DOCSIS, or Data Over Cable Systems Interface Specification, is a set of documents that defines interface requirements or specifications for developing standard, interoperable cable modems. A cable modem is a device that allows high-speed data access via the cable TV network.

Before DOCSIS, different vendors were making their own proprietary cable modems and other interface equipment. Due to this, interoperability amongst the equipment was a major issue. If a cable company was using network equipment from one vendor, it couldn’t use another vendor’s equipment.

DOCSIS takes care of this problem by introducing a set of 12 cable modem specifications (covering various equipment) that would make them interoperable. These include the Cable Modem to Customer Premise Equipment Interface (CMCI), which is the interface standard between a customer’s computer and the cable modem; Cable Modem Termination System-Network Side Interface, which is the interface standard between the cable modem termination system (CMTS) and the data network; Operations Support System Interface (OSSI), which is the network management layer interface standards between the network elements and the operating system; Telephony Return Interface, which is the interface between the cable modem and a telephone return path; Radio Frequency (RF) Interface specification that defines the RF interfaces between the cable modem and the cable network; and the Security (Baseline Privacy) specifications, which covers the data over cable security specifications.

These specifications contain detailed information about how each of these equipment should be made. Covering them, therefore, is not possible in this little space. You can check out www. cablemodem.com for details.

CableLabs is the certifying authority for DOCSIS compliance. It’s a research and development consortium of cable TV system operators. Cable modem vendors have to submit their products to this lab. If their equipment conforms to the DOCSIS specifications, they get an interoperability seal from CableLabs. Before receiving the seal of interoperability, a cable modem supplier will have to complete the CableLabs conformance checklist, submit an affidavit of DOCSIS conformance, and successfully complete CableLabs’ test suite for DOCSIS compliance. A list of CableLabs certified products is available at www.cablemodem.com/CQ.pdf.

Neelima Vaid