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CHAPTER 9 CONNECTING TO THE INTERNET
Table 9-1. Common Broadband Networking Technologies
Technology Description
DSL Digital subscriber line (DSL) is, along with cable, one of the most popular broadband
technologies used today. DSL sends a digital signal over traditional phone lines,
making it easily available to many existing phone customers. There are a number of
variants of DSL; the most common today is asymmetric DSL (ADSL). The big drawback
to ADSL is that its speeds start to diminish over distance, making this technology less
effective for rural areas. ADSL also provides fast download speeds while limiting its
upload speed; this makes it suitable for most home users but less useful for businesses.
SDSL, on the other hand, provides the same upload and download speeds. ADSL is
commonly referred to as residential DSL, while business DSL is usually SDSL.
VDSL VDSL is a newer “very high-speed” DSL technology that is starting to be rolled out all
over the world. This DSL technology is currently able to provide up to 100 Mbps
upload and download speeds over traditional POTS copper wiring. As with DSL, this
speed diminishes over distance; still, VDSL promises higher speeds and longer
distances than earlier versions of DSL. (AT&T is rolling out VDSL as U-Verse to selected
communities across the United States.)
Cable Cable broadband is another big broadband technology used today. This provides
access over existing cable TV lines. Unlike DSL, cable broadband does not lose its
effectiveness over distances and traditionally has been able to provide faster data
speeds than DSL; on the other hand, cable is also generally more expensive, and most
cable companies provide cable broadband only to cable TV subscribers, raising the
costs associated with cable even higher.
ISDN ISDN is one of the original broadband technologies available to consumers. It provides
faster-than-dial-up speeds; however, there are lots of higher costs associated with it.
ISDN has for the most part been replaced with other less expensive, faster
technologies today.
T1 T1 lines (also called DS1 and E1) are the traditional broadband, high-speed
connections that are common in many commercial offices. Originally, T1 connections
were special telephone lines designed to carry voice communications for large
organizations; however, early in the expansion of the Internet, digital T1 lines were
used to provide high-speed Internet connections. T1 lines are still in use in many
businesses for both voice and data. The downside to T1 lines is that even today they
are regulated and require special lines to be run to connect the provider with the user.
This makes their costs high. There are also T2 and T3 lines, which are similar yet faster
than the traditional T1 lines.
SONET Synchronous optical networking (SONET) technologies are slowly replacing T1 as the
commercial data connection of choice. Using fiber-optic lines to carry the digital
information allows OC-x technologies to provide extremely high-speed data
throughput over long distances (though at a very high cost).
Wi-Fi Wi-Fi is a blanket term that covers wireless 802.11 technologies including Apple’s
AirPort technologies. Although the range of Wi-Fi is relatively low, in high density and
commercial areas it is quite popular. (Being short range, Wi-Fi is usually used in
conjunction with a hardwired broadband technology such as DSL, cable, T1, or OC-x.)
WiMAX WiMAX is a new emerging wireless broadband technology that attempts to provide
faster speeds and more important greater range than traditional Wi-Fi technologies.