DSL meets dial tone: The next communications revolution

Nothing is more appealing to the average person than getting something for nothing. This has certainly been a driving force behind voice over IP. The current flat-rate pricing for unlimited access does away with the metered charges of traditional phone service and results in virtually free telephone calls.

In fact, the real benefit of voice over IP within an enterprise is not low-priced telephone calls but rather the efficiencies that can be gained from a converged data and telephony infrastructure. There is another way to achieve convergence that is a lot easier to implement than voice over IP now reaching the market: voice over digital subscriber line (DSL).

DSL is a way of delivering broadband data that fits nicely between inexpensive-but-slow analog dial-up services and expensive-but-fast T-1 services. Now vendors are ready to exploit another important feature of DSL: the ability to enable up to 16 voice telephone lines as well as high-speed Internet access using a single DSL connection.

Several venture-backed companies, including Accelerated Networks, CopperCom, Jetstream, Sylantro and TollBridge Technologies, have begun to offer voice-over-DSL products. Jetstream, in which Mayfield Fund has an investment, currently is delivering a voice-over-DSL product in conjunction with Cabletron subsidiary FlowPoint. FlowPoint offers integrated access devices (IAD) that are compliant with Jetstream's multiservice access network architecture. FlowPoint's IAD will reside at a subscriber's premises, connect to a DSL circuit and deliver up to 12 standard telephone lines as well as continuous high-speed Internet and remote LAN services over a single copper pair.

Start-ups are not the only ones interested in the voice-over-DSL market. Lucent recently announced a voice-over-DSL product that combines its PathStar portfolio of IP-based, multiservice central office products and MultiDSL access concentrators with Copper Mountain Networks' CopperEdge DSL concentrators and packet-based IADs. This product promises to deliver eight or more telephone lines and high-speed data services over a single unbundled local loop.

While voice over DSL is currently being aimed at households with multiple telephone lines and small to midsize businesses, it does have implications for large enterprises. Voice over DSL offers a highly cost-effective way to connect branch offices and teleworkers to the enterprise. In the case of branch offices, just four analog phone lines could yield enough carrying capacity for at least 24 simultaneous telephone calls and still leave plenty for high-speed Internet access.

For network managers who need to support a decentralized work force, voice over DSL looks to be the most cost-effective way to go.