Asymmetric Digital Subscriber Line (ADSL)

What is an asymmetric digital subscriber line (ADSL)?

Asymmetric Digital Subscriber Line (ADSL) is a technology that brings high transmission speeds for video and voice to homes over ordinary copper telephone wire. It will be more cost-effective in areas where cable TV penetration in the market is low.

Understanding an Asymmetric Digital Subscriber Line (ADSL)

Asymmetric digital subscriber line (ADSL), sometimes simply referred to as DSL, is considered the main competitor to cable modems. DSL and cable systems are compared by bandwidth, a measure of how much data a network can transfer. Internet providers typically list bandwidth speeds in millions of bits per second, or megabits (Mbps), and billions of bits per second, or gigabits (Gbps). Generally speaking, the higher the bandwidth, the faster a computer downloads information from the Internet, whether users are checking emails or streaming movies.

The US Federal Communications Commission (FCC) defines broadband Internet speeds as connections with a minimum bandwidth of 10 Mbps for downloads and 1 Mbps for general streaming.

Providers report the bandwidth metric to customers, but it may not be the actual speed of bandwidth a customer is receiving. Connection can have a bottleneck where a network is limited by the lowest speed going to multiple computers at once. More computers connected at the same bandwidth speed can cause slower bandwidth for everyone sharing the same connection.

Cable vs Internet vs Fios

In terms of theoretical peak performance, a cable modem typically has higher bandwidth than DSL. The cable technology, which transmits data over buried copper coaxial cables originally intended for television, currently supports a maximum of 1,000 Mbps of bandwidth in many regions, while DSL speeds generally peak at 100 Mbps. Actual speeds may vary in practice depending on the quality of the copper telephone line installation. Additionally, the length of telephone line required to reach the service provider’s central office may also limit the maximum speed a DSL installation can support.

In 2017, Verizon Communications Inc. (VZ) launched a new service, Fios Instant Internet, which increased the Internet speeds it provides to residential and business customers. The broadband service provides customers with equal download and upload speeds of 750 Mbps. Verizon claimed that with symmetrical speeds, the new service could handle multiple Internet-connected devices without compromising the performance of any one.

Most types of DSL service are asymmetric or ADSL. Generally, ADSL offers higher download speeds than upload speeds, which is usually not a disadvantage as most households download more data from the internet than they upload. Symmetric DSL maintains equal data rates for uploads and downloads.

The main selling point of DSL is its widespread availability; Phone infrastructure is already deployed virtually everywhere, so it doesn’t take much setup to connect most customers to the Internet via DSL, especially in rural areas where cable is less likely to be an option.