SIP PSTN Number Association
This document describes a specific requirement for associating SIP endpoints with PSTN (Public switched telephony Network) endpoints, not for the SIP endpoint to replace the PSTN endpoint, but to allow them to be used together. It outlines some potential ways of addressing this requirement and proposes one of the options as the best case approach. Additionally, it describes a general requirement that fell out from this scenario and that might be a good candidate for further study.