Com21
Encyclopedia
Com21 was an early pioneer in developing cable modem
networks in the era before the standard DOCSIS
was introduced for Internet
access via cable television
networks. The company filed for bankruptcy in 2003.
using CMTO as symbol. The headquarters of the company was located in Milpitas, California
. Com21 had offices in 13 countries. The European head office was located in Delft
and had a development centre in Cork, Ireland
.
In 2000 the company had over 260 employees.
was available. The Com21 portfolio can be divided into three segments: the central or head end equipment, cable modems or CPE
, and the management platform.
or CATV hub locations were called ComControllers. A ComController provided the same function as a CMTS in modern Docsis networks. A ComcCntroller was a 19" rack module that was built around an integrated ATM
switch and needed several modules to become a functional cable modem head end system.
The main components or modules in a ComController were:
The management module provided the interface between each ComController system and the Com21 network management platform NMAPS. The management module offered a single Ethernet
interface to an out of band management network.
Each ComController had one HF Downstream module. The downstream controller had two F-connector interfaces to connect a coax cable towards the distribution section of a hybrid fibre coax cable TV network. Below the primary interface a test interface connector was available, making it possible to connect test equipment without having to disconnect the main downstream signal from the network. The frequency of the downstream signal was configurable via the management interface.
A ComController needed at least one upstream receiver module. Each upstream receiver module offered two interfaces towards the HFC network.
To connect the cable modem network to the Internet, a ComController had one or more network modules. In the early models of the ComControllers, network modules offered two 10BaseT interfaces. Each of these Ethernet interfaces could be linked to a VLAN within the Com21 network. After a while, the 10 Mbit Ethernet interfaces didn't offer sufficient bandwidth, as the offered speeds required faster network interconnection. The first successor was a network module with a fast Ethernet
(100 Mbit/s) interface, but this interface lacked the option of VLANs.
As VLAN support was really needed to offer reliable services to the users of a cable modem network, the next version of the network controller was a single ATM
interface offering an OC3 or STM-1
- 155 Mbit/s optical interface. In most configurations, a ComController used a single ATM network controller.
The early models of the modems also offered a hidden interface providing a 4-wire serial communication interface for debugging or monitoring purposes. Via a special connector a systems-engineer could connect this interface to the serial communications (RS-232
) port of a PC to monitor the activity of a cable modem. With the help of a simple terminal emulator one could monitor the booting of the modem and then follow the process of finding a downstream signal, synchronizing the upstream channel and then registering to the ComController.
All proprietary ComPort modems could be used on the platform. Com21 developed early DOCSIS cable modems, obtaining DOCSIS 1.1 certification on Broadcom 3350 (DOXPort 1110) and 3345 (DOXPort 1110XB) designs.
. ComControllers were configured via NMAPS: setting the frequencies for the downstream and upstream signals, define VLANs and enabling the cable modems in one of the created VLANs. Via NMAPS the network managers could specify the speed of the modems, set filtering (e.g. only allowing a specific IP address that could be used behind that modem), etc. NMAPS was only available to run on a Sun
server or workstation.
and its DOCSIS cable modem assets were sold to Arris
. At that time the company had 113 employees.
Cable modem
A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...
networks in the era before the standard DOCSIS
DOCSIS
Data Over Cable Service Interface Specification is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable TV system...
was introduced for Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
access via cable television
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
networks. The company filed for bankruptcy in 2003.
The company
Com21 Inc. was an American public company. Com21 shares traded on NasdaqNASDAQ
The NASDAQ Stock Market, also known as the NASDAQ, is an American stock exchange. "NASDAQ" originally stood for "National Association of Securities Dealers Automated Quotations". It is the second-largest stock exchange by market capitalization in the world, after the New York Stock Exchange. As of...
using CMTO as symbol. The headquarters of the company was located in Milpitas, California
Milpitas, California
Milpitas is a city in Santa Clara County, California. It is a suburb of the major city of San Jose, California. It is located with San Jose to its south and Fremont to its north, at the eastern end of State Route 237 and generally between Interstates 680 and 880 which run roughly north/south...
. Com21 had offices in 13 countries. The European head office was located in Delft
Delft
Delft is a city and municipality in the province of South Holland , the Netherlands. It is located between Rotterdam and The Hague....
and had a development centre in Cork, Ireland
Cork (city)
Cork is the second largest city in the Republic of Ireland and the island of Ireland's third most populous city. It is the principal city and administrative centre of County Cork and the largest city in the province of Munster. Cork has a population of 119,418, while the addition of the suburban...
.
In 2000 the company had over 260 employees.
Products
Com21 was quite successful with their cable modem line of products in the years before the new standard DOCSISDOCSIS
Data Over Cable Service Interface Specification is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable TV system...
was available. The Com21 portfolio can be divided into three segments: the central or head end equipment, cable modems or CPE
CPE
-Biochemistry:* Carboxypeptidase E* Clostridium perfringens enterotoxin* Cytopathic effect* Cytoplasmic polyadenylation element-Telecommunications:...
