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SIP Trunking Termination Calling is Now More Flexible with Master CPS


  • Enhancement to Calls Per Second (CPS) feature for SIP Trunking termination.
  • Save money and gain more control over capacity planning.
  • Available in beta.

Today, we’re excited to announce a huge enhancement to the Calls Per Second (CPS) feature for SIP Trunking termination. Master CPS is a feature that will save you money if using our traditional CPS feature today while allowing you to have more control over your capacity planning. It’s a win-win!

What is CPS?

Before getting into all the exciting details of this enhancement, let’s take a step back for a moment to understand what CPS is and how it relates to concurrency, a term more familiar amongst traditional SIP providers like AT&T and Verizon.

Concurrency refers to how many simultaneous calls can occur at same time. These traditional providers require you to plan for your highest peak traffic days, determine the highest number of concurrent calls that you may need to support, and pay for the number of “channels” that support that traffic for the duration of your contract term. Twilio, simply put, doesn’t require any upfront capacity planning—we allow you to scale as needed, and you won’t be charged for concurrency.

CPS refers to how many calls can be initiated in the same second. A business with 100 phone agents will need to be able to handle concurrency of 100 so that all their agents can be on the phone at the same time. However, they do not need CPS of 100, because it is extremely unlikely that all 100 agents would need to initiate calls during the same second. Twilio offers unlimited call concurrency, but since there is overhead in setting up a call, we do charge for CPS. Twilio will reserve extra outbound dialing capacity for users who have heavy dialing workloads.

Trunking CPS vs. Master CPS

There are two options for increasing Termination CPS for SIP Trunking: Trunking CPS and Master CPS.

An existing feature we offer is Trunk Level CPS, which allows you to provision each individual trunk with the CPS you require for each region. Pay per trunk, per region.

Master Account CPS is what we’re really excited about! If you are currently using our traditional Trunk Level CPS capabilities, you’ll have the opportunity to see your bill decrease! Master CPS allows you to provision your master account with the CPS you require for each region. Pay per region, per master account. The Master CPS settings are a pooled resource used by any trunk in the given account or corresponding sub-accounts. We also give you the ability to over-provision on the trunk level.

Would I Benefit From this New Feature?

Master CPS is the best fit for your needs if you have several trunks across multiple sub-accounts that need increased CPS, but you aren’t sure what level you’ll need on each of those trunks. For example, you have 4 trunks and based on your call volume, each trunk may require 2-6 CPS at a given time in the US1 region. To ensure successful calls are placed, you would want 6 CPS on each trunk to handle your highest peak times. You would be charged 4*6*$75 = $1,800. In reality, you probably aren’t initiating 6 calls per second all that often, therefore, you’re paying a lot for something that used all that often.

With Master CPS, we’re giving you the ability to apply that 6 CPS at the master account level and only pay $75 flat vs $450. You can provision your trunks to whatever CPS level you’d like, but you’ll always be limited to 6 CPS since that’s what is set at the master account level.

How the Magic Happens

There are two “checkpoints” used to determine when calls will be allowed or rejected.

  1. Actual calls on each trunk vs. Trunk CPS Limits: Do actual calls on a specific trunk exceed the CPS settings set on that trunk for a given region?
    • Yes – Calls start to be rejected based on the Trunk CPS settings
    • No – Go to next rule
  2. Total actual calls across all trunks vs. Master Account CPS Limits: Do total actual calls across all trunks exceed the Master CPS settings in a given region?
    • Yes – Calls start to be rejected based on the master account CPS settings
    • No – All calls will go through

We have two debugger alerts set up in case calls are rejected. These alerts will tell you whether you hit a trunk limit or a master account limit. Then if you wish, you can change your CPS levels appropriately.

Here’s an example of how this works:

Master Account CPS Setting:

North America – Oregon (US2): 25 CPS

How to Get Started with Master CPS

If you’d like to start taking advantage of CPS, contact Sales and they will help you get your CPS levels modified.

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