The architecture working group of Next- Generation Network Architectures (NGNA) posed the question to the industry if a cable modem termination system (CMTS) architecture could be developed that could leverage edge quadrature amplitude modulation (QAM) devices that have been developed for the video-on-demand (VOD) environment. The author of this paper started working on this problem with a team of engineers in December 2003. The resulting design was submitted to CableLabs in May 2004 and formally adopted by CableLabs in January 2005 as the baseline design for the Modular CMTS (M-CMTS) specification. The author of this paper is now serving as lead author for the Downstream External PHY Interface (DEPI) working group.