provides consumers an affordable, easy to use, always-on high-speed connection for Internet and other broadband applications.

 

Digital Subscriber Line (DSL) Solutions

Key Benefits

•   Leverage existing copper lines to deliver high-speed, high-value data services

•   Gain the ability to offer a range of data transport rates to meet diverse customer requirements

•   Gain a fully integrated, end-to-end solution that generates revenues today and helps build the market for continuing DSL deployment


With today’s ever-growing requirements for additional bandwidth, service providers need to leverage every opportunity to provide customers with the high performance they demand. DSL technology provides an ideal way to make use of existing network resources, by transforming traditional inexpensive copper phone lines into high-speed, high-value data service lines—which offer continuous connection without draining network resources. Ascend MultiDSL solutions offer the first integrated approach to providing multiple DSL services, with speeds ranging from 128 Kbps to 6 Mbps.

A digital subscriber line (DSL) that conveys all information in an ISDN can be:

 

 

What is DSL service?

DSL stands for Digital Subscriber Line. DSL service in this context refers to a new high speed digital data service called MegaSubscriber, being offered by USWest in selected market areas  throughout USWest territory. It offers previously unobtainable internet access speeds (from 256kbps to 7Mbps) at reasonable rates. As a digital service, it offers continuous (dedicated) connections to the Internet. Along with the DSL line, you will need an Internet Service Provider to access the Internet.

Does this replace my current phone service?
No. You can order a separate line for DSL service, but there is no need to do so. You can use your current voice line for both voice and data, at the same time, using DSL.

What speed is appropriate for me?
For most users, a 256K connection represents the best combination of price and performance. This speed, nearly ten times that of a 28.8K modem, is sufficient for all but the most demanding tasks. It is easily fast enough to support real time video and audio, and allows one to download even the largest files in just a few minutes. The difference between a 256K connection and a 1.54 Mbps (T1) connection (for single users) is almost too small to notice. The only reason to get a faster connection is if you need large amounts of bandwidth. Generally, this only applies to those running a very popular server on their connection. This is allowable, but you will be billed for the bandwidth consumed.

What is the ISP's role in DSL?
ISPs, like DataWest, are here to connect you to the Internet. They also provide e-mail, web space, dialup access, and other Internet-related services. A DSL line alone would be a fast link to nowhere. ISP service is necessary to use DSL.

The DSL terminates in the NT1 at the customer premises and in the line termination (LT) at the central office ISDN switch.

The DSL terminates in the NT1 at the customer premises and in the line termination (LT) at the central office ISDN switch.

The line code that is transmitted along the DSL between the switch and the NT1 is 2B1Q, a coding scheme that maps two bits of information into a single pulse which contains information in both its polarity and its amplitude.

These are called quaternary symbols because they have four possible values.

They can be predicted or generated by treating the two bits to be encoded as the sign and magnitude of the pulse to be transmitted.

This distant end, either the NT1 device or the switch, detects the magnitude and the polarity of the received symbol and recovers the two bits of information.

Why would customers want Frame Relay service when they could have DSL service?
Frame Relay is an excellent choice for enterprise networking where many points must interconnect with each other. In addition, as with DS1 Internet service, Frame Relay provides higher bandwidth options for upstream traffic from a customer's site to the Internet. Furthermore, Frame Relay is a proven technology more suitable to business critical applications, making it a better choice for many businesses. Finally while Frame Relay Internet service is available throughout most of California, DSL Internet access is not yet widely available.

What is xDSL or DSL?

Will DSL service include transmission of regular voice telephone service?
Yes, DSL service will share a customer's telephone line (POTS) without affecting the customer's ability to place and receive voice calls. This means that customers do not need to provision a second phone line for DSL service. They can keep their existing phone number and add DSL as a feature to that line. Therefore, they will be billed for both the analog line (1 MB or FR) and the DSL service. If the line is a measured business line, usage will only be measured on the voice calls. DSL Internet access is billed at a flat rate.

