Cable Modem Standards

    by Jeff Langer

    Introduction

    The recent explosive growth and popularity of the Internet has created a demand for fast, reliable residential and business Internet connections. Cable companies believe they have the answer to this demand. Their plan is to use existing cable TV (CATV) networks to deliver high-speed Internet access to anyone who can be wired with a cable TV connection. Proponents of this strategy believe the CATV network is ideal for this purpose, since it allows for much faster transmission speeds than using a telephone line and a standard telephone modem. For a summary of cable modem advantages, see www.cablemodems.com/advantages.html.

    In order to implement this service, cable companies will need to provide an interface between their cable lines and customers'’ computer. This interface is the cable modem (see www.cox.com/modemfaq.html). The cable modem essentially allows the transmission and reception of data over cable lines. Whenever computers transmit data, there must always be an agreed-upon protocol, which ensures that each machine can understand what the other is “saying.” These protocols must be governed by standards. Standards ensure that equipment from different manufacturers can communicate properly.

    In the case of cable modems, standards are vital if all cable operators worldwide want to share equipment, content, and networks. Having a standard for cable modems will also help market cable modems because many manufacturers would then be able to produce cable modems that would be compatible with all cable companies'’ networks. A standard would also make the technology easier and less expensive to deploy, and would create a greater consumer demand by creating competition among many modem manufacturers.

    This paper provides a brief, non-technical overview of the major standardization efforts on cable modems.

    The Standards


    Cable modems are much more complex than standard telephone modems. This is because cable modems must perform many more functions than the simple modulation/demodulation required by telephone modems. Non-technically, cable modems must handle many functions of sending and receiving data over a network. These functions can be extremely complex, and require explicit rules covering all aspects of their operation, from how the hardware is physically connected, to the binary computer "language" the modem must use to communicate to other machines on the network. The standardization work for cable modems addresses the issues of operation within a network. The major standardization efforts for cable modems are based on the combination of two existing network standards; ethernet and ATM(Asynchronous Transfer Mode).
    www.yahoo.com/Business_and_Economy/Companies/Computers/N etworking/Asynchronous_Transfer_Mode/
    www.yahoo.com/Computers_and_Internet/Communications_and_Networking/LANs/Ethernet//

    Players, Efforts and Progress


    Currently, many cable companies around America are test marketing cable modems for Internet access. Additionally, there are many different manufacturers who are producing or plan to produce cable modems employing different designs or strategies. www.cablemodems.com/mfg.html Because of the lack of an established standard, many of these different designs will only be compatible within the networks of certain cable companies. There is definitely a rush to market with cable modems ahead of the standardization effort, however all cable companies recognize standards as vital to the success of the cable modem effort. The cable companies demonstrate their recognition of the importance of standards by participating in the standardization process.

    The IEEE (Institute of Electrical and Electronics Engineers) is one of the major players in the standardization effort for cable modems. While not a cable company, the IEEE is responsible for the ethernet standard, which as mentioned above, is closely related to the needs of cable modem standardization. IEEE working group 802.14 is the group responsible for creating the cable modem standard. Many of the other groups and companies working on other cable modem standards efforts also have representatives at IEEE 802.14. The IEEE effort is extremely comprehensive; they are attempting to create a broad, extensible standard which will be able to handle data and multimedia traffic. The main criticism of the IEEE effort from the cable industry is that the IEEE is taking too long to develop the standard. This timeliness problem is certainly not unique to this effort, as standards development groups often operate too slowly to satisfy the market. Working group 802.14 formed at the end of 1994, and is still working on the standard. Based on IEEE’s success with ethernet and technical orientation, a complete IEEE standard would likely be a good foundation on which to standardize cable modems. The IEEE standard would also be an open standard, in contrast to standards developed by MCNS/SCTE, another major player in the standardization effort.

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    last revised 2/22/97
    Jeff Langer