Digital Subscriber Line is an increasingly popular method used for branch office connectivity. A family of DSL types has been developed to provide high-speed Internet services over the existing telephone line infrastructure. The idea behind DSL technologies is to use a wider frequency band for communicating data over the existing twisted pair lines (telephone lines) at the same time as voiceband. This means that a second frequency band, above the voiceband, must be defined to perform data modulation. The two different frequency bands for voice and data are illustrated in Figure 10-8: