Always worth pointing out that in March 2020, Somos rolled out TFNIdentity. We 
have it set up on customers who want to source from their TFNs, I haven't seen 
many carriers actually look it up, but it does exist.

> On Jul 7, 2023, at 5:34 PM, Nathan Anderson via VoiceOps 
> <[email protected]> wrote:
> 
> I suspect things might be different now (& I just haven't kept up), but 
> although it is clearly *possible* to transmit a TFN as the calling number / 
> CID, I seem to remember that even just a mere few years ago, it was HIGHLY 
> discouraged, and if you ever were to receive a call bearing a TFN as its CID, 
> it had a very high likelihood of being fraudulent or spam.  This was of 
> course back when the vast, vast majority of TFNs were essentially implemented 
> as a call forward or alias to a number that hung off of a local exchange.  So 
> of course outbound calls that many? most? companies with TFNs would make 
> would typically be sourced from their local exchange number(s) and not from 
> the TFN(s) (unless maybe a given company had a PRI and their provider allowed 
> them to source calls from their TFN?).  Thus the expectation for a long time 
> (as I understood it) was that TFNs were truly inbound-only and should be 
> treated as such.
>  
> Loosely tangentially related, as a purely anecdotal report, I will note that 
> I have yet to see a S/S signature/PASSporT attached to ANY calls made *to* 
> ANY of our TFNs, via any of the 3 SIP wholesalers we have used as both 
> RespOrgs & for actual traffic.
>  
> -- Nathan
>   <>
> From: VoiceOps [mailto:[email protected]] On Behalf Of David 
> Frankel via VoiceOps
> Sent: Friday, July 7, 2023 7:52 AM
> To: 'Ivan Kovacevic'; 'Voice Ops'
> Subject: Re: [VoiceOps] STIR/SHAKEN warning!
>  
> Ivan asks: “How are you handling TFN atestations?”
>  
> When the signer of a call gives A-level attestation, it means that the signer 
> knows that the caller “is authorized to use” the calling number.
>  
> The signer can “know” that in any of a variety of ways. For toll-free 
> numbers, the most sophisticated and secure is probably via Delegate 
> Certificates. SOMOS, the North American Toll-Free Number Administrator, has 
> commented about this in a current FCC proceeding: 
> https://www.fcc.gov/ecfs/document/10605623514445/1
>  
> As the signer, there are other ways you could determine that the caller is 
> authorized to use the number. For example, you could solicit some 
> documentation from them (like an invoice from their RespOrg and/or service 
> provider) and you could call the number and verify that your caller answers. 
> The regulations (today) do not specify exactly how you “know” so you (as the 
> signer) need to act in the spirit of the rules.
>  
> This problem is not unique to toll-free numbers. I might have a geographic 
> number that I obtain from provider A (and that’s how I get inbound calls to 
> the number), but I make outbound calls from that number via providers B and C 
> for redundancy and cost reasons.
>  
> Bear in mind that providers can set their own rules for what calls they will 
> accept and what attestations they will assign, and those rules can be more 
> restrictive than what might be dictated by regulation. For example, a 
> provider might say “I will only assign A-level attestation to calls that use 
> calling numbers assigned by me.” That’s their prerogative.  In fact, a 
> provider might say: “I will only accept calls that use calling numbers 
> assigned by me. Those calls will get A-level attestation. I will reject all 
> other calls.” There are no rules (to my knowledge) that prohibit providers 
> from setting these kinds of rules.
>  
> From: VoiceOps <[email protected] 
> <mailto:[email protected]>> On Behalf Of Ivan Kovacevic via 
> VoiceOps
> Sent: Friday, July 7, 2023 7:27 AM
> To: Voice Ops <[email protected] <mailto:[email protected]>>
> Subject: Re: [VoiceOps] STIR/SHAKEN warning!
>  
> Hopefully on-topic. How are you handling TFN atestations?  
>  
> Although a part of NANP - it's a different technology at the network level in 
> terms of chain of authority and routing.
>  
> RespOrg manages the number, but can provision and use many carriers to make 
> outbound calls using the TFN Caller ID (and to receive inbound calls via the 
> same TFN)... RespOrgs is not necessarily a carrier - who and how checks that 
> RespOrg has the authority in case of delegated attestation. I may be 
> overcomplicating it in my mind.. but it doesn't feel like the regulation maps 
> 1-to-1 over to TFNs... Just wondering what everyone's experience is. 
>  
> Thanks,
>  
> Ivan
>  
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