Easier, Cheaper DSL: Replacing Central Office Hardware With Access Concentrator Technology.

Content-rich, bandwidth-hungry applications continue to drive the demand for high-speed network access. For businesses in Multi-Tenant Unit (MTU) buildings, getting that essential bandwidth has been difficult and there has been no satisfactory alternative to expensive dedicated T1 lines or slow dial-up connections.

According to the Building Office Management Association, there are 750,000 large multi-tenant commercial buildings worldwide. The Table shows the number of these buildings in the U.S. This market offers the greatest growth opportunities for broadband services, as small- and medium-sized building owners and hotels catering to the business traveler are finding that providing high-speed broadband access is a competitive necessity. Installing an effective, affordable and profitable broadband access technology is the most important issue currently facing MTU owners.

In addition, the American Hotel and Motel Association lists 51,000 MTU properties among its members, representing 3.9 million rooms. The customers in these buildings are prime candidates for high-speed networks because access to the Internet, email, and their corporate Websites are requirements for doing business while on the road.

Recently, DSL (Digital Subscriber Line) appeared on the scene with the promise of being such a solution. DSL is coming on strong because it carries voice and data over existing phone lines at very high speeds. Analyst group Cahners In-Stat predicts that the installed base of DSL subscribers will surpass cable modem service by the end of 2001 and the investment firm US Bancorp Piper Jaffrey estimates there will be 12.9 million installed DSL lines by 2002 at an estimated value of $4.4 billion.

One of the most compelling technological developments driving the analysts' estimates is access concentrator technology, which provides the benefits of DSL without the conventional technical and economic constraints. No equipment has to be installed in the central office and no local loops have to be conditioned. Access concentrator systems are designed to reside on the MTU premises in the central wiring closet and work seamlessly with the existing copper wiring system. This new deployment model, based on Customer Premise Equipment (CPE) does not interrupt ordinary phone service when the Web is accessed or an email message is sent.

Simpler And More Cost-Effective DSL Deployment

The new deployment technology is built with equipment that resides on the MTU premises in the central wiring closet and operates seamlessly with the existing copper-based local loop telephone wires, regardless of distance from the central office. By pushing the intelligence of the network as close as possible to the customer, DSL deployment is free from conventional technical and economic constraints. Thus, the access concentrator model represents a cost-effective solution to the service providers, to the MTU property owners, and to their tenants.

The scalability of access concentrator technology networks permits the deployment of high-speed Internet access to MTU structures more easily, more quickly, and more profitably than ever before possible. The operative concept of the new deployment model is providing DSL service as a local network connected to a readily available digital WAN such as a T1 or El line.

The installation process is fast and simple. A service provider chooses a high-speed WAN connection for an MTU such as a T1 line and connects it to the access concentrator in the wiring closet. From there, the access concentrator delivers DSL-based data to individual offices at rates from 1.5Mbps to 2.3Mbps over the existing copper wiring. In each office, the DSL signals terminate in a router connected to the office LAN (See Fig).

Alternatively, an Ethernet LAN can be deployed in-between the T1 link (or El or other WAN type) and the access concentrator when that is more convenient. For example, an ISDN line can be converted to Ethernet and then connected to the access concentrator or an El line can be converted to Ethernet and then connected to the access concentrator. Ethernet provides a universal high-performance extension cord, which means that the access concentrator and wiring closet do not have to be located in the same place.

Access concentrator technology also offers the following advantages.

* Form Factor. The small footprint fits easily into the wiring closet and is rack-mountable.

* Interoperability. Using the same line-coding scheme, access concentrators are compatible with HDSL-T1, ISDNBRI, ISDN-PRI, and two-channel digital carriers.

* Scalability. Access concentrators are highly scalable and can be stacked to provide DSL lines for larger MTUs with more than 32 tenants.

* Throughput. The VPN capability and fast data rate (2.3Mbps) make maximum bandwidth available to each user. Service providers and property managers can offer a multitude of services, including voice, data, or streaming video.

* Tiered Levels of Service. Service providers can offer different levels of services, ranging from various fixed rates to high-speed bursting. Access concentrator technology employs a software solution to set the data rate independently of the wire speed to any fixed rate, a fixed rate with burst capability, or no fixed rate.

* Security. The access concentrator' s frame-relay switching or IP-forwarding technology is better suited to MTU service than simple bridges. Traffic from one office suite cannot pass to another via bridging, as the access concentrator controls access at the frame-relay or IP-switching level.

A Compelling Value Proposition

With access concentrator technology, service providers can offer profitable DSL-based services that save time and money. The price per port for an access concentrator solution is about $450 with no additional expense for Telco Central Office (CO) equipment. Building owners and managers are able to offer a service that adds significant value to their space at a reasonable cost and the tenants have convenient high-speed broadband access, just like their larger competitors do.

Some DSL equipment providers have developed detailed business-case justifications for investing in their equipment, either for data-only services or for converged voice and data. In one model, the non-recurring CO and line-provisioning costs were estimated at $35,000 per CO with $100 per line costs. In addition, there may be recurring per month costs for CO rent and power charges of $1,400 and line charges of $20 for an unbundled loop.

Contrast these CO-based DSL service cost-estimates with those of the new CPE-based deployment model. A point-to-point T1 circuit is installed at CLEC (Competitive Local Exchange Carrier) rates, along with an access concentrator and number of CPE routers. The low monthly cost of the T1 circuit is amortized over all subscribers in the building and the range of offerings means the up-front costs of equipment closely match the expected initial revenue.

It is even more compelling to be able to deliver broadband access for MTUs while bypassing the Telco CO and the problems of the local loops. Access concentrator solutions use existing conventional telephone wiring, making expensive rewiring unnecessary. In less than an hour, office building tenants can share the high-speed DSL network connection as a common resource and hotel owners can offer the same advantage to their guests.

A New Network With Intelligence At The Edge

The new deployment model pushes the intelligence of the network as close as possible to the customer, using a T1 line to connect to a network system in the MTU wiring closet to provide DSL services to every user that wants to subscribe. This notion of intelligence at the edge is, of course, the genius of packet networking in general and the Internet in particular. It contrasts with the centralized approach taken by host-based data networks (like SNA) and the circuit-switched voice network (PSTN). Peter Sevcik, a well-known consultant and columnist, analyzed the two approaches to offering value-added features to IP-based data networks: (1) using Customer Premise Equipment (CPE) or (2) using the Telco Central Office (CO).

Sevcik notes that there are benefits to each approach but concludes that, " . . . the CPE approach has two strong advantages. The CPE vendors will be able to create many targeted niche solutions that are out of reach for the CO-based, one-size-fits-all approach. There is simply more flexibility in what you do and how you introduce new functions at the small-device level." (Business Communications Review, 11/99).

Access concentrator technology is creating a new deployment model for high-speed Internet access in MTU buildings. Service providers can deliver broadband access while bypassing the telephone company central office and property managers can provide high-bandwidth services to tenants, profitable within hours.

Seton Kasmir is the founder and chief technology officer at RC Networks