Posted: 12/2000
Uncorking the Bottleneck
Hope for DSL Delivery Rests with
Access Modes
By Fred Dawson
It may take awhile, but there's reason to hope the bandwidth horse is finally going to get out in front of the enhanced services cart that service providers of every stripe see as the key to growing their businesses.
Today, amid all the talk about the revenue potential of enhanced services, nothing stands as a bigger impediment to realizing that potential than the primitive state of affairs surrounding use of DSL, fixed wireless and other so-called "broadband" techniques to supply the bandwidth that such services require. Not only is availability of these access modes a hit-or-miss proposition, but the delays incurred in getting services up and running are often fatal to closing the deal even when one or more options are available.
"The current killer app is just getting the service to the customer," observes Jim Crow, founding partner and CTO at BroadJump Inc. (www.broadjump.com), an Austin, Texas-based startup devoted to streamlining services provisioning using "virtual truck roll" software. "You can't begin to leverage the value-added service opportunity if you can't provide the service, which is why our first product is intended to speed implementation."
Such software, which allows service providers to prequalify customers' computers and other equipment without sending out technicians, is one of the many innovations entering the marketplace as a way to more efficiently connect customers and to more readily add new services as demand dictates. Most fundamentally, these solutions involve the introduction of DSLAMs that support the transition to a more purely IP-based transport environment from today's ATM-based DSL transport. They also support the emergence of new edge distribution platforms that accommodate aggregation of multiple access facilities--DSL, fixed wireless, T1 and cable--at a single location, thereby allowing service providers to provision services in a uniform manner regardless of the type of access facility a particular customer is on.
When it comes to making DSLAMs more IP friendly, the vendor community agrees it must be done. Suppliers, however, who are already well entrenched among ILECs and CLECs, speak of evolving the technology. Further, those who are battling to make new inroads talk of the need for revolutionary approaches that do away with the existing ATM-based approach altogether.
In the former camp is Alcatel USA (www.alcatel.com), the leading supplier of asymmetric DSL (ADSL) systems to ILECs, which is focused on getting "the plumbing out to the customer as fast as possible," says Kevin Sheehan, vice president of marketing for Alcatel's DSL business unit.
"You have to reach 100 percent of your customers," Sheehan says.
This means the next step in DSLAM evolution is the introduction of DSL processors that will support multiple DSL systems from a single DSLAM, thereby ensuring that even the most distant customers can gain access at speeds above 100kbps, and that business class and consumer class services can be provisioned from the same platform at speeds suited to needs as well as line distances.
"You can't ignore ATM" in the rush to migrate to IP, says Robert Balsamo, vice president of DSL business management at Paradyne Corp. (www.paradyne.com), another leading DSL supplier.
"If [LECs] jump to the next thing, wholesalers won't go with them," Balsamo says. "It's got to be a solid end-to-end QoS solution for the wholesale market."
The answer is a distributed Layer 2 switching architecture in the form of edge concentrators that make provisions for Layer 3 IP processing engines that can assign QoS on a per-virtual-circuit basis, either in the ATM mode or in IP, Balsamo says. This will preserve the wholesalers' need to provision at low costs without "reading" what's going on at the edge, while allowing other service providers to exploit the growing wealth of IP-based options, from VoIP to network-based security to hosted apps of every description.
A big factor in vendors' abilities to provide highly flexible edge solutions where the distinctions between DSLAMs, switches and routers disappear is the emergence of high-speed processors operating anywhere from 15 to 50gbps, says Steve Eich, CTO at Nortel Networks Corp.'s (www.nortelnetworks.com) broadband access unit.
"We're seeing a number of chip vendors building the network processor and core switch on a single chip, supporting interfaces at up to OC-192 [10gbps]," Eich says. "We'll see a movement from where we are today where everything at the access port is ATM, to a more agnostic state with IP or ATM neutral modems, and we'll see dynamic spectrum management with DSPs [digital signal processors] that automatically adjust the bit rates as needs vary."
Nortel, which already has DSLAMs in the market that support multiple versions of DSL from a single unit, is also taking a leading role in creating multiprotocol edge platforms that accommodate different types of access facilities. This is the other general category of advances that bode well for service providers' efforts to reach customers, no matter where they are or what types of services they require.
"We can connect the [Nortel] Universal Edge [UE] as a shelf peripheral directly into the core fabric of the [Class 5 Nortel] DMS switch or connect [to the distribution network] as a data-only DSLAM that supports ADSL, SDSL [symmetric DSL], IDSL [ISDN-rate DSL] or other versions of DSL," says Scott Bell, director of strategic and product marketing for Nortel's Access Networks.
The UE also can be used to support voice over packet connections, either on the carrier's CO shelf, at a CLEC's collocation cage or at the customer premises. And, used in conjunction with Nortel's Service Adaptive line card, the UE is implemented easily as a shelf upgrade to the access node, thereby turning the digital loop carrier, which is the link that extends the reach of the CO to remote terminals, into a next-generation broadband access node, Bell adds.
This versatility is made possible by the use of Nortel Service Modules, which, in plain old voice and ADSL applications, can be configured to support just voice, just DSL, or voice and DSL on each port, Bell says.
"We're supporting two WAN streams where we can aggregate various line-side services into ATM or TDM, depending on the carrier's architecture," he says, adding that all of this aggregation and configuration can be managed through simple software interfaces.
