, we advise giving your snapshot a meaningful Subject title so you can differentiate calculator snapshots.

Anyone can view a calculator snapshot; they do not require a ThousandEyes login. For anyone without a ThousandEyes login, the link opens in a pared-down ThousandEyes browser window.

The calculator snapshot is not static. Anyone who opens the snapshot can subsequently make edits to it. Any edits made to the snapshot on the link are local to the viewer; these edits will not be seen by any other viewers with the link. That said, anyone who makes edits can create a new link and share the new snapshot with anyone else.