Coming in second in our subscriber-based popularity contest is DSL (digital subscriber line), a technology that uses your garden-variety copper phone wires to give you high-speed data transmission. DSL requires a phone line, a DSL modem (often included with service), either an Ethernet card or a router that has an Ethernet connection, and someone that can provide service wherever you happen to be located.
The acronym DSL originally meant digital subscriber loop, but now its meaning has morphed to digital subscriber line. DSL group types fall into two categories based upon the upstream or downstream speed connections:
Symmetrical DSL The speed for both downstream and upstream connections are equal, or symmetrical.
Asymmetrical DSL Different transmission speeds occur between two ends of a network— downstream speed is usually faster.
Figure 1 shows an average home user with xDSL, which is a transmission technology that moves data over copper pairs.
The term xDSL covers a number of DSL variations, such as ADSL, high-bit-rate DSL(HDSL), Rate Adaptive DSL (RADSL), Synchronous DSL (SDSL), ISDN DSL (IDSL), and very-high-data-rate DSL (VDSL).
DSL flavors that don’t use the voice frequencies band, like ADSL and VDSL, allow DSL lines to carry both data and voice signals simultaneously. Others, like SDSL and IDSL, that occupy the complete frequency range, can only carry data. And by the way, the data service that the DSL connection gives you is always on.
The speed that DSL service can offer depends on how far you are from the CO—the closer the better. In fact, you can blaze at rates up to around 6.1Mbps if you’re physically close enough!
The acronym DSL originally meant digital subscriber loop, but now its meaning has morphed to digital subscriber line. DSL group types fall into two categories based upon the upstream or downstream speed connections:
Symmetrical DSL The speed for both downstream and upstream connections are equal, or symmetrical.
Asymmetrical DSL Different transmission speeds occur between two ends of a network— downstream speed is usually faster.
Figure 1 shows an average home user with xDSL, which is a transmission technology that moves data over copper pairs.
xDSL connection from home user to central office
All types of DSL are layer 1 technologies.
ATU-R = ADSL Transmission Unit - Remote
ATU-C = ADSL Transmission Unit - Central
ATU-R = ADSL Transmission Unit - Remote
ATU-C = ADSL Transmission Unit - Central
The term xDSL covers a number of DSL variations, such as ADSL, high-bit-rate DSL(HDSL), Rate Adaptive DSL (RADSL), Synchronous DSL (SDSL), ISDN DSL (IDSL), and very-high-data-rate DSL (VDSL).
DSL flavors that don’t use the voice frequencies band, like ADSL and VDSL, allow DSL lines to carry both data and voice signals simultaneously. Others, like SDSL and IDSL, that occupy the complete frequency range, can only carry data. And by the way, the data service that the DSL connection gives you is always on.
The speed that DSL service can offer depends on how far you are from the CO—the closer the better. In fact, you can blaze at rates up to around 6.1Mbps if you’re physically close enough!
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