Calls per second (CPS) surcharges

Understanding CPS surcharges, their impact, and how Telnyx manages high CPS rates.

Telnyx Engineering avatar
Written by Telnyx Engineering
Updated over a week ago

Are calls per second (CPS) limits changing?

No. Currently, users who send SIP Trunking outbound calls are subject to a limit of 50 calls every 3 seconds from the same IP address or SIP username–this limit is not changing.

Calls that exceed these limits are rejected with response code 503 CPS limit. Telnyx can extend these limits by setting exceptions for specific users that demonstrate they have a legitimate use case for this traffic.

How do I know if I am sending bursts of traffic?

In order to help you understand your traffic patterns, we have added a new Outbound Peak Calls Per Second (CPS) dashboard to the Mission Control Portal that shows your outbound traffic patterns. This feature will allow you to view your peak outbound call attempts for every hour on a timeline report.

Monitoring your outbound traffic will help to ensure that your usage is spread out evenly throughout the day to avoid sending large bursts of outbound traffic and a high CPS surcharge.

What is the 95th percentile peak CPS value?

95th percentile peak CPS value is calculated per customer on a monthly basis in the following way:

  1. The peak CPS value per hour is calculated for each customer by determining the highest CPS value in a given hour.

  2. The peak CPS value per hour is calculated for each hour of every month to create the monthly dataset.

  3. From this dataset, the 95th percentile peak CPS value is calculated for every customer, every month–this is the value that will be used to calculate the surcharge as below.

How are CPS surcharges calculated?

CPS surcharges will be calculated based on a Graduated Pricing model.

At the end of each month, we will calculate the 95th percentile peak CPS value for each customer, which will be used to calculate the monthly surcharge.

The outbound peak CPS pricing model is calculated as follows:

  • First 5 CPS = free

  • Any Additional CPS up to 25 = $12/CPS

  • Any Additional CPS up to 200 = $16/CPS

  • Any Additional CPS up to 250 = $24/CPS

  • Any Additional CPS (251+) = $30/CPS

As an example, if the 95th percentile peak CPS is found to be 163 in a given month then the surcharge would be:

(5 CPS x $0) + (20 CPS x $12) + (138 CPS x $16) = $2,448

How will CPS surcharges be billed?

CPS surcharges will appear on your monthly invoice as a new line item –reflecting any usage that exceeds the CPS limits that we currently enforce.

Will my programmable voice usage be subject to CPS surcharges?

At this time only SIP Trunking traffic will be subject to CPS surcharges.

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