assign upstream frequencies and upstream time slots. The CMTS controls data traffic on the cable network through the use of a special control channel. When the cable modem is turned on, it scans all its assigned channels to locate the control channel, which can be identified by its unique header signal. The CMTS control channel tells each subscribers cable modem when it can transmit, on which frequency band, and for how long. The data that passes through the MAC mechanism goes into the computer interface of the cable modem, which is 10Base-T Ethernet for the majority of current cable modems (Ostergard, 1998). A cable data system is comprised of many different technologies and standards. The first generation of cable modems used various proprietary protocols that made it impossible for the CATV network operators to use multiple vendors cable modems on the same system. Cable operators have long believed success in the high-speed data business would require that cable modems be interoperable, low-cost and sold at retail like telephone modems and data network interface cards. This way, MSOs could avoid the capital burden associated with purchasing cable modems and leasing them back to subscribers, and consumers would be able to choose products from a variety of manufacturers.The Institute of Electronic and Electrical Engineering's (IEEE) 802.14 Cable TV Media Access Control (MAC) and Physical (PHY) Protocol Working Group was formed in May 1994 by a number of vendors to develop international standards for data communications over cable. The original goal was to submit a cable modem MAC and PHY standard to the IEEE in December 1995, but the delivery date slipped to late 1997 (Van Matre, 1999). The cable operators were anxious to get into the high-speed data business as soon as possible, and became impatient waiting IEEE 802.14. So, the cable operators combined their purchasing power to jump-start the standards process. In January 1...
