Both Digital Subscriber Line (DSL) and cable modem services offer high-speed Internet access. Compared to traditional dial-up access, these two technologies open up homes and small businesses to a new realm of possibilities for network connectivity and applications. Video-on-demand, multimedia conferencing, and online gaming are just a few examples of services on the Net that don’t work so well at 56 Kbps.
DSL and cable modem differ in some fundamental ways. The two technologies can be compared and contrasted along these dimensions:
- speed
- cost
- security
- reliability and availability
- usability and quality of service
Some of the differences between DSL and cable modem arise from the history of the technologies they are built on. Others originate with differences in the approach of service providers. In fact, the speed, cost, availability, and many other elements of DSL or cable modem service can vary significantly depending on the provider.
In terms of theoretical peak raw performance, cable modem generally wins the speed battle over DSL. Cable technology can, in theory, achieve networking speeds of approximately 30 Mbps (using a 100 Mbps network interface card), whereas most forms of DSL cannot reach 10 Mbps
In practice, though, the speed advantage of cable over DSL is much lower than might first be apparent. Both cable modem and DSL performance vary from one minute to the next depending on the pattern of use and traffic congestion on the Internet. This means that both services will rarely — if ever — reach peak performance.
Cable modem technology delivers shared bandwidth within the local neighborhood while DSL delivers dedicated local bandwidth. With cable, performance at any given time depends on how many cable subscribers in the neighborhood are currently actively using the network as well as load on the Internet generally. This “double whammy” suggests that cable modem will perform relatively slower during peak usage periods.
Summary
Cable modem retains a slight performance advantage over DSL but this advantage seems to be a short-term one. Most cable networks have not yet reached high enough subscriber levels to make the shared bandwidth issue critical. With technologies like dedicated-bandwidth VDSL, however, DSL threatens to erase cable’s speed advantage even before cable services become overcrowded.
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