Editing Cable modem (section)

===Com21===
{{main|Com21}}
[[Com21]] was another early pioneer in cable modems, and quite successful until proprietary systems were made obsolete by the DOCSIS standardization. The Com21 system used a ''ComController'' as the central bridge in CATV network head-ends, the ComPort cable modem in various models and the NMAPS management system using [[HP OpenView]] as the platform. Later they also introduced a return path multiplexer to overcome noise problems when combining return path signals from multiple areas. The proprietary protocol was based on [[Asynchronous Transfer Mode]] (ATM). The central ComController switch was a modular system offering one downstream channel (transmitter) and one management module. The remaining slots could be used for upstream receivers (2 per card), dual Ethernet 10BaseT and later also [[Fast Ethernet]] and ATM interfaces. The ATM interface became the most popular, as it supported the increasing bandwidth demands and also supported [[VLAN]]s.
Com21 developed a DOCSIS modem, but the company filed for bankruptcy in 2003 and closed. The DOCSIS CMTS assets of COM21 were acquired by [[ARRIS]].