DOCSIS

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