Benocs Benocs CERN Yale University Yale University Qualcomm Application-Layer Traffic Optimization (ALTO) provides means for network applications to obtain network information. Although ALTO is inherently multi-domain, in that the ALTO server representing the network and the ALTO client requesting the network information belong to different trust domains, there are more general cases where the path from the source and the destination spans multiple autonomous networks, which we call multi-domain settings. This document first gives three multi-domain use cases, and the challenges to address the challenges. It then gives a brief update on the implementation solutions that we explored to address the challenges.