Inbound Calls
Flowroute provides inbound calls to customers from both of the following STIR/SHAKEN-based insights:
TN validation info via the ‘verstat’ tel URI, a parameter in either the P-Asserted Identity (PAI) header field or the FROM header field. This parameter will contain one of the following 3 values denoting the result of a TN validation check:
TN-Validation-Passed
TN-Validation-Failed
No-TN-Validation
If Flowroute receives a "TN-Validation-Passed” result in the verstat, we will prepend “[V]” to the CNAM, right-truncating CNAM if the addition of “[V]” causes the 15-character limit to be exceeded.
For calls that have the above-mentioned verstat result, we’re also putting logic in place that will overwrite any CNAM content that originating networks or phone systems would supply, so that the pre-pended [V] doesn’t inadvertently communicate invalid/nefarious CNAM content.
If the CNAM content from our content provider is either blank or the response is NULL, the CNAM will simply be “[V]”.
All other calls will have normal CNAM treatment.
Additional Comments (Inbound):
Flowroute does not block inbound traffic based on STIR/SHAKEN verification results.
The reasoning for offering both options (1) and (2) together is to allow customers who can handle/parse SIP headers to apply their own treatment if they so choose, while also providing for others who cannot. The CNAM-based approach solves for a large variety of end-customer-device restrictions without the need for service providers to individually do so.
Outbound Calls
For outbound calls from customers, Flowroute applies the following call signing methodology:
Attestation A - Calls from TNs that a customer purchased from Flowroute, and are associated with that specific customer’s Flowroute account.
Attestation B - Calls from TNs other than those that a customer purchased from Flowroute.
Attestation C - Calls from toll-free numbers not hosted on Flowroute, invalid TNs (invalid per North American Numbering Plan), or with caller ID “Anonymous”.
External Attestation - Flowroute passes through, unaltered, any attestation received on calls arriving to Flowroute.
Additional Comments (Outbound):
Flowroute has implemented a Level 0 - Do Not Originate (DNO) block for all outbound traffic utilizing blacklisted FROM CIDs (ex. banks, law enforcement agencies, government bodies, etc.). This does not affect numbers purchased from Flowroute.
Flowroute has also implemented a block on all outgoing traffic with invalid FROM CIDs which include the following formats: blank, non-numeric, less than 7 digits, greater than 15 digits.
As is the case with inbound calls, Flowroute does not block outbound calls based on a particular attestation level.
NOTE: Some call routing information is carried by the SS7 protocol when origination is not VoIP. Due to the way SS7 is handled by public telephone lines, SIP headers cannot be sent to VoIP end users and will cause an unreliable check on a STIR/SHAKEN event.