A forwarded call that presents the original caller's number is usually signed at B or lower by the forwarding provider, because that number is not one the forwarding provider assigned; keeping the original signature needs a mechanism such as RFC 8946 'div' or a vendor passthrough like Twilio's CallToken.
inferred · Checked 2026-10-02
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- call forwarding
- Deployment
- multi-tenant
- Region
- us
- Release range
- current as of 2026-10-02
- Status
- inferred
- Checked
- 2026-10-02
Sources
- SHAKEN/STIR Onboarding — Twilio · tier 2 current vendor documentation · Level B attestation requirements, read with RFC 8946 section 3
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting STIR/SHAKEN attestation levels on outbound calls: source note stir-shaken-attestation-troubleshooting-inf-fwd-not-a. WarmTransfer. https://warmtransfer.net/knowledge/claims/stir-shaken-attestation-troubleshooting-inf-fwd-not-a
BibTeX
@misc{warmtransfer-claim-stir-shaken-attestation-troubleshooting-inf-fwd-not-a,
title = {Troubleshooting STIR/SHAKEN attestation levels on outbound calls: source note stir-shaken-attestation-troubleshooting-inf-fwd-not-a},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/stir-shaken-attestation-troubleshooting-inf-fwd-not-a},
note = {Source note stir-shaken-attestation-troubleshooting-inf-fwd-not-a, checked 2026-10-02}
}