This is the ratified version of the IP Interconnection Routing Report, published by the joint ATIS/SIP Forum NNI Task Force. The IP-NNI Routing Technical Report documents mechanisms for identifying the preferred IP interconnection point for a given TN. This report presents multiple views of current IP interconnection mechanisms based on aggregate PSTN constructs, interim solutions based on all-IP routing using a per-TN registry, and a consideration of hybrid approaches across both mechanisms during the transition to all-IP.