Carriers such as WorldCom Inc. (www.wcom.com), Sprint Corp. (www.sprint.com), XO Communications Inc. (www.xo.com, formerly NEXTLINK Communications Inc.) and AT&T Corp. (www.att.com) that plan to use fixed wireless--over-the-air substitutes for broadband telecommunications lines--in combination with wireline access modes to reach end users, present the biggest challenge to service integration at the edges, given the very different types of delivery systems involved. But they make clear such integration is vital to their success.
XO, for example, is preparing to put DSL to use in tandem with the local multipoint distribution system (LMDS, a wireless broadband category) and a nationwide network of long-haul and regional fiber links in a bid to snatch the hottest segments of the local market for broadband services away from the major players in telecom, says Gerard Salemme, senior vice president for external affairs and industry relations.
"We don't have to worry about protecting a legacy customer base, which gives us greater freedom to deliver new services and applications where demand is strongest," he says.
After spending about $800 million to amass 1,150 to 1,300 MHz of spectrum in the LMDS block covering 50 markets overall and 95 percent of the population in the top 30 markets, XO is equipping its own collocation PoPs in COs with DSLAMs and preparing to use the DSLAM facilities of CLECs Rhythms NetConnections Inc. (www.rhythms.com) and Covad Communications Co. (www.covad.com) to ensure complete coverage of its target market segments, Salemme says.
"The key is to find the right tool to meet demand," he adds. "We're not centered on just one technology."
Tight integration of multiple delivery platforms at the network edge, where LMDS or the microwave multipoint distribution system (MMDS) transmitter base stations offer a potentially complementary PoP with DSLAMs, is a key selling point of an edge system introduced by the former Newbridge Networks, which has been acquired by Alcatel. The company's MainStreetXpress ATM switch is designed to aggregate a variety of access platforms, including LMDS, MMDS, DSL and, eventually cable at a local service node that serves as the wireless base station, says Bernard Herscovich, formerly Newbridge's vice president for broadband wireless networks.
"Our vision is to support a multiple-service network," Herscovich says. "Basically, we've made the ATM switch a base station by designing an interface card that directly integrates ATM functionality into the RF [radio frequency] signal, which turned out to be a very difficult thing to do."
At the same time, the company is developing a VoDSL interface in conjunction with the DSL card that slides into the same ATM switching module that is used for the wireless components, thereby providing for the complete integration of voice and data services over various wireline and wireless platforms at the combination base station/ATM switch, Herscovich says.
"Whichever line cards you use for the physical access link, the switch is designed to work with all the native protocols on the access side, including IP, Ethernet and the TDM flavors, as well as ATM, so you can mix and match however you want," he adds.
One of the more exotic approaches to multiple service edge capabilities is represented by a new line of gear being developed by Piscataway, N.J.-based startup Aplion Networks Inc. (www.aplion.com). The company plans to supply intelligent machines that interact with routers and switches to set up a means of streaming hosted applications from various service providers that may be operating over a given network, ensuring that the precise QoS and other parameters required for any given application from any given ASP are assigned by the network as customers use the applications.
"We're providing network operators a means of supporting applications service providers with efficient use of network resources, which makes the provisioning and costs of their services much simpler and more attractive to their customers," says Aplion president and CEO John Holobinko.
Aplion's "Active Service" architecture allows service providers to remotely set bandwidth, QoS and other parameters that fit specific applications such as VPNs and IP voice-enhanced services that have been tailored to specific customer needs, all on the same hardware platform, he says.
"With the Active Services architecture, we build a service with object-oriented programming, using service objects as very small building blocks to provide the quality of service, usage measurement and instruction sets that define the service," Holobinko explains. "We allow you to optimize the network to provide the key parameters of a specific service, whether it's a high-priority application with voice or something that is less latency- or jitter-sensitive."
These elements are apportioned to the application stream by Aplion's small rack-mounted hardware module at the network edge. Another box employing Aplion's intelligent agent software sits at the customer premises. This model is "agnostic" as to the type of protocols running on the access network, Holobinko says.
For example, he says, if ATM is used in the distribution system, its function becomes strictly transmission, because all the functions associated with network provisioning of the application are added without requiring component devices to "look inside" the packet payloads.
"The network is simply a dumb pipe between the two boxes, which means it can be a clear channel T1, DSL or simple PVC [permanent virtual circuit] in the ATM world," Holobinko says. "You don't have to wait for a CLEC to put in DSL, because if you have enough T1s available from the central office, you can collocate at the CO and tackle the market on a LATA-by-LATA basis."
The routing and stream switching at the backbone PoP is done by the Aplion box in a way that, from the network's standpoint, looks like a standard network element, which means it works with whatever interfaces to ATM, IP, TDM or other formats are appropriate to that network environment, Holobinko says. The unit can perform the gateway function for IP telephony as well as the importation of SS7 call setup and feature provisioning from the circuit world to the IP voice environment, and works with voice over ATM as well as standard switched-circuit voice, he adds.
It's very early in the cycle of new edge products, but, if vendor claims are matched by performance in the widespread field trials now getting under way across the country, a key bottleneck to effective implementation of packet-based services will be on its way to elimination.
Without such innovations, the new generation of service providers who have based their strategies on using whatever access means are at hand to serve end users with whatever services they need would be hard-pressed to deliver on such promises.
Fred Dawson is vice president of editorial operations for Virgo Publishing Inc.
