Broadband Technologies

Until recent times, people connected remotely to their offices or the Internet using dialup connections. An "always on" remote network connection was not possible for a reasonable price. To connect to the remote network, the user ran a program that dialed a phone number. Unless he had a second phone line, being online prohibited incoming or outgoing phone calls.

The user entered a user ID and password to gain access to the system. The fastest speed available over phone lines was 56 kbps, which was fine until the web became popular in the 1990s. Downloading large pictures, documents, applications, or audio files took what seemed like forever.

Then, along came broadband. Broadband networking offered a reasonable high-speed alternative to traditional dialup networking. Using existing cabling to houses (either phone or cable TV), service providers offered Internet services at 5 to 15 times the speed of dialup. Downloading a 100 MB file became palatable with broadband.

Broadband technologies allow service providers to offer "always on" connectivity similar to what people use in a corporate network. Computers on the broadband network always have access to the network; there is no intermediate dialup step. Sit down, load the browser, and off you go.

High-speed Internet access to homes offers new levels of productivity and entertainment not possible before the commercialization of the Internet and the web. Aside from apparent uses such as online shopping and video streaming, corporations can accommodate road warriors and work-from-home folks in a way not previously possible. Using encryption technologies, an employee with a laptop computer can securely access her corporate network from any Internet access point in the world. Additionally, employees can attach IP phones, allowing them to work on their computers and make calls from their office-phone extensions as if they were sitting at their desks.

Broadband Technology Evolution
Integrated Services Digital Network (ISDN) was the first commercially viable broadband option available. Using existing phone lines, home users commonly subscribed to a Basic Rate Interface (BRI), which had a throughput maximum of 128 kbps. In the US, ISDN was eclipsed by more cost-effective broadband technologies before it had a chance to become commonplace.

Cable modem and digital subscriber line (DSL) services became the premier broadband technologies. Although other broadband technologies existed, the primary determination of a technology’s viability was access to "last mile" wiring to houses. Anything that required new wiring probably wouldn’t make it. Other technologies that take advantage of other media exist, such as satellite television dishes, but for quality issues did not become as popular.

Cable Modem
Cable modems provide high-speed data communication using existing cable- television coax cabling. Current implementations of cable-modem technologies offer speeds as fast as Ethernet (10 Mbps), which means a file that takes two minutes to transfer over ISDN takes two seconds over cable modem. Cable modem can provide higher speeds than traditional leased lines, with lower cost and easier installation.

Because a cable-modem connection is permanently established, it cannot dial multiple locations directly. As a result, cable-modem access must be to the Internet. This restriction means that employees can connect to their company’s network only if the company provides access through the Internet.

DSL
Like cable modem, DSL provides high-speed Internet access for reasonable cost using existing cabling to houses and businesses. DSL carves off a portion of the telephone line to use for data transmission without interfering with existing phone service.

Because of the multiple flavors of DSL services, DSL is generically referred to as xDSL. The two popular forms of xDSL service currently available are Asymmetrical DSL (ADSL) and Symmetrical DSL (SDSL). ADSL provides faster download speeds because traffic toward the user is given more bandwidth than traffic from the user. SDSL assigns equal bandwidth in both directions.

Which One Is Better?
Both DSL and cable modems provide high-speed Internet access at a relatively low cost. Both provide "always on" connectivity. Both have technical advantages and disadvantages over each other. Either technology makes a good to-the-home or small-office solution for Internet connectivity. Because both technologies are "always on," a firewall must protect the local network from Internet-based attacks.

Some practical issues affect how widespread the technologies become. Virtually all businesses and homes have telephone lines, which mean DSL is possible, but fewer homes and businesses have cable television lines.