, and the management platform.
ComController
The central system, typically installed in the head endHead end
Head end may refer to:* A cable television headend, a master facility for receiving television signals for processing and distribution over a cable television system* gateway...
or CATV hub locations were called ComControllers. A ComController provided the same function as a CMTS in modern Docsis networks. A ComcCntroller was a 19" rack module that was built around an integrated ATM
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
switch and needed several modules to become a functional cable modem head end system.
The main components or modules in a ComController were:
- the management module (one per system)
- the downstream HF controller (one per system)
- upstream HF controllers, each providing two upstream channels (at least one per system)
- network controllers, providing interconnection with the internet (or private IP network)
The management module provided the interface between each ComController system and the Com21 network management platform NMAPS. The management module offered a single Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
interface to an out of band management network.
Each ComController had one HF Downstream module. The downstream controller had two F-connector interfaces to connect a coax cable towards the distribution section of a hybrid fibre coax cable TV network. Below the primary interface a test interface connector was available, making it possible to connect test equipment without having to disconnect the main downstream signal from the network. The frequency of the downstream signal was configurable via the management interface.
A ComController needed at least one upstream receiver module. Each upstream receiver module offered two interfaces towards the HFC network.
To connect the cable modem network to the Internet, a ComController had one or more network modules. In the early models of the ComControllers, network modules offered two 10BaseT interfaces. Each of these Ethernet interfaces could be linked to a VLAN within the Com21 network. After a while, the 10 Mbit Ethernet interfaces didn't offer sufficient bandwidth, as the offered speeds required faster network interconnection. The first successor was a network module with a fast Ethernet
Fast Ethernet
In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the...
(100 Mbit/s) interface, but this interface lacked the option of VLANs.
As VLAN support was really needed to offer reliable services to the users of a cable modem network, the next version of the network controller was a single ATM
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
interface offering an OC3 or STM-1
STM-1
The STM-1 is the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s. Higher levels go up by a factor of 4 at a time: the other currently supported levels are STM-4, STM-16, STM-64 and STM-256...
- 155 Mbit/s optical interface. In most configurations, a ComController used a single ATM network controller.
Cable modem
Com21 named their cable modems ComPort. Over the years, Com21 offered several models of their cable modems. All ComPort modems offered two interfaces: one coax connector to link to the TV network and an RJ-45 Ethernet interface. The early ComPort modems had also a module slot for a telephone module. The idea of this module slot was that a cable modem network would also offer a telephone service. These telephone modules never reached the market. Later (smaller) models of the ComPort modems didn't provide for a telephone module.The early models of the modems also offered a hidden interface providing a 4-wire serial communication interface for debugging or monitoring purposes. Via a special connector a systems-engineer could connect this interface to the serial communications (RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
) port of a PC to monitor the activity of a cable modem. With the help of a simple terminal emulator one could monitor the booting of the modem and then follow the process of finding a downstream signal, synchronizing the upstream channel and then registering to the ComController.
All proprietary ComPort modems could be used on the platform. Com21 developed early DOCSIS cable modems, obtaining DOCSIS 1.1 certification on Broadcom 3350 (DOXPort 1110) and 3345 (DOXPort 1110XB) designs.
DOXcontroller
Com21 also made a CMTS called the DOXcontroller 1000XB, which was OEMed by ARRIS (as the Cadent C3). Upon Com21's Chapter 7 bankruptcy, it was purchased by ARRIS, and was later DOCSIS 2.0 certified.NMAPS
To manage a network with one or more ComControllers and all connected cable modems, Com21 offered their network management platform, called NMAPS. NMAPS was a proprietary platform using the HP OpenView platform. A typical feature of a Com21 network was that the cable modems didn't get an IP address. A modem was addressed using its MAC addressMAC address
A Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
. ComControllers were configured via NMAPS: setting the frequencies for the downstream and upstream signals, define VLANs and enabling the cable modems in one of the created VLANs. Via NMAPS the network managers could specify the speed of the modems, set filtering (e.g. only allowing a specific IP address that could be used behind that modem), etc. NMAPS was only available to run on a Sun
Sun Microsystems
Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
server or workstation.
Deployment
Before the worldwide acceptance of the DOCSIS standard, Com21 was highly successful in the industry. By 2000, Com21 had shipped over 500,000 modems and 1,000 ComControllers. The networks using the Com21 system passed 15 million households worldwide.Demise
On July 15, 2003 Com21 went out of business. The company filed for Chapter 11 bankruptcyChapter 11, Title 11, United States Code
Chapter 11 is a chapter of the United States Bankruptcy Code, which permits reorganization under the bankruptcy laws of the United States. Chapter 11 bankruptcy is available to every business, whether organized as a corporation or sole proprietorship, and to individuals, although it is most...
and its DOCSIS cable modem assets were sold to Arris
Arris
Arris is an architectural term that describes the sharp edge formed by the intersection of two surfaces, such as the corner of a masonry unit; the junction between two planes of plaster or any intersection of divergent architectural details...
. At that time the company had 113 employees.