Regulations • Last Updated 9/29/2023

SHAKEN/STIR and Call Forwarding with Telnyx

In this article we’ll take a look at the effect of call forwarding on attestation levels and what it means for your business.


By Fiona McDonnell

SHAKEN/STIR Call Forwarding

SHAKEN/STIR Background

SHAKEN/STIR is a new industry framework that is mandated by the FCC to reduce the number of fraudulent and spam robocalls made over IP networks. With the implementation date of June 30th, 2021 past, many businesses are now wondering- what does SHAKEN/STIR mean for my business?


Before we dive in, let’s quickly recap the different attestation levels:

Full Attestation (A) is applied to a call when the provider knows the customer, knows they have a right to use the originating number, and knows that the call originated on their network. Numbers purchased on the Telnyx portal will receive an 'A Attestation'.

Partial Attestation (B) is given when the provider knows the customer, knows the call originated on their network, but the customer may be using another provider's phone number. The call is legitimate but the provider can’t give full attestation because some information is missing.

Gateway Attestation (C) is a given when the provider can’t verify the customer or the phone number and therefore has no way of knowing whether the call is legitimate. The originating provider will still attest to the call in order to mark that the call originated on their network.

If you think you need a little more context on attestaion, check out one of our previous posts that takes a deeper dive into the different levels.

Call Forwarding & Attestation

In the past, the process for signing forwarded calls did not differentiate between signed and unsigned inbound calls. This meant each forwarded call was signed with B attestation by Telnyx, regardless of whether the call had a toKEN from the originating service provider.

To address that challenge, call forwards in the SHAKEN/STIR framework will now have an identify header that contains a div-PASSporT.

For inbound calls that contain an identity header, Telnyx will pass the identity header received for the incoming call and add a div-PASSporT to the call. In this case, the attestation will be determined by the originating service provider that originally signed the call.

For those inbound calls that are not signed, Telnyx will default to the original process where we will start a new call and assign it a B attestation. It will not have a div-PASSporT attached.

What is a Div-PASSporT?

A div-PASSporT is a new type of PASSporT that contains the diversion information and verifies the destination number that forwarded the call. In this way, a terminating network verification service has sufficient information to perform a reliable caller ID verification.

If you’d like to read more about SHAKEN/STIR, check out our recent posts to our Resource Center which take a deep dive into robocalling, attestations, and call signing. For more information on how Telnyx verifies a forwarded call, check out our support article.

If you still have questions, reach out to our team of experts.

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