Broadband Technologies: How They Compare

Last week I provided a brief history of DSL and cable high-speed Internet. But the differences between DSL and cable run far deeper than pedigree. For businesses deciding between the two, the following breakdown of key attributes may prove informative.


DSL has made great strides in recent years, with significant improvements in speed. But those increases still may not be sufficient for many businesses. Major DSL providers can today offer speeds exceeding 20 megabits per second – and at least one company has announced speeds of 45 Mbps coming soon. But this is still below the 50 Mbps threshold that has become the de facto standard for business. High-speed cable, on the other hand, has not only been able to deliver that 50 Mbps benchmark for the past couple of years, but has gone far beyond it. Leveraging DOCSIS 3.0, top-tier cable providers are providing 100 Mbps service today, and speeds reaching 250 Mbps are expected in the near future – as early, perhaps, as 2014.


By running over twisted-pair cabling, DSL relies on a proven technology. But it is also a century-old technology, and not one designed with data in mind. While voice calls can be carried vast distances over twisted-pair wires with no degradation in quality, data does not fare as well. In fact, if subscribers are located more than a couple of miles from a phone company’s central office, DSL performance degrades markedly – so much so, that the service may not be available at all.

Consider, for example, today’s most common type of DSL technology: Asymmetric Digital Subscriber Line. With ADSL, broadband service is technically possible over a range of about 18,000 feet (roughly 3.4 miles). But because of performance degradation, providers generally limit service to a shorter distance – and even then, top speeds may be hard to obtain. Twisted-pair wires may provide a reliable way to call a client or colleague, but they may not work so well – or at all – for sending them a large file, sharing cloud-based data with them, or joining them in a videoconference.

Designed from the ground up for transmitting data, high-speed cable is not distance sensitive. Whether subscribers are located next door to the cable company or many miles away, they can enjoy the same broadband speeds.


With so much of a company’s operations depending on fast, reliable Internet access, consistency is crucial. If the speed businesses expect is not the speed they get, undesired results occur, including degraded video and Voice over IP (VoIP) quality, sluggish downloads, and slow connections to mission-critical applications and data in the cloud.

The true test for consistency comes during peak usage hours, when Internet traffic – and stress on networks – is at its highest. For businesses, these are the periods when they rely on their broadband most and when the consequences of slowdowns are greatest. To explore how different providers and technologies stack up, the Federal Communications Commission launched the Measuring Broadband America program in 2011. Its most recent study, published in February 2013, found that DSL-based services delivered, on average, 85 percent of advertised speeds during peak periods. Cable-based services, on the other hand, delivered 99 percent of advertised speeds.


The distance limitations of DSL mean that for a large percentage of a phone company’s footprint, the service will not be available. This is especially true in rural areas, where the cost of installing DSL infrastructure, combined with low population density, means that DSL is rarely economically viable for providers. Indeed, some of the largest phone companies in the country can offer DSL to just 25 percent – or less – of their customers.

Since high-speed cable Internet doesn’t degrade over distance, and runs over the same infrastructure that brings cable TV to both densely and sparsely populated areas, it is available to a far wider customer base in cities and rural areas alike.

Roadmap for the future

A broadband technology should meet a business’s current bandwidth needs, but it should be positioned to meet tomorrow’s needs, as well. The use of tools like videoconferencing, the cloud, and VoIP are growing; so, too, are emerging trends like centralized data warehouses and Big Data. As they grow, bandwidth demands will grow.

Both DSL and high-speed cable will continue to improve, but in different ways, with different results. New DSL technologies like ADSL2 and VDSL (Very high bit rate Digital Subscriber Line) and VDSL2 will offer higher maximum speeds than today’s DSL, but even the highest rates now envisioned will just barely meet the 100 Mbps standard most businesses will require in the very near future. Nor will these technologies get around the distance and availability issues inherent with all DSL service. Top speeds will be achievable by just a fraction of a phone company’s footprint – the subscribers located close to a central office.

Cable’s roadmap is ambitious and far-reaching, intended to take speed and reach well beyond what next-generation DSL will offer. While DOCSIS 3.0 is already enabling cable providers to deliver 100-Mbps broadband, this is just the beginning. DOCSIS 3.0 will reach speeds of up to 250 Mbps in the near future, and its successor – the forthcoming DOCSIS 3.1 – is expected to turbocharge bandwidth even more, bringing speeds of 500 Mbps to 1 gigabit per second (Gbps) to a coverage area far and wide.

The differences between DSL and cable run far deeper than pedigree. For businesses deciding between the two, the following breakdown of key attributes may prove informative.

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