DSL stands for high-speed Digital Subscriber Line. It is a dedicated digital circuit from your home to the telephone company's central office, using normal, copper telephone line. DSL also provides a separate channel for voice phone conversations, which means analog calls (voice, fax. etc.) can be carried at the same time high-speed data is flowing across the line. xDSL is a generic term that includes several variations:

ADSL (Asymmetric Digital Subscriber Line): 1.5 Mbps/64 Kbps-384 Kbps
HDSL (High-bit-rate Digital Subscriber Line): 1.5 Mbps/1.5 Mbps
SDSL (Single-line Digital Subscriber Line: 1.5 Mbps/1.5 Mbps
VDSL (Very high-data-rate Digital Subscriber Line): 13 Mbps-52 Mbps/1.5 Mbps- 2.3 Mbps
RDSL (Rate Adaptive Digital Subscriber Line): various speeds

 

Scheduled for mass production in first quarter, 1999

What kind of security tips does Pacific Bell Internet Services recommend for DSL?
Pacific Bell Internet Services filters out all non-IP protocols for DSL customers, however, this does not guarantee the security of your computer or LAN. If file and print sharing is not required on your computer or network, we recommend that you turn it off as a minimum security solution.
Why would customers want ISDN or analog modems when they could have DSL service?
ISDN and analog modems are switched access technologies that offer the ability for customers to dial many different locations for Internet access or other online services. With DSL services, the connection is a permanent connection to the Internet Service Provider. ISDN and analog modem customers who qualify for DSL service and only need to connect to the Internet from one location will want to switch to DSL in order to take advantage of the benefits of higher speeds and an "always on" connection. However, customers who do not have DSL service available from their central office, or who live beyond the local loop requirements, or need the mobility and flexibility of a switched service will remain as ISDN or analog modem customers.

 

Will business customers want to replace their existing DS-1 (T-1) Internet service with DSL?
There are clear technological differences between DSL and T1 Internet service. The first of which is that T1 service is 1.5Mbps both ways. This is important to many business applications including the hosting of a Web site. In addition, DS1 is a proven technology. While our technology tests demonstrate that DSL is very reliable, businesses tend to rely on established technologies when business critical data is at stake. The final difference is in regard to availability. Currently, DS1 Internet service is more widely available than DSL service.
Will all customers qualify for DSL service?
In addition to having DSL available in their central office, customers must be less than 17,500 feet or three miles from their central office to qualify for DSL service. Approximately 60 - 65% of customers out of each central office will qualify for the service. Eventually, the evolution of network technology will allow us to reach the small percentage of customers who are on the most distant ends of our local networks.

 

Are DSL speeds guaranteed?
The actual throughput rate that a customer receives may be impacted by conditions on the Internet. Pacific Bell will make every attempt to connect the customer's service at the optioned speed. It is important to note that DSL service is provided with a best-effort (Unspecified Bit Rate) Quality of Service on the ATM backbone, and as such, does not guarantee a specific constant or throughput rate.

 

What is (A)DSL ?

Digital Subscriber Line (DSL)
is a complex of technologies that provide high speed Internet access through existing copper phone lines. There are a number of subtypes, but Asymmetric DSL (ADSL) is the most common.

Speed
For typical ADSL, 1.5 megabits per second (1,500K) for downloading, and 64K for uploading. Future versions of ADSL promise even higher rates. In order to reduce the price, many companies are now moving towards slower versions of DSL, such as Universal DSL.

Availability
Like ISDN, ADSL is subject to length limits. For the fastest speeds with the least expensive equipment, the limit is 12000 cable feet from the phone company switch. The maximum distance is 18000 cable feet. Though DSL uses existing copper phone lines, the phone company must install new switches, which is expensive and logistically challenging. It has been predicted that 3% of U.S. homes with Internet access will use DSL/ADSL by the year 2000.

db Tech and ADSL
As yet ADSL has not been made available by the phone company in the dbTechnology areas. When it is made available, if customer demand deems it necessary and when the technology involved has been proven stable and reliable, db Technology will start to support it.

For more information

All Delays Solved Later
dejanews (custome r comments on ADSL)
NetBits (A very honest look at the pro's and con's of ADSL)

 

Imagine if you could plug a box into your phone jack at home that 1) gave you a network connection as fast as the one at your office, 2) let you use the phone at the same time on the same line, and 3) cost as little as US$2 per day to use. Would you stay home to work today? If so, you should use that phone line now to tell your phone company and Congress member to get a move on and deploy ADSL.

ADSL - Asymmetric Digital Subscriber Line - is a technology approaching its 10th year of development. ADSL runs a digital connection between your home and the phone company's central office over existing copper phone wires. Technology futurists used to wonder who was going to pay to wire every house on the planet with fiber-optic cable. The hardest and most expensive cable to replace was known as "the last 100 yards," or the distance between the nearest telephone pole and a home phone jack. With ADSL, we won't have to rewire those last 100 yards, because the bandwidth capacity of that tired old copper phone line is plenty big enough.

While ADSL uses existing phone lines, cable modems use the less common cable TV lines or specially installed cable lines. ADSL can use the conventional copper wire because there's plenty of unused bandwidth in our nationwide telephone infrastructure. Human speech only uses a small portion of the available frequency spectrum on a phone line, the same way a radio station only takes up a small part of the dial. ADSL grabs a much larger chunk of the remaining frequency spectrum to run a two-way digital connection that doesn't interfere with ongoing speech transmission.

ADSL connections restrict outbound traffic from your computer to an immodest 640 Kbps, in order to free up much more bandwidth "downstream." This asymmetric allocation leaves a wider path in your information superdriveway for downloading graphics and software. Speeds comparable to a T1 line - 1.54 Mbps - are available for users up to 18,000 feet away from the closest telephone company switching station. But 640 Kbps is still five times faster than commercial ISDN and 20 times faster than most analog modems in use. And that's the slow channel.

Over shorter distances, ADSL is even faster. Real-world testers are reporting throughput averaging around 5 to 6 Mbps over their lines, which are usually running less than 10,000 feet from the nearest switching station to the subscriber. That's about the same bandwidth an office's busy Ethernet cables might carry during work hours. Workers who only go to the office because the network is faster there would be better off staying home.

So what does it cost? The biggest consumer-side expense is the ADSL modem that plugs into the phone jack and splits the voice line and digital network. By bundling modems with services and amortizing costs, telephone companies expect to offer T1-speed (1.54 Mbps) ADSL services for as low as $60 per month. Higher bandwidths (up to 6 Mbps) will be priced higher, but will still fall below the current $400-and-up monthly cost of a T1, and without any installation hassles beyond plugging the modem into your existing phone jack.

Telco representatives estimate that 65 to 75 percent of their existing customers already meet the physical distance and wiring requirements for ADSL service. In congested areas like Silicon Valley, New York City, Seattle, or Washington, DC, many workers waste hours each day commuting, often because they don't have or can't afford the bandwidth to work from home at least part time. If ADSL were made available at corporate rates to major employers or office buildings, workers could stay home, as do @Home subscribers with their cable modems.

More and more local ISPs are offering jump-start ADSL service to anyone willing to lease an additional copper line (called a "dry pair") from their phone provider. However, the installation hurdles and costs - $500 to $700 for a modem, $12 to $100 per month to lease the dry pair, $20 to $30 per month in access charges to the ISP - are still closer to today's T1 overhead than to a cable-modem solution. It will take telco-sized operations and resources to offer whole cities easy access at consolidated-service prices.

But ADSL isn't happening as quickly as analysts predicted. Dataquest recently revised its estimate down from 2 million lines installed in the United States by the year 2000 to 1 million. The telcos say the problems aren't technical or organizational, but political.

The Telecommunications Act of 1996 forces ISPs in a given area to resell their technology and services to their competitors in the interest of an open market, even if the new competitor is a spinoff of another large provider (like AT&T or the Baby Bells, for example). Naturally, the Baby Bells are busy spinning off local competitors, after which they limit ADSL to trial markets, so the government won't sic its anti-monopoly dogs on their companies. So while the provision in the telecom bill was intended to keep prices low, it effectively prevents ADSL from being deployed at all.

Plug-and-play ADSL probably won't show up until the Telecommunications Act's regulations have been amended or negotiated. Stuck between corporate interests and federal regulators, the only choice most consumers will have for the next two to five years is to keep waiting. Might as well go start the car.