DALLAS The wide variety of carrier types offering digital subscriber line (DSL) services meant, almost from the beginning, that all of the carriers were not going to adopt the asynchronous transfer mode interfaces favored by the ADSL Forum. DSL access multiplexers (DSLAMs) introduced in the last two years have used a variety of ATM and simpler Internet Protocol interfaces to bring in data traffic from end users.
That trend has sparked an ongoing debate, evident in the product rollouts at the recent DSLcon show here. Some OEMs with experience in customer-premises equipment, notably Efficient Networks Inc. and Cabletron subsidiary FlowPoint Corp., are offering small routers for branch offices, putting a DSL remote-terminal function in a small platform that offers full routing capabilities in a modemlike form factor. At times, DSLAM vendors have even helped existing remote-access router vendors gain expertise in DSL, as Copper Mountain Networks Inc. (San Diego) has done for Netopia Inc. (Alameda, Calif.), the Farallon Computing spinoff.
The other model suggests that the DSLAM itself should embed routing capabilities as part of its access-concentration functions. This method was pioneered by Brooktrout Technology Inc. subsidiary Interspeed Inc., and the Interspeed architectural model is finding many imitators.
The debate not only affects the router itself but determines how new DSL markets can be served. Tut Systems Inc. (Pleasanton, Calif.), one of the first companies to develop an IP-only DSLAM designed for the basements of multiple-dwelling apartment buildings, is expanding its high-rise market efforts to hotels, hospitals and similar multifloor building markets. Copper Mountain, meanwhile, is concentrating on the business side of the high-rise building market, offering its first dedicated DSLAMs for multitenant business units. Whether the service is symmetric or asymmetric and the network protocol is IP or ATM, virtually all DSL OEMs are betting that a significant part of their business moving forward will involve equipment residing in the basement of a high-rise rather than in a carrier's central office.
Efficient Networks (Dallas), which already had offered enterprise bridging capabilities through its Ethernet-enabled customer-premises systems, is expanding to IP routing based on ATM encapsulation, in the new SpeedStream 5660 router, a tiny desktop system for small-office and home-office applications.
Peter Bourne, director of marketing for Efficient, said the key feature set for the entire planned family of 56XX routers is not breadth of route protocols, less important in a SOHO environment, but breadth of functionality. The 5660 can serve as a network address-translation system, dynamic host-configuration protocol server and domain-name service proxy-server, allowing a small office to perform all end-user access-aggregation functions before the system interfaces with a central-office DSLAM.
The name of the game at FlowPoint, meanwhile, is integrated support for voice over IP. Dano Ybarra, vice president of marketing for the Cabletron affiliate, said that small businesses were quickly moving voice services into VoIP to reduce overall access costs. FlowPoint was an early partner of Jetstream Communications Inc. (San Jose, Calif.) in developing a voice gateway for DSLAMs. The Jetstream architecture uses the ATM Adaptation Layer 2, developed for continuous-bit-rate voice services, thus allowing FlowPoint to offer full quality-of-service prioritizing for four separate voice lines.
Because of FlowPoint's past experience with ISDN routers, the company moved directly to SDSL data services based on the 2B1Q line code from ISDN, using the the ZipWire chips from Conexant Systems Inc. FlowPoint plans to upgrade its access devices with a second generation of ZipWire chip able to reach 2.3 Mbits/second.
But the real interest in small businesses is in adding voice over DSL, said Ybarra. The new 2200V access device includes full routing features, including firewall and NAT support, as well as four channels of analog phone-line support with on-board DSP for voice codec functions and voice packetization. Ybarra said that VoIP and Voice Over Frame Relay can be handled via encapsulation protocols, but the advantage of VoDSL is that it is compatible with the existing public switched telephone network after passing through a gateway like the Jetstream system.
The smaller version of the FlowPoint system, shipping next month, offers four analog ports for $995. A larger 12-port system, shipping in the fourth quarter, has yet to be priced.
As carrier backbones become simpler, many installations will be able to centralize routing functions directly on the DSLAM, in central offices, Internet service provider points of presence, or high-rise basements. Interspeed is finding its System 500 and 1000 route-switch DSLAMs are gaining a lot of imitators in the market, as vendors realize that not all DSLAMs need full ATM support. Chris Whalen, vice president of marketing at Interspeed, said his company tries not to make a strict distinction about where in the network particular routing functions should reside, especially because Interspeed works in partnership with small customer-premises router vendors such as FlowPoint.
The competitive local exchange carriers remain an important target for Interspeed, but Whalen said that the multitenant-building market may have the fastest growth rates, with some market analysts predicting a $1 billion market for broadband services by 2002. Whalen said that Interspeed's opportunities in the Far East may be even bigger in this market, as the bulk of small businesses in locations like Seoul and Singapore reside in high-rise buildings.
This trend has been visible to the DSLAM pioneers, as Copper Mountain is expanding from telco central offices to large office buildings with a new CopperPowered Building family, including a reconfigured version of its earlier CopperEdge 200 DSLAM, and a special smaller, horizontal-slot DSLAM called the CopperEdge 150. Lucent Technologies Inc. will be OEMing the latter 24-port system as part of its own access solutions.
Diana Helfrich, vice president of communications for Copper Mountain, said that the company's imminent stock offering prevents executives from providing estimates of the multitenant unit (MTU) market, but Copper Mountain has created a dedicated marketing group to sell into property management and bundled service-provider markets. The CopperCompatible subscriber-unit branding program that Copper Mountain launched last year will be leveraged for MTU markets, with routers from partners like FlowPoint, Cayman Systems, Ramp Networks, and Netopia.
The hidden trick for competitive local exchange carriers and Internet service providers in the MTU market, said Copper Mountain MTU marketing manager Charles Dauber, is the ability to set up SDSL links as T1 backhaul services. By linking the 150 in the MTU with a 200 in the central office, all services can be set up as SDSL services, virtually eliminating the need for any leased T1 lines. This will make DSL cost-effective to deploy to virtually any small business within the reach of a local loop, Dauber said.