s with video servers, including storage capacity and processing power, VOD was largely abandoned at that time. On the other hand, Internet access was emerging as a highly desirable service, and with 80% of the traffic flow on Internet being in the downstream direction, ADSL presented a perfect solution. ADSL, also referred to as G.dmt, was ratified by the ITU-T under recommendation G.992.1 in 1999. It is also standardized under ANSI T1.413, Issue 2. The asymmetric operation is the key distinguishing characteristic of ADSL. Traditional ADSL, operating over a bandwidth of 1.1MHz, supports downstream data rates from 256Kbps to 7Mbps and upstream rates from 64Kbps to 800Kbps. The maximum reach is 3.5 miles (5.5 km). There is also a version of ADSL known as ADSL Lite, or G.lite. By limiting the data band to 550KHz, ADSL Lite operates at lower speeds, typically up to 1.5Mbps downstream and up to 512Kbps upstream. It is rarely used today. Again, remember that the real-world performance of ADSL, like that of any other DSL, depends on a number of factors, including the distance from the CPE to the DSLAM, the signal-to-noise ratio, the signal attenuation, the cable diameter, the line impedance (which is affected by changes in weather as well as the number of taps on the cable), and the general condition of the cable. Chapter 12 Broadband Access Alternatives Because ADSL carries a mixture of traffic, including voice, data, Web access, and multimedia, a multiplexing technology is required to carry both time-critical and less time-critical data. ADSL is therefore commonly deployed with ATM, which serves this purpose. In addition, because different ATM virtual circuits (VCs) can be allocated for different services, ATM ensures that service providers can provide triple-play services. However, recently, some network operators have been moving away from the use of ATM, for reasons of cost savings, and replacing it with Ethernet-based solutions. ADSL service providers offer either static or dynamic IP addressing. Static IP address