ATIS 1000096

This specification extends the SHAKEN framework to enable the transmission of Personal ASSertion Tokens (PASSporTs), as defined in RFC 8225, Personal Assertion Token, for calls that use TDM signaling and/or TDM switches during transit. This specification adheres to the following core principles:

1. The solution does not place any new requirements on SHAKEN-compliant VoIP service providers.

2. Preferably, the solution supports the most common call scenarios representing a majority of traffic but does not need to support all possible call scenarios.

3. The solution supports and facilitates the long-term industry goal of migrating to VoIP-based networks.

Within the specification, cryptographically signed PASSporT(s) are exchanged out-of-band, that is, separate from the telephone network signaling. The mechanism of exchanging PASSporT(s) out-of-band is based on draft-ietfstir- servprovider-oob-01, Out-of-Band STIR for Service Providers. 

It is recommended that ATIS-1000097, Technical Report on Alternatives for Caller Authentication for Non-IP Traffic, evaluating the viability of implementing this call authentication mechanism for TDM networks, be considered along with this document.