Deciphering DSL

Overview

The impact of the Internet on businesses, organizations and individuals has been heralded over the past several years. But although larger organizations have benefited from high speed access via expensive leased lines, individuals and small organizations have had to make do with dial-up services. Digital Subscriber Line, DSL, is a technology poised to revolutionize the delivery of information via affordable high speed services.

DSL technologies leverage the cable installed by the Plain Old Telephone System (POTS) by installing equipment designed to communicate at high speeds. Phone subscribers communicate via cables connected to a central offices (CO) which are also known as wire centers. DSL service is implemented by the installation of digital subscriber line access multiplexers (DSLAM) at the CO. These communicate to DSL capable devices at the customer site via the POTS cable system. Once the equipment is installed and configured, information is carried via high speed lines to an Internet Service Provider (ISP) which then links it to the Internet.

Broadband Service

RECOL, LLC provides Internet services in partnership with SNET, a member of the SBC global network. There are several competing technologies designed to implement DSL over voice grade circuits. The RECOL/SNET solution is based on broadband technology. Broadband is an approach that is rapidly growing in popularity since it is fostered by many telco companies such as SBC and Bell Atlantic. In broadband, several services are supported on the line. At the time of this writing, data and voice services are provided via the RECOL/SNET offering, but additional services such as video are possible and may be offered in the future.

The RECOL/SNET broadband service works by providing three channels for the transfer of information:

• Voice
• Data sent to the Internet (Upstream)
• Data received from the Internet (Downstream)

An analogy would be channels on a TV set. Just as clicking through the channel selector provides access to television stations, computer data and phone communication are supported via their respective channels. Although the technology is termed digital, broadband utilizes analog signals similar to voice to carry information. This supports increased distances over the voice grade phone cables without requiring the expensive electronic line conditioning equipment found in leased line solutions. Actually, the device used to connect customer equipment is termed an ADSL modem and other than for operating speed, works quite similarly to common PC based phone modems.

The form of DSL provided by the RECOL/SNET offering is labeled ADSL and will be described below. The following diagram illustrates channels on an ADSL circuit.

Service Roll Out and Availability

SNET will be rolling out ADSL services in the years 2000 and 2001. In January 2000, service became available in 10 towns in Connecticut. As DSLAM's are installed service will spread throughout the state. SNET has stated that it will not only install DSLAM's in Central Offices but also in smaller remote/satellite stations. Termed "Project Pronto" by its parent SBC, this initiative plans to provide complete coverage in each city that has DSLAM's. Thus SNET/RECOL DSL service is projected to be available to 80% of the state.

At the current time, service is available to any customer located within 17,500 feet of a CO with a DSLAM. This is actual cable length not physical distance "as the crow flies". In order to determine if service is available, the customer must be qualified. SNET technicians normally will automatically qualify the customer if they are with in 12,000 feet of the DSLAM. Those customer located at 12,000 to 17,500 feet may require line conditioning to obtain service. If required and upon request by the customer, SNET will condition and test a line to bring it into ADSL compliance for a one time fee of $995..

Customer circuits may be disqualified or their installation may not work based on environmental considerations. These may relate to Radio Frequency Interference (RFI), conditioning devices on the lines or the presence of high speed leased services in the customer's building. Thus it is important that customers develop realistic expectations about the availability of service. Also, once service is installed, occasional outages are a possibility since circuits do not utilize expensive electronic conditioning devices as found on expensive leased circuits. Finally, as part of the phone network, DSL is subject to the same conditions that effect phone service such as weather conditions.

Add-On to Voice Services

SNET and most Telcos treat ADSL services as an add on to voice service. Although voice will be treated as a separate and distinct service, a customer must have a current phone line or have a new one installed that will also carry DSL traffic. A simple filtering device termed a splitter is used to separate data from voice. The network diagram included below shows the wiring design at the customer location and also the connections to the CO and ISP.

Performance and Service Bandwidth

DSL service is optimized for download speeds. This follows the most common use of the internet by information consumers for browsing the WEB, downloading files and receiving email. Thus the SNET/RECOL offering is labeled Asymmetric Digital Subscriber Line (ADSL). The following table lists two services provided by SNET and RECOL.

• Basic/Business - 384 Kbps up to 1.5 Mbps downstream with 128k fixed upstream.
• Enhanced/Premium - 1.5 Mbps up to 6 Mbps downstream with 384k fixed upstream.

The above speeds will be supported from the customer to the DSLAM. From the DSLAM to Internet sites, however, many factors will impact total performance including remote server operation, Internet congestion, ISP performance, and customer equipment configuration. Overall, customers will experience much improved performance compared to dial-up. Note that the minimum rates listed above will be guaranteed for downstream with maximum rates being influenced by line and distance factors.

Commercial & Business Application

RECOL's business plan is to focus on delivering services for commercial and business application. Except in cases where customers may require value added services such Virtual Private Networks (VPN), RECOL will often recommend that home or small office home office (SOHO) users with limited budget or sensitivity to pricing work directly with other ISPs such as the SNET ISP. This is especially germane in single PC applications. In a commercial environment, customers will attach multiple devices to the network via a communications server or a dedicated Internet appliance. Based on extensive experience with ISDN and dial-up solutions as well as leased lines that require routers, RECOL recommends connection via an appliance. Whatever the choice, RECOL can assist the customer in the selection, purchase and implementation process by working with the customer's current support organization or by recommending a qualified and experienced reseller/integrator from its growing base of partners.

The following diagram demonstrates connections via an appliance/router. The diagram shows a DSL Modem. Although units are available that integrate the modem and router, RECOL's recommended design will be separate units. For the technically inclined reader, the Internet appliance implements the attributes of a router and includes firewall features that assist in securing the network.

Service and Support

Service and support is always a key question. Qualifying service responsibilities and implementing problem resolution is challenging when working with Local Area Networks (LAN) that link to remote sites via Wide Area Networking (WAN) links. RECOL has experience working with dedicated communications technologies since 1995 and its technology officer has developed expertise working with telecommunications dating back to the mid 1970s. RECOL will take the customer's first call and will manage problem resolution working in partnership with SNET technicians and customer support organizations. RECOL's experience and management skills will be enhanced via the following systems and services:

• DSL customers are managed via a sophisticated subscriber management system (SMS) from Redback Systems.
• Technicians work from scripts tuned to help get the problem resolved as quickly as possible.
• Troubleshooting will be expedited via Unix and NT monitoring and diagnostic software tools.
• RECOL Web and Database Development teams provide on-line databases to track user configurations, contacts and trouble histories.
• RECOL provides training and support to customer integration and support departments and vendors.

Alternative or Temporary Solutions

For those customers where ADSL is not presently available, RECOL offers interim solutions such as supporting Windows NT servers or analog routers that can connect to the Internet via one, two or three phone modems that dial local phone numbers. Termed multi-linking, RECOL is one of few ISPs that offer increased bandwidth solutions via standard phone lines. ISDN is also an alternative. Organizations requiring a high level of service and availability may elect to implement a leased service such as Frame Relay, Point to Point or ATM. Finally, larger organizations will often connect to the Internet via high speed leased services, and then connect smaller remote offices, home and mobile users via other technologies such as dial-up or ADSL. By providing all of these services, RECOL is strongly positioned to design and implement affordable and secure systems to fit any application and need regardless of service availability.

Summary 

DSL technologies support new and exiting services that provide high speed and affordable connections to the Internet. When connecting office systems on Local Area Networks, however, customers require enhanced support to not only connect but also service the link. RECOL, LLC and its growing base of business partners stand uniquely positioned to provide affordable and dependable communications technologies.