Comment by dredmorbius

This is why fees should be structured such that all carriers are on the hook, but upstream carriers inherit the obligation, possibly with an increased liability per hop, implying that downstream carriers can utilise enforcement as a profit rather than cost centre.

Scenario:

- Spamford places an unsolicited call to subscriber Alice initiating from MalTelCo, transiting carrier hops BunnTel1 and BunnTel2, to Alice's telco carrier, EndTelCo.

- Carriers MalTelCo, BunnTel1, BunnTel2,[1] and EndTelCo have all placed surety bonds, held by BondCo, to practice telephony operations within the jurisdiction (regional/national). The carriers are the Principals, BondCo is the Surety, and receiving subscribers (or telcos, see below) are the Obligees.[2]

- Unbonded carriers may have their traffic refused by peers. Peering to an unbonded carrier places the bond obligation on the receiving carrier.

- Alice flags the call as spam. A per-call surety of $100 is paid to Alice, and charged to EndTelCo against its BondCo contract. As an additional option the call may be flagged as fraud through the phone system, in which case it is automatically referred to LEO by EndTelCo. Obligation of surety is independent of any fraud finding and is based SOLELY on the unsolicited nature of the call.

- EndTelCo has the option of 1) eating the charge or 2) filing a claim against its peer, BunnTel2, the 2nd hop in the chain, which EndTelCo does.

- BunnTel1 similarly files a claim on BunnTel2.

- BunnTel2 files a claim on MalTelCo.

- MalTelCo now eats the claim (it's paid out by BondCo). MalTelCo may seek further compensation from Spamford, but that's Out Of Scope of the bonding / surety schema, and would be covered by MalTelCo's own terms of use.

- BondCo assesses risks and adjusts its surety rates correspondingly based on observed behaviours (and financial risks) of EndTelCo, BunnTel1, BunnTel2, and MalTelCo. If risks are excessive and no surety can be issued, MalTelCo is unbonded, and hence, decertified. Peers may now refuse traffic without penalty.

Note that no one carrier needs to know anything more about a call's routing than its own network boundary. If EndTelCo has no idea that BunnTel2 and MalTelCo were involved, it doesn't matter, because BunnTel1 is on the hook for passing on the call. Spoofing or falsifying records doesn't save you.

There are some questions over how this might be implemented, though generally:

- If Spamford and Alice are both subscribers to EndTelCo, then EndTelCo eats the surety, which is paid to Alice. There's no upstream. Moral: Telcos, don't spam your own customers.

- One thought is that the surety is split among telcos and the subscriber. Rather than just facing a potential cost, transiting and reciving-end-point carriers could see revenue by tracking and prosecuting unsolicited calls. This could include calls received by monitoring numbers set up strictly to assess unsolicited call activity directed to the network. This would mean that calls transiting multiple carriers would be subject to compounded surety claims ... and ... I think I'm OK with that.

- There would all but certainly be classes of calls which would be exempted from claims. Those should be very limited, preferably to government and specifically qualified emergency services only. No political exemptions, no non-profit / NGO exemptions.

- How often claims are settled and risks re-assessed is open for discussion. Daily might be too often, weekly or monthly seems most likely. Longer than that gives too much free-run for malevolent actors to operate.

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Notes:

1. "BunnTel", because bunnies hop.

2. For an overview of surety bonds, see <https://www.suretybondsdirect.com/educate/what-is-surety-bon